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The effect on perception of pain sensation, distress and incentive spirometry performance when cholecystectomy… Brazier, Linda Diane 1988

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THE EFFECT ON PERCEPTION OF PAIN SENSATION, DISTRESS AND INCENTIVE SPIROMETRY PERFORMANCE WHEN CHOLECYSTECTOMY PATIENTS ARE MOBILIZED AT ONSET, PEAK OR POST PEAK OF OPIOID (MEPERIDINE) ACTION By LINDA DIANE BRAZIER B.S.N. , University of Br i t ish Columbia, 1975 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN NURSING in THE FACULTY OF GRADUATE STUDIES The School of Nursing We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA October 1988 © Linda Diane Brazier, 1988 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, 1 agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. The University of British Columbia Vancouver, Canada Department DE-6 (2/88) ABSTRACT There has been l i t t l e study of ways to decrease pain generated by painful postoperative exercise. The purpose of this study was to determine the effect of performing painful act iv i t ies at various times of analgesic action on pain sensation, pain distress and inspiratory capacity of one day postoperative cholecystectomy patients. In addition, the relationship of inspiratory capacity to pain sensation and distress was explored. The theoretical framework for this study was based on Melzack and Wall's Revised Gate Control Theory of Pain. This experimental study used a randomized balanced incomplete block design in which the subjects served as their own control . Subjects ranged in age from 25 to 59 years and were free of chronic disease, pain syndromes, chemical abuse and psychiatric disorders. Twelve subjects were randomly assigned to two out of three possible combinations: ambulation at 15, 60, or 110 minutes after receiving an intramuscular injection of meperidine. These times represented the predicted onset, peak and post peak of analgesic action. After ambulation, subjects scored a visual analogue scale measuring pain sensation and a rating scale measuring level of d istress, and then performed 5 maximal inspirations using a Volurex incentive spirometer. An analysis of variance found no signif icant difference in pain sensation, distress or inspiratory capacity when subjects were ambulated at different times after meperidine in ject ion. Overal l , moderate but variable levels of pain sensation and distress were reported. Decreases in postoperative inspiratory capacity ranged from 40 to 90% of the i i 1 p r e o p e r a t i v e b a s e l i n e . The r e l a t i o n s h i p between i n s p i r a t o r y c a p a c i t y and p a i n s e n s a t i o n s c o r e s was non s i g n i f i c a n t b u t a s t r o n g t r e n d was n o t e d . When t h e change i n i n s p i r a t o r y c a p a c i t y between two a m b u l a t i o n t i m e s was c o r r e l a t e d w i t h t h e change i n p a i n s e n s a t i o n , a s i g n i f i c a n t n e g a t i v e c o r r e l a t i o n was f o u n d . The r e l a t i o n s h i p between i n s p i r a t o r y c a p a c i t y and d i s t r e s s was non s i g n i f i c a n t . A d d i t i o n a l c o r r e l a t i o n s were pe r f o r m e d among s e l e c t e d v a r i a b l e s r e l a t e d t o sample c h a r a c t e r i s t i c s . A n e g a t i v e c o r r e l a t i o n between age and p a i n s e n s a t i o n was t h e o n l y s i g n i f i c a n t a n c i l l a r y f i n d i n g . The f i n d i n g s were d i s c u s s e d i n r e l a t i o n t o t h e o r e t i c a l e x p e c t a t i o n s , o t h e r r e s e a r c h s t u d i e s , and m e t h o d o l o g i c a l problems i n h e r e n t i n t h e s t u d y . I m p l i c a t i o n s o f t h e f i n d i n g s f o r n u r s i n g p r a c t i c e , e d u c a t i o n and t h e o r y were s u g g e s t e d . Recommendations f o r f u t u r e r e s e a r c h were made. iv TABLE OF CONTENTS ABSTRACT i i LIST OF TABLES v i i LIST OF FIGURES v i i i ACKNOWLEDGEMENTS i x CHAPTER ONE: INTRODUCTION 1 Background to the Problem 1 Problem Statement 3 Purpose 3 Conceptual Framework 3 Overview of the Major Concepts Within the Conceptual Framework . 4 The Specific Concepts Within the Study 7 Hypotheses 7 Definition of Terms 8 Assumption 11 Limitations 11 Significance 11 Overview of the Thesis Content 12 CHAPTER TWO: REVIEW OF THE LITERATURE . . . 13 Effect of Meperidine on Postoperative Pain (Sensation and Distress) 13 Antinociceptive Action of Meperidine 13 Optimal Analgesic Dose 14 Pharmacokinetics of Meperidine 15 Time course (Time-action curve) 16 Absorption of meperidine 18 Distribution of meperidine 18 Elimination of meperidine 20 Physiological Variables Related to Analgesic Consumption . . . 20 Psychological Variables Related to Analgesic Consumption . . . 21 Current Controversy Related to I.M. Meperidine Use 22 Effect of Intramuscular Meperidine on Postoperative Inspiratory Capacity 23 Negative Effects of Upper Abdominal Surgery on Breathing . . . 23 Respiratory Depressant Action of Opioids . 24 Improvement in Pain-Induced Restricted Breathing with Opioids 25 Probable Enhancement of Exercise Tolerance with Opioids . . . . 27 Summary of the Literature Review 29 V CHAPTER THREE: METHODOLOGY 31 Design 31 Setting 32 Sample 33 Data Collection Instruments 34 Pain Sensation Scale 34 Pain Distress Scale . , 35 Volurex Incentive Spirometer 36 Data Collection Sheets 36 Preoperative data sheet 36 Perioperative data sheet 37 Postoperative data sheets 37 Data Collection Procedure 37 Ethics and Human Rights 39 Data Analysis 41 CHAPTER FOUR: PRESENTATION AND DISCUSSION OF RESULTS 43 Introduction 43 Characteristics of the Sample 43 Demographic Characteristics of the Sample 43 Health Characteristics of the Sample 44 Postoperative Characteristics of the Sample 45 Findings 48 Hypothesis 1. The Relationship Between Pain Sensation and Predicted Action Times of Meperidine 49 Hypothesis 2. The Relationship Between Level of Distress and Predicted Action Times of Meperidine 51 Hypothesis 3. The Relationship Between Inspiratory Capacity and Predicted Action Times of Meperidine 53 Hypothesis 4. The Inverse Relationship Between Pain Sensation and Inspiratory Capacity 56 Hypothesis 5. The Inverse Relationship Between Distress and Inspiratory Capacity 59 Ancil lary Findings 59 Discussion 62 Characteristics of the Sample 62 Pain Sensation 64 Pain Distress 70 Inspiratory Capacity 71 The Effect of Ut i l i z ing the Predicted Peak Action Times of Me peri di ne 74 The Relationship of Inspiratory Capacity to Pain Sensation and Distress 77 Summary 81 CHAPTER FIVE: SUMMARY, CONCLUSIONS, IMPLICATIONS AND RECOMMENDATIONS 82 Introduction 84 Summary 84 Conclusions 90 Implications 92 Recommendations for Future Research 95 REFERENCES 97 APPENDICES A. Level of Pain Scale and Pain Distress Scale 103 B. Volurex Spirometer 104 C. Testing of Volurex Against Vortex Flow Sensor 105 D. Testing Volurex - RT-200 Calibration Analyzer 106 E. Data Collection Sheets (1, 2, 3, 4) 107 F. Surgeon's Consent I l l G. Explanatory Letter to Ward 112 H. Patient Information Sheet 113 I. Patient Consent 115 J . Details of the Analysis of Variance of a Balanced Incomplete Block Design Using Levels of Distress 1 as an Example 116 K. Comparison of the Change in Pain Sensation with the Change in Inspiratory Capacity (IC) From The Morning to the Afternoon 121 v i i LIST OF TABLES Table 1. Age Distribution for Sample 44 Table 2. Body Mass Index (BMI) for Sample 45 Table 3. Time and Amount of I.M. Meperidine Received Postoperatively 47 Table 4. Untoward Effects Experienced by Sample 48 Table 5. Pain Sensation at Predicted Onset, Peak or Post Peak of Me peri di ne Action 50 Table 6. Effect of Predicted Analgesic Action Time on Pain Sensation 51 Table 7. Level of Distress at Predicted Onset, Peak or Post Peak of Me peri di ne Action 52 Table 8. Effect of Predicted Analgesic Action Times on Level of Di stress 53 Table 9. Inspiratory Capacity at Predicted Onset, Peak or Post Peak of Meperidine Action 54 Table 10. Effect of Predicted Analgesic Action Times on Inspiratory Capacity 55 Table 11. A Comparison of Four Studies Measuring Pain and Distress in Postoperative Patients, After Ambulation 66 Table 12. Treatment Times (Onset, Peak and Post Peak) Affording the "Better" Analgesic Effect for the Sample . . . . 77 vi i i LIST OF FIGURES Figure 1. Conceptual framework of pain 5 Figure 2. Stylized plasma concentration versus time plot i l lus t ra t ing onset, intensity and duration of a pharmacological effect 16 Figure 3. Time course of drug concentration in plasma and the biophase and the pharmacological response 17 Figure 4. Research design 32 Figure 5. Scattergram of postoperative IC scores and pain sensation scores 57 Figure 6. Scattergram of postoperative IC scores and pain sensation scores with the out l ier (subject #11) deleted 57 Figure 7. Scattergram of percentage of preoperative IC and pain sensation scores 58 Figure 8. Scattergram of the change in IC between two treatments and the change in pain sensation between two treatments 58 Figure 9. Scattergram of postoperative IC scores and distress scores 60 -Figure 10. Scattergram of postoperative IC scores and distress scores with the out l ier (patient #11) deleted . . . . 60 Figure 11. Scattergram of percentage of preoperative IC and distress scores . 61 Figure 12. Scattergram of the change in IC between two treatments and the change in distress between two treatments . . 61 i x ACKNOWLEDGEMENTS I would l ike to thank the members of my thesis committee, Dr. Ann Hilton (chairperson) and Judy Mogan for sharing their expertise and providing much needed guidance. I would l ike to thank my husband Wayne, for his support and forbearance; my parents, for their encouragement; and my friend Arleigh, for "being there". My appreciation is extended to the following groups who were associated with the hospital where my study was conducted: the nursing administration, nursing staf f , Admissions staf f , respiratory therapists and surgeons. These individuals were unstinting in their cooperation. I am grateful for the assistance of Dr. Jonathan Berkowitz, Department Head of the UBC Stat ist ics Consulting Service. I am also grateful for the assistance of the enthusiastic staff at Associated Respiratory Services and to al l of the other individuals who shared their time and advice. F ina l l y , I would l ike to thank the patients who so wi l l ingly participated in this study. 1 CHAPTER ONE Introduction Background to the Problem Despite advances in preoperative, perioperative and postoperative care, patients s t i l l suffer from signif icant postoperative pain (Bonica, 1982; Cohen, 1980). Bonica (1982) derived data from an extensive review of l i terature describing the incidence, intensity and duration of pain after various surgeries and found that out of 13 types of major surgery, upper abdominal surgery was associated with the highest incidence (60%) of severe steady wound pain. Furthermore, 100% of these patients complained of moderate to severe pain and muscle spasm on movement. In order to minimize pain intensif ied by movement of the thorax and upper abdomen during breathing, the patient with an upper abdominal incision will adopt a shallow breathing pattern (Bonica, 1982). This leads to a signif icant drop in vital capacity and a concomitant high incidence of postoperative pulmonary complications ( C e l l i , Rodriguez & Snider, 1984). Consequently, pain management is not only necessary for the re l ie f of suffering, i t is also imperative for improving the restr ict ive breathing pattern seen after upper abdominal surgery (Bromage, 1955; Bryan-Brown, 1986). Opioid analgesics via the intramuscular route are the most common means of postoperative pain management (Phi l l ips & Cousins, 1986). Although designated pro re nata (p.r .n.) i t is necessary that they be given regularly during the immediate postoperative period so as to maintain adequate opioid blood levels ( Inturrisi & Foley, 1984). However, even with regular administration, the pharmacokinetics of intramuscular 2 opioids, especially meperidine, result in fluctuations in blood concentration levels (Austin, Stapleton & Mather, 1980). The waxing and waning of analgesic efficacy can be i l lustrated on a time-effect or time-serum concentration curve. The curve ref lects the onset and duration of minimum analgesic action and the maximum or peak of analgesic action (Hahn, Barkin & Oestreich, 1982; Inturrisi & Foley, 1984). In addition to fluctuations in blood-opioid concentration leve ls , movement is known to cause breakthrough or "peak incident" pain (Phi l l ips & Cousins, 1986). Fear of this "breakthrough" pain can lead to lack of patient compliance with postoperative exercises (Bryan-Brown, 1986). Consequently, there are two problems associated with p . r .n . intramuscular opioids as a pain management technique. In the f i r s t place, there may be a fluctuation in analgesic efficacy between inject ions. Secondly, patients may require more analgesia when performing pain e l i c i t i n g act iv i t ies than when they are at rest. Given the problems associated with using p . r .n . intramuscular opioids for pain management after upper abdominal surgery, is i t possible for nurses to u t i l i ze knowledge of time-effect or time-serum concentration curves to decrease pain during part icularly painful act iv i t ies? That i s , would patients have less pain on ambulation and an improved ab i l i ty to deep breathe i f these act iv i t ies were performed at the predicted peak of analgesic action? Since the timing of these act iv i t ies is a nursing decision, such an approach would be within the scope of independent nursing practice. Nurses DiBlasi and Washburn (1979) recommend that this approach be used. However, i t is the investigator's experience that nurses do not consistently and deliberately plan for pain e l i c i t i n g 3 act iv i t ies to coincide with peak analgesia. Furthermore no research was found that investigated the effectiveness of such a practice. Problem Statement Surgery of the upper abdomen e l i c i t s a high level of postoperative pain that is intensif ied by deep breathing and ambulation. Consequently, these patients are reluctant to move and deep breathe after surgery and are at increased risk for developing postoperative pulmonary complications. Regular administration of intramuscular opioids decreases pain at rest but the level of analgesia fluctuates between injections and patients may s t i l l experience pain when performing part icularly painful ac t i v i t i es . A logical approach suggested by nurses DiBlasi and Washburn (1979) is to time pain e l i c i t i n g act iv i t ies in concert with the peak of analgesic action. However, this is not common nursing practice. Furthermore, no studies were found that compared the performance of potentially painful act iv i t ies at particular times related to expected analgesic action in terms of pain sensation and distress reduction and improved ab i l i ty to perform deep breathing exercises. Purpose The purpose of this study is to determine the effect of performing painful ac t iv i t ies at various times of analgesic action, on pain sensation, pain d ist ress, and inspiratory capacity of one day postoperative cholecystectomy patients. Conceptual Framework The conceptual framework for this study is based on the Revised Gate Control Theory of Pain (Melzack & Wall, 1983) and incorporates new information related to pain neurophysiology. It is important to realize 4 that pain theory is in transition and that no existing theory is complete. The Revised Gate Control Theory is currently controversial because some of i ts explanatory mechanisms have not been substantiated (Nolan, 1987). Melzack and Wall state "We wish to emphasize that the assumption that the substantia gelatinosa is the primary vehicle for gating is an assumption and is not yet fact" (1983, p. 236). However, despite th is , the Gate Control Theory of Pain is cited as being one of the major catalysts stimulating the current explosion in pain research (Liebeskind & Paul, 1977). Furthermore, this comprehensive theory integrates the sensory, emotional, cognitive and behavioural dimensions of pain (Kelly, 1985) and thereby serves as an appropriate framework for this study. Figure 1 diagrams the major concepts within the Gate Control theory and the specif ic concepts within the study. Overview of the Major Concepts Within the Conceptual Framework Pain arises from mechanical, chemical and thermal trauma which stimulates free nerve endings cal led nociceptors. Nociceptive impulses are transmitted via A delta and C nerve fibres to the dorsal horn of the spinal cord where they terminate on small neurons in the horn's outer layers (lamina). These neurons form dense interconnections, especially in lamina II, the substantia gelatinosa, where they either inhib i t or mediate transmission of nociceptive impulses through a "gating" mechanism. Inhibition occurs when nociceptive inputs coincide with other sensory inputs from large A beta f ibres transmitting l ight pressure. Inhibition also results from downward inhibitory control from the brain. Nociceptive impulses are transmitted from the cord to the brain via sensory nerve tracts such as the neospinothalamic and the AUGMENTORS Movement (Deep bre a t h -i n g & M o b i l i z a t i o n ) N o c i c e p t i o n * Pain Source N 1 1 t . Cholecystectomy c m m m P e r c e p t i o n o f Pain Sensation P e r c e p t i o n o f Pain D i s t r e s s INHIBITORS Meperidine I.M. (Peak A c t i o n ) ACTION SYSTEM ' <T ACTIVE Pain Behaviour Requesting Meperidi ne REACTIVE Pai n Behaviour Decreased I n s p i r a t o r y C a p a c i t y Figure 1. Conceptual framework of pain incorporating concepts specif ic to the study. Adapted from the Revised Gate Control Theory of Pain (Melzack and Wall, 1983). Note. *Nociception: N - Nociceptors; G - Gating Mechanism; C -Central Processing System; t—• - transmission of nociceptive impulses; 4—m - modulation (inhibition) of nociceptive impulses. Broken l ines ( — - - • ) indicate the antinociceptive effect of Inhibitor (Meperidine) which decreases pain sensation and distress and decreases pain behaviour (inspiratory capacity). paleospinothal amic t racts. The many and diverse parts of the brain involved in nociception are col lect ive ly conceptualized as the Central Processing System. These include the ret icular activating system, limbic system, thalmus and cerebral cortex. This system integrates nociceptive inputs with related sensory information, past experience and learning. At 6 this point, nociceptive impulses can be modulated by inhibitory mechanisms within the Central Processing System. If these impulses are not subject to modulation, then they are consciously perceived as pain. Certain factors are also known to augment pain by enhancing nocicep-tion at some l eve l . Examples include anxiety, depression, prolonged pain, and movement. Anxiety and depression may be preexisting t ra i ts or may be manifestations of distress arising from the painful experience. The conscious perception of pain has two components: the sensation of pain with respect to i ts intensity and a degree of associated emotional distress (Beecher, 1956; Melzack & Wall, 1983). Both components are uniquely experienced and subject to many influencing variables. The Action System responds to the level of pain sensation and distress and direction from the Central Processing System through voluntary and involuntary motor t racts . The measurable outcome of the Action System stimulation is reactive (involuntary) and active (voluntary) pain behaviour. The c lassic reactive pain behaviours are reflex withdrawal and immobilization of the injured part (Guyton, 1981). Crying, wincing and sympathetic nervous system responses also comprise the reactive component of pain behaviour. The active component may be a simple measure such as the universal act of rubbing the injured part and thereby e l i c i t i n g the gating mechanism. More complex behaviour tends to be variable due to the influence of culture, past experience and personal meaning of the pain. The aversive nature of pain always motivates the individual to eliminate i ts source and to attempt to reduce the painful sensation and emotional d istress. This can be achieved i f the individual u t i l i zes an inhibitor that is antinociceptive at some level of the nociceptive system. Examples 7 of inhibitors include analgesics, the application of heat and cold , massage, transcutaneous electr ical nerve stimulation (TENS), d istract ion, relaxation exercises, guided imagery and severe stress. Inhibitors wil l decrease pain sensation and distress. Diminished pain behaviour is commensurate with decreases in pain perception. The Specific Concepts Within the Study In this study, cholecystectomy surgery is the pain source. Mobilization and movement of the chest wall through deep breathing are augmentors because both act iv i t ies place tension on the high abdominal incision that is requisite to this surgery. Pain sensation and distress are increased postoperatively, especially during mobilization and deep breathing. Pain behaviour is also increased. A shallow breathing pattern is adopted as a reaction to breathing-induced incisional tension. This results in a decreased inspiratory capacity. Active behaviour consists of requesting and/or accepting regular injections of meperidine. Meperidine, an inhib i tor , modulates nociceptive impulses generated by the pain source and the aforementioned augmentors by stimulating inhibitory mechanisms in both the brain and the spinal cord. This results in a decrease in perception of pain sensation and distress. As a result , reactive pain behaviour is diminished and inspiratory capacity increases. This effect will be greater at the time when meperidine is at i ts "peak" action since the intramuscular route results in fluctuations in analgesic efficacy between injections (Inturrisi & Foley, 1984). Hypotheses 1. One day postoperative cholecystectomy patients mobilized at peak of analgesic action will experience less pain sensation than 8 cholecystectomy patients mobilized at onset or post peak of analgesic action. 2. One day postoperative cholecystectomy patients mobilized at peak of analgesic action will experience less distress from pain than cholecystectomy patients mobilized at onset or post peak of analgesic action. 3. One day postoperative cholecystectomy patients mobilized at peak of analgesic action will have a greater inspiratory capacity than cholecystectomy patients mobilized at onset or post peak of analgesic action. 4. One day postoperative cholecystectomy patients wil l demonstrate an inverse relationship between level of pain sensation and inspiratory capacity. 5. One day postoperative cholecystectomy patients will demonstrate an inverse relationship between level of pain distress and inspiratory capacity. Definition of Terms Definitions will be expressed in (a) theoretical and (b) operational terms when a differentiation is required. 1. Cholecystectomy a surgical procedure involving removal of the gall bladder and l igat ion of the cystic duct. 2. Inspiratory Capacity (a) the maximum amount of a i r inhaled from the resting expiratory level and recorded in l i t e r s or m i l l i l i t e r s (Luckmann & Sorensen, 1980, p. 1189). 9 (b) a position on a 4 l i t e r Volurex Incentive Spirometer scale that is measured in m i l l i l i t e r s of a i r . 3. Mobilization (a) the act of moving or being moved. (b) to move from the patient's bed (supine) to a chair placed closely beside the bed. 4. Nociception the recognition by the nervous system or organism of a traumatic or hurtful stimulus. Derived from the term nociperception (International Dictionary of Medicine and Biology, 1986, p. 1937). 5. One day Postoperative (a) the day after surgery. (b) the morning and the afternoon of the f i r s t day after cholecystectomy. 6. Opioid Analgesic Action Onset a) the f i r s t sign of a drug (opioid) effect which signif ies the minimum effective plasma concentration of the drug (opioid) (Hahn et a l . , 1982, p. 53). b) 15 minutes after an injection of intramuscular meperidine. Note: Since the actual onset for meperidine is 10 minutes (Jaffe & Martin, 1985), 15 minutes was selected for the study to ensure that al l patients received at least a minimum level of analgesia. Peak a) the maximum drug (opioid) effect which signif ies the maximum therapeutic plasma concentration of a drug (opioid) (Hahn 10 et a l . , 1982, p. 53). b) 60 minutes after an injection of intramuscular meperidine (Jaffe & Martin, 1985). Post Peak a) a term created for the study to denote the minimum opioid effect that occurs after peak but prior to a fa l l in plasma-opioid concentration below the minimum effective l eve l . b) 110 minutes after an injection of intramuscular meperidine. Note: Since the duration of meperidine is 2-4 hours (Jaffe & Martin, 1985), 110 minutes was selected to ensure that al l patients received at least a minimum level of analgesia. 7. Opioids (a) a generic term that encompasses both natural and synthetic opiumlike or morphinelike analgesics (Jaffe & Martin, 1985, p. 492). (b) meperidine hydrochloride. 8. Pain (a) " . . . a n unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage (International Association for the Study of Pain, 1979, p. 250). (b) the perception of pain sensation and pain distress. 9. Pain Sensation (a) the perception of physical discomfort arising from noxious stimuli (definition based on the work of Melzack and Wall, 1983). (b) a designated level on a 10 centimeter visual analogue scale measuring pain intensity in millimeters (Taenzer, Melzack & Jeans, 1986). 10. Pain Distress (a) the perception of emotional suffering that is generated in response to the sensation of pain (definit ion based on the work of Beecher, 1956; Johnson, 1973; Johnson & Rice, 1974; and Melzack & Wall, 1983). (b) a designated level on Johnson's Distress Scale. Assumption 1. That there will be no signif icant variation in level of pain sensation or pain distress from the morning to the afternoon, by factors other than the independent variable. Limitations 1. The sample size in each group is small and therefore generalization of the results is not possible. 2. Intramuscular injections of meperidine are reputed to cause widely variable blood-meperidine concentration levels . 3. The analgesic dosage has not been control led. 4. There is no control over regularity of the dosage interval prior to or during the study. 5. The subject is unable to experience a l l three treatments due to potential fatigue. Significance This is an important study for nursing practice because i t explores a safe, simple and practical nursing intervention that may decrease patient's pain sensation and distress when performing particularly painful act iv i t ies in the immediate postoperative period. At present, there are 12 no nursing studies that provide direction to nurses with respect to u t i l i z ing maximum analgesic action as an organizing point around which to plan pain-e l ic i t ing ac t iv i ty . Furthermore, there is a dearth of nursing research in general that is related to parenteral opioid administration (Cohen, 1980). If nurses have the " l ion 's share" of responsibi l i ty with respect to opioids (McCaffery, 1979), and i f they are to be accountable for "pain work" (Fagerhaugh & Strauss, 1977), then they require a strong theoretical base from which to accomplish th is . Overview of the Thesis Content This thesis is comprised of f ive chapters. In Chapter One, the background to the problem, problem statement, purpose, conceptual framework, hypotheses, def ini t ions, and significance of the study were given. In Chapter Two, a review of selected l i terature is presented under two headings: the effects of intramuscular meperidine on postoperative pain (sensation and distress) and the effects of intramuscular meperidine on postoperative inspiratory capacity after upper abdominal surgery. Chapter Three addresses the research methodology including a description of the research design, sampling procedure, data col lect ion instruments and procedure, ethical considerations and sta t is t ica l procedures used in data analysis. In Chapter Four, the description of the sample, a report of the findings and a discussion of the results are presented. The summary, conclusions, implications, and recommendations for future research are presented in Chapter Five. 13 CHAPTER TWO Review of the Literature The review of the l i terature is divided into two sections which focus on the variables specif ic to this study. The f i r s t section reviews the effects of intramuscular meperidine on postoperative pain (sensation and distress) . Here emphasis is placed on the relationship of the time course of an opioid to optimal analgesic action. The second section reviews the effects of intramuscular meperidine on postoperative inspiratory capacity after upper abdominal surgery. Effect of Meperidine on Postoperative Pain (Sensation) and Distress Opioids are considered to be the most effective means of inhibit ing postoperative pain (Bonica, 1982; Hug, 1980). The following section will include discussion of the antinociceptive action of opioids, speci f ica l ly meperidine, and wil l explore some of the factors which influence i t s ef f icacy. These factors include the dose, route, pharmacokinetics (time course), and a variety of physiological and psychological variables. F ina l ly , the current controversy related to intramuscular meperidine use wil l be br ief ly discussed. Antinociceptive Action of Meperidine Meperidine, l ike a l l pure agonist opioids, decreases the perception of pain by binding to opioid receptor si tes within the central nervous system and mimicking the antinociceptive actions of the endogenous opioids (Jaffe & Martin, 1985). The three basic families of endogenous opioids, the enkephalins, endorphins and dynorphins, have receptor sites in the dorsal horn of the spinal cord ("gating" mechanism) and within the descending control systems in the brain. Specific sites in the brain 14 include the midbrain periaqueductal gray (PAG) and the rostral ventral medulla (Fields, 1985). Both endogenous and exogenous opioids are believed to decrease pain sensation by inhibit ing the release of certain nociceptive neurotransmitters, such as Substance P (Jaffe & Martin, 1985). Opioids are believed to decrease the level of distress by binding to opioid receptors in the amygdala, hippocampus and locus ceruleus. The locus cereleus contains both adrenergic neurons and a high concentration of opioid receptors and is postulated to play a c r i t i ca l role in feelings of alarm, panic, fear and anxiety (Jaffe & Martin, 1985). Opioids also inhibit acetylcholine release in sympathetic ganglia (Fields, 1985). Optimal Analgesic Dose While some opioid receptors are associated with analgesia (primarily mu and kappa), others mediate a wide variety of untoward effects such as respiratory depression, sedation, dizziness, headache, miosis and decreased gastrointestinal moti l i ty (Jaffe & Martin, 1985). In order to maximize analgesia and minimize the incidence of distressing side ef fects, i t is necessary to determine an optimal dose. Lasagna and Beecher (1954) conducted a study of 122 general surgical patients who alternately received 10 mg and 15 mg of morphine subcutaneously for postoperative pain. Pain re l ie f was measured using a simple verbal descriptor scale at 45 and 90 minutes post inject ion. Subjects served as their own control . The 10 mg dosage afforded a mean of 67.5% pain r e l i e f , whereas the 15 mg dosage afforded a mean of 77.7% pain r e l i e f , or a 15% increase over the 10 mg dose. The second part of this study compared the incidence of side effects in 10 mg and 15 mg doses of morphine given to 20 normals. The incidence of side effects was found to be increased by 94% with the 15 15 mg dose as compared to the 10 mg dose. As a result of these two studies and a comprehensive review of similar studies available at the time, Lasagna and Beecher determined that the optimal dose of morphine is 10 mg/70 kg of body weight. This is s t i l l considered to be the optimal dose of morphine, and is the standard against which al l other opioids are compared (Jaffe & Martin, 1985). While morphine sulphate is the opioid of choice for acute pain, meperidine hydrochloride is usually used after cholecystectomy because morphine is reputed to increase b i l iary pressure and spasm (Jaffe & Martin, 1985). Meperidine provides comparable analgesia to 10 mg of morphine when given intramuscularly in equianalgesic doses of approximately 75 mg (Mather & Meffin, 1978) and provides superior analgesia i f increased to 100 mg (Lasagna & Beecher, 1954). Pharmacokinetics of Meperidine The traditional practice of selecting the "right" drug for a particular c l in ica l problem does not guarantee a desired ef fect . In order to be therapeutic, a drug must arrive at i ts biological s i te of action (receptor site or biophase) in suff ic ient amounts to produce a minimum effective concentration (MEC) for a suff icient duration. This movement of drugs through the body is cal led pharmacokinetics. Pharmacokinetics is the study of the time course of drug absorption, d istr ibut ion, metabolism, and excretion. It also concerns the relationship of these processes to the intensity and time course of pharmacologic (therapeutic and toxicologic) effects of drugs and chemicals (Gibaldi & Perr ier , 1982, p. i i i ) . 16 Time course (Time-Action curve). The time course of a drug can be i l lustrated graphically on a "time-action" or "time-effect" curve. The "action" or "effect" is plotted as a function of time after drug administration. The "action" is usually a measure of therapeutic effect such as pain r e l i e f , but other drug related variables, such as untoward effects can also be plotted. The curve plots the "onset" or beginning of a therapeutic ef fect , the "peak" or maximum therapeutic ef fect , and the duration of action, thereby ref lect ing pharmacokinetic factors (Figure 2). Onset • Time Figure 2. Stylized plasma concentration versus time plot i l lus t ra t ing onset, intensity and duration of a pharmacological ef fect . Reproduced by permission of MTP Press Limited, Lancaster, England, from D.W.N. Bourne, E . J . Triggs and M.J. Eadie, (1986) Pharmacokinetics for the  non-mathematical (p. 16). (Lancaster: MTP Press Ltd.) Until recently, analgesic "action" was determined by the patient's pain level or analgesic response, primarily through the use of a rating scale. 17 Through measuring patient response, the onset of meperidine was determined as being 10 minutes and the peak action as 60 minutes (Gilbert, Hanover, Moylan, & Caruso, 1976; Houde & Wallenstein, 1957, cited in Inturrisi & Foley, 1984). The subjects' blood meperidine levels were inferred by the subject's response. Recent technological advances have allowed the determination of accurate blood-opioid leve ls . Comparison can now be made between the therapeutic action and the blood concentration of the drug (see Figure 3). Figure 3: Time course of drug concentration in plasma and the biophase (receptor s i te f l u i d , e . g . , C.S.F. ) and the pharmacological response. Reproduced by permission of MTP Press Limited, Lancaster, England, from D.W.N. Bourne, E . J . Triggs and M.J. Eadie, (1986) Pharmacokinetics for the  non-mathematical (p. 8). (Lancaster: MTP Press L td . ) . Because i t is usually not possible to measure drug concentration levels at the receptor s i tes , this is calculated using mathematical models to determine the drug concentration levels in theoretical body "compartments" — Plasma Concentration • - - Biophase Concentration — Pharmacological Response 2 18 that ref lect the volume of distribution of the drug. The f i r s t , or "central," compartment is the vascular compartment since i t is the f i r s t volume of body f lu id the drug enters after absorption. The second, or "peripheral" compartment is the volume of f lu id that comes in direct contact with the receptors. This is also cal led the biophase. Drug ef fects , such as analgesia, will have a close correlation to the drug concentration in the central compartment and an even closer one to the concentration in the peripheral compartment (Greenblatt & Shader, 1985). Time action curves measuring subject response may d i f fer from curves measuring blood concentration levels in terms of the time of onset and peak action (see Figure 3). Absorption of meperidine. The most common method of administering meperidine for postoperative pain is via the intramuscular route on a "pro re nata" (p.r .n. ) basis. The rationale for the popularity of this route is that i t is safe, easy to give by nurses and inexpensive (Mather, 1983; Phi l l ips & Cousins, 1986). Intramuscul ar meperi di ne has a rapid rate of absorption because i t is highly l ipophi l ic and therefore crosses biological membranes rapidly (Mather, 1983). The rapid onset is approximately 10 minutes, but is variable depending on blood flow from the muscle s i t e . The deltoid has the highest blood flow followed by the vastus lateral us and then the dorsal gluteal muscles. Absorption may be even slower from the lat ter i f the meperidine is injected into adipose tissue (Greenblatt & Shader, 1985). Distribution of meperidine. Approximately 60-80% of meperidine is bound to plasma proteins (Edwards, Svenson, Visco, & Lalka, 1982). It is widely and rapidly diffused to highly perfused tissue such as the brain 19 and so the analgesic effect is highly correlated to meperidine-blood concentration levels (Mather, 1983). Austin and colleagues (1980) found a high level of var iab i l i ty in peak meperidine action times. In a study of 10 women during the f i r s t two days after cholecystectomy or hysterectomy surgery, peak meperidine blood concentration levels were found to range from 18 to 108 minutes. Analgesic effect was measured simultaneously using a 3 point self-report rating scale and 3 point observer scale. Meperidine blood levels were found to be inversely related to the pain scales. However, a 3 point scale may not provide a very sensitive measure (Rosen, 1977). The time of injection after surgery appeared to influence analgesic ef fects. For example, the f i r s t injection after surgery gave a poor level of analgesia in that 60% of subjects complained of moderate to severe pain after one hour. At the 28 hour injection time, 100% of the subjects were "pain free" one hour post injection whereas only 20% were "pain free" three hours post inject ion. Furthermore, meperidine's steep onset and short duration caused high peaks and valleys so that blood levels exceeded the minimum analgesic level for only 35% of each 4 hourly dosing in terva l . Austin and colleagues (1980) attributed the differences to var iab i l i ty in absorption rates from the gluteal s i t e . However, subsequent research has attributed var iab i l i ty to differences in drug elimination (Mather, 1983; Tamsen, Hartvig, Fagerlund, & DahlstrOm, 1982). The findings of Austin and colleagues contradict those of another study (Stambaugh, Wainer, Sanstead & Hemphill, 1976) that found peak meperidine blood levels to occur 60 minutes after intramuscular in ject ion. According to Mather (1986) the discrepancy occurred because the subjects in the study by Stambaugh and colleagues were "normals" and were not affected by 20 altered hemodynamic and pharmacokinetic variables as were the postoperative patients in the Austin et a l . study. Elimination of meperidine (metabolism and excretion). Meperi di ne i s mainly biotransformed in the l iver with only approximately 5% excreted in the urine as unchanged drug. However, this percentage is markedly increased in acid urine. Meperidine is biotransformed to the metabolite normeperi di ne by the l i v e r . Metabolism is impaired in the elderly and in those patients with reduced hepatic blood flow (Mather & Meffin, 1978). The accumulation of the metabolite normeperidine, a CNS stimulant, has been associated with feelings of anxiety, tremors, seizures, and some fa ta l i t i es (Armstrong & Bersten, 1986). Clearance of meperidine is directly linked to perfusion dynamics (Mather & Meffin, 1978). While there is l i t t l e difference in meperidine blood-concentration levels in normals (Stambaugh et a l . , 1976) there is great var iab i l i ty in patients with altered hemodynamics. Meperidine clearance is reduced by 50% in patients with l iver disease and 25% in postoperative patients (Edwards et a l . , 1982). Tamsen et a l . (1982) found that meperidine clearance increased by 35% from the f i r s t to the third postoperative day in 12 patients who had had major abdominal surgery. Physiological Variables Related to Analgesic Consumption The foregoing discussion included examples of physiological variables that will affect analgesic consumption. It was mentioned that any factor that alters perfusion dynamics will also alter analgesic requirements. In a related way, i t has been shown that extremes of age also affect analgesic requirements (Faherty & Grier, 1984). In patients over 70, the 21 volume of distribution is smaller and both the plasma clearance and plasma protein binding is reduced. Consequently, there is a higher and more prolonged blood-opioid concentration level and increased c l in ica l sensit iv i ty to opioids (Mather, 1983). There are certain physical variables such as weight that are usually considered in analgesic and pain studies. Although opioid drugs have tradit ional ly been ordered according to body weights, Mather and Meffin (1978) found no support for a correlation between volume of drug distribution and body weight. Austin and colleagues (1980) administered regular injections of 100 mg of intramuscular meperidine to 10 female patients with hysterectomy or cholecystectomy surgery and found no signif icant correlation between maximum blood-meperidine concentration and body weight or lean tissue mass. Mather (1983) reports that individual differences in meperidine requirements appear to be inversely related to differences in cerebrospinal f lu id concentration of endorphins. It may be that this could explain some of the individual differences in analgesic consumption seen in apparently homogeneous samples. Psychological Variables Related to Analgesic Consumption In addition to the physiological variables affecting analgesic requirements, i t is now known that psychological variables affect analgesic consumption and pain re l ie f (Peck, 1986). Taenzer and colleagues (1986) have noted the discrepant results in data arising from the many studies of diverse demographic and psychological variables related to postoperative pain. In their study of 40 patients undergoing cholecystectomy surgery, correlations were made between a large number of 22 variables and postoperative pain, mood and analgesic consumption. Variables were measured preoperatively using seven val id and rel iable psychological tests . Postoperative pain was measured with a 10 cm visual analogue scale with the anchors "no pain" and "worst possible pain," the Present Pain Intensity Scale from the McGill Pain Questionnaire, and analgesic consumption. Results showed that t ra i t anxiety, neuroticism, depression, extroversion and history of chronic pain correlated to increased levels of postoperative pain and analgesic consumption. Educational levels correlated to decreased postoperative pain measures. Preoperative fear and anxiety, t r a i t anxiety, neuroticism and depression were correlated to increased levels of postoperative distress as measured by the State-Trait Anxiety Inventory and the Beck Depression Inventory. Current Controversy Related to I.M. Meperidine Use Traditional postoperative pain management techniques using p . r .n . protocols with intramuscular opioids have recently come under attack. Although the optimal dose of opioids has been known for several decades, recent l i terature has exposed a tendency for physicians to underprescribe opioids in terms of amount and dosing interval . Underprescribing by physicians and underadministrati on of opioids by nurses have been linked to poor drug knowledge, inadequate assessment of pain and unwarranted fear of patient addiction (Cohen, 1980; Marks & Sachar, 1973; Utting & Smith, 1979). Cohen (1980) replicated the c lassic study of Marks and Sachar using postoperative rather than medical subjects. She found that in 109 patients with elective abdominal surgery, 75% stated they had moderate to severe pain on the morning of their third postoperative day. She found that nurses tend to lower the physician prescribed dose, even when the 23 physician's order is inadequate. The " p . r . n . " system incurs delay in pain management because pain is not treated until the patient actually "complains" and then the nurse requires additional time to assess the pain, prepare and document the opioid and administer the intramuscular injection (Coleman, 1987). Furthermore, i t is now known that there is high intra and interindividual var iabi l i ty with I.M. meperidine due to pharmacokinetic variables and that this makes i t d i f f i c u l t to predict the appropriate analgesic dose and frequency of administration (Austin et a l . , 1980). These problems have generated research into alternate methods of postoperative pain management such as I.V. opioids, "on demand" analgesic systems, intercostal blocks and TENS. However, these al ternate methods have their own problems in that they are more expensive in terms of nursing time and/or equipment and may be associated with more patient complications (Coleman, 1987). Effect of Intramuscular Meperidine on  Postoperative Inspiratory Capacity (IC) This section will describe the negative effect of upper abdominal surgery, anesthetics and postoperative pain on breathing. It will be shown that despite their respiratory depressant action, opioids have a beneficial effect on restricted breathing patterns resulting from postoperative pain. Furthermore, opioids may further enhance lung function by increasing tolerance for inspiratory exercise and early ambulation. Negative Effects of Upper Abdominal Surgery on Breathing Anesthetics and surgical trauma have an adverse effect on breathing. Inhalation and intravenous anesthetics depress the central control of 24 respiration and the c i l i a ry act iv i ty of respiratory epithelium. Anesthetic agents and altered perfusion dynamics during surgery cause oxygen desaturation in the blood. Neuromuscular blocking agents depress diaphragmatic excursion (Didier, 1984). Paralytic ileus and immobility res t r ic t breathing through upward displacement of the diaphragm (Crosbie & Sim, 1986). Surgical trauma, such as incision into the upper abdominal musculature, inhibits the inspiratory and expiratory phases of respiration because movement of the chest wall and abdominal muscles exert tension on the incision with concomitant pain. Tonic contraction of the abdominal muscles due to pain, causes upward displacement of the diaphragm and decreases inspiratory capacity (Crosbie & Sim, 1986). Deep inspiration causes so much pain that a sighless ventilatory pattern is usually adopted (Drain, 1981). The adverse effects of postoperative pain, surgery and anesthetic agents on breathing cause a reduction in vital capacity to about 40% of the preoperative value within 1-4 hours after surgery. This drop in vi tal capacity remains at this level for 12-24 hours and returns to 65% of the preoperative value in 7 days (Bonica, 1982). These factors result in an exceedingly high incidence of postoperative pulmonary complications, with a reported range of 25-80%, depending on c r i te r ia for measurement (Cell i et a l . , 1984). Respiratory Depressant Action of Opioids Opioids have a depressant action on breathing through stimulation of a subpopulation of mu receptors on the brain stem respiratory centers. The primary mechanism of respiratory depression involves a reduction in 25 responsiveness of the brain stem respiratory centers to increases in carbon dioxide tension (PCO2). Therapeutic doses of opioids depress a l l phases of respiratory act iv i ty (rate, minute volume and t idal exchange) in a dose related fashion. The diminished respiratory volume is primarily due to a slower rate of breathing. Meperidine depresses the respiratory centers as much as morphine in equianalgesic doses (Jaffe & Martin, 1985). Catley et a l . (1985) compared two groups of sixteen postoperative patients who had had a cholecystectomy or total hip replacement. The f i r s t group received a continuous IV morphine infusion and the second group received regional anesthesia with bupivacaine. The pain scores, as measured on a 10 cm visual analogue scale, were very similar for both groups. However, the group receiving the morphine infusion experienced a total of 456 episodes of pronounced oxygen desaturati on which occurred only when the patients were sleeping. Improvement in Pain-Induced Restricted Breathing with Opioids Since pain generated from upper abdominal surgery restr icts breathing and lowers inspiratory capacity, al leviat ion of pain through opioid administration will improve chest expansion, thereby improving inspiratory capacity (Bonica, 1982; Bromage, 1955; Bryan-Brown, 1986). Despite the fact that opioids are known to cause respiratory depression, pain is believed to antagonize this effect (Bonica, 1982). Jaffe and Martin (1985, p. 501) state that the patient with severe pain can tolerate three to four therapeutic doses of morphine over a few hours, but wil l experience respiratory depression should the pain suddenly subside. Bromage (1955) tested the hypothesis that analgesia improves postoperative vital capacity. He used spirometry measurements as a quantitative measure 26 to compare the efficacy of four analgesic treatments in 20 patients with upper abdominal surgery. After surgery, vi tal capacity measurements were taken when the patient complained of pain and then throughout each of the four analgesic treatments. The degree of improvement from the analgesic was measured by computing the respiratory restoration factor (RRF) from the following formula: RRF = A n a l g e s i c VC - P a i n VC i n n  K K r P r e o p e r a t i v e VC - P a i n VC x 1 U U Increases in RRF for each analgesic treatment were 80.2% with epidural block, 13.5% with I.V. meperidine, 35.4% with I.V. amidone and 22.8% for I.V. xylocaine. This study had some methodological problems in that I.V. technology was not highly advanced at the time and rates were maintained by regular drop rate. Fluctuations in rate produced drowsiness, and as a resul t , patients were not always able to participate fu l ly in the spirometry exercises. Perhaps the experiment was too ambitious in comparing four analgesic treatments and an unspecified number of spirometry readings over 8-20 hours. No mention was made of a fatigue factor or of potential contamination of one analgesic treatment on subsequent treatments. However, this study does demonstrate that there is a signif icant improvement in vital capacity with analgesia. As a result of Bromage's f indings, a number of studies used vi tal capacity (VC) as a measure of analgesic efficacy (Conaghan, Jacobsen, Rae & Ward-McQuaid, 1966; Masson, 1962; Parbrook, Rees & Robertson, 1964). These studies found the VC to be a val id measure of analgesic efficacy after upper abdominal surgery. Parbrook and colleagues used the RRF 27 formula developed by Bromage to present resul ts . Masson and Conaghan and colleagues converted VC scores to a percentage of the preoperative baseline. Probable Enhancement of Exercise Tolerance with Opioids Inspiratory exercises and ambulation are known to improve inspiratory capacity after upper abdominal surgery. Inspiratory exercises stretch the lungs and produce a r t i f i c i a l sighs necessary to prevent atelectasis (Dohi & Gold, 1978; Marini, 1984). Alexander, Schreiner, Smiler and Brown (1981) examined the relationship of maximal inspiratory volumes to the development of postoperative pulmonary complications in 377 patients after abdominal surgery. Of these, 134 patients had a cholecystectomy, 123 had a hysterectomy, and 120 had a herniorrhaphy. The patients were divided into six groups. Five of the groups had a program involving one or more forms of inspiratory exercise, while the control group received only routine preoperative instruction to deep breathe and cough. There were no signif icant differences in incidence of pulmonary complications among the six groups. However, i t was found that of the 113 patients who achieved less than 70% of their preoperative inspiratory capacity (IC), a fu l l 53% developed pulmonary complications, while only 16.5% of the patients achieving 80% of their preoperative IC developed pulmonary complications. This study indicates that i t is the quantity of inspired air that is the c r i t i c a l factor in preventing postoperative pulmonary complications, rather than the nature of the equipment or the frequency of i ts use. Early postoperative ambulation also improves inspiratory capacity through the lowering of the diaphragm. Crosbie and Sim (1986) compared the pulmonary function of 20 patients who had undergone cholecystectomy 28 surgery. Using a Vitalograph spirometer, each patient was tested s i t t i ng , supine, slumped and in the l e f t and right side lying posit ions. They found signif icant improvement in the forced expiratory capacity (FEC) and the forced vital capacity (FVC) in patients in the s i t t ing posit ion. Dull and Dull (1983) found that early mobilization was just as effective as incentive spirometry in preventing pulmonary complications in post cardiopulmonary bypass surgery. Unfortunately, inspiratory exercise and early ambulation are very painful for the patient with upper abdominal surgery. Several authors assert that opioids contribute to the beneficial effects of exercise on postoperative lung volumes by increasing patient tolerance of pa in-e l ic i t ing act iv i ty (Be l l , 1979; Bonica, 1982). Some authors believe that not only should opioid analgesia improve tolerance for painful a c t i v i t i e s , additional analgesia should be provided when painful exercise is performed. Phi l l ips and Cousins (1986) state that even when patients on I.V. opioids are pain free, that pain will "break through" when performing breathing and coughing exercises. They describe this as peak incident pain. They recommend an extra bolus of I.V. opioid or inhalation analgesia for peak incident pain during chest physiotherapy. Nurses DiBlasi and Washburn (1979) suggest that the way to obtain "extra" analgesic coverage during this time is to synchronize pain-e l ic i t ing act iv i t ies with peak analgesic action. However, no studies were found that evaluated the benefit of administering additional opioids for peak incident pain or manipulating the times of painful act iv i t ies to coincide with predicted peak blood opioid leve ls . 29 Summary of the Literature Review The review of the l i terature was organized to focus on the effect of meperidine, an inhibi tor , on the three dependent variables: pain sensation, pain distress, and inspiratory capacity. In addition, the time-action of meperidine was stressed. Where possible, l i terature was selected that described samples with the same or comparable pain source to that of the subjects in the current study. Simi lar ly , attempts were made to f ind studies where movement, an augmentor, was involved. The review of the l i terature revealed some problems, points of controversy and areas requiring further research. A number of problems have emerged associated with the use of opioids, part icularly meperidine, for postoperative pain management. Some of these include underprescription, underadministrati on, and var iab i l i ty in analgesic action. In addition, analgesic efficacy is influenced by a large number of physiological and psychosocial variables. Several areas of controversy have also emerged. On the one hand, an optimal dose and standard analgesic action times have long been established. On the other hand, recent pharmacokinetic studies indicate that a wide var iab i l i ty in peak blood-meperidine levels requires that the dose and frequency be f lex ib le . Furthermore, the long established p . r .n . intramuscular protocol has been c r i t i c i z e d for providing uneven analgesic coverage. At the same time, this method is hailed as providing the best and most practical method of managing postoperative pain. Despite a l l c r i t i c ism, this method retains i ts popularity, and yet , a variety of alternative methods are currently being studied. 30 The negative effect of pain on breathing after upper abdominal surgery was reviewed in the l i terature in terms of the signif icant reductions found in postoperative vi tal capacity and inspiratory capacity. Analgesic studies.have focused on improving the VC through improvements in analgesic e f f icacy. However, in order to prevent known pulmonary complications, these patients must ambulate, deep breathe and cough. These act iv i t ies increase pain further. However, no studies were found that explored ways of decreasing pain during the performance of painful a c t i v i t i e s . Furthermore, few studies were found that investigated the relationship between movement and pain. 31 CHAPTER THREE Methodology This chapter reviews the methodology ut i l i zed in this study. Content will include discussion of the research design, sample selection, data collection instruments, data collection procedures and a review of procedures related to ethics and human r ights. Design This study used a randomized balanced incomplete block design in which the subject served as his/her own control (see Figure 4). This is also known as a repeated measures design (Kachigan, 1986). There were three treatments: ambulation at onset, peak, and post peak of expected analgesic action. Each subject received two of the three possible treatments. A block is defined as a homogeneous experimental unit receiving more than one treatment. There were val id constraints preventing the subject from experiencing all three treatments. Three treatments would extend over twelve hours and this was thought to be too fatiguing for the patient. Consequently, this was an incomplete block design. However, the design was balanced because the three treatments occur equally in al l possible pairs of two to form three groups, each with four subjects. In order to nul l i fy the effects of the passage of time on pain, each group was divided into two subgroups. Each subgroup had a reversed treatment order within their respective sub groups (see Figure 4). Subjects were randomly assigned to the block by a protocol u t i l i z ing random numbers. This research design was appropriate for this study because i t l imits var iab i l i ty known to influence responses to pain (Peck, 1986). It was also 32 sensitive to the rea l i t ies of the c l in ica l s i tuat ion, such as patient fatigue. 1st dose 2nd dose n n n n n n 2 R 2 R 2 R 2 R 2 R 2 R Xi Y i Y 2 Y 3 X 2 Y i Y 2 Y 3 X i Y i Y 2 Y 3 X3 Y i Y 2 Y 3 X 2 Y i Y 2 Y 3 *3 Y i Y 2 Y 3 X 2 Y i Y 2 Y 3 X i Y i Y 2 Y 3 *3 Y i Y 2 Y 3 X i Y i Y 2 Y 3 *3 Y i Y 2 Y 3 X 2 Y i Y 2 Y 3 Total n = 12 Figure 4. Research design Xj = onset (15 minutes after injection) X 2 = peak (60 minutes after injection) X 3 = post peak (110 minutes after injection) Y i = level of pain sensation Y 2 = level of pain distress Y 3 = inspiratory capacity. Setting Subjects for this study were selected from one non-teaching community hospital within a 30 mile radius of a large Western Canadian c i t y . Three 20 bed general surgical wards were used for the study. 33 Sample The sample was comprised of 12 patients who completed the study. The following c r i te r ia determined the composition of the sample: 1. Scheduled for elective cholecystectomy surgery only. 2. Meperidine prescribed postoperatively. 3. Age 25 to 64 years. 4. No postoperative complications. 5. No serious chronic disease(s). 6. No chronic pain syndrome. 7. No psychiatric disorder. 8. No alcohol or drug abuse. 9. Must speak and write English. 10. Must have the consent of their surgeon. Cholecystectomy surgery was selected because the extent of trauma is limited to a small circumscribed area and the surgical procedure is relat ively standardized (Anson & McVay, 1984). Postoperative analgesia was restricted to meperidine because i t is a common analgesic used after cholecystectomy (Jaffe & Martin, 1985) and is the predominant analgesic used for this purpose in the selected hospital . Inclusion of other opioids, even i f converted to morphine equivalents, might have contaminated the data due to dif fer ing pharmacokinetics (Jaffe & Martin, 1985). Patients with extremes of age, postoperative complications, chronic diseases and alcoholism were also excluded because these factors have been found to alter the pharmacokinetics of meperidine (Edwards et a l . , 1982). In addition, these patients may not have been able to participate fu l ly in the study due to fluctuations in health status. 34 Extremes of weight such as anorexia nervosa or morbid obesity were considered to be chronic diseases. Other than these extremes, weight was not controlled as recent studies of meperidine blood concentration levels have not supported a relationship between weight and analgesic requirements (Austin et a l . , 1980; Mather, 1983). Patients with chronic pain or a history of mental i l lness were excluded due to the relationship of chronic pain, depression and t ra i t anxiety to postoperative pain, mood and analgesic consumption (Taenzer et a l . , 1986). Patients with a drug dependency were excluded due to increased analgesic requirements after surgery (Jaffe & Martin, 1985). F ina l l y , al l of the subjects were able to speak and write English so they could understand verbal and written instrut ions, answer questions and give verbal and written consent. Data Collection Instruments The four instruments used to col lect data in this study were the Pain Sensation Scale, the Pain Distress Scale, Volurex Incentive Spirometer and Data Collection Sheet. Pain Sensation Scale Pain sensation was measured using a visual analogue scale (VAS) (Taenzer et a l . , 1986). It is comprised of a 10 cm l ine with anchors of "no pain" at the extreme l e f t and "worst possible pain" at the extreme right (Appendix A). The patient conceptualizes the scale as a continuum and marks a level on the line corresponding to a subjective feeling of pain intensity. McGuire (1984) reports that the advantage of this scale is that i t is easy to use and has increased sensi t iv i ty (val idity) because there are no a r t i f i c i a l levels imposed. Scott and Huskisson (1976) 35 compared six different types of VAS and graphic rating scale (GRS) to a verbal descriptor scale in groups of 100 for each comparison. Horizontal VAS produced more uniform distributions of response, and appeared more sensitive to intensity (as perceived by patients) than the descriptor scales. Construct va l id i ty of the scale was found in the work by Rosen (1977) who found that an increase in pain score was correlated with cervical d i la tat ion. Taenzer et a l . (1986) used the Present Pain Intensity Scale from the McGill Pain Questionnaire and a 10 cm VAS scale to measure correlation of a variety of psychological variables to pain intensity. In three out of four correlat ions, there was agreement between the two scales. Pain Distress Scale Pain distress was measured using an adapted version of Johnson's Distress Scale (Mogan et a l . , 1985), which is a numeric rating scale (Stewart, 1977) comprised of a 10 cm l ine with 10 equal intervals (see Appendix A). The descriptors: no distress, moderate distress and maximum distress imaginable, appear along the line from l e f t to r ight . McGuire (1984) reports that the r e l i a b i l i t y and val idi ty of this scale are unclear because the psychometric development of the scale was not discussed in Johnson's research. However, the adapted scale was used by Mogan and colleagues (1985) and by Wells (1982) to measure the effect of teaching a simple relaxation technique on postoperative pain sensation and pain distress. Both studies reported a signif icant decrease in postoperative distress within the experimental group. Furthermore, in both studies the scale differentiated between pain sensation and pain distress. 36 Volurex Incentive Spirometer Inspiratory capacity was measured using the 4000 ml Volurex Incentive Spirometer (see Appendix B). A tape was placed along the 200 ml calibrations on the spirometer. By dividing the distance between each calibration into 4 subcalibrations, i t was possible to measure inspired volumes to 50 mis. The manufacturer's l i terature claims an accuracy rate of plus or minus 1% of total volume (40 ml) (see Appendix B). Independent testing of one spirometer was performed using the Vortex Flow Sensor (refer to Appendix C for deta i ls ) . All spirometers were then tested with a 3,000 ml pulmonary syringe before and after use to ensure consistency of measurements. After the study was completed, the one and two l i t e r levels were tested using a RT200 Calibration Analyzer. The mean level of error was found to be 1% at the 2 l i t e r level (refer to Appendix D for deta i ls ) . Data Collection Sheets Four data col lection sheets were developed to col lect preoperative, perioperative and postoperative data (see Appendix E). Preoperative data sheet. The preoperative data sheet was designed to col lect data related to sex, age, height, weight, baseline vital signs and baseline inspiratory capacity. Data related to smoking history, past surgery, regularly prescribed medications, medication bias, and allergies were also collected to provide data related to the subjects' health status. Height and weight data were necessary to determine Body Mass Index, an important indicator of healthy weight levels which has been adopted by the Canadian Dietetic Society and which will be adopted by the Canadian Ministry of Health (Canadian Dietetic Association, 1987). 37 Perioperative data sheet. The perioperative data sheet was designed to col lect data related to the surgery (duration, tubes, type of incision) to provide information related to the degree of trauma. Data were also collected on the type of anesthesia and other medications received in the Operating Room. Information was also e l ic i ted about the subjects' physical status in the Postanesthetic Recovery Room and on return to the ward. Postoperative data sheets (treatments 1 and 2). Data related to ac t iv i ty , analgesic consumption, general physical status, untoward drug effects and vital signs were included on the postoperative data sheets. Injection times and ambulation times were also recorded. Data Collection Procedure Permission to conduct the study was obtained from the selected agency. "Blanket" consents for patient participation (see Appendix F) were obtained from the four participating surgeons prior to in i t ia t ing the study. The investigator v is i ted the head nurses on the three participating wards to explain the study and answer questions. An explanatory le t ter (see Appendix G) was posted on the communication board for ward staf f . The Patient Admissions Department of the hospital was telephoned to compile a l i s t of patients aged 25-64 who were slated for cholecystectomy surgery the next day. The researcher v is i ted the ward that evening and reviewed the charts to ensure that the patients met the c r i t e r i a . The investigator would introduce herself to the potential subject and request permission to explain the study. The investigator then reviewed the Patient Information Sheet (see Appendix H) with the patient. It was 38 stressed that the study conformed with usual postoperative routines as detailed in the preoperative teaching slide tape presentation that was viewed by al l preoperative patients, but that the study also incorporated additional procedures necessary to obtain accurate measurements. The investigator demonstrated the use of the Volurex Incentive Spirometer and then reviewed the Informed Consent sheet (see Appendix I) with the patient. Three copies of the Informed Consent were signed by the patient and witnessed by the researcher. A copy was retained by the patient and the researcher respectively and the final copy was placed on the patient's chart. Without exception, all patients who were approached agreed to participate in the study. After consent was obtained, the investigator br ief ly interviewed the patient to obtain relevant demographic data on the preoperative portion of the Data Collection Sheet (see Appendix E). A "tr ial run" of the exact procedure to be followed on the f i r s t postoperative day was practiced with the patient. After ambulating the patient to a chair , the patient was shown a copy of the Level of Pain Scale. The patient read the instructions explaining the difference between pain sensation and distress. The researcher then asked the patient to remember a recent pain experience and to mark the level of pain sensation and distress for that experience. The patient then performed f ive maximal inspirations with the Voluex and these were recorded by the researcher. On the morning of the f i r s t postoperative day, the investigator reviewed the patient's chart and completed the perioperative and postoperative sections of the Data Collection Sheet (see Appendix E). At this time, i t was established that the patient continued to meet the study 39 c r i t e r i a . The investigator then approached the patient's nurse, br ie f ly explained the study and the investigator's ro le , and established the time and dose of the next analgesic. Nursing care act iv i t ies were planned around the treatment times in the study. The investigator then performed a brief patient assessment, consulted with him/her regarding the time of the next injection of meperidine, and informed the patient of the time of ambulation after the injection as established by the predetermined treatment schedule. A few minutes prior to the f i r s t treatment, the investigator again assessed the patient and made adjustments to the furniture as necessary, to expedite the procedure. The patient was then ambulated to a chair placed beside the head of the bed. The patient marked the Level of Pain Scale and then performed five maximal inspirations with the Volurex. Following this the patient was walked to the bathroom and assisted back to bed. The Data Collection Sheet for the f i r s t treatment was completed. The second treatment occurred that afternoon following the next injection of meperidine. The protocol was identical to the f i r s t treatment except that the time of ambulation after the injection was dif ferent. Ethics and Human Rights This study protected the human rights of i ts subjects and was conducted in an ethical manner. A proposal of the study received approval from both the Ethics Committee of the University of Bri t ish Columbia and that of the selected hospital . The attending surgeons were supplied with copies of the proposal and a written physician's consent (see Appendix F) 40 was obtained from each surgeon for a l l patients under his care, prior to in i t ia t ing the study. S t r ic t confidential i ty has been maintained throughout this study. The names of the hospital and the attending surgeons have been omitted from this report. Patient names or identifying details do not appear on any documents other than the three signed consent forms. One copy is on the patient's chart, one was given to the patient and the third copy was retained by the investigator. The investigator's copies will be f i l e d in a sealed envelope for three years and then wil l be shredded. No persons, other than the investigator, have had access to these consents. The patients' privacy was respected by l imit ing data col lect ion to information deemed essential to the study. The original data sheets are numbered one through twelve and wil l be destroyed after acceptance of this thesis. Patient safety was a primary consideration. Patients were assessed prior to mobilization to ensure that they were well enough to ambulate. Pulse rates were measured before ambulation. The patient was constantly attended when up. The investigator was prepared to withdraw any patient who experienced a deterioration in physical status. F i n a l l y , an individual Volurex spirometer was provided for each patient and was not re-used during the study. The procedures used in this study did not deviate from usual postoperative care at this hospital . All patients slated for a cholecystectomy are v is i ted by a physiotherapist who assesses their respiratory status. If patients are deemed a high risk for developing postoperative pulmonary complications, the physiotherapist wil l prescribe 41 and demonstrate the Inspirex Incentive Spirometer postoperatively. Written material provided by the hospital advises patients to perform 10 maximal inspirations per hour. Each inspiration should be sustained for 3 seconds. Patients manage the incentive spirometer with minimal supervision after surgery. The use of a different model of spirometer would not affect the patient because the inspiratory manoeuver is the same. Patients are encouraged to ambulate at least twice in their f i r s t postoperative day at the proposed hospital . Times of ambulation are not specified with respect to analgesia. In this study, the intervals between meperidine administration and ambulation were selected carefully so that patients would ambulate within a range of expected adequate analgesia and yet the times would be suff ic ient ly separated to provide for a possibi l i ty of measureable differences. The onset, peak and duration of analgesic action for 75 mg of meperidine are as follows: onset, 10 minutes; peak, 60 minutes; and duration, 2-4 hours (Jaffe & Martin, 1985). These times were altered s l igh t ly , for ethical reasons, so that a minimum analgesic effect would be anticipated. Therefore, for this study, onset was designated as 15 minutes, peak was 60 minutes, and post peak was 110 minutes so that i t fe l l within the duration of analgesia, but after the peak. Furthermore i ts position on the time-effect curve is very close to the position of onset on the other side of the curve, (Figure 2). Data Analysis Hypotheses 1, 2, and 3 were tested using an Analysis of Variance specif ic to the balanced incomplete block design (refer to Appendix J for deta i ls ) . Descriptive s ta t is t ics were computed for each of the dependent 42 variables. Hypotheses 4 and 5 were tested using the Pearson product-moment correlat ion. This correlation s ta t is t ic was also used to analyze relationships between selected variables related to characteristics of the sample. The level of significance established for this study was 0.05. 43 CHAPTER FOUR Presentation and Discussion of Results Introduction This chapter will outline the characteristics of the sample, the findings related to the hypotheses, anci l lary findings and a discussion of the resul ts . Characteristics of the Sample Patients slated for cholecystectomy surgery at one hospital were recruited for the study during early f a l l , 1987 and early summer, 1988. Of the 51 patients available during these times, 37 were rejected because of fa i lure to meet the study c r i t e r i a . Seventeen were outside the age range, 8 had a major chronic i l l n e s s , 5 had chronic pain syndromes, 3 had additional surgery, 2 were chemical substance abusers and 2 had psychiatric disorders. All patients who met the c r i te r ia agreed to part icipate. There were no patient requests for withdrawal from the study. One patient was withdrawn by the investigator when she developed a serious reaction to meperidine. The remaining twelve patients successfully completed the study. The sample is described in terms of demographic, health and postoperative character ist ics. Demographic Characteristics of the Sample Demographic data collected from the patients were sex, age, and educational l eve l . Eleven females and one male comprised the sample. The age distribution of the sample ranged from 25-59 years (M = 42, SD = 10.35) (see Table 1). 44 Table 1. Age Distribution For Sample Age Frequency Percentage 25-34 3 25 35-44 4 33 45-54 3 25 55-64 2 17 Totals 12 100 Five patients had college or university education, f ive patients completed grade twelve and two patients had less than grade twelve education. Health Characteristics of the Sample All twelve patients were admitted in stable condition for elective cholecystectomy. There was no incidence of nausea, vomiting or severe pain preoperatively. None of the patients required intravenous therapy on admission. Hemoglobin levels and urinalysis results were within normal l imi ts . Al l patients were afebr i le . Ten patients were non-smokers. The two patients who smoked used less than one package of cigarettes per day. The weight of the patients ranged from 56.5 to 122.2 kilograms (M = 73.81; SD = 17.80). Body Mass Index (BMI) ranged from 20.99 to 34.59 (M = 26.45; SD = 3.86) (see Table 2). Six patients had previous experience with minor surgery such as tubal l igation and three patients had experience with major surgery such as 45 Table 2 Body Mass Index (BMI) For Sample BMI Frequency Percentage 20-253 5 42 25-27b 3 25 27+c 4 33 Totals 12 100 Note: BMI is computed by dividing the weight in kilograms by the height in meters squared. aNormal range for ages 25 to 65 years. U A range that may be associated with health problems (caution). C A range associated with increased risk of heart disease, hypertension, and diabetes. From "Healthy Weight" (p. 6) by The Canadian Dietetic Association, 1987, Toronto: CNC Communications Inc. cesarean section, hysterectomy and endarterectomy. Two patients had no prior surgical experience. Ten patients had given b i r th . All twelve patients denied a medication bias providing the medication was "necessary". Postoperative Characteristics of the Sample The duration of cholecystectomy surgery ranged from 65 to 139 minutes (M = 98.9; SD = 23.98). General anesthesia was standard and consisted of induction with thiopental sodium, a neuromuscular blocking agent and maintenance of anesthesia with nitrous oxide and isoflurane. One or both of the anesthetic adjuncts fentanyl sodium and droperidol were given to a l l patients. Patient #6 required narcan in the Operating Room due to 46 respiratory depression. However, her condition was stable in the PAR and on return to the ward. All twelve patients experienced an uneventful postoperative recovery up to and including their f i r s t postoperative day and were able to participate fu l ly in the study. There were no complications of surgery evidenced. All patients maintained a normal temperature, blood pressure, pulse and urine output. None of the patients required special medical interventions, such as a blood transfusion or oxygen administration. All twelve patients had a wound drainage tube. Five patients had hemovacs and seven patients had a 1/2 inch penrose drain. No other drainage tubes were used. The nurses administered meperidine fa i r ly regularly in the f i r s t 24 hours after surgery (see Table 3). The mean consumption of meperidine was 414.58 mg (SD = 44.54) from the time the patient returned to the ward up to and including the last injection in the study (18.25 to 28.25 hours). The mean injection frequency was 5.25 injections (SD = 0.62) during this interval . All patients received 75-100 mg of meperidine. The most common dosage and frequency was 75 mg q4h. Ten out of 12 patients (83%) complained of untoward symptoms which they associated with meperidine injections (see Table 4). Eight patients (66%) complained of only one untoward effect (nausea, dizziness or drowsiness) and two patients (16%) complained of both nausea and dizziness. Untoward effects were described as "slight" or "moderate". Table 3. Time and Amount of I.M. Meperidine Received Postoperatively 3 Subject Prior to treatments Treatment 1 Treatment 2 1 75 mg x 4 75 mg 75 mg (1140, 1845, 2300, 0645) (1044) (1448) 2 75 mg x 4 75 mg 75 mg (1715, 2200, 0245, 0715) (1024) (1330) 3. 75 mg x 4 75 mg 75 mg (1800, 2200, 0230, 0715) (1115) (1515) 4. 75 mg x 3 75 mg 75 mg (1700, 0140, 0640) (1041) (1444) 5. 75 mg x 3 75 mg 75 mg (2000, 0015, 0615) (1012) (1433) 6. 75 mg x 3 75 mg 75 mg (2005, 0130, 0530) (0930) (1326) 7. 75 mg x 4) 75 mg 75 mg (1630, 2130, 0130, 0620) (1021) (1426) 8. 75 mg x 3 75 mg 75 mg (1800, 2300, 0415) (0815) (1215) 9. 75 mg x 3 75 mg 75 mg (1755, 2310, 0420) (0822) (1228) 10. 75 mg x 1 (1620) 100 mg 100 mg 100 mg x 2 (2030, 0100) (0820) (1230) 11. 75 mg x 1 (0115) 100 mg 100 mg 100 mg x 1 (0540) (0945) (1347) 12. 75 mg x 3 75 mg 75 mg (1740, 2130, 0315) (0800) (1207) Total s 3,000 mg 975 mg 975 mg Note. Meperidine was computed from the time the patient returned to the ward after surgery. I.V. narcotics given in PAR were not included. 48 Table 4 Untoward Effects Experienced by Sample Untoward Effect(s) Frequency Percentage Nausea 1 8 Dizziness 4 33 Nausea and Dizziness 2 17 Drowsiness 3 25 None 2 17 Totals 12 100 Findings The findings of the study are presented as they relate to each of the f ive research hypotheses. Descriptive s ta t is t ics for each variable will be given prior to the presentation of results related to the hypotheses. The sample size wil l be identi f ied as n = 8 or n = 12 where applicable. The treatment groups (Hypotheses 1-3) are comprised of eight subjects due to the incomplete block design. Other descriptive s ta t is t ics will apply to the sample as a whole (n = 12). The f i r s t three hypotheses were tested using analysis of variance (ANOVA) and results are displayed using ANOVA tables. The ANOVA used for a block design is more complex than a simple ANOVA. The total sum of squares is partitioned into a treatment sum of squares, a block sum of squares and a random error sum of squares (Montgomery, 1984). This study used a special application of the randomized block design which is known 49 as a " r e p e a t e d measures" o r " s u b j e c t - a s - t h e i r - o w n - c o n t r o l " d e s i g n . The ANOVA used t o a n a l y z e t h i s d e s i g n i s e q u i v a l e n t t o t h a t used t o a n a l y z e a b l o c k d e s i g n , where each s u b j e c t i s c o n s i d e r e d a b l o c k s i n c e each s u b j e c t r e c e i v e s a l l l e v e l o f t r e a t m e n t s ( K a c h i g a n , 1986). However, i n t h i s s t u d y each s u b j e c t r e c e i v e d o n l y two o u t o f t h r e e t r e a t m e n t s so t h e b l o c k s were i n c o m p l e t e . C o n s e q u e n t l y , t h e t r e a t m e n t sum o f squares had t o be a d j u s t e d because each t r e a t m e n t l e v e l was a s s o c i a t e d w i t h a d i f f e r e n t s e t o f b l o c k s ( s u b j e c t s ) . E s t i m a t e s o f t h e magnitude o f t h e s e t r e a t m e n t e f f e c t s were c a l c u l a t e d . When a t r e a t m e n t e f f e c t i s added t o t h e o v e r a l l mean, an e s t i m a t e o f t h e mean o f t h a t t r e a t m e n t l e v e l i s d e t e r m i n e d (Montgomery, 1984). F o r a d e t a i l e d d e s c r i p t i o n o f the ANOVA used i n t h i s s t u d y , r e f e r t o Appendix J . Hypotheses 4 and 5 were t e s t e d u s i n g t h e Pearson product-moment c o r r e l a t i o n s t a t i s t i c . In a d d i t i o n t o s i m p l e c o r r e l a t i o n s between i n s p i r a t o r y c a p a c i t y and p a i n s e n s a t i o n and i n s p i r a t o r y c a p a c i t y and d i s t r e s s , a d d i t i o n a l a n a l y s e s were per f o r m e d w i t h i n s p i r a t o r y c a p a c i t y c a l c u l a t e d as a p e r c e n t a g e o f t h e p a t i e n t ' s p r e o p e r a t i v e b a s e l i n e . P r e v i o u s s t u d i e s t h a t have compared the i n s p i r a t o r y c a p a c i t y (IC) o r v i t a l c a p a c i t y (VC) t o p a i n , have c a l c u l a t e d t h e IC o r VC as a p e r c e n t a g e o f t h e p r e o p e r a t i v e b a s e l i n e (Anscombe, 1957; B o n i c a , 1982; Masson, 1962). H y p o t h e s i s 1. The R e l a t i o n s h i p Between P a i n S e n s a t i o n and P r e d i c t e d  A c t i o n Times o f Meperidine" L e v e l o f p a i n s e n s a t i o n , measured on a 10 cm v i s u a l a n a l o g u e s c a l e (VAS) i s shown i n T a b l e 5. O v e r a l l , p a i n s e n s a t i o n v a r i e d from a low o f 0.9 t o a h i g h o f 8.8 w i t h a mean o f 5.57 cm (SD = 2.30). The l e v e l o f 50 Table 5. Pain Sensation at Predicted Onset, Peak or Post Peak of Meperidine Action Subject Onset Peak Post-Peak Di fference 4 7.4 8.3 0.9 5 6.6 6.3 - 0.3 7 2.7 5.0 - 2.3 11 3.4 4.2 0.8 1 - 6.5 4.6 1.9 3 - 6.9 7.3 0.4 6 - 3.3 2.3 1.0 8 - 7.7 8.8 1.0 2 6.9 - 3.6 3.3 9 8.8 - 6.9 1.9 10 0.9 - 1.0 0.1 12 7.4 - 6.9 0.5 Total s 44.1 48.2 41.4 14.4 Means 5.51 6.03 5.18 1.2 Note. Pain sensation was measured using a 10 cm visual analogue scale from no pain (0) to worst possible pain (10). Increases in number ref lect increases in the level of pain sensation. pain sensation for the patients ambulated at the predicted onset of meperidine action time ranged from 0.9 to 8.8 cm (M = 5.51; SD = 2.28). Pain sensation levels for patients ambulated at peak ranged from 3.3 to 8.3 cm (M = 6.03; SD = 1.73), whereas those ambulated at post peak 51 reported levels from 1.0 to 8.8 cm (M = 5.18; SD = 2.73). The mean difference in level of pain sensation for the sample (n = 12) from the morning to the afternoon treatments, was 1.2 cm (SD = 0.96). An analysis of variance (ANOVA) indicated no signif icant difference among the treatments (F (2, 10) = 1.56; £ = .26) (see Table 6). The adjusted treatment ef fects, as compared to the mean level of pain sensation (M = 5.57) for the sample (n = 12) were estimated as follows: onset, 0.16 cm; peak, 0.43 cm and post peak, -0.58 cm. Therefore, the adjusted mean for onset became 5.73; peak = 6.0 and post peak = 4.99. While these estimates may have indicated a trend, they were not s ta t is t ica l ly s igni f icant , and thus Hypothesis 1 was not supported. Table 6 Effect of Predicted Analgesic Action Time on Pain Sensation Source Sum of Degrees of Mean F-value p-value Squares Freedom Square Treatments9 3.27583 2 1.6379 1.5625 .257 Blocks 116.80459 11 10.618 Error 10.50917 10 1.0509 Total 130.589 59 23 Note: a ) Treatment error is adjusted. Hypothesis 2. The Relationship Between Level of Distress and Predicted  Action Times of Meperidine Level of d istress, measured on a 10 point scale (Mogan et a l . , 1985) is shown in Table 7. Overall , level of distress varied from a low 52 Table 7 Level of Distress at Predicted Onset, Peak or Post Peak of Meperidine Action Subject Onset Peak Post-Peak Difference 4 8 6 2 5 7 7 - 0 7 3 5 - 2 11 3 2 - 1 1 6 5 1 3 7 6 1 6 4 4 0 8 4 6 2 2 7 6 1 9 7 4 3 10 7 7 0 12 9 8 1 Totals 51 41 46 14 Means 6.38 5.13 5.75 1.17 Note. Level of distress was measured on a the numbers ref lect an increase in 10 point scale. Increases in the level of d istress. of 2 to a high of 9 with a mean of 5.75 points (SD = 2.67). The level of distress for the eight patients ambulated at the predicted onset of meperidine action time ranged from 3 to 9 points (M = 6.38; SD = 2.2). Level of distress for patients ambulated at peak ranged from 2 to 7 points (M = 5.13; SD = 1.73) whereas those ambulated at post peak reported levels from 4 to 8 points (M = 5.75; SD = 1.39). The mean difference in 53 levels of distress for the sample (n = 12), between morning and afternoon treatments, was 1.17 points (SD = 0.94). An analysis of variance (ANOVA) indicated no signif icant difference among the treatments (F (2, 10) = 1.24; £ = .33) (see Table 8). Table 8 Effect of Predicted Analgesic Action Times on Level of Distress Source Sum of Degrees of Mean F-value £-value Squares Freedom Square Treatments3 2.583 2 1.2915 1.24 3.33 Blocks 61.50 11 5.909 Error 10.417 10 1.0417 Totals 74.50 23 Note: a)Treatment error is adjusted. The adjusted treatment effects, as compared to the mean level of distress (M = 5.75) for the sample (n = 12) were estimated as follows: onset, 0.5; peak, -0.08; and post peak, -0.42 cm. Therefore, the adjusted mean for onset was 6.25; peak = 5.67 and post peak = 5.33. While these estimates may have indicated a trend, they were not s ta t i s t i ca l l y s igni f icant , and thus Hypothesis 2 was not supported. Hypothesis 3. The Relationship Between Inspiratory Capacity and  Predicted Action Times of Meperidine Inspiratory Capacity (IC), measured by a 4,000 ml Volurex Incentive Spirometer, is shown in Table 9. 54 Table 9 Inspiratory Capacity at Predicted Onset, Peak or Post Peak of Meperidine Action Subject Basel ine Onset Peak Post Peak Di fference 4 2600 2100 1800 - 300 5 2100 950 1150 - 200 7 2200 1550 1350 - 200 11 4000a 3300 3200 - 100 1 2050 - 1350 1500 , 150 3 2850 - 1600 1400 200 6 2100 - 1250 1300 50 8 1800 - 950 800 150 2 2000 800 - 1000 200 9 2300 1050 - 1200 150 10 1500 1350 - 1100 250 12 1500 950 - 900 50 Totals 12,650 12,050 9,200 2,000 Means 2250 1,506.25 1,581.25 1,150 74.87 Note. IC was measured using a 4,000 ml Volurex spirometer. a)The preoperative baseline IC of subject No. 11 may have been greater since 4000 mis is the maximum volume on the spirometer. The IC measurement given is the highest IC attained out of f ive maximal inspirations (Anscombe, 1957). Overall , postoperative IC measurements ranged from a low of 800 mis to a high of 3300 mis (M = 1412.5; SD = 655.87). The IC for the patients ambulated at the predicted onset of meperidine action time ranged from 800 to 3300 ml (M = 1506.25; 55 SD = 838.55). IC for patients ambulated at peak ranged from 950 to 3200 mis (M = 1,581.25; SD = 704.04), whereas those ambulated at post-peak ranged from 700 to 1500 mis (M = 1150; SD = 244.95). The mean difference in IC for the sample (n = 12) from the morning to the afternoon treatments was 166.67 ml (SD = 74.87). An analysis of variance (ANOVA) indicated no signif icant difference among the treatments (F (2,10) = .21; £ = .81) (see Table 10). The adjusted treatment ef fects, as compared to the mean IC (M = 1412.5) for the sample (n = 12) were estimated as follows: onset, 29.2 mis; peak, -20.8 mis and post-peak, -8.3 mis. Therefore, the adjusted mean for the onset was 1.441.7; peak = 1,391.7 mis and post peak = 1,404.2 mis. While these estimates may have indicated a trend, they were not s ta t is t ica l ly s igni f icant , and Hypothesis 3 was therefore not supported. Table 10 Effect of Predicted Analgesic Action Times on Inspiratory Capacity Source Sum of Degrees of Mean F-value p-value Squares Freedom Squares Treatments9 8,125 2 4,062.5 0.2145 0.81 Blocks 9,463,750 11 860,340.5 Error 189,375 10 18,937.5 Total s 9,661,250 23 Note: a ) Treatment error is adjusted. 56 Hypothesis 4. The Inverse Relationship Between Pain Sensation and  Inspiratory Capacity ~~ Results obtained using the Pearson product-moment correlation showed a negative non signif icant correlation between pain sensation and IC (r = - .22; £ = .48) (See Figure 5). Since subject #11 was approximately three standard deviations beyond the mean IC, this subject was removed from the calculations and the analysis was redone. The correlation thereby obtained decreased (r_ = -.02; £ = .94). (see Figure 6). All subjects experienced a drop in their postoperative IC as compared to their preoperative IC (see Table 9). This is an expected outcome after upper abdominal surgery and so the postoperative IC (or VC) is frequently given as a percentage of baseline in order to i l lus t ra te the extent of the decrease (Bonica, 1982). Accordingly, the overall percentage of baseline was found to range from 40% to 90% (M = 61.74; SD = 13.52). When these percentages were compared with pain sensation leve ls , a negative correlation was obtained (r = - .56; £ = .06) (see Figure 7). All subjects experienced a difference in both IC and pain sensation from the morning to the afternoon treatments. When the percentage change in IC was correlated with the percentage change in pain sensation, a signif icant negative correlation was obtained (r_ = - .69; £ = .02) (see Figure 8). The percentage change in IC and pain sensation for each subject is given in Appendix K. The results of a simple correlation between pain sensation scores and IC volumes did not support Hypothesis 4. However, when additional correlational analyses were performed, these results did indicate support for Hypothesis 4. 57 i 8 2-& o s IT) 8 4 6 Pain Sensation (Mean) 10 Figure 5. Scattergram of postoperative IC scores and pain sensation scores. Both measures are the mean of two treatments, for the sample (n = 12). _ 2 4 6 8 Pain Sensation (Mean) - #11 deleted Figure 6. Scattergram of postoperative IC scores and pain sensation scores with the out l ier (subject #11) deleted. Both measures are the mean of two treatments, for the sample (n = 11). 58 2-0 2 4 6 8 10 Pain Sensation (Mean) Figure 7. Scattergram of percentage of preoperative IC and pain sensation scores. Both measures are the mean of two treatments, for the sample (n =12). o to O -30 -20 -10 0 10 20 Pain Sensation: % of total scale 30 40 Figure 8. Scattergram of the change in IC between two treatments and the change in pain sensation between two treatments, for the sample (n = 12). 59 Hypothesis 5. The Inverse Relationship Between Distress and Inspiratory  Capacity Results obtained using the Pearson product-moment correlation showed a signif icant negative correlation between level of distress and IC (r_ = - .58; £ = .05) (see Figure 9). However, when the out l ier was removed (patient #11) the negative correlation was non signif icant (_r •= - .11; £ = .74) (see Figure 10). When IC measurements were calculated as a percentage of the preoperative baseline and correlated with level of d istress, the negative correlation remained non signif icant (r = - .21; £ = .51) (see Figure 11). While al l subjects demonstrated a change in IC from the morning to the afternoon, only nine subjects reported a change in level of distress between the two treatment times. When the percentage change in IC was correlated with the percentage change in level of d istress, the negative correlation was non signif icant (_r = - .24; £ = .51) (see Figure 12). The results of three correlational analyses were non s igni f icant , and therefore Hypothesis 5 was not supported. Ancil lary Findings Additional correlations were done between the dependent variables (pain sensation and distress) and selected variables related to characteristics of the sample. The Pearson product-moment correlation was used to obtain the findings. In terms of demographic character ist ics, the correlation between age and pain sensation was the only signif icant finding (r_ = - .65; £ = .02). The correlation between age and distress was negative but non signif icant (r = - .33; p = .30). 60 o S to 8 •1 a. CO O m 8 8 I 1 1 i i i i 2 3 4 5 6 7 8 9 : Pain Distress (Mean) Figure 9. Scattergram of postoperative IC scores-and distress scores. Both measures are the mean of two treatments for the sample (n =12). 1 ° 3 S 1 4 " 5 8 i * 8 cf i -•a 8 c 2 8 6 7 Pain Distress (Mean) - #11 deleted Figure 10. Scattergram of postoperative IC scores and distress scores with the out l ier (patient #11) deleted. Both measures are the mean of two treatments for the sample (n = 11). 61 5 6 7 Pain Distress (Mean) Figure 11. Scattergram of percentage of preoperative IC and distress scores. Both measures are the mean of two treatments, for the sample (n = 12). CO O -20 -10 0 10 Pain Distress: % of total scale 20 30 Figure 12. Scattergram of the change in IC between two treatments and the change in distress between two treatments for the sample (n = 12). 62 The health characteristics of weight and BMI were compared to pain leve ls . The negative but non signif icant correlations were as follows: weight and pain sensation (r = - .22; £ = .49); weight and distress (r = - .19; £ = .55) and BMI and pain sensation (r_ = - .15; £ = .62). The correlation between BMI and distress was also non signif icant (r = .06; £ = .86). With respect to postoperative character ist ics, correlations were performed between pain sensation and distress and between analgesic consumption and pain (sensation and d ist ress) . Pain sensation was not s ignif icant ly correlated to pain distress (r_ = 0.57; £ = .08) but a strong trend was evidenced. Meperidine consumption had a negative non signif icant correlation to pain sensation (r_ = - .45; £ = .14) and a positive non signif icant correlation to distress (_r = .22; £ = .49). Discussion The results of the study will be discussed under the following headings: characterist ics of the sample, pain sensation, pain distress, inspiratory capacity, the effect of u t i l i z ing the predicted peak action times of meperidine and the relationship of inspiratory capacity to pain (sensation and distress) . Consideration of the anci l lary findings will be incorporated into the discussion where appropriate. It is important to note that the small sample size precludes making generalizations. Characteristics of the Sample The sex distribution of the sample (one male and eleven females) does not conform to the national distribution of cholecystectomy patients. 63 Current s ta t is t ics show a 2.6:1 female to male ratio across age groupings but age related variation occurs. For example, there is a 5.9:1 female to male ratio for cholecystectomy surgery in the 25-34 age grouping (Stat ist ics Canada, 1988). A possible explanation for the atypical sex distribution may be that of the 37 patients rejected for fai lure to meet the study c r i t e r i a , 35% of these were male. The incidence of cholecystectomy surgery for males increases with age (Stat ist ics Canada, 1988) as does the incidence of chronic i l l n e s s . The age distribution of the sample (M = 42) is within two to nine percentage points of the national average in each of the four age groupings between 25 to 64 years (Stat ist ics Canada, 1988). The stat is t ics used are for female cholecystectomy patients since eleven out of twelve subjects were female. Seven subjects (58%) exceeded the recommended 20-25 norm for BMI levels and thus are considered overweight. Two subjects had a BMI in excess of 27, the level associated with increased health risks (The Canadian Dietetic Association, 1987). These findings are not surprising since obesity is associated with an increased incidence of cholecysti t is (Weedon, 1984). All patients experienced a stable early recovery period. However, 83% complained of untoward symptoms. These symptoms were l ike ly due to side effects of meperidine rather than side effects from the anesthetic agents since they occurred approximately 24 hours after surgery. Dizziness (50%) was the most common complaint followed by nausea (25%) and drowsiness (25%). In a study comparing two doses of Butorphanol with two doses of meperidine given to patients (n = 41) after major surgery, 64 drowsiness was found to be the most common side effect of meperidine (Gilbert et a l . , 1976). The difference in incidence of side effects between the two studies could be explained by the fact that the patients in the Butorphanol/Meperidine study were non-ambulatory whereas in this study, the patients reported untoward effects after ambulation. The dizziness could be attributed to postural hypotension which is a common side effect of meperidine (Jaffe & Martin, 1985) and the increased incidence of nausea could be explained by the increase in movement (Talbert, 1985). Conversely, the act iv i ty may have counteracted some of the patients' perception of drowsiness. Furthermore, in the study by Gilbert and colleagues (1976), the meperidine was administered as a single dose approximately one hour after surgery. At this time, the patient would s t i l l be experiencing the effects of the anesthetic. On the other hand, Harmer, Slattery, Rosen & Vickers (1983) compared the effect of "on demand" intramuscular meperidine, buprenorphine, morphine and meptazinol on 40 cholecystectomy patients for the f i r s t 24 hours after surgery. The meperidine group (n = 10) reported much higher scores for dizziness than the other three groups. Pain Sensation The mean level of pain sensation for the sample was 5.57 cm. According to Johnson's rating Scale for Pain Sensation (1973), a rating of 5 indicates a moderate level of pain. Furthermore, Scott and Huskisson recommend that anchors for moderate pain be centered on a 10 cm VAS (1976). Therefore, the mean level of pain in this study indicates a moderate level of pain. This is consistent with findings that 100% of patients with upper abdominal surgery complain of moderate to severe pain 65 on movement (Bonica, 1982). It is d i f f i c u l t to equate levels of pain in the current study with others, because the majority of pain studies assess patients at rest (Parkhouse & Holmes, 1963) or do not give information about the patients' act ivi ty level at the time of pain assessment (Cohen, 1980; Sriwatanakul et a l . , 1983). In addition, pain scales often d i f fer among studies. Three nursing studies were found that were conducted under similar conditions to the present study (see Table 11). These studies measured pain sensation and distress after ambulation using a 10 point rating scale. While the current study uses a 10 cm VAS to measure pain sensation, i t seems numerically comparable to a 10 point ordinal scale. The f i r s t (Flaherty & Fi tzpatr ick, 1978) and third (Mogan et a l . , 1985) studies showed a higher mean pain sensation than the current study. However, the lower analgesic consumption in these studies might help to explain the discrepancy. Furthermore, the f i r s t study was conducted within eight hours of surgery. Pain sensation would be expected to be higher at this time, not only because the surgical trauma was more recent, but also because the f i r s t few injections after surgery offer the least effective pain control (Austin et a l . , 1980). The second study (Wells, 1982) showed a lower mean pain sensation level and a lower analgesic consumption. However, the mean age of the sample was over 11 years greater than the other three studies and increasing age is associated with lower levels of pain and analgesic consumption (Flaherty & Grier, 1984). It is interesting to note that the mean age of the f i r s t , third and current study were v ir tual ly the same. It would appear, based on the foregoing discussion, that the mean level of pain sensation in the current study is l ike ly quite comparable to the three similar studies. 66 Table 11 A Comparison of Four Studies Measuring Pain and Distress in Postoperative Patients, After Ambulati ion . . . - - . . — -STUDY TOOL SAMPLE AMBULATION TIME (AFTER SURGERY) ANALGESIA/ 24 HOURS PAIN SENSATION & DISTRESS LEVEL 1. Flaherty & Fitzpatrick ! (1978) 1 Johnson1s Control group: - Cholecystectomy - Hemorrhoidectomy - Herniorrhaphy Age: M = 42.4 n = 21 6-8 hrs Meperidine M = 348.8 Tequivalent to 46.5 mg Morphine) Sensation: M = 7.45; ID: 2.2 Di stress: M = 6.76; "S"D: 2.4 2. Wells (1982) Johnson's Control group: - Cholecystectomy Age: M = 53.5 n = 6 24 hrs (approx.) Mixed -equivalent to: M = 49 mg Morphine Sensation: M = 4.24; 1 ID: 1.6 Distress: M = 5.04; ID: = 2.5 3. Mogan, Wells & Robertson (1985) Modified Johnson's Control group: - Cholecystectomy3 Age: M = 41.5 n = 10 24 hrs (approx.) Mixed -equivalent to: M = 42 mg Morphine Sensation: M = 6.8 ! Distress: M = 5.8 4. Current Study (1988) Modified Johnson's (using VAS for Sensa-tion) Cholecystectomy Age: M = 42 n = 17 24 hrs (approx.) Meperidine0 M = 415.58 mg equivalent to 55.41 mg of Morphine Sensation: M = 5.57 SD = 2.3 Distress: M: 5.75; SD: 1.67 Note: Only control groups are used for comparison purposes. The experimental groups in the three studies practiced a relaxation technique. a h n study #3, pain sensation and distress were measured for cholecystectomy patients (n = 10) whereas mean age and analgesic consumption were for the whole sample (n = 72) which also included hysterectomy, bowel and gastrectomy surgery. b t o t a l s for meperidine were taken from the time the patient returned to the ward up to and including the last treatment. This interval was between 18.25 to 28.25 hours and not 24 hours exactly. 67 At the present time, there is no agreement as to what constitutes an optimal or even acceptable level of pain after upper abdominal surgery. Intuit ively, a mean pain sensation level of 5.57 cm seems high when a recommended dose of meperidine was given at f a i r l y regular intervals. However, a closer inspection of the data reveals that meperidine consumption may have been insuf f ic ient . For example, 50% of pain sensation scores were within the upper third of the VAS. On the other hand, the two subjects with the lowest mean pain sensation scores also received the highest dose of meperidine (100 mg). Furthermore, an above average mean pain score (6.34 cm) was reported by the seven subjects who experienced one or more dosing intervals greater than five hours. The duration of meperidine is known to be 2-4 hours (Jaffe & Martin, 1985). A number of studies have found that physicians order less than the recommended dose and frequency of opioid and that nurses further reduce the ordered amount (Cohen, 1980; Sriwatanakul et a l . , 1983). In this sample, the majority of "orders" were within the recommended dose and frequency. However, this was not the case for two subjects with the lowest BMI leve ls . Despite having very high pain scores (M = 8.1 cm) their "orders" were limited to 50-75 mg of meperidine q4-6h. It is a common misconception that opioids should be prescribed according to body weight (Austin et a l . , 1980; Mather & Meffin, 1978). In the current study, correlations of pain sensation to weight and BMI levels were not s igni f icant . In terms of the amount of meperidine administered by the nurses, 90% of the doses were of 75 mg and 96% of the dosing intervals were of four or more hours. This suggests that the nurses may have had a preference for 68 this dose and frequency. In addition, nursing work load factors may have influenced injection frequency as there were fewer nurses available during the evening and night sh i f ts . Patient preference may have also influenced analgesic consumption. During the study, subjects with moderate to high pain scores were offered higher doses but they refused. The reason for this was not explored. Donovan (1983) found that in a group of 200 patients recovering from abdominal surgery, only 27% would have preferred larger doses while 63% expressed a preference for more frequent inject ions. In the present study one possible explanation for the refusal of higher doses may be related to the high incidence of untoward effects experienced (83%). Level of pain sensation ranged from 0.9 to 8.8 cm and thus were highly variable. This is consistent with current pain theory which states that the perception of pain is unique to each individual (Melzack & Wall, 1983). A number of studies have found a multitude of demographic, physiological and psychological variables that influence pain scores (Mather, 1983; Peck, 1986; Taenzer et a l . , 1986). In this study, age may have contributed to overall var iab i l i ty in that a signif icant negative correlation was found between age and pain sensation (r_ = - .65; £ = .02). This is consistent with findings that increasing age is associated with increasing fractions of unbound blood meperidine (Mather, Tucker, Pflug, Lindrop & Wilkerson, 1975a), decreased meperidine elimination rates (Holmberg, Odar-Cedarltif, Boreus, Heyner & Ehrnebo, 1982) and decreased analgesic consumption (Faherty & Grier, 1984). These studies had older samples than the current study. For example, Holmberg and colleagues (1982) compared a group of "old" patients (M = 74.4 years) with a group of 69 "young" patients (M = 24.6 years). It is interesting that in the current study, a strong negative correlation occurred in such a young sample (M = 42 years) within a relat ively narrow age range (25-59 years). A second influencing factor, with respect to variable pain scores, may have been related to the amount of act ivi ty performed outside the treatment times. Some subjects did not ambulate at al l outside the prescribed times, whereas others were out of bed between treatments, on two or three occasions. A third factor may have been related to differences in analgesic consumption. In this study, analgesic consumption was negatively correlated to pain sensation (r_ = - .45; p = .14). While this is not s ta t is t ica l ly signif icant for this sample s ize , a strong trend is indicated. One subject received narcan in the Operating Room for respiratory depression. Fortunately, this did not appear to alter her pain scores as they were low at 2.3 and 3.3 cm respectively. This is l ike ly due to the fact that I.V. narcan has a duration and half l i f e of under two hours (Jaffe & Martin, 1985). Aside from variations in meperidine consumption, individual differences in pharmacokinetics and endogenous opioid levels may have contributed to differences in pain scores. This aspect will be dealt with later in the discussion. The visual analogue scale used to measure pain levels was quick and simple to use. Subjects appeared to understand the concept of the analogue well and showed no d i f f i cu l ty in marking the scale or in making the decision where the mark should be made. Informally, i t was observed that uninitiated subject comments related to changes in pain levels , did correspond to the changes they marked on the VAS. 70 Pain Distress The mean level of distress was 5.75 points which, according to Johnson's Distress Scale (1973), indicates a moderate distress l eve l . This mean is very close to that of the three similar studies in Table 11 (see p. 66). The level of distress in the current study is less than that by Flaherty & Fitzpatrick (1978) or Mogan and colleagues (1985). A possible reason for this is that the level of pain sensation was also lower. While pain sensation and distress are thought to be separate sensations, a relationship should also exist because distress is believed to be a reaction to pain sensation (Beecher, 1956; Johnson, 1973; Melzack & Wall, 1983). Furthermore, the pain scale instructs the subjects to think of their distress in terms of their pain. In this study, the correlation between pain sensation and distress was not s igni f icant , but a strong trend was shown (r_ = .57; £ = .08). Another possible reason why the distress level was lower in the current study could be related to increased contact with the investigator. Of the subjects who did report a change in d istress, 66% had less distress in the afternoon whereas the subjects' highest pain scores were equally divided between the two treatments. Diers and colleagues (1972) suggest that the nurse-patient relationship may decrease patient distress leve ls . On the other hand, the subjects were more familiar with the study protocol by the afternoon and this could also have influenced their d istress. The distress scores ranged from 2 to 9 points and thus were highly variable. This is consistent with the range of pain scores. The subjects' age, weight, BMI and analgesic consumption were not s ignif icant ly correlated to d istress. It is known that there are numerous 71 psychosocial variables influencing levels of distress (Melzack & Wall, 1983). However, such variables were not measured in this study. Informal observation gave no indication that any subjects were experiencing distress related to factors external to the pain experience, but the l ikelihood of this occurring had been decreased by excluding subjects who were subject to chronic disease, other pain syndromes, psychiatric disorders and chemical substance abuse. The mean difference between pain sensation and distress was wider in the three studies described in Table 11. The reason for this is unclear, since a range of differences did occur in the present study (0.1 to 6 points). It is possible that the distance between the two measures was greater in the other studies because two rating scales were used rather than a VAS and a rating scale. Inspiratory Capacity The postoperative IC volumes, measured on a Volurex spirometer, ranged from 800 to 3300 mis and thus appeared highly variable. However, i t is not possible to interpret ventilatory measures such as IC volumes without comparing the results with the predicted norms for the particular individual (Luckmann & Sorensen, 1980). Inspiratory Capacity volumes vary over threefold for normal adults. To determine the norm for an individual , i t is necessary to use a formula or a nomogram that incorporates the individual 's age, height and sex. One nomogram shows increments of 200 mis for every 2 inches of height and decrements of 50 mis for each f ive year increase in age (DHD Medical Products, 1986). Separate nomograms are used for males and females. Consequently, IC volumes are highly variable in any population that is heterogeneous with 72 respect to age, sex, and height. For example, a 2,000 ml IC may represent a 50% decrease for a ta l l young man and a 25% increase for a short middle aged woman. The preoperative IC volumes ranged from 1500 to 4000 mis. Volumes are considered to be within normal l imits i f they are within 20% of the predicted normal values (Luckmann & Sorensen, 1980, p.1191). Calculations of predicted normal volumes using a nomogram (DHD, 1986), indicate that 9 subjects were within the norm and 3 subjects were outside the predicted norm by 30-38%. Of the la t ter , one subject smoked and another was obese (BMI = 32). There was no apparent reason for the third subject to be outside the normal range. In the current study, the interpretation of the IC measures was further complicated because these are postoperative volumes. It is known that the postoperative VC drops to approximately 40% of baseline in the f i r s t 12-24 hours after upper abdominal surgery, mainly due to pain (Bonica, 1982). The decrease is attributed to pain because of the improvement in pulmonary function seen after intercostal block (Coleman, 1987) and epidural block (Bromage, 1955; Cuschieri , Morran, Howie & McArdle, 1985). However, the decrease is variable (Masson, 1962). Consequently, postoperative ventilary volumes (IC and VC) are normally reported as a percentage of the preoperative baseline (Bonica, 1982). This is a very useful measure for two reasons. In the f i r s t place i t standardizes the measures among patients so that comparisons can be made. Secondly, the degree of impairment from pain or other factors, can be evaluated. The inverse relationship between VC and pain (from upper abdominal surgery) was found to be strong enough to use the VC as a 73 measure of analgesic efficacy (Bromage, 1955; Conaghan et a l . , 1966; Masson, 1962; Parbrook et a l . , 1964; Parkhouse & Holmes, 1963). Although Anscombe (1957) found the IC and VC to be comparable measures, no studies were found that used IC as a measure of analgesic ef f icacy. The IC for the sample was calculated as a percentage of the preoperative baseline and was found to range from 40-90% (M = 61.74%). Anscombe (1957) measured the IC, VC and FEV on 10 subjects after cholecystectomy surgery. The mean IC was found to be 40% of baseline 24 hours after surgery. The higher mean in the current study might be explained by more recent improvements in surgical , anesthetic and pain management techniques (Bonica, 1982). In the current study, 41% of the sample had had one or both readings under 50% of baseline and 83% had one or both readings under 70%. In a study by Alexander and colleagues (1981) IC volumes under 70% were associated with a 53% increase in pulmonary complications. It is l ike ly that the decreased volumes were due to pain. It was observed that i t was painful to perform the inspiratory manoeuvre and one subject (#12) developed muscle spasms during the procedure. It was also observed that increases in pain sensation levels were associated with decreases in IC volumes (see Appendix K). Of the two smokers, one had a low mean IC (50%) and the other had a high mean IC (82%). There was no evidence of any other factors, such as pulmonary complications, which might have contributed to the drop in volumes. The Volurex incentive spirometer proved to be easy for the subjects to use. It was possible to measure increments of 50 mis of a i r by applying and marking a tape placed beside the 200 ml cal ibrat ions. It was 74 determined that the measurements remained constant by testing the 1, 2, and 3 l i t e r levels with a pulmonary syringe before and after use. The accuracy of the calibrations were tested after use with the RT-200 Calibration Analyzer (Timeter Instrument Corp.) and were found to be accurate to within 1% of Volume (mean) at the 2 L leve l . Had the spirometers been tested both before and after use with the RT-200, the testing with the pulmonary syringe would have been unnecessary. The pulmonary syringe was awkward and time consuming to use. The Effect of Ut i l i z ing the Predicted Peak Action Times of Meperidine An Analysis of Variance was used to test the f i r s t three hypotheses related to the effect on pain sensation, distress and IC when patients were ambulated at the predicted peak action time of meperidine. Results suggest that there was no signif icant difference among these three variables when subjects were ambulated at onset, peak, or post peak times. Possible reasons for this include the small sample s ize , differences in act iv i ty among subjects, the short interval selected for ambulation times and var iab i l i ty in peak blood-meperidine levels . A possible reason for the lack of a treatment effect could be that the sample size was too small to reveal signif icant f indings. In addition, the incomplete block design had the effect of further decreasing the sample size from 12 to 8 subjects, which is a 33% reduction. It is also possible'that differences in the subjects' act ivi ty level influenced the findings. While some subjects remained in bed between ambulation times, others did not. Furthermore, the interval between scheduled ambulation times differed depending on their configuration. The 75 shortest interval between ambulation time was 2.5 hours whereas the longest interval was 5.75 hours. It is conceivable that had the time interval been greater between onset and post peak, the treatment effect might have been more pronounced. Since the duration of meperidine is 2-4 hours, i t is l ike ly that some subjects were experiencing peak at 110 minutes rather than post peak. However, ethical considerations prompted the selection of the ear l ier time (110 minutes). Another explanation for these results may be related to var iabi l i ty in peak action times due to pharmacokinetic factors. Austin and colleagues (1980) found that cholecystectomy patients experienced variable peak action times, measured by blood opioid levels and pain scores, when they received regular q4h injections of intramuscular meperidine for the f i r s t 28 hours after surgery. It was found that the time required to attain peak blood meperidine levels ranged from 15 to 108 minutes among patients. It is interesting to note that this range is v ir tual ly identical to the range of treatment times in the current study (15 to 110 minutes). In addition to inter patient var iab i l i ty , a high level of intra patient var iab i l i ty occurred. For example, one patient in Austin's study achieved the peak blood mepedirine level 18 minutes after the 24 hour inject ion, but required 108 minutes to reach the peak level after the 28 hour in ject ion. Austin et a l . (1980) attributed the marked inter and intra patient var iabi l i ty to individual differences in IM absorption rates from the gluteal s i t e . However more recent studies have found that the stress of surgery causes redistribution of body f l u i d , decreases hepatic blood flow 76 thereby slowing meperidine breakdown and decreases meperidine clearance rates (Edwards et a l . , 1982; Mather, 1986; Tamsen et a l . , 1982). These studies contradict findings in older well designed studies that have established peak meperidine action at 60 minutes (Gilbert et a l . , 1976; Houde & Wallenstein, 1957, cited in Inturrisi & Foley, 1984; Stambaugh et a l . , 1976). In fact , the 60 minute peak action time is given in some of the foremost pharmacological texts (Jaffe & Martin, 1985). Mather (1986) explains that the older studies either used normals or single doses of meperidine. Austin and colleagues (1980) report that the f i r s t dose of meperidine is the least representative dose. Mather explains that " . . . volunteers are not subject to pain stress and the same degree of hemodynamic and autonomic instab i l i ty as patients recovering from surgery" (1986, p. 158). Mather states further that analgesic effects " . . . seem impossible to predict on an individual basis" (1986, p. 161). The findings in this study appear to be consistent with Mather's conclusion. Although only two "action times" were measured, subjects did have individual "better" times as evidenced by lower pain scores and higher IC scores. It can be seen that these "better" effect times appear to be fa i r ly evenly distributed among the three treatment times (Table 12) and thus were highly variable. It cannot be said that these times are comparable to peak times since only two measures were taken. Furthermore, ethical considerations forestalled the ambulation of subjects more frequently or at times outside of the 15 to 110 minute post injection interval . Therefore, the information given in Table 12 is incomplete. Despite th is , the partial "picture" is consistent with the findings of Austin and colleagues (1980). 77 Table 12 Treatment Times (Onset, Peak and Post Peak) Affording the "Better"  Analgesic Effect for the Sample Dependent Variables Onset Peak Post Peak 1. Pain Sensation 4 3 5 (1 owest) 2. Pain Distress 9 1 3 5 (1 owest) 3. Inspiratory Capacity 5 3 4 (highest) Note: The "better" time is defined as that time affording the lowest pain sensation score, lowest distress score or highest IC Volume. aThree subjects were excluded from the distress category because they did not experience a change in distress level between the two ambulation times. The Relationship of Inspiratory Capacity to Pain Sensation and Distress Hypotheses 4 and 5 related to the relationship of inspiratory capacity and pain (sensation and distress) were tested using the Pearson product-moment correlat ion. With respect to Hypothesis 4, related to the relationship between IC and pain sensation, a weak non signif icant correlation was found between pain sensation scores and IC volumes, both with and without the out l ie r . This is to be expected due to the wide variation in IC volumes known to occur in a sample that is heterogeneous with respect to age, height, and sex (Luckmann & Sorensen, 1980). In order to obtain a signif icant correlat ion, i t would l ike ly be necessary to use a large sample that was controlled for these variables. 78 In accordance with common practice (Bonica, 1982) IC volumes were converted to percentages of the preoperative baseline and correlated to pain sensation scores. The negative correlation approached significance (r_ = - .56; £ = .06) and thus suggests a strong trend. However, when the change in pain scores was correlated with the change in IC (between two treatments), a strong signif icant negative correlation was seen (jr = - .69; £ = .02). This correlation would l ike ly have been stronger i f subject #12 had not developed muscle spasms during the second IC reading. Parkhouse and Holmes (1963) explain the benefits of analyzing the change in a measurement as opposed to only analyzing the mean of a l l measurements: The change brought about by each drug can be estimated by taking the average "amount" of pain in a group of patients before treatment and subtracting the average "amount" after treatment. Such averages give no information about individual patients. . . If the change in each patient is recorded, one can see at a glance how many got better and how many got worse with each drug and to what extent. S t a t i s t i c a l l y , the mean of the change is a more sensitive index than the change of the mean, and i t provides more useful information (p. 581). In this study, the selection of the "patient-as-their-own-control" block design was based on the known var iab i l i ty of pain measures among patients. This design allows the measurement of the change in effect between two treatments in the same patient. Therefore, the advantage this design gives in terms of i ts increased power (Kachigan, 1986) should be carried though in the stat is t ica l analysis. The question of whether the findings lend support to Hypothesis 4 is open to interpretation. If support for the hypothesis is based on a correlation between IC volumes and pain sensation scores, then Hypothesis 4 is not supported. On the other hand, i t was argued that a simple 79 correlation was inappropriate when the variables of age, sex, and height have not been control led. It was further argued that since the design was selected to control for the known var iab i l i ty in the pain measures, then the s ta t is t ica l analysis should f i t the design. In other words, since the design allows a change in treatment effect to be measured in the same individual , then i t is this change that should be s ta t i s t i ca l l y analyzed. Accordingly, i t shall be stated that there was s ta t is t ica l support for an inverse relationship between inspiratory capacity and pain sensation when the change in IC between two treatments was correlated with the change in pain sensation between two treatments. With respect to Hypothesis 5, related to the relationship between inspiratory capacity and distress, a signif icant negative correlation (r_ = - .58; £ = .05) was found between level of distress and IC. However, when the out l ier was removed from the sample, the negative correlation was very weak and non signif icant (r_ = - .11; £ = .74). This may have occurred because patient #11 (the outl ier) had the lowest distress level (M = 2.5) and the highest IC (M = 3250). That one patient could exert such a disproportionately strong effect on the correlation coeff icient lends further support to the preceding argument that isolated scores give a less rel iable correlation than scores measuring the degree of change between two treatments. When level of distress was correlated with the percentage of baseline IC the negative correlation was non signif icant {r_ = - .21; £ = .51). The correlation remained essential ly the same when the change between level of distress and IC were compared (_r = - .24; £ = .51). Consequently, the findings of this study do not indicate a signif icant inverse relationship 80 between distress and IC and therefore Hypothesis 5 was not supported. This was not surprising in that the correlation between pain sensation and distress was non signif icant (r_ = .57; £ = .08). However, the consistently negative direction of the correlation suggests that a signif icant relationship might be shown in a larger sample. The Gate Control Theory of Pain suggests that such a relationship would occur. The findings related to Hypothesis 5 are consistent with the theory that pain sensation and distress are dist inct sensations (Beecher, 1956; Cassel, 1982). No studies were found that explored a relationship between IC or VC and distress. The findings of this study can be explained within the Revised Gate Control Theory of Pain (Melzack & Wall, 1983). Hypotheses 1, 2, and 3 related to the effect on pain sensation, distress and inspiratory capacity when ambulation times occur at different analgesic action times, were not supported by the f indings. This l ike ly occurred because the inhibitor (meperidine) was prescribed to modulate postoperative pain at rest. It is known that movement wil l augment pain by stimulating nociceptors and that "break through" pain will occur with act iv i ty . It was hoped that by timing ambulation to coincide with "peak" meperidine action times, that the subject would in effect receive "more" inhibitor with the hoped for result that this would override or diminish the nociceptive action of the augmentor. Recent studies suggest that peak action times cannot be easily predicted and i f this is so the inhibit ion of nociceptive impulses would be more d i f f i c u l t to enhance through manipulation of predicted peak meperidine action times. 81 Hypothesis 4, related to the inverse relationship between inspiratory capacity and pain sensation, was supported when the change in pain sensation was correlated with the change in inspiratory capacity between the morning and the afternoon treatments. In terms of the conceptual framework, this is an expected outcome. If an inhibi tor , such as meperidine, modulates nociceptive impulses at both the Gate and the Central Processing System, there will be a decrease in the perception of pain. When perceived pain is diminished, there is decreased stimulation of the Action System and decreased reactive pain behaviour. Since the pain source is incisional tension, the reactive behaviour involves immobilizing the chest wall thereby decreasing inspiratory capacity. With decreased stimulation to the Action System, this response is diminished and inspiratory capacity increases. Hypothesis 5, related to the relationship between inspiratory capacity and pain distress would be expected to have a similar outcome. However, since the perception of distress is a reaction to the pain, a reaction that is governed by a variety of personal and psychosocial variables, i t would be expected that this relationship would be less strong. The findings of the study did not support the hypothesis. However, the correlations were consistently negative. This suggests that i t may be possible to obtain signif icant results in a larger sample. Summary The characterist ics of the sample, report of the f indings, and a discussion of the results have been presented in this chapter. The sample was comprised of one male and 11 females from 25 to 59 years of age. Subjects were in stable condition preoperatively and 82 postoperatively. There was a high incidence of untoward effects after surgery. Overal l , a moderate but variable level of pain sensation was experienced. The mean level of pain sensation was similar to other studies. The level of pain was attributed to ambulation, and possible insuff ic ient analgesic consumption. The var iabi l i ty was attributed to differences in'analgesic consumption, possible var iab i l i ty in peak meperidine action times, differences in act ivi ty levels between treatments and age. Age was found to have a signif icant negative correlation to pain sensation. The overall level of distress was also moderate but variable. The mean level was consistent with other similar studies. Both the moderate level of distress and the wide var iab i l i ty in scores was seen as being related to and consistent with the pain sensation scores. Support for this interpretation is found in the Gate Control Theory of Pain (revised 1983) and from the correlation between pain sensation and distress which approached significance thus indicating a strong trend. The inspiratory capacity volumes were highly variable and were signi f icant ly lower than preoperative baseline yolumes. Although the mean decrease was less than that reported in the l i terature , 41% of the sample experienced one or more readings of less than 50% of baseline volumes. IC decreases were attributed to pain leve ls . Hypotheses 1, 2, and 3, related to the effect on the dependent variables when ambulation occurred at different analgesic action times, were tested using an ANOVA specif ic to the incomplete block design. Results were non signif icant and predicted trends were weak. This may 83 have been due to the small sample s ize , differences in the amount of unscheduled act iv i ty , differences in the time interval between scheduled ambulation, and possible var iabi l i ty in peak meperidine action times. Hypothesis 4, related to the relationship between IC and pain sensation was tested using the Pearson product-moment correlat ion. The correlation between IC volumes and pain sensation was non signif icant whereas the negative correlation between the percentage baseline IC and pain sensation levels approached signif icance. Changes in IC volumes were correlated with changes in pain sensation levels and a strong signif icant negative relationship was demonstrated. Hypothesis 5, was related to the relationship between IC and distress. The correlation between these variables was found to be non s igni f icant . 84 CHAPTER FIVE Summary, Conclusions, Implications and Recommendations Introduction This study was designed to test the effect on pain sensation, distress and inspiratory capacity when one day postoperative cholecystectomy patients are ambulated at the predicted onset, peak or post peak time of meperidine action. In addition, the relationship between pain sensation and pain distress to inspiratory capacity was tested. This chapter will include a summary of the study, followed by conclusions, implications for nursing practice, education and theory and recommendations for future research. Summary Despite advances in health care, a review of the l i terature suggests that patients having upper abdominal surgery continue to experience moderate to severe postoperative pain, especially when deep breathing, coughing and ambulating. Furthermore, even normal breathing causes pain by exerting tension on the high abdominal inc is ion . In order to minimize discomfort, the patient automatically adopts a restr icted breathing pattern. This results in a decreased inspiratory capacity and a concommitant high incidence of pulmonary complications. Thus restricted breathing, as evidenced by a decreased IC, can be a secondary problem to the primary problem of pain. The most common method of attenuating pain after upper abdominal surgery is through p . r .n . administration of intramuscular opioids. Meperidine is often used after cholecystectomy surgery because i t is 85 believed to cause less b i l ia ry spasm than morphine. Opioids decrease the perception of pain by binding to opioid receptors and mimicking the antinociceptive actions of endogenous opioids. Opioids decrease the perception of distress by binding to sites in the brain that mediate sensations of alarm, panic, fear and anxiety. The efficacy of an opioid is determined by the concentration of unbound drug at opioid receptor s i tes . This is determined by pharmacokinetic factors that cause fluctuations in receptor site opioid concentration with parallel fluctuations in analgesic action. This can be plotted on a time-action curve. The minimum effective blood-opioid concentration that is necessary for an analgesic response is called the "onset" of action and the maximum effective blood-opioid concentration that gives a maximum response is called the "peak" action. The onset and peak action of meperidine have been established at 10 and 60 minutes respectively. Two nursing authors suggested that postoperative pain management could be enhanced by planning patient act iv i ty to coincide with peak analgesic action times. Since no studies were found that investigated the feas ib i l i ty of this suggestion, this study was designed to test whether ambulation at peak action times would decrease pain sensation and distress and increase inspiratory capacity. This experimental study was conducted in a hospital in Western Canada. The conceptual framework used for the study was adapted from Melzack and Wall's Revised Gate Control Theory of Pain (1983). The design was a randomized balanced incomplete block design in which the subjects 86 served as their own control . This is also known as a repeated measures design. Twelve subjects were randomly assigned to two of the three possible combinations of onset, peak or post peak analgesic action times. All subjects were one day post cholecystectomy and were within an age range of 25 to 64 years. Subjects were fluent in English and were free from major disease, other pain syndromes, psychiatric disorders, substance abuse and postoperative complications. All subjects had their surgeon's consent to participate and orders for intramuscular meperidine postoperatively. Subjects received instruction related to the study protocol on the evening prior to surgery. On the morning of their f i r s t postoperative day, they were ambulated to a chair beside their bed at exactly 15, 60, or 110 minutes (onset, peak or post peak) after receiving an intramuscular injection of meperidine. Subjects scored the visual analogue pain sensation and pain distress scales. Each subject then performed five maximal inspirations with a Volurex incentive spirometer with the highest inspiration being used for analysis. The treatment was repeated in the afternoon at a different but randomly predetermined time (onset, peak or post peak). The sample was comprised of one male and eleven females whose ages ranged from 25 to 59 years (M = 42). Al l subjects were in stable condition preoperatively. Their weight ranged from 56.5 to 122.2 kilograms (M = 73.81). Body Mass Index ranged from 20.99 to 34.59 (M = 26.45) indicating that 58% of the sample were overweight. The duration of cholecystectomy surgery, conducted under standard general anesthesia, was 65 to 139 minutes (M = 98.9). Postoperatively, 87 meperidine was administered in doses of 75-100 mg approximately q3-6h. The consumption of meperidine ranged from 375 to 500 mg (M = 414.58) over 18 to 28 hours. Slight to moderate untoward effects were experienced by 83% of subjects. These included dizziness (50%), nausea (25%) and drowsiness (25%). Pain sensation scores ranged from 0.9 to 8.8 cm with a mean of 5.57 cm which indicates a moderate level of pain. This mean is consistent with that of three similar nursing studies. It is possible that insuff ic ient analgesia contributed to the level of pain sensation. Differences in age, ac t iv i ty , analgesic consumption, and pharmacokinetic factors may have influenced the var iabi l i ty in scores. Pain distress scores ranged from 2 to 9 points with a mean of 5.75 points, which indicates a moderate level of d istress. This mean is close to that of three similar nursing studies. Levels of distress were believed to be dist inct from, but related to , pain leve ls . The correlation between pain sensation and distress was not s igni f icant , but a strong trend was shown (jr = .57; £ = .08). Postoperative IC volumes ranged from 800 to 3300 mis. Preoperative baseline volumes ranged from 1500 to 4000 mis. These volumes were within predicted norms for 75% of the sample. The postoperative IC calculated as a percentage of the preoperative baseline ranged from 40% to 90%. The mean (61.74%) was higher than expected but 41% of subjects had one or more readings under 50% of their normal volume. The decrease in IC percentages was attributed to pain. The findings of the study were related to each of the five research hypotheses. An ANOVA specif ic to the balanced incomplete block design was 88 used to test the f i r s t three hypotheses related to whether getting ambulated at peak times versus onset or post peak, decreases pain sensation, pain distress and increases inspiratory capacity. There was no signif icant difference in level of pain sensation (F (2, 10) = 1.56; £ = .26), level of distress (F (2, 10) = 1.24; £ = .33) or inspiratory capacity (F (2, 10) = 0.21; £ = .81) when one day postoperative cholecystectomy patients were ambulated at the predicted onset, peak or post peak of analgesic action. Furthermore, the estimated treatment effects or trends calculated for each of the dependent variables, were found to be weak. Consequently, there was no stat is t ica l support for the f i r s t three hypotheses. A lack of signif icant findings could be related to the small sample size which was further decreased by the incomplete block design. Subject differences in the amount of unscheduled act ivi ty and differences in the time interval between scheduled ambulation, may have influenced the f indings. It is also possible that var iabi l i ty in peak meperidine action times, a finding in other studies, contributed to the small treatment ef fects. Hypothesis 4 tested the relationship between IC and level of pain sensation. When postoperative IC volumes were correlated with pain sensation scores, a non signif icant correlation resulted (r_ = - .22; £ = .48). The correlation remained non signif icant when an out l ier was removed from the calculat ions. The lack of significance was attributed to sample variance in age, height, and sex. These variables l ike ly exerted a strong influence on individual IC volumes. When IC was given as a percentage of the preoperative baseline and then compared with pain sensation scores, the negative correlation approached significance 89 (r = - .56; £ = .06). This strong trend is consistent with a number of studies that have found a signif icant negative correlation between VC impairment (percentage of preoperative baseline) and level of pain. When the percentage change in IC scores between two treatments was compared with the percentage change in pain sensation scores in two treatments, a strong negative correlation was shown (r_ = - .69; £ = .02). Therefore, support for Hypothesis 4 can only be found in the measure of the change in IC and pain sensation, between two treatments and not in a simple correlation between IC volumes and pain sensation. A signif icant negative correlation between raw IC volumes and level of distress was found (_r = - .58; £ = .05). However, when the out l ier was removed, the negative correlation was non s igni f icant . The negative correlation remained non signif icant when IC scores were given as a percentage of the preoperative baseline and compared with level of distress scores. A comparison between the percentage change in IC scores with the percentage change in level of distress also yielded a negative non signif icant correlat ion. Therefore, Hypothesis 5 was not supported. However, the consistently negative correlation suggests a trend that may be signif icant in a larger sample. Ancil lary findings related to characterist ics of the sample were reported. A strong signif icant negative correlation between age and pain sensation was found (r_ = .69; £ = .02). Weight and BMI levels were not found to be signi f icant ly correlated to pain sensation or distress leve ls . Meperidine consumption was not s ignif icant ly related to pain sensation or distress. F ina l ly , a non signif icant relationship was found between level 90 of pain sensation and level of pain d ist ress, but a strong trend was indicated. In terms of the conceptual framework, the findings related to ambulating patients at predicted peak times, were not in the expected direct ion. Further information suggests that var iabi l i ty in peak blood meperidine levels may have influenced the results. In addition, the range of ambulation times selected for the study (15 to 110 minutes) may have been too short to realize a difference between peak and post peak times in some patients. However, the findings related to the relationship of inspiratory capacity to pain sensation and distress, were in the expected direct ion. Furthermore, the dist inct difference in these findings suggest that pain sensation and distress are separate perceptions, a premise which is conceptually consistent with the Gate Control Theory. Conclusions The following conclusions are based on the findings of this study. However, due to the small sample s ize , the findings and conclusions cannot be generalized. Overal l , one day postoperative cholecystectomy patients experience moderate but variable levels of pain sensation immediately following ambulation at the predicted onset, peak or post peak of analgesic action. While some patients experience mild pain sensation and are relat ively comfortable, other patients experience severe pain and are highly uncomfortable. Given that pain is uniquely appraised and influenced by a variety of physiological and psychosocial variables, var iabi l i ty is expected within the conceptual framework. Differences in age among the 91 sample and insuff ic ient analgesia may have exerted a salient influence on var iabi l i ty in pain scores. On average, one day postoperative cholecystectomy patients experience moderate but variable levels of distress immediately following ambulation at the predicted onset, peak, or post peak of analgesic action. While some patients are mildly distressed by the level of pain, other patients are more severely distressed. Given that distress is uniquely perceived and is influenced by a variety of factors, var iabi l i ty in distress levels is expected. While the level of distress closely paral lels the level of pain for some patients, other patients perceive a greater divergence between pain sensation and distress. Given that pain sensation and distress are dist inct from each other, i t follows that patients will experience a difference between the two sensations. Ambulating cholecystectomy patients at the predicted onset, peak or post peak meperidine action times does not appear to make a difference in their level of pain sensation, distress or inspiratory capacity. Recent studies have found marked var iabi l i ty in peak meperidine blood levels and peak analgesic action times among cholecystectomy patients. This suggests that i t may not be possible to accurately predict peak action times of meperidine. Cholecystectomy surgery is associated with decreased inspiratory capacity volumes postoperatively, although the extent of the decrease is variable. At least part of the postoperative drop in inspiratory capacity is l ike ly attributable to pain. The postoperative decrease in inspiratory capacity does not appear to be directly related to the level of distress after cholecystectomy 92 surgery. Given that inspiratory capacity and distress are both reactions to pain, i t does not necessarily follow that they share a direct relationship. Implications The findings in this study suggest major implications for nursing practice, education and research. Implications for nursing practice are related to opioid administration, the timing of pa in-e l ic i t ing act iv i t ies and the decrease in inspiratory capacity associated with cholecystectomy surgery. F i r s t , the l i terature acknowledges that nurses assume the " l ion 's share" of responsibil i ty for pain management with opioids (McCaffery, 1979). In the current study, nurses administered standard doses of meperidine on a f a i r l y regular basis. However, the subjects' pain scores were variable. While the mean level of pain sensation experienced was moderate, 50% of subjects reported pain scores in the upper third of the VAS and 25% reported pain scores in the lower th i rd . This suggests that routine formulas such as "Meperidine 75 mg IM q4-6h" may not meet the needs of a l l patients. Therefore, i t is recommended that nurses ta i lor analgesic administration to individual patient requirements. This concept, often referred to as "t i trat ion" in the l i terature, implies certain requisites. These include a need for objective assessment tools, a means of monitoring dose-response relationships ( i . e . , a flow-sheet), and increased involvement by patients in their own pain management. In addition, f l e x i b i l i t y in physicians' orders is necessary for the adjustment of the dose and frequency as required. Furthermore, i t is also recommended that nurses administer opioids regularly "around the clock" 93 rather than p . r .n . in the early postoperative period, in order to maintain more stable blood opioid levels and avoid the "peaks and valleys" found with irregular administration (The American Pain Society, 1988). It may be that these recommendations are more time intensive than a standard protocol. However, since i t is believed that "pain work" is one of the primary responsibi l i t ies of the nurse (Fagerhaugh & Strauss, 1977), i t is also believed that an increased expenditure of time is jus t i f i ed in this instance. The second major implication that has evolved from this study is related to the u t i l i t y of timing pain e l i c i t i n g ac t i v i t i es , such as ambulation, to coincide with peak meperidine action times. In as much as this study fa i led to show a difference in pain sensation, d istress, and inspiratory capacity when different ambulation times were used and that other studies report that peak blood meperidine levels occur at variable times, i t may not be possible to predict peak action times of meperidine. While i t may be possible to assess the individual peak meperidine action time of a patient through frequent objective assessments, i t is unlikely that this would be practical in view of reports that peak meperidine action times are variable between dosing intervals in the same patient. However, i t is logical to ambulate patients within a time interval where blood-meperidine levels are known to peak. One study reports that this interval occurs from 15 to 108 minutes after intramuscular meperidine injection (Austin et a l . , 1980). It is possible that other strategies are required to decrease pain sensation during the performance of painful act iv i t ies postoperatively. One method of accomplishing this may l i e in improving opioid 94 administration in general, as was previously discussed. In addition, other pain management techniques have been recommended, such as distract ion, spl int ing, and encouragement (McCaffery, 1977). However, the efficacy of these techniques have not been rigorously investigated. Relaxation exercises have been found to decrease levels of distress but not pain sensation, after ambulation (Mogan et a l . , 1985; Wells, 1982). A third major implication is related to the decreased inspiratory capacity associated with cholecystectomy surgery. While the range of the decrease was variable, the majority of subjects experienced decreases that were in a range associated with an increased incidence of pulmonary complications. This suggests a need for accurate assessment of the depth of respiration after surgery. Unfortunately, precise measuring tools are currently too costly for general ward use, but there are indications that this may change in the future (Herman, 1986). In addition, nursing interventions should focus on maximizing the patients' inspiratory capacity. Incentive spirometry and early ambulation are known to accomplish this (Alexander et a l . , 1981; Dull & Dul l , 1983). The discussion of implications for nursing practice has highlighted a major implication for nursing education. It was suggested that nurses "titrate" analgesics to the patient's level of pain. This requires a sophisticated grasp of pharmacodynamic and pharmacokinetic pr inciples. However, the l i terature has identi f ied that nurses' knowledge of this theory is deficient (Boggs, Brown-Molnar & De Lapp, 1988; Cohen, 1980; Marks & Sachar, 1973; Sriwatanakul et a l . , 1983). This suggests that nursing educational inst i tut ions should review nursing curricula to ensure 95 that there is an adequate theoretical foundation for such complex c l in ica l decision making. F ina l l y , the findings of this study suggest an important implication for nursing theory. The Revised Gate Control theory was an appropriate conceptual framework for this study. However, while the conceptual framework provides a means for predicting relationships between pain (sensation and distress) and behaviour (active and reactive), i t does not appear to discriminate between the behaviour and a specif ic relationship with either pain sensation or d ist ress. In other words, the conceptual framework appears to suggest that all behavioural outcomes will be directly related to both pain sensation and distress. However, inspiratory capacity and immobility are two reactive behaviours that do not appear to have a theoretical basis for a relationship with distress. Recommendations for Future Research Recommendations will be made regarding future research. These are related to replicating the current study, comparing the effects of meperidine and morphine, comparing the difference between a standard and f lexible analgesic regimen, measuring the difference between resting and post act ivi ty pain, and further exploration of the relationship between inspiratory capacity and pain. This study should be replicated to test the val id i ty of the findings with a larger sample and a complete block design. The i n i t i a l rationale for using the balanced incomplete block design was valid in that i t was feared that three treatments would be too fatiguing for patients on the f i r s t postopertative day. However, the subjects tolerated the two treatments very well and in fact ambulated between treatments. Therefore, 96 i t now seems highly probably that subjects could tolerate a third treatment in the late afternoon or early evening. A complete block design using three treatments per block would provide more complete information with respect to peak analgesic times. It is recommended that both resting and post act iv i ty pain levels be measured. Secondly, since morphine is also used for cholecystectomy patients despite the possib i l i ty of increased b i l ia ry spasm, a further study should be done with one group receiving morphine and the other group receiving meperidine. It is recommended that both resting and post act iv i ty pain levels be measured. Thirdly , since i t was suggested that patients may not have received suff icient analgesia, analgesic administration should be tai lored more to patient requirements. A further study should be designed whereby one group receives a standard analgesic regimen and a second group receives a range of analgesic dose and frequency that allows for t i t rat ion to pain leve ls . It would be important to closely monitor patient tolerance ( i . e . , incidence of side effects) as well as level of analgesia. It is also recommended that both resting and post act ivi ty pain levels be measured. F i n a l l y , further exploration of the relationship between inspiratory capacity and pain is needed. This could be accomplished by using IC measurements with pain sensation measurements in other pain studies where the sample is comprised of subjects with upper abdominal surgery. Inspiratory capacity measurement is well tolerated by patients and has the side benefit of improving ventilatory function. 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Effects of preoperative teaching on postoperative pain: A replication and expansion. International Journal of Nursing Studies, 22(3), 267-280. Montgomery, D.C. (1984). Design and analysis of experiments (2nd ed. ) . New York: John Wiley & Sons. Nolan, M.F. (1987). Anatomic and physiologic organization of neural structures involved in pain transmission, modulation and perception. In John L. Echternach, (Ed.) Pain (pp. 1-37). New York: Churchill Livingston Inc. Parbrook, G.D., Rees, G.A.D. , & Robertson, G.S. (1964). Relief of post-operative pain: Comparison of a 25% nitrous-oxide and oxygen mixture with morphine. Br i t ish Medical Journal, 2, 480-482. Parkhouse, J . , & Holmes, C M . (1963). Assessing post-operative pain r e l i e f . Proceedings of the Royal Society of Medicine, 56, 579-585. Peck, C.L (1986). Psychological factors in acute pain management. In M.J. Cousins & G.D. Ph i l l ips (Eds.) , Acute pain management (pp. 251-274). New York: Churchill Li vi ngTtow: 102 P h i l l i p s , G.D., & Cousins, M.J. (1986). Practical decision making. In M.J. Cousins & G.D. Phi l l ips (Eds.) , Acute pain management (pp. 275-290). New York: Churchill Livingstone. Scott, J . , & Huskisson, E.C. (1976). Graphic representation of pain. Pain, 2, 175-184. Sriwatanakul, K., Weis, O . F . , Al loza, J . L . , Kelvie, W., Weintraub, M., & Lasagna, L. (1983). Analysis of narcotic analgesic usage in the treatment of postoperative pain. Journal of the American Medical  Association, 250(7), 926-929. Stambaugh, J . E . , Wainer, I.W., Sanstead, J . , & Hemphill, D.M. (1976). The c l in ica l pharmacology of meperidine—Comparison of routes of administration. The Journal of Cl inical Pharmacology, May-June, 245 - 256. Stat is t ics Canada. (1988). Surgical Procedures and Treatments 1984-85. Catalogue #82-208. Ottawa: Minister of Supply & Services. Stewart, M.L. (1977). Measurement of c l in ica l pain. In A.K. Jacox (Ed.) Pain: A source book for nurses and other health professionals (pp. 107-137). Boston, MA: L i t t l e , Brown and Company. Taber, C.W. (1965). Taber's Cyclopedic Medical Dictionary (10th ed. ) . Toronto: The Ryerson Press. Taenzer, P. , Melzack, R., & Jeans, M.E. (1986). Influence of psychological factors on postoperative pain, mood and analgesic requirements. Pain, 24, 331-342. Talbert, R.L. (1985). Pharmacotherapeutic modification of the stress response: analgesics. Cr i t ica l Care Quarterly, _7(4), 27-40. Tamsen, A . , Hartvig, P. , Fagerlund, C , <S Dahlstrtim, B. (1982). Patient-controlled analgesic therapy, Part I: Pharmacokinetics of pethidine in the per-and postoperative periods. CIinical  Pharmacokinetics, 7_, 149-163. Utting, J . E . , & Smith, J.M. (1979). Postoperative analgesia. Anaesthesia, 34, 320-332. Weedon, D. (1984). Pathology of the gall bladder. Chicago: Yearbook Medical Publishers Inc. Wells, N. (1982). The effect of relaxation on postoperative muscle tension and pain. Nursing Research, 31(4), 236-238. 103 APPENDIX A LEVEL OF PAIN SCALE I want you to think of your pain in two ways. F i r s t , in terms of the intensity of the sensation, second in terms of the degree of distress you experience (how much the pain bothers you). Think of your pain as you would a l ight ; you can say how bright a l ight is separately from how much i t bothers you. Consider the sensation and distress scales as different measurements that can vary separately. Pain Sensation Scale Please place a stroke through the l ine at the level that best ref lects your level of pain. Pain Distress Scale Please c i rc le the number that best describes how distressing the sensation is right now. no pain worst possible pain no distress moderate distress maximum distress imagi nable f 1 1 1 1 1 i 1 1 1 1 0 1 2 3 4 5 6 7 8 9 10 VOLUREX® The True Volume Displacement Incentive Spirometer 12 units per case D H D 22-2390 Standard Unit (formerly ?239ANV) D H D 22-2395 Deluxe Unit With Non Rebreathing \£lve. (formerly #239A) FEATURES: • U)lume displacement means consistent accuracy at any inspiratory flowrate • Durable construction, molded from impact resistant plastic • Low resistance bellows minimizes patient effort required to perform SMI • Accurate t o + / - 1% of full scale (40 cc's) • Full 4000 cc capacity • Calibrated in 200 cc increments • Inspiratory capacity nomograms pro-vided with each unit • Available with or without a non re-breathing valve • Easy to use properly 105 APPENDIX C TESTING OF VOLUREX AGAINST VORTEX FLOW SENSOR The accuracy of one Volurex Incentive Spirometer was tested against the Vortex Flow Sensor owned by Associated Respiratory Services, Burnaby, B .C . . Derek Smith, a biomedical electronics technician, tested the Volurex by inspiring a i r manually to three levels: 1.0, 2.0 and 2.8 l i t e r s . Each reading was tested three times. Results were as follows: Inspired Liters Vortex Reading (x3) Error #1 1.0 1.01 .01 #2 1.0 1.00 0 #3 1.0 1.00 0 #1 2.0 1.92 .08 #2 2.0 1.94 .06 #3 2.0 1.95 .05 #1 2.8 2.76 .04 #2 2.8 2.74 .06 #3 2.8 2.76 .04 Note: Because the test was done manually, the Inspired Li ter rates are close approximations. APPENDIX D Results of Calibration Testing of Volurex Incentive Spirometer Usi RT-200 Calibration Analyzer at 1000 ml and 2000 ml Levels Spirometer No. 1000 ml 2000 ml 1 1020 1960 2 1030 1990 3 970 1890 4 1010 2020 5 1020 1990 6 1010 1970 7 1000 1990 8 1030 1950 9 1050 1970 10 1000 1940 11 990 1950 12 1050 2030 Mean Error {%) 2% 1% Timeter Instrument Corp. Cert i f icat ion Record Serial M13B5. Note: Spirometers were tested after use. O.R. time Consents signed: #1 Sex ; Age APPENDIX E DATA SHEET #1 PREOPERATIVE INTERVIEW Subject # ; Cr i ter ia met ; #2 ; #3 ; Ht BP ; P. ( ly ing); P. Smoker ; Education Allergies Preoperative f i lm viewed Previous surgery: Medication Bias: Regularly Prescribed Medications: IC (cm): #1 ; #2 ; #3 Other: 108 APPENDIX E DATA SHEET #2 PREOPERATIVE DATA Subject # Procedure: Started hrs; Completed hrs. Anaesthetic Agents: Blood loss cc Replacement cc Tubes (Drains, T-tubes, N.G., Catheter, other): Location & type of inc is ion: PAR Arrived hrs; Departed hrs; Analgesic Consumption (type, time, amount, route): Other: WARD (day of surgery) Analgesic Order: Analgesic Consumption (type, time, amount, route) Other: 109 APPENDIX E DATA SHEET #3 ONE DAY POSTOPERATIVE Treatment 1 (morning) Subject # Activity since 0001 hrs: Analgesic consumption since0001 hrs (type, time, amount, route): Last dose since 0730 hrs Time treatment dose due ; Received Time of ambulation after treatment dose hrs General condition of patient: Pulse (lying) ; Pulse (sitt ing) VAS cm; Distress scale cm I.C. (cm) #1 ; #2 ; #3 ; #4 ; #5 Incentive Spirometer prescribed Untoward drug effects (nature, duration, time, frequency): Activi ty from time of mobilization to return to bed: Other: APPENDIX E DATA SHEET #4 ONE DAY POSTOPERATIVE Treatment 2 ( a f t e r n o o n ) S u b j e c t # A c t i v i t y s i n c e l a s t t r e a t m e n t : Time t r e a t m e n t dose due h r s ; R e c e i v e d h r s Time o f a m b u l a t i o n a f t e r t r e a t m e n t dose h r s General c o n d i t i o n o f p a t i e n t : P u l s e ( l y i n g ) ; P u l s e ( s i t t i n g ) VAS cm; D i s t r e s s s c a l e cm IC (cm): #1_ ; #2 ; #3 ; #4 ; #5 Untoward drug e f f e c t s ( n a t u r e , d u r a t i o n , t i m e , f r e q u e n c y ) : A c t i v i t y from time o f m o b i l i z a t i o n to c o m p l e t i o n o f I.C.: Ot h e r : I l l APPENDIX F The Effect on Perception of Pain Sensation, Distress And Incentive Spirometry Performance When Cholecystectomy Patients Are Mobilized At Onset, Peak, or Post Peak of Analgesic Action SURGEON'S CONSENT I hereby give my consent that patients under my care who are slated for cholecystectomy surgery at Hospital may participate in the above study. I realize that after receiving an intramuscular analgesic in accordance with my postoperative orders, that one-day postoperative patients will be ambulated at a time specified in the study protocol. I am aware that the patient will then perform five maximal inspirations using a Volurex Incentive Spirometer (single use). I understand that the patient's written informed consent wil l be obtained by the nurse investigator and that a copy will be placed on the patient's chart. Surgeon Nurse Investigator Date 113 APPENDIX H PATIENT INFORMATION SHEET The Study The purpose of this study is to learn more about how patients feel when they get up after gall bladder surgery, and their ab i l i ty to deep breathe at this time. These are essential act iv i t ies necessary to prevent complications. Your Participation in the Study This will include: 1. answering a short l i s t of questions prepared by myself, such as your age, past experience with surgery and whether or not you smoke. The questions are asked because these factors may influence the results of the study. 2. getting out of bed in the morning after your surgery. I will help you to s i t in a chair by your bed. This will occur at a specified time after your nurse has given you your regular injection for pain. The times will change from the morning to the afternoon but al l times will be within two hours of your in ject ion. 3. f i l l i n g out the level of discomfort scale. I will show you a copy and explain how i t is done. This takes only a minute or two. 4. answering a few questions about how you are feel ing. I will take your pulse before and after you get up. 5. performing the deep breathing exercises with the incentive spirometer: a) s i t up straight and close your l ips about the mouth piece; b) take in as deep a breath as possible; c) hold the breath in for 3 to 5 seconds (count one one thousand, two one thousand, three one thousand); d) exhale the breath normally. Take a short rest and repeat these steps 4 more times. 114 APPENDIX H (Continued) 6. walking from the chair to the door (or to the washroom) and then back to bed; 7. repeating steps 2 through 6 again in the afternoon of the same day. This will involve about 20 minutes in the morning and 20 minutes in the afternoon. Points to Know 1. The deeper the breath that you take i n , the more effective the exercise will be. 2. The act iv i t ies you perform in this study are usual act iv i t ies that are encouraged after surgery. The difference is that when you participate in this study, these act iv i t ies are carried out in a precise way so that accurate measurements can be made. 3. Not all patients are given incentive spirometers after surgery because they are very expensive. If your physiotherapist feels you particularly need this treatment on an hourly basis after surgery, he/she will provide the hospital brand and you wil l perform those exercises according to your physiotherapist's instructions. This will in no way affect your ab i l i ty to participate in this study. 4. Although not part of the study, you should perform the other postoperative exercises described in the hospital brochure. These include coughing, ankle pumping, ankle c i r c l i n g , and knee bending and straighteni ng. This is for your information only. You do not have to learn the steps, as I will t e l l you again at the time. Please feel free to ask any questions. Thank you for giving me the opportunity to present this to you. Sincerely Nurse Investigator 116 APPENDIX J Details of the Analysis of Variance of a Balanced Incomplete Block Design Using Levels of Distress as an Example An incomplete block design occurs when not al l treatment combinations can be run in each block. It becomes a balanced incomplete block design when any two treatments occur together an equal number of times. If there are a treatments and b blocks, each block contains k treatments and each treatment is replicated r times, then the total number of observations is N = ar = bk. Also, the number of times each pair of treatments appears in the same block is A = r (k - l ) / (a - 1). The values of these parameters for the current study design are: a = 3 (i • e . , 3 treatments, at onset, peak, and post-peak) b = 12 (i 12 blocks, where each patient is a block) k = 2 (i . e . , 2 treatments per block/patient) r = 8 (i . e . , 8 replications per treatment) N = 24 (i • e . , 3 x 8 = 1 2 x 2 = 2 4 observations) A = 4 (i . e . , each pair of treatments appears in the same block 4 times, e . g . , Peak & Post-peak are together in blocks/ patients #1, 3, 6, 8). The model for this design i s : Yn-j = y + t i + Sj + e i j where Yjj means the observation corresponding to the i^h treatment and the j t n patient (e .g . , Y32 = 6, Post-peak for patient #2). The right-hand-side of the model means that there is an overall average response for everyone ( y ) , an effect due to the different treatments (t-j), an effect due to different patients (gj) and a random error term (si j ) for measurement error and other factors beyond the investigator's control . The objective of analysis of variance is to take the total variation and partit ion i t into quantities which can be attributed to specif ic sources plus a remainder which is associated with random error. When a source (or variable) contributes a large part to the total variat ion, as compared with the random error component, then that source has a signif icant ef fect . The steps in the procedure for calculating the ANOVA for a balanced incomplete block design are outlined on p.118. The in i t i a l step involves producing a table of the measurements for the sample with the block and treatment tota ls . APPENDIX J (Continued) The construction of the table, using distress measurements as an example is i l lustrated below. Post-Patient Onset Peak peak Raw Totals ( = Blocks Totals = Y.j) 1 - 6 5 11 2 7 - 6 13 3 - 7 6 13 4 8 6 - 14 5 7 7 - 14 6 - 4 4 8 7 3 5 - 8 8 - 4 6 10 9 7 - 4 11 10 7 - 7 14 11 3 2 - 5 12 9 _ 8 17 Column Totals 51 41 46 138 (Treatment Totals Yi. ) Notes: 1) Yj = sum of a l l observations at the i t n treatment i . e . , Y i . = 51, Y 2 . = 41, Y 3 . = 40. 2) Y.j = sum of al l observations for the j t n block (patient) i . e . , Y . i = 11, Y.2 = 13, etc. 3) Y . . = sum of al l observations = 138 4) E l Y 2 i j = sum of al l squared observations = 7 2 + 8 2 + . . . + 8 2 = 868 5) N = 24 observations. 118 APPENDIX J (Continued) Procedure: Step 1. Compute the row and column tota ls , the overall total and the sum of the squared observations (see p..1117). Step 2. SSTotal = E E Y 2 i j - Y 2 . . / N = 868 - (138)2/24 = 74.5 Step 3. SSBlocks = E Y 2 . j / k - Y 2 . . / N = 1/2 ( l l 2 + 13 2 + 13 2 + + 172) - (138)2/24 = 1/2 (1710) - 793.5 = 61.5 Step 4. Compute "adjusted treatment totals ." This is where the ANOVA for an incomplete block design dif fers from that for a complete block design. The adjustment is necessary because each treatment is represented by a different set of r blocks. The adjusted treatment totals are denoted by Q-j and are found using: Qi = Y i . - 1/k E Nij Y . j , where: N-jj = 1 i f treatment i appears in block j or N-jj = 0 i f the above condition is not met. Therefore Qx = 51 - 1/2 (13 + 14 + 14 + 8 + 11 + 14 + 5 + 17) (these are the block totals for those blocks that do have treatment 1 in them) = 51 - 1/2 (96) = 3.0 Q 2 = 41 - 1/2 ( 1 1 + 1 3 + 1 4 + 1 4 + 8 + 8 + 1 0 + 5 ) = 41 - 1/2 (83) = -0.5 Q 3 = 46 - 1/2 (11 + 13 + 13 + 8 + 10 + 11 + 14 + 17) = 46 - 1/2 (97) = -2.5 (Note that Qi + Q 2 + Q 3 = 0. This serves as a check on the calculat ions. Step 5. SSTreatments (adjusted) = k E Q-j2/xa = 2 (3.0 2 + (-0.5) 2 + (-2.5) 2) / 4(3) = 2.583 119 APPENDIX J (Continued) Step 6. Compute SSError (by subtraction): SSError = SSTotal - SSBlocks - SSTreatments (adjusted) = 74.5 - 61.5 - 2.583 = 10.417 Step 7. Form the ANOVA table Source of Degrees of Variation Sum of Squares Freedom Mean Square F Treatments (adjusted) k E 0 -^2/ a a- l SSTreat's (adj) MSTrt / (a - l ) MSError Blocks E Y 2 . j / k - Y 2 . . / N b-1 SSB1ocks/(b-l) Error (by subtraction) N-a-b+1 SSError/(N-a-b+l) Total E E Y 2 i j - Y 2 . . / N N-l For the i l lust ra t ion here, the ANOVA table i s : Source SS d.f . M.S. Treatments (adj) 2.583 Blocks 61.500 Error 10.417 2 11 10 1.2915 5.5909 1.0417 1.24 Total 74.50 23 Step 8. Compute the F-ratio and a P-value F = MSTreatment (adj) = 1.2915 =1.24 MSError P-value = 0.330 1.0417 120 APPENDIX J (Continued) Estimates of the treatment effects can be computed using t i = k Qi/xa For the current i l lus t ra t ion : = 2(3.0)/4(3) = 0.500 = 2(-0.5)/4(3) = -0.083 = 2(-2.5)/4(3) = -0.417 How are treatment effects interpreted? If there were a signif icant difference among treatments, then the treatment effect estimates would say how much higher (or lower) the_response is due to that treatment. For example, in this i l lustrat ion t.- = 0.500 means that treatment 1 is responsible for adding an extra 0.5 units to the Pain distress leve l , on average. That i s , patients who receive treatment 1 (onset) would expect to have a Pain Distress level about 0.5 units above the overall average level of 5.75 ( i . e . , Y . . /N = 138/24). Similar ly, treatments 2 and 3 lower the Pain Distress levels by -0.083 and -0.417, on average. Note however that the treatment effect was not signif icant (see ANOVA) so these treatment effect estimates cannot be considered to be signif icant ly different from zero. They do give some idea of what direction the effects would take i f they were signif icant ly different from zero. Source: Formulas taken from Montgomery, 1984, pp. 165-177. The computations and accompanying explanations were prepared with the assistance of Dr. Jonathan Berkowitz, former Department Head of Stat ist ics Consulting Service, University of Br i t ish Columbia, Vancouver, B.C. 121 APPENDIX K COMPARISON OF THE CHANGE IN PAIN SENSATION WITH THE CHANGE IN INSPIRATORY CAPACITY, FROM THE MORNNG TO THE AFTERNOON Pain Sensation (10 cm VAS) IC (4000 ml Volurex) itient Tl T2 % Change5 Ba seli ne Tl T2 % Change0 2 3.6 6.9 +33 2000 1000 800 -10 3 6.9 7.3 +4 2850 1600 1400 ^7 6 2.3 3.3 +10 2100 1300 1250 -2 9 6.9 8.8 +19 2300 1200 1050 -]_ 10 0.9 1.0 +1 1500 1350 1100 -17 11 3.4 4.2 +8 4000 3300 3200 -3 1 6.5 4.6 -19 2050 1350 1500 +7 4 8.3 7.4 -9 2600 1800 2100 +12 5 6.6 6.3 ^3 2100 950 1150 +10 7 5.0 2.7 -23 2200 1350 1550 +9 8 8.8 7.7 -11 1800 800 950 +8 12 7.4 6.9 -5 1500 950 900 -3 Note: Data are presented to show the inverse relationship between the percentage change (underlined) of pain sensation and IC that occurs from treatment 1 to treatment 2. aThe treatments are ambulation at onset, peak or post-peak of predicted meperidine a c t i o n . The patients (n = 12) had two out of the three treatments. DPercentage change in Pain Sensation is the change between treatments measured in cm divided by the 10 cm scale. cPercentage change in IC is the change between treatments divided by the preoperative basel ine IC. 

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