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Effects of flush solutions on radial artery catheter patency Budz, Bernice 1995

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EFFECTS OF FLUSH SOLUTIONS ON RADIAL ARTERY CATHETER PATENCY By BERNICE BUDZ B . S . N . , Un ivers i ty of Lethbridge, 1986 A THESIS SUBMITTED IN PARTIAL FULFILMENT THE REQUIREMENTS FOR THE DEGREE OF MASTERS OF SCIENCE IN'NURSING i n THE FACULTY OF GRADUATE STUDIES School of Nursing We accept th i s thes is as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA December 1995 © Bernice Budz, 1995 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I 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 DE-6 (2/88) Abstract This randomized, double b l i n d experimental study was designed to test the effects of f l u s h solutions on r a d i a l a r t e r i a l catheter patency. Factors influencing haemostasis, ' endothelial damage, rate and t u r b i d i t y of blood flow, and inherent coagulation factors, provide the framework to examine the a r t e r i a l catheter f l u s h system. The purpose of t h i s study was to compare the effectiveness of two concentrations of heparin, 2 U/mL and 1 U/mL, and one of. normal saline i n maintaining patency of r a d i a l artery catheters. It was hypothesized that when subjects' r a d i a l a r t e r i a l catheters were provided routine catheter care and continuous flushing with 3 .mL/hr of either heparin 2.0 U/mL, heparin 1.0 U/mL, or saline f l u s h solution there would be: (1) no difference i n occlusion r i s k between f l u s h solution groups as indicated by: prothrombin time (PT), p a r t i a l thromboplastin time (PTT), p l a t e l e t count, and the presence of c l o t s i n the solution flushed through the catheter and/or on the catheter t i p a f t e r removal; and (2) no difference i n frequency of occlusion between f l u s h solutions groups as indicated by removal of the catheter for any of the following reasons: (a) the i n a b i l i t y to I l l f l u s h the catheter, (b) the i n a b i l i t y to aspirate blood from the catheter, (c) loss of a r t e r i a l catheter waveform on the monitor. Th i r t y cardiac surgery patients were randomly assigned to one of three groups. Each group consisted of 10 subjects who received a flu s h solution containing either heparin 2.0 U/mL, heparin 1.0 U/mL or sal i n e . Hypothesis one could not be supported. Of the coagulation tests, measured two to three times postoperatively, the 1 U/mL group had more normal PT times on admission and s i g n i f i c a n t l y higher p l a t e l e t counts at 24 hours than the saline and 2 U/mL groups. Since the 1 U/mL group also had s i g n i f i c a n t l y shorter pump times, these findings may be related to the mechanical actions of the pump, the high concentration of heparin on pump, and the d i l u t i o n a l e f f e c t on the coagulation factors. The finding that seems to be most related to the amount of heparin i n the fl u s h solution, i s that three catheters i n the saline group had c l o t s when removed, while there were no cl o t s i n the catheters for the other 2 groups. Hypothesis two also could not be supported. Although there were no s i g n i f i c a n t differences i n the frequency of i v d i f f i c u l t y with f lushing the catheter, dampened waveform pat tern , and complete loss of a r t e r i a l waveform pat tern , the sa l ine group had s i g n i f i c a n t l y more d i f f i c u l t i e s with a s p i r a t i n g blood and more catheters removed because of occ lus ion . Furthermore, although not s t a t i s t i c a l l y d i f f e r e n t , the sa l ine group had more p o s i t i o n a l catheters and t h e i r catheters were flushed more often. Although the sample was small , the re su l t s of t h i s study tend to indicate that heparin continues to be required i n the f lush so lut ion to maintain a r t e r i a l catheter patency. Table of Contents v Page Abstract i i Table of Contents v L i s t of Tables v i i L i s t of Figures v i i i Acknowledgements i x CHAPTER ONE: INTRODUCTION Background to the Problem 1 Problem Statement 8 Purpose " 9 Theoretical Framework 9 Endothelial Damage 9 Rate and Turbidity of Bloodflow 10 Ci r c u l a t i n g Coagulation Components 11 A r t e r i a l Catheter System 12 Hypotheses 13 D e f i n i t i o n of Terms 17 Organization of the Thesis 22 CHAPTER TWO: REVIEW OF THE LITERATURE Introduction 24 A r t e r i a l Catheter System 24 Surgical Factors Influencing 33 Occlusion and Occlusion Risk Review of Studies Comparing 3 7 Flush Solutions V I CHAPTER THREE: METHODS Introduction 52 Research Design 52 Sample 55 Data C o l l e c t i o n Procedure 56 Instruments for Data C o l l e c t i o n 61 P i l o t Study 65 Data Analysis 65 Assumptions and Limitations 66 Ethics and Human Rights 68 CHAPTER FOUR: PRESENTATION AND DISCUSSION OF FINDINGS Introduction 71 Characteristics of the Sample 71 Findings 76 Discussion of the Findings 93 Summary 103 CHAPTER FIVE: SUMMARY, CONCLUSIONS, IMPLICATIONS AND RE COMMENDATIONS Introduction 104 Summary 104 Conclusions 110 Implications for Practice 111 Implications for Research 112 Concluding Remarks 112 REFERENCES 114 APPENDICES Appendix A. Standards of Care for A r t e r i a l 122 Pressure Monitoring Appendix B. Data C o l l e c t i o n Tools 132 Appendix C. Guidelines for Nursing on Data Col l e c t i o n Tools ' 135 Appendix D. Patient Informed Consent 13 8 Appendix E. Guidelines for Perfusionists 142 V l l L i s t of Tables Table Page 1 Summary of Literature on Various Flush Solutions 40 2 Age D i s t r i b u t i o n of the Sample' 72 3 Duration of Pump and Clamp Time 73 4 Time Catheter Insitu per Flush Solution Group 75 5 Prothrombin Time Values per Flush Solution 77 6 P a r t i a l Thromboplastin Time Values per Flush Solution 80 7 P l a t e l e t Count Values per Flush Solution 82 8 Frequency of Catheter Occlusion Indicators 87 9 Reasons for Catheter Removal 89 10 Frequency of Flushing the A r t e r i a l Catheter 91 v i i i L i s t of Figures Figure Page I Components of an A r t e r i a l Catheter System 14 II Three Group Double B l i n d Experimental Design 53 i x Acknowledgements I would l i k e to thank the members of my thes i s committee, Dr. Ann H i l t o n (chairperson), and professors Anne Wyness and Ethe l Warbinek for t h e i r pat ience, guidance, and scho lar ly analys is throughout the past years . I would l i k e to thank my family and fr iends for t h e i r support and encouragement throughout t h i s endeavour. Spec ia l thank you to Kathy, Ivy, Debbie and Kenna, your ongoing support and ins ights sustained me through t h i s chal lenging time. I a lso wish to thank a l l the s t a f f of the Cardiac Surgery Intensive Care Unit and my colleagues at St . Paul ' s Hosp i ta l for t h e i r patience and understanding while I f in i shed th i s pro jec t . My apprec ia t ion i s p a r t i c u l a r l y extended to the nursing s t a f f of the CSICU who c o l l e c t e d the data. F i n a l l y , I would l i k e to acknowledge the i n d i v i d u a l s who so generously agreed to p a r t i c i p a t e i n th i s study. 1 CHAPTER ONE Introduction Background to the Problem A r t e r i a l catheters are used for patients who require either hemodynamic monitoring or frequent blood sampling. Catheters may • be percutaneously inserted into the brachial or femoral artery, however, the r a d i a l artery i s most commonly cannulated. Patients who are hemodynamically unstable must have t h e i r blood pressure monitored continuously. The monitoring involves the conversion of the blood pressure from the artery into a pressure waveform pattern on a video monitor. The pressure wave i s transmitted from the catheter, v i a hard-bore tubing, to a transducer which converts i t into a waveform on an oscilloscope and a d i g i t a l reading. C r i t i c a l l y i l l patients require numerous blood tests, e s p e c i a l l y a r t e r i a l blood gases, which can be drawn from the catheter, thus eliminating the need for repeated a r t e r i a l and venous punctures (Holloway, 1993; Gardner, Schwartz, Wong, & Burke, 1974). The i n s e r t i o n of an a r t e r i a l catheter has greatly f a c i l i t a t e d d i r e c t access for blood sampling and has made a major 2 contribution to patient comfort. Maintaining the patency of r a d i a l artery catheters i s a high p r i o r i t y i n patient care. Occlusion of the catheter by a c l o t necessitates the prompt removal of the catheter, otherwise the c i r c u l a t i o n to the hand may be compromised. The patient who s t i l l requires blood tests, must have a catheter re-inserted, or may have blood drawn by a r t e r i a l or veni-puncture depending on the type of sample required. Both consequences cause discomfort and increase r i s k of a thrombus and/or a r t e r i a l occlusion. A c l o t or thrombus may also send micro-emboli to a d i s t a l extremity (Thelan, Davie, & Urden, 1990). Over time, various methods to prevent c l o t t i n g have been implemented. When r a d i a l a r t e r i a l catheters were f i r s t introduced, the flushing mechanism was intermittent i n j e c t i o n s of 5 m i l l i l i t r e s (mL) of saline s o l u t i o n containing two units of heparin per mL. This method resulted i n a 38% incidence of thrombosis (Bedford & Wollman, 1973; Gardner et a l . , 1974). The rate of catheter occlusion was s i g n i f i c a n t l y reduced to less than 1% (Oh, Opie, & Dans, 1976) with the advent of a pressurized, continuous i r r i g a t i o n system using a f l u s h solution of 4 units of heparin per mL of normal sa l i n e . 3 The continuous heparinized f l u s h system i s thought to prevent thrombus formation at the t i p of the catheter i n three ways. F i r s t , the pressurized system, which has a higher pressure than the blood pressure, prevents a r t e r i a l blood from flowing back into the tubing, and so decreases the r i s k of c l o t t i n g i n the system. Second, a pressurized system also permits manual, intermittent flushing of the catheter as required, such as following blood sampling (Darovic, 1987). A 3-second manual f l u s h d e l i v e r s approximately 3 mL of heparinized solution, which quickly clears blood from the tubing to prevent c l o t t i n g (Thelan et a l . , 1990). Third, thrombus formation may be prevented because heparin i s an anticoagulant (Wright _ Shelton, 1993). Today, a r t e r i a l catheter patency i s maintained using a pressurized system to d e l i v e r a f l u s h solution containing porcine heparin continuously at 3 mL/hr. The concentration of heparin varies from 0.25 units/mL to 4 . 0 units/mL i n 500 mL of saline depending on the i n s t i t u t i o n . Unfortunately, maintaining the patency of catheters continues to be a problem i n hospitals, but i t i s unclear whether the occurrence of catheter occlusion can be ) 4 a t t r i b u t e d to the heparin concentration, the continuous pressurized f l u s h system, or a combination of the two. However, the r i s k s associated with heparin administration have spurred a re-evaluation of the need for heparin i n the f l u s h system. Administration of heparin as an anticoagulant presents several r i s k s , the most serious being bleeding and thrombocytopenia. Although 'bleeding i s a major complication of heparin therapy, i t i s not a s i g n i f i c a n t concern for those patients receiving a heparinized f l u s h solution, because the dose of heparin i s small (Johnson, Hannah, & Zerr, 1992). However, Johnson et a l . d i d report that a small number of patients receiving heparin developed thrombocytopenia of unknown o r i g i n . Thrombocytopenia i s a recognized side e f f e c t of heparin. The low p l a t e l e t count, associated with an increase of platelet-bound IgG, i s reversed a f t e r heparin i s withdrawn. Kay (1988) suggests that the p l a t e l e t s are rendered susceptible to a c t i v a t i o n by an antibody and, i n the presence of a r t e r i a l atheroma, aggregation i s triggered, with p l a t e l e t consumption i n the r e s u l t i n g thrombus. Heparin-associated thrombocytopenia i s a r e l a t i v e l y 5 \ \ common complication of heparin therapy, occurring i n approximately 5% of patients who receive the drug. The incidence i s higher with bovine heparin than with porcine heparin. Onset of heparin-associated thrombocytopenia i s usually 6 to 12 days afte r i n i t i a t i o n of treatment. By i t s e l f , heparin-associated thrombocytopenia has a low morbidity (King & Kelton 1984) . However, heparin-induced thrombocytopenia (HITP) p o t e n t i a l l y increases morbidity due to thrombosis (King & Kelton, 1984; Johnstone, 1991). Becker and M i l l e r (1989) reviewed the l i t e r a t u r e on 600 reported cases of HITP, and found 50% of the cases involved thromboembolic events. Prospectively, they estimated that 10% of the 1% to 2% patients receiving heparin would have thromboembolic events. Warkentin and Kelton (1990) and Scott (1989) estimated the incidence of HITP to be 5% and between 3% and 7%, respectively. Tangible benefits could be r e a l i z e d by discontinuing the use of heparin i n flush solutions. Not only could r i s k s of thrombocytopenia and bleeding assocaited with heparin be eliminated (Johnstone, 1991) but f i n a n c i a l saving for the health care system would also be a s i g n i f i c a n t gain. 6 Since bleeding and thrombocytopenia adversely a f f e c t patients' courses of recovery, t h e i r h o s p i t a l i z a t i o n i s prolonged which increases health care costs (Peterson & Kirchhoff, 1991). Moreover, discontinuing the use of heparin would save money spent on preparation of the drug. Various centres i n Canada and the United States predicted cost savings range from $2,000 to $66,000 per year i n heparin and drug-related supplies (Swerling, 1982; Cyganski, Donahue, & Heaton, 1987; Dunn & Lenihan, 1987; Barnes, 1989; Taylor, Hutchision, Miliken, & Larson, 1989) . It i s d i f f i c u l t to predict the average cost savings for organizations i f heparin could be discontinued i n a r t e r i a l catheter flush systems. Savings estimates reported i n the l i t e r a t u r e do not address differences among centres i n the preparation of heparin solutions. In some centres preheparinized f l u s h bags are purchased, while i n smaller centres, nurses add heparin to the intravenous solutions. It i s unknown how such v a r i a b i l i t y impacts on the ov e r a l l savings that a centre may expect. As early as 1976, some f a c i l i t i e s (Deeb & DiMattia, 1976; DeFina, 1976) began using saline as the f l u s h 7 so lu t ion to maintain the patency of intermit tent venous devices (IVD). Research supported the e f f i cacy of sa l ine as compared to heparin for maintaining IVD patency (Hook, Reul ing, Luettgen, N o r r i s , E l sesser , & Leonard, 1987; Dunn & Lenihan, 1987; Taylor et a l . , 1989; Ashton, 'Gibson, & Summers, 1990) . It was suggested that the f lush ing ac t ion i t s e l f i s the major factor that i n h i b i t s c l o t t i n g , rather than the anticoagulant propert ies of heparin (Thelan et a l , 1990) . These f indings re su l t ed i n the p r a c t i c e of using sa l ine so lu t ion to f lush IVDs. Some i n s t i t u t i o n s i n Canada and the United States , decided that i f a sa l ine so lu t ion maintained patency i n IVDs, t h i s so lu t ion might also maintain patency i n a r t e r i a l catheter systems. Thus some i n s t i t u t i o n s abandoned the prac t i ce of adding heparin to the f lush so lu t ion (Barnes, 1989; Ashton, Gibson & Summers, 1990). However, there i s i n s u f f i c i e n t research to support t h i s p r a c t i c e . Studies to date are d i f f i c u l t to compare because some focus on adults while others examine c h i l d r e n . A c h i l d ' s a r t e r i e s are of a much smaller diameter than those of adul t s . In add i t ion , studies examining adults have included diverse populat ions. Some studies were 8 done with patients who had long-term catheter placement while other studies investigated patients with short-term catheter placement. Differences i n the concentration of heparin used i n the studies makes comparisons d i f f i c u l t . Outcome measures of c l o t t i n g and patency have also varied among studies. Problem Statement The most common method of maintaining a r t e r i a l catheter patency i s to use an i r r i g a t i o n system with a heparinized saline f l u s h solution. Because heparin increases the r i s k of heparin-induced thrombocytopenia (HITP), some i n s t i t u t i o n s use saline alone i n the i r r i g a t i o n system and have not reported any d i f f i c u l t i e s maintaining patency of the catheter. Although research has shown that heparin i s not required i n order to maintain an intermittent venous devices (IVD), research has yet to support the practice of using saline alone to maintain patency i n a r t e r i a l catheters. Because of inconsistencies i n the l i t e r a t u r e i t i s unknown whether heparin may be discontinued from fl u s h solutions. Moreover, i f heparin i s required to maintain patency, i t i s unknown what dose would be most b e n e f i c i a l . 9 Purpose The purpose of th i s study was to compare the ef fect iveness of two concentrations of heparin and one of sa l ine i n maintaining the patency of r a d i a l a r t e r y catheters . Theoret i ca l Framework The t h e o r e t i c a l framework for this-study i s based on factors in f luenc ing haemostasis. Three major factors relevant to haemostasis are: the degree of endothe l ia l damage, the rate and t u r b i d i t y of blood flow, and the presence of s u f f i c i e n t inherent coagulation fac tor s . Each of these factors i s discussed, followed by an explanation of how the catheter f lush system, with and without heparin, impacts c l o t t i n g i n the catheter system. Endothe l i a l damage C l o t t i n g i s l i k e l y to occur fo l lowing trauma to the vesse l because endothe l ia l damage i n i t i a t e s vasocons tr i c t ion , thus reducing blood flow from the ruptured s i t e . The body's response to i n j u r y involves smooth muscle spasm and the release of serotonin, epinephrine, and l i p o p r o t e i n , which leads to contract ion of the blood vessel (Potter & Rose, 1983) . When p l a t e l e t s come i n contact with the in jured vesse l they 10 secrete adenosine diphosphate (ADP), which t r i g g e r s p l a t e l e t aggregation to form a s t i c k y "platelet plug", which occludes the vesse l preventing further blood l o s s . Endothe l i a l damage also act ivates the coagulat ion cascade. Thus c lo t s form when vessels are i n j u r e d . Rate and t u r b i d i t y of blood flow Since p l a t e l e t s are more e a s i l y ac t iva ted and ac t iva ted coagulation factors are not washed away from the s i t e , c l o t t i n g i s more l i k e l y to occur when blood flow slows. According to P o i s e u i l l e ' s law, four factors determine the rate of blood flow: pressure i n the vesse l , length and diameter of the vesse l , and blood v i s c o s i t y . Pressure di f ferences between the various parts of the c i r c u l a t o r y system provide the force that overcomes res i s tance to blood flow, since blood flows from an area of higher pressure to an area of lower pressure. Given a constant pressure gradient , blood flow diminishes as res is tance increases . The smaller the vesse l diameter, the slower the blood flow. Plaque or other debris along a vesse l wal l decreases diameter, and therefore slows blood flow. When the vesse l wal ls are not smooth, turbulence i s created, and t h i s turbulence a f fects the free laminar flow. Eddies are formed, and 11 these can predispose to p l a t e l e t aggregation and decreased rate of flow (Thelan et a l . , 1990). C l o t t i n g also occurs more r e a d i l y with viscous blood, because blood flow varies inversely with v i s c o s i t y . C i r c u l a t i n g coagulation components In order for c l o t t i n g to occur, c i r c u l a t i n g coagulation factors must be available. Twelve factors, commonly designated by Roman numerals, have been i d e n t i f i e d (Corbett, 1992). The c l o t t i n g process includes the i n t e r a c t i o n of p l a t e l e t s , plasma, and tissue factors to culminate i n the formation of a f i b r i n meshwork. Coagulation occurs i n three phases: a) conversion of prothrombin activators, b) conversion of prothrombin to thrombin, and c) conversion of fibrinogen to f i b r i n . Just as the presence of coagulation factors sustains the c l o t t i n g process, the presence of heparin i n t e r f e r e s with i t . Heparin interferes with c l o t formation by a c t i v a t i n g the heparin cofactor or antithrombin III which prevents the following factors from working; XI l a , k a l l i k r e i n , XIa, Xa, I l a and X HIa (Corbett, 1992; Johnson et a l . , 1992) . Heparin also reduces p l a t e l e t adhesion, attenuates p l a t e l e t release e f f e c t s , and 12 impedes f ibrinogen uptake (Johnson et a l . , 1992). Therefore, when endothelium i s damaged, when blood i s stagnant, or when the concentration of any of the inherent coagulants i s high, coagulation may occur (Selkurt, 1984) . A r t e r i a l Catheter System Idea l ly , an a r t e r i a l catheter system should include the fo l lowing c h a r a c t e r i s t i c s . The catheter should be constructed of smooth materia l which decreases turbulence and does not st imulate an inflammatory response. The catheter should be of a small diameter i n order to decrease t i s sue trauma (endothel ial damage). The catheter must be inserted into a large ar tery to prevent interference with blood flow and the f lush ing s o l u t i o n must be de l ivered at s u f f i c i e n t pressure to prevent blood from backing up into the small catheter (Figure I) . Intermittent f lushing a f ter blood sampling should be i n s t i t u t e d to c l ear the catheter of blood components which could i n i t i a t e c l o t t i n g . In add i t ion , the f lush ing so lu t ion may be heparinized to decrease the l i k e l i h o o d of c l o t formation. The pressur ized f lush so lut ion prevents blood from backing up into the catheter. Because the so lu t ion used 13 var ie s from i n s t i t u t i o n to i n s t i t u t i o n , a formal comparison among the types of f lush so lut ions i s required to determine i f a p a r t i c u l a r so lu t ion can r e s u l t i n a d i f ference i n patency of a r t e r i a l catheters . To date, there has been a lack of consensus as to what type of f l u s h so lu t ion i s most e f fec t ive i n achieving patency. In th i s t h e o r e t i c a l framework the three major factors relevant to haemostasis, the degree of endothe l ia l damage, the rate and t u r b i d i t y of blood flow and the presence of s u f f i c i e n t inherent coagulat ion factors are out l ined . Components of an a r t e r i a l catheter system which may inf luence coagulat ion have a lso been discussed. Hypotheses In t h i s study i t was hypothesized that when rout ine catheter care and continuous f lush ing with 3 mL/hr of e i t h e r heparin 2.0 U/mL, heparin 1.0 U/mL, or sa l ine f l u s h so lu t ion was provided there would be: 1. no di f ference i n the occ lus ion r i s k of subjects ' r a d i a l a r t e r i a l catheters among f lush so lut ions as ind ica ted by: prothrombin time, p a r t i a l thromboplastin time, p l a t e l e t count, and the presence of c l o t s i n the so lu t ion flushed through the catheter and/or on the 14 Figure I Components of an A r t e r i a l Catheter System Pressure bag IV solution Connecting tubing cn cn X I E £ 6 E rv o •o o-Pressure monitor a 1 • 1 1 £ 1 1 Modif ied vers ion . Copyright permission obtained (1995). D a i l y , K . , & Schroeder, J . (1994) . Techniques i n bedside hemodynamic monitoring(5th ed). St . Louis : C . V . Mosby. 15 catheter t i p a f t er removal. 2. no di f ference i n frequency of occ lus ion of subjects ' r a d i a l a r t e r i a l catheters among f lush so lut ions as ind ica ted by removal of the catheter for any of the fo l lowing reasons: (a) the i n a b i l i t y to f lush the catheter , (b) the i n a b i l i t y to aspirate blood from the catheter , (c) loss of a r t e r i a l catheter waveform on the monitor. S igni f icance of the Research S c i e n t i f i c s ign i f i cance The f indings of th i s study may help i d e n t i f y some of the elements contr ibut ing to blood c l o t t i n g i n catheters . If no s i g n i f i c a n t dif ferences are noted i n catheter patency comparing three f lush so lut ions , then catheter patency may be more dependent upon the mechanical ac t ion of f lush ing and/or the pressur ized system, rather than on the anticoagulant propert ies of heparin. S ign i f i cance to pat ient care The information c o l l e c t e d from the comparison of the three types of f lush solut ions w i l l add to the body of knowledge about types of f lush so lut ions used to maintain a r t e r i a l catheter patency. The most s i g n i f i c a n t benefit r e a l i z e d to the 16 pat ients i f heparin was el iminated from the catheter f lush so lu t ion i s "the decreased r i s k of thrombocytopenia. By subs t i tu t ing a common intravenous f l u i d such as s a l i n e , pat ients would be at a reduced r i s k for developing a heparin-induced coagulation d isorder from having an a r t e r i a l catheter i n s i t u while i n the c r i t i c a l care s e t t i n g . There would be numerous f i n a n c i a l benef i ts from having heparin removed from the f lush so lu t ion of a r t e r i a l catheters . Barnes (1989) has stated that using sa l ine instead of heparin would also save nursing time. Nurses would no longer have to (a) check the p a t i e n t ' s chart for contra indicat ions to heparin, or (b) monitor the p a t i e n t ' s blood resu l t s for ef fects on coagulat ion and evidence of heparin-induced thrombocytopenia. In addi t ion to time, money would a lso be saved i f sa l ine was used to i r r i g a t e catheters . Sal ine i s less expensive than heparin and requires no extra suppl ies to prepare. The l a b e l l i n g required for the f lush bags would be s i g n i f i c a n t l y reduced. Wagner (1992) estimates that a heal th care agency of approximately 50 0 beds could save a minimum of $19,000 per year by converting to s a l i n e . 17 D e f i n i t i o n Of Terms Coronary artery bypass surgery Coronary artery bypass surgery i s a type of cardiac surgery i n which a stenosed coronary artery i s bypassed with a graft from either the i n t e r n a l mammary artery or the saphenous vein. Radial a r t e r i a l catheter A catheter inserted i n the r a d i a l artery to obtain continuous, accurate measurement of blood pressure and to allow frequent sampling of a r t e r i a l blood for tests (Holloway, 1993). Patency Patency i s a state of being open and unblocked (Como, 1990) . In the case of a r t e r i a l catheters, i t i s evidenced by (a) the a b i l i t y to e a s i l y aspirate blood from the a r t e r i a l catheter, (b) the a b i l i t y to r a p i d l y f l u s h the a r t e r i a l catheter with f l u s h solution from the bag and f l u i d i s observed flowing into the drip chamber while the f l u s h valve i s open, and (c) the appearance on the monitor of a normal a r t e r i a l waveform pattern with a d i c r o t i c notch or an acceptable a r t e r i a l pressure waveform (Como, 1990). 18 A r t e r i a l catheter occ lus ion A r t e r i a l catheter occ lus ion i s an obs truct ion of blood flow through the catheter. This i s evident i f there i s (a) i n a b i l i t y to aspirate blood from the a r t e r i a l catheter, (b) i n a b i l i t y to f lush the a r t e r i a l catheter and (c) the loss of the a r t e r i a l waveform on the monitor (Como, 1990). P o s i t i o n a l catheter A p o s i t i o n a l catheter resu l t s from a kink i n the catheter or tubing which usua l ly occurs when pat ients bend t h e i r wr i s t s . This kink dampens the waveform and hinders the drawing of blood. The waveform resembles an occluded catheter but once the arm/hand i s repos i t ioned catheter patency and the waveform returns . Occlus ion r i s k Occlus ion r i s k i s defined as the p r o b a b i l i t y of complete catheter blockage. The coagulation tests that ind ica te high occ lus ion r i s k include an abnormally low prothrombin time (PT) and p a r t i a l thromboplastin time (PTT), and an increase i n p l a t e l e t s . Clots on or i n the catheter a lso indicate a high r i s k for occ lus ion . Continuous Flushing Continuous f lushing i s a ongoing flow of water or 1 19 other l i q u i d (Como, 1990) . The a r t e r i a l i r r i g a t i o n system i s designed so that a pressur ized f lush so lu t ion i s c o n t i n u a l l y infused at 3 mL per hour through the a r t e r i a l catheter i n order to maintain patency. Intermittent Flushing Intermittent f lushing occurs when the i n - l i n e f l u s h valve i s open, thus al lowing the pressur ized IV f l u i d to infuse f r e e l y into the catheter (see Figure I) . A 3-second f lush de l ivers approximately 3 mL of f l u i d through the catheter (Hook et a l . , 1987). This type of f lush i s u s u a l l y performed fol lowing blood sampling, when checking the waveform, or a f ter repos i t ion ing the cannulated arm for re-establishment of a waveform. A r t e r i a l waveform An a r t e r i a l waveform resu l t s when changes i n a r t e r i a l blood pressure, (which occur over the cardiac c y c l e ) , are transduced into an e l ec t ron ic s igna l which i s d i sp layed on the cardiac monitor at the bedside. Dampening of an a r t e r i a l waveform Dampening of an a r t e r i a l waveform i s a d i s t o r t i o n of the pat tern seen as a decrease i n s y s t o l i c pressure, an increase i n d i a s t o l i c pressure, and loss of the d i c r o t i c notch (Hahn, 1985). 20 Haemostasis Haemostasis i s the body's rapid, controlled, l o c a l i z e d response to a blood vessel tear whereby a c l o t i s formed to prevent blood leakage from the damaged vessel and blood flow i s maintained u n t i l the torn vessel i s repaired (Wright & Shelton, 1993). Heparin Heparin i s an anticoagulant which i n h i b i t s c l o t formation. Heparin acts by means of a plasma cofactor, the heparin cofactor or antithrombin III, which inactivates several c l o t t i n g factors: X l l a , k a l l i k r e i n , XIa, Xa, H a and X HIa (Corbett, 1992) . 0.9% Sodium Chloride (saline) Saline i s an isotonic 0.9% sodium chloride solution. This solution does not contain any factors which a f f e c t blood coagulation. Clot A c l o t i s defined as "a s e m i - s o l i d i f i e d mass, as of blood or lymph" (Miller & Keane, 1992, p. 226). In t h i s study, presence of c l o t s was detected by aspira t i n g blood from the a r t e r i a l catheter and expressing i t onto a gauze pad. At the time of catheter removal, microaggregates not v i s i b l e to the human eye are not considered 21 c l i n i c a l l y s i g n i f i c a n t (Ashton et a l . , 1990). Prothrombin Time (PT) Prothrombin, or Factor II , i s a coagulation fac tor (plasma protein) produced i n the l i v e r that i s necessary for c l o t t i n g i n the e x t r i n s i c system. Prothrombin time (PT) measures the a c t i v i t y of c l o t t i n g factors V, VII , X, prothrombin, and f ibr inogen. A def ic iency i n any of these factors leads to a prolongation of the PT. PT i s the only laboratory test used to measure the ef fect iveness of anticoagulant drugs such as warfar in sodium (Corbett, 1992). The normal PT i s 11 - 13.5 seconds (S) (as per Hospi ta l Laboratory normals, 1987) . P a r t i a l Thromboplastin Time (PTT) P a r t i a l thromboplastin time, a nonspeci f ic t e s t , can demonstrate a lack of any of the various c l o t t i n g factors that funct ion i n the i n t r i n s i c c l o t t i n g system, except Factors VI and XIII . The PTT i s a very useful test for detect ing the presence of many types of bleeding disorders caused by defect ive or de f i c i en t c i r c u l a t i n g factors within the i n t r i n s i c system. P a r t i a l thromboplastin time (PTT) i s used to monitor heparin therapy because heparin, a shor t -ac t ing anticoagulant that c i r c u l a t e s i n the plasma, increases the PTT 2 2 (Corbett, 1992) . Normal PTT i s 25-34 seconds (S) (as per Hosp i ta l Laboratory normals, 1987). P l a t e l e t Count P l a t e l e t s are fragments of cytoplasm. As p l a t e l e t s adhere to the wal l of an in jured vesse l , they clump together (or aggregate) and release substances that begin the coagulat ion process (Corbett, 1992) . Normal p l a t e l e t count (PC) ranges between 150 - 400 G/L (as per Hosp i ta l Laboratory normals, 1987). Organizat ion of the Thesis This thes is i s comprised of f ive chapters. In Chapter One, the background to the problem, problem statement, purpose, t h e o r e t i c a l framework, research questions, s ign i f i cance of the research, and d e f i n i t i o n s have been presented. In Chapter Two, a review of se lected l i t e r a t u r e pert inent to the research problem i s presented. In Chapter Three, the research methods, inc lud ing a descr ip t ion of the research design, sampling procedure, data c o l l e c t i o n instruments and procedure, data ana lys i s , assumptions, l i m i t a t i o n s , e th ic s , and human r ight s are out l ined . Chapter Four includes the d e s c r i p t i o n of the sample, presentat ion of f ind ings , and a d i scuss ion of the r e s u l t s . The summary, conclusions , 23 impl ica t ions for nursing p r a c t i c e , and recommendations for future research are presented i n Chapter F i v e . 24 CHAPTER TWO Review of the L i t e r a t u r e Introduction The purpose of th i s chapter i s to present an analys i s of se lected l i t e r a t u r e r e l a t i n g to the c e n t r a l elements i d e n t i f i e d i n the t h e o r e t i c a l framework. The f i r s t sect ion examines the l i t e r a t u r e i n r e l a t i o n to the a r t e r i a l catheter system, the three major factors r e l a t e d to haemostasis, and how the a r t e r i a l catheter system af fects and i s affected by the components of haemostasis. Next, because the sample i n th i s study was cardiac surgery pat ients , ways the surgery may af fec t the a r t e r i a l catheter system and haemostasis are descr ibed. F i n a l l y , the l i t e r a t u r e focusing on the f lush so lu t ion required for the a r t e r i a l system i s discussed. A r t e r i a l Catheter System The a r t e r i a l catheter must remain patent for as long as the pat ient requires blood sampling and/or blood pressure monitoring. Thrombus formation i n the catheter lumen compromises catheter funct ion and the p a t i e n t ' s c i r c u l a t i o n . Thus the a r t e r i a l catheter system i s designed to prevent thrombus formation and subsequent a r t e r i a l occ lus ion (Civetta , Taylor & Kirby , 1988). 25 As out l ined i n Chapter One, the three factors that inf luence thrombus formation are: endothe l ia l damage, rate and t u r b i d i t y of blood flow, and coagulat ion fac tor s . The a r t e r i a l catheter system i s designed to reduce the impact of each of these three f a c t o r s . Catheter design and i n s e r t i o n techniques l i m i t endothe l ia l damage and allow blood to flow f r e e l y around the catheter . The pressur ized, continuous f lush system prevents blood from stagnating i n the catheter lumen. The f lush so lu t ion d i l u t e s coagulation fac tors , and, i f i t contains heparin, may have an anticoagulant e f fect on blood i n the lumen. Catheter Endothe l ia l damage stimulates haemostasis. Work has been done i n two areas to decrease damage to the endothelium and i n h i b i t coagulation: the design of the catheter and the i n s e r t i o n techniques. Design The catheter may stimulate coagulation because i t i s fore ign object . Advances i n technology have improved a r t e r i a l catheters so that the body's response to the catheter as a foreign body i n the ar tery i s minimized. Bedford and Wollman (1977), and Gardner et a l . (1974) 2 6 compared polyethylene to t e f lon catheters and determined that t e f l o n catheters were less thrombogenic. The authors found that the t e f l on coating i n h i b i t s p l a t e l e t a c t i v a t i o n which reduces haemostasis (Gardner et a l . , 1974). Barret t & Lester , (1990) stated that t e f l o n catheters provided a smooth catheter in ter face with blood and reduced the r i s k of c l o t t i n g complicat ions . Insert ion techniques A r t e r i a l cannulation creates trauma which r e s u l t s i n endothe l ia l damage. Vascular i n j u r y t r iggers vasospasm, haemostasis and inflammatory responses (Wright & Shelton, 1993). Insert ion techniques have been re f ined to minimize endothe l ia l i n j u r y to decrease the r i s k of haematoma. Haematomas may cause compression on the a r t e r i a l vesse l and are assocaited with vasospasm. The more times the a r t e r i a l wal l i s transgressed the greater the r i s k of endothe l ia l damage. Repeated cannulations or attempts at cannulation increase the r i s k of vasospasm and/or scar t i s sue formation, both of which increase the r i s k of a r t e r i a l occ lus ion . Some degree of endothe l ia l damage does occur when the anaesthetist inser t s the a r t e r i a l catheter p r i o r to cardiac surgery. However, over time the improvements i n i n s e r t i o n techniques have 27 minimized i n j u r y to the vesse ls . Flush System Slowed and stagnant blood flow promotes haemostasis. The f lush system i s designed to'al low adequate blood flow around the catheter and prevent blood from stagnating i n the catheter lumen. The s ize of the ar tery , s ize of the catheter , pressur ized f lush system, and durat ion of cannulat ion a l l inf luence catheter patency. Size of the ar tery The rate of blood flow i s d i r e c t l y proport iona l to the s i ze of the ar tery; the smaller the diameter of the ar tery the less the blood flow and the greater the l i k e l i h o o d of occ lus ion . Since women have smaller a r t e r i e s than men, they are more l i k e l y than men to experience occ lus ion (Civetta et a l . , 1988; American Assoc ia t ion of C r i t i c a l Care Nurses, 1993). It i s recommended that catheters be inserted in to large a r t e r i e s to prevent i n t e r r u p t i o n of blood flow. The r a d i a l ar tery i s the most commonly se lected a r t e r y for cannulation i n adults because i t i s easy to access and v i s u a l i z e . Moreover i t i s associated with fewer problems re la ted to k inking due to limb p o s i t i o n i n g . I f c i r c u l a t i o n i s compromised by cannulat ion, the u lnar 28 ar tery w i l l provide s u f f i c i e n t blood flow to the hand (Woods, F r o e l i c h e r , Halpenny, & Motzer, 1995). Blood vesse l diameter i n c h i l d r e n i s s i g n i f i c a n t l y smaller than i n adul t s . When a r t e r i a l l i n e s are inser ted i n in fants , the u m b i l i c a l cord i s the pre ferred s i t e , un l ike the r a d i a l ar tery used i n c h i l d r e n and adul t s . Size of the catheter Obstructions to blood flow promote thrombus formation. The s ize of the catheter must be propor t iona l to the diameter of the cannulated ar tery to allow unobstructed blood flow around the catheter . In r a d i a l a r t e r i e s , a 20-gauge, 3.8 -- 5.1 cm", non-tapered t e f l o n catheter i s rout ine ly u t i l i z e d . Bedford and Wollman (1977) reported a higher incidence of thrombus formation with the 18-gauge catheter. The 18-gauge catheter has a 20% greater surface area than the 20-gauge catheter . Downs, Chapman, and Hawkins (1974) a lso found a s i g n i f i c a n t l y lower incidence of vascular occ lus ion with 2 0-gauge catheters than with 18-gauge catheters . Pressurized system A pressur ized f lush system was developed to prevent blood from c o l l e c t i n g i n the catheter. Stagnant blood i n the catheter lumen i s at r i s k of c l o t t i n g . The purpose for both the continuous and the intermit tent f lush i s to keep blood out of the catheter lumen and f lush f i b r i n deposits from the catheter wal l s . Continuous f lush The pressur ized system continuously f lushes blood from the catheter lumen to maintain patency. An infuser bag pressurizes the f lush system to 300 mm Hg which d e l i v e r s a regulated amount of f lush so lu t ion (3 mL per hour) to c l ear the catheter of blood. Reducing the pressure of the infuser bag decreases the amount of f l u s h so lu t ion de l ivered , increas ing the r i s k of blood backing up into the catheter and c l o t t i n g (Hart, Gibbs, Cameron, Hi l lman, Thompson, & Oh, 1984) . Intermittent f lush Intermittent f lushing of the a r t e r i a l catheter system i s a lso necessary to maintain catheter patency. The i n - l i n e f lush device i s used to c l ear blood from the catheter lumen. Blood sampling, waveform dampening and a p o s i t i o n a l catheter are associated with the presence of blood or f i b r i n bui ld-up which may occlude the catheter lumen. Samples are obtained by a s p i r a t i n g blood from the tubing. Once sampling i s complete, the tubing must be manually f lushed to c l ear the blood remaining i n the 30 tubing and catheter (Holloway, 1993) . A dampened a r t e r i a l waveform, as v i s u a l i z e d on the cardiac monitor may be caused by f i b r i n build-up or c l o t formation (Holloway, 1993) which i s removed by the mechanical action of the pressurized flush. When the p o s i t i o n of the patient's wrist obstructs catheter patency, the wrist must be repositioned and a manual fl u s h performed to cl e a r the catheter of any blood or debris. The number of intermittent flushes required could be a s i g n i f i c a n t factor influencing catheter patency. Hook and colleagues (1987) and Hook (1988) both indicated t h i s was an important issue to be considered and included a 3 mL manual f l u s h each hour i n t h e i r studies. Conceivably, the more times the catheter i s flushed the less the l i k e l i h o o d of thrombus b u i l d up or c l o t formation i n the catheter. Duration of Cannulation The duration of r a d i a l artery cannulation appears to be a factor contributing to a r t e r i a l occlusion. Bedford and Wollman (1973) found that 2 0-gauge cannulas inserted for 1 to 3 days produced an 11% rate of a r t e r i a l occlusion, whereas those inserted for 4 to 10 days resulted i n a 29% incidence of occlusion. The longer the 31 catheter remains i n s i t u , the more l i k e l y i t i s that thrombin and other debris can c o l l e c t i n and around the catheter (Hart et a l . , 1984). This b u i l d up of debris gradual ly diminishes blood flow which then aids i n coagulat ion. Although t e f l on catheters are less thrombogenic, the i r r i t a t i o n of the catheter t i p on the a r t e r i a l wal l increases the r i s k of endothe l ia l damage creat ing an increased r i s k of occ lus ion . Furthermore, arm movement re su l t s i n an increased r i s k of inflammation i n the vesse l (Woods et a l . , 1995). In t h i s researcher's experience, over time, the catheter also begins to kink at the s i t e of i n s e r t i o n due to limb p o s i t i o n i n g . Any obs truct ion of blood flow can increase the chances of c l o t formation. Flush So lut ion U n t i l recent ly , f lush solut ions contained heparin, an anticoagulant which in ter feres with the coagulat ion cascade (Civet ta , 1988). T h e o r e t i c a l l y , any blood backed up into the catheter lumen does not c l o t i n the presence of heparin therefore the r i s k of thrombus formation i s decreased. However, the use of heparin i n f l u s h so lut ions places the pat ient at r i s k for bleeding problems. Therapeutic doses of heparin increase the 32 p o t e n t i a l for haemorrhage. Although the concentrat ion of heparin i n f lush solut ions i s far less than the therapeutic dose, there have been reports of heparin-induced thrombocytopenia i n pat ients who received smal l , in termit tent bolus doses of heparin from catheter f lushes ( R i z z o l i , M i l l e r , Rick & Lotze, 1988; and Young, Ehrenpreis , Ehrenpreis , & Kirshblum, 1989). It has been shown that heparin-dependent p l a t e l e t antibodies are present i n the serum of most pat ients su f f er ing thrombocytopenia, and i t i s general ly be l ieved that the thrombocytopenia resu l t s from i n j u r y to p l a t e l e t s (Cines, Tomaski, & Tannenbaum, 1987). A higher incidence of thrombocytopenia has been reported i n pat ients who receive bovine heparin compared to porcine heparin (King & Kelton, 1984) . The r i s k of HITP has led nurses and other heal th care profess ionals to question the necess i ty of using heparin for routine catheter maintenance (Thelan et a l . , 1990; Broughton, S. 1995). A v a r i e t y of f lush solut ions have been reported to maintain a r t e r i a l catheter patency. However, there remains no consensus i n the l i t e r a t u r e about which i s the best s o l u t i o n . In th i s inves t i ga tor ' s experience a v a r i e t y of f lush solut ions have been used i n the f l u s h 33 system without loss of catheter patency. General ly , the amount of heparin i n the f lush so lu t ion i s very minute. Bolgiano, Subraniam, Montanari and Minich , (1990) compared .25 U/mL of heparin to sa l ine and found there was no di f ference i n catheter patency. The question remains, i s sa l ine alone s u f f i c i e n t to keep the catheter patent? The answer i s s t i l l unknown and a c r i t i q u e of the relevant research i s presented i n the f i n a l p o r t i o n of t h i s chapter. Surg ica l Factors Influencing Occlusion and Occlusion Risk Because the populat ion studied consisted of pat ients undergoing cardiac surgery, the e f fects of the surgery on the f lush system and haemostasis are reviewed. The s u r g i c a l factors discussed are: ra t iona le for cannulat ion, frequency of cannulation attempts, and the cardiopulmonary bypass pump. Rationale for Cannulation Every pat ient who has cardiac surgery requires an a r t e r i a l catheter for hemodynamic monitoring and blood sampling p e r i - and pos t -operat ive ly . The average durat ion of cannulation for the f i r s t time cardiac surgery pat ient i s 24 to 48 hours. Patients are assessed 34 for c o l l a t e r a l c i r c u l a t i o n to the hand p r i o r to the catheter i n s e r t i o n to ensure patent r a d i a l and u lnar a r t e r i e s (Woods et a l . , 1995). In the operating room a #20 Tef lon r a d i a l ar tery catheter i s inserted in to the pat ient by the' anaesthet is t . Catheter i n s e r t i o n i s performed by experienced anaesthetists to minimize f a i l e d cannulat ion attempts and reduce the r i s k of endothe l ia l damage. Bypass Pump During coronary bypass surgery, the heart i s arres ted and the lungs are not v e n t i l a t e d . A cardiopulmonary bypass machine oxygenates and removes carbon dioxide from the blood, then pumps i t through the p a t i e n t ' s body to perfuse t i ssues and preserve organ funct ion . The bypass pump in ter feres with coagulat ion i n several ways. R o l l e r pumps compress the venous blood f i l l e d c i r c u i t r y , continuously p r o p e l l i n g blood through the oxygenator for gas exchange and then back to the pat ient (Holloway, 1993) . These r o l l e r s can act ivate p l a t e l e t s and other coagulation factors deplet ing the components necessary for haemostasis. To maintain free flow through the c i r c u i t r y tubing, 35 the p a t i e n t ' s blood i s hemodiluted. The a d d i t i o n a l f l u i d decreases blood v i s c o s i t y and improves blood flow through the c a p i l l a r i e s but d i l u t e s the components necessary for haemostasis. To prevent the blood from c l o t t i n g i n the cardiopulmonary c i r c u i t , high doses of the ant icoagulant , heparin, are administered. Heparin i s given as a 20,000-3 0,00 0 un i t IV bolus at the s tar t of heart - lung bypass, followed by a d d i t i o n a l boluses to maintain the ac t iva ted c l o t t i n g time 4-6 times greater than normal (Holloway, 1993) . At the conclusion of cardiopulmonary bypass, heparin i s reversed with protamine sulphate, a heparin antagonist . Inadequate heparin reversa l i s a p o t e n t i a l cause of postoperative bleeding abnormal i t ies , as i s heparin rebound. Rebound occurs when heparin that has been sequestered i n t i ssues i s released in to the c i r c u l a t i o n . Heparin Candidates for cardiac surgery may be rece iv ing anticoagulants p r i o r to t h e i r surgery. A s p i r i n i s commonly prescr ibed for pa t i en t ' s with coronary ar tery disease . A s p i r i n has a profound i n h i b i t i n g a f fec t on p l a t e l e t funct ion . Although a s p i r i n consumption i s 36 u s u a l l y discontinued p r i o r to the surgery, i t s e f fec ts may continue into the postoperative per iod . P l a t e l e t i n h i b i t i o n may decrease the r i s k of catheter occ lus ion i n the postoperative per iod . Heparin i s a potent anticoagulant . Just as the presence of coagulation factors sustains the c l o t t i n g process, the presence of heparin in ter feres with i t . Heparin exerts i t s anticoagulant ef fect i n the presence of the plasma cofactor , ant i thrombin-III , a n a t u r a l l y occurr ing a lpha-2 -g lobu l in . Together, heparin and ant i thrombin-III complex bind and prevent conversion of c e r t a i n coagulation factors (King & Kelton, 1984) . However heparin may increase the r i s k of thrombocytopenia. Although the heparin administered during the surgery i s reversed by protamine sulphate, i t s inf luence i s monitored postoperat ive ly . Coagulation studies are done to determine any re s idua l e f fects of the heparin . Heparin has i t s greatest ef fect on PTT. PT i s a lso measured. P la te l e t counts help measure t h e i r consumption by the bypass machine and the e f fects of heparin . Coagulation studies done immediately a f t er the surgery ind icate the status of the pa t i en t ' s a b i l i t y to c l o t . Prolonged PT and/or PTT or decreased p l a t e l e t counts ind icate a l t ered haemostasis which could poss ib ly lessen the r i s k of a r t e r i a l catheter occ lus ion . Heparin i s added to intravenous f l u i d (usually 0.9% sodium chloride) and i s continuously infused through the a r t e r i a l catheter to maintain catheter patency and to reduce thromboembolic complications ( C l i f t o n et a l . , 1991) . H i s t o r i c a l l y , heparin has always been added to the f lush so lu t ion to maintain a r t e r i a l catheter patency. The use of heparin i n the f lush so lu t ion has now become quest ionable. Review of Studies on Flush Solut ions Eight studies compared the ef fect iveness of d i f f e r e n t f lush solut ions i n maintaining a r t e r i a l catheter patency (Table 1). These studies are described i n r e l a t i o n to the sample, f lush so lu t ion , catheter type, outcome var iab le s and r e s u l t s . A c r i t i q u e of the research follows the presentat ion of the i n d i v i d u a l s tudies . Of the eight studies reported, two studies used c h i l d r e n and s ix used an adult populat ion. Some of the studies were done with adult s u r g i c a l pat ients and others were done with a combination of medical and s u r g i c a l 38 pat i en t s . Studies var i ed i n the information reported. For instance, they d id not speci fy the catheter type or used d i f f e r e n t types of catheters . Adult Studies The re su l t s of the s ix studies of adul ts , were d i f f i c u l t to compare because the samples were not s i m i l a r i n diagnosis , age (not accounted f o r ) , and reasons for admittance to the ICU se t t ing . There was no information as to how long the pat ients required t h e i r a r t e r i a l catheters , the durat ion of the cannulation nor i f other a r t e r i a l catheters had to be inserted during the stay i n the ICU. Both Hook and colleagues (1987) and ' Hook (1988) compared 2.5 U/mL heparin i n 500 mL of Ringer's Lactate to non-heparinized Ringer's Lactate i n two groups of 25 adult cardiovascular surgery pat i ents . These studies were the only ones with open heart surgery pat ients i n t h e i r sample, which makes i t more comparable to t h i s i n v e s t i g a t o r ' s study. However, the sample was not l i m i t e d to type of surgery, or to e l e c t i v e versus emergency scheduling, or to f i r s t time operation versus re -operat ion . Although many of the subjects were rece iv ing some form of anticoagulant p r i o r to t h e i r 39 surgery, and some subjects received more than one, no contro ls were put i n place for th i s v a r i a b l e . No s t a t i s t i c a l l y s i g n i f i c a n t di f ferences i n p l a t e l e t counts were reported i n e i ther f lush group before or a f t er surgery. No c lo t s were observed i n e i ther of Hook's studies when the catheters were removed wi th in 72 hours of i n s e r t i o n . These were a lso the only studies that found there was no s i g n i f i c a n t d i f ference i n patency of a r t e r i a l catheters between those maintained with sa l ine versus a heparinized f lush so lu t ion . Two weaknesses of these studies were that the samples were not randomized and there was no double b l i n d process which could have been a confounding fac tor . Ouelette and Eisner.(1992) compared the e f fects of sa l ine and 2.0 U/mL of heparin i n f lush so lut ions i n 78 adult s u r g i c a l ICU pat ients . Half of the subjects had the f lush so lu t ion containing heparin 2 U/mL i n sa l ine and the other ha l f received sa l ine as the f lush s o l u t i o n . Information about catheter and coagulation studies were not provided. The strength of th i s study was the double b l i n d randomized design. This study i s a lso i n t e r e s t i n g 03 E E co i -_ i 3 CO I U J DC CO U J I CQ < OC U J O o 3 o PL _ U J < o g r-3 _ l o I co z o 3 0 OC < O o Q. < CO oj ra t-o x h-3 < ID £ ra CL c 0 1 3 0) •c 0 CL o> c g ra £ tw c (fl 0 3 c res ra —* a. w <- > <u 8 w <2 — tn -O C ± S o ui .ra = tr 1 ra oj in 1 £r o a> _ <D ro £ a. ra (U •a o •§ E C C CM 1 1 r-_ 3 § & cog a) 2 o> _ i OJ 6 ra ™ £ ? •= _ i ro 3 _ E «= a: t o Q. m o CM o 1 IT) CL E 0 tn ro ra "c <fl co it ca pat 0 c CD z> 'c x> 0) ro O ) > c 0 0 m 0 a) (0 O O fl) o o .£ 1 1 a less T J less c aj less o> N 3 cf O" 0 OJ « Q . ra a) 0J 3 -C T J mo c mo ro etei £ j= J Z 3 E ro 0 ess efon a3 0. > ra on *= 3 - sh O O "o co a. >. c 3 0 'c 0 ra (D CO CO ccur amp roup z ro T J CO ro o. 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(fl 0) 0J E E ra T J CL C ro 3 oj _ O E g T T S 3} 0 0 3 T ~ _ (fl S T J = 0) JO N ro O CO . = C L c 9 -- C L O (fl * J ^ oj c a; 0 OJ c c « £ 3 ™ sg 5 a- 5 c c 0 S U= CO g 0J E i o<=± ~° u= "= 0) !*= 52 ro c o £ S2 = c £ ° = — co -5 ro U) (fl c co ro £ (fl o y-co 'c c «> o> o ra = Q. 1 S CO £ S a> 1 ra a> ° I (n ra ra u oc3 O V N C » . a CM — E B o (U •n CJ O OJ 0J 0 - E O =J ' € ° "> CD =J T J S s co £ co 5 ro i_ cn 0) o » C M £ * ro 1 o [em line tn ra (A tn c si * tn c Z3 (C= ro tn 0) Q . c 0) x; 0 tn ra ZJ CL (A _ l c no 0 s E on a> 01 3 0 CN 0 3 O oj E o ro ~ oj (n -± oj > o 5 ro j= oj " S 0) o 0J ra -5 o E •sz to 3. *- v. O TJ 0) (n 0 T J uj c: j= 3 a) (fl cn 5= CM oj ^ 1- ra T J C r-oj ra c IM x: •- — o 4 0 ro ~ i_ ,^ ro 5 E 0) CD 8 ?ifi S •j= OJ _ (n ra >-_^ 0J 0) L . OJ £ £ c u> ra ro oi 3 o o o> (£= to ro o E " S B ^ 0) o £ OJ £ 3? a) „ u - •53 00 0J CN j— CN CJ) ro co — cn co o) 00 aj 1 1 S 1 o (fl CO T J rj 0 c 0) T J ifie ns eta "c 0 ro de "3 tn — 0 <D tn CO on: T J rin ro ize 0) c c: c 0) ro "ro 0 a. en c= OJ 0 J Z ra c 0 c no no cz 0 — 1 c ra —1 0) -jz: _ g . N J] 0) O ) = ± ! - S J O E <2 E = c g 3 ro 0 co ?5 E T J fc C) C O 0) CO < < O Z g l 3 I CO UJ DC I CO LU _J CO. < 2 o o Z5 o Q. _ UJ X < o o I -_ o co z o CO _ < 0 . _ o o UJ _l a. < CO TJ <D O ro a. o c -•5, <" S _ j_ _ _ ra o Q. »- TJ <D _ = 1 a) o 01 V. ra a> cu 2 1 £ » S S <u CD j r 2> ro ro o ra o _ , 5 2 _ E CO CO c 2 Z c c c T — _1 _i o E E » = ^ IS Co T - urr -i .1 CO CO (/) a a D a) a) t J C _= . _ : "ra "O •— CD a i $ 2 O) _ ro o o c o >* (0 TJ •- > .2 CD |> 0 CD c § -g 5 1 'ro | ro J> o _ O) S _2 o 3 c o c c (/> >> ra TJ CM TJ c ra Q. Q. _ _ o O O) O) TJ TJ 0) CD N . _ C _C ra ro CL Q. CD <D J_ J_ I/) _ 0 C <= S .2 °-_ 3 _ ro _ o ro o o CD o. & TJ CO c ro co TJ o <D <D = roe J 3 ° p ro n c D) _ 3 • (0 i •_ TJ ro <= t £ co « 41 42 because i t was the only study to evaluate observable c r i t e r i a for catheter occ lus ion , such as: d a i l y assessment of waveform q u a l i t y , the c o r r e l a t i o n of i n t r a - a r t e r i a l blood pressure to cuff blood pressure, the ease of blood withdrawal, the a b i l i t y to f l u s h the a r t e r i a l l i n e , and the number of times the l i n e was accessed and l a t e r f lushed for blood sampling. The sa l ine f l u s h group experienced a shorter durat ion of catheter patency, less accurate blood pressure readings v i a the a r t e r i a l l i n e as compared to cuff pressures, and more frequent dampening of the waveform than the heparinized group. Four areas that could af fect the f indings of th i s study were not discussed: (a) the s u r g i c a l procedures performed on the subjects; (b) the length of time the a r t e r i a l catheters were i n s i t u , (c) i f anticoagulants were administered i n the pre-operative or post-operat ive phase of recovery, and (d) r e s u l t s of any coagulat ion t e s t s . Bolgiano and colleagues (1990) compared catheter patency using two concentrations of heparin, 1.0 units/mL and 0.25 units /mL, i n 104 medical and s u r g i c a l adult ICU pat i en t s . The #20 j e l c o a r t e r i a l catheter was discontinued a f ter three days, the routine durat ion of cannulation i n t h e i r s u r g i c a l intens ive care u n i t . PT, PTT and p l a t e l e t s were monitored p r e - i n s e r t i o n , on the f i r s t and t h i r d days of cannulat ion and fo l lowing removal of the a r t e r i a l catheter . Only two l i n e s c l o t t e d out of the 104 catheters; one, u t i l i z i n g a f l u s h 43 so lu t ion of 0.25 U/mL heparin, was i n place for 108 hours, and the other catheter, u t i l i z i n g a f lush so lu t ion of 1 U/mL, was i n s i t u for 23 hours. This was the only study that measured the e f fects of such a small concentration of heparin i n the f lush s o l u t i o n . The strengths of Bolgiano et al. . ' s study were the use of a large sample, the comparison of two types of f l u s h so lu t ion , and the comparison of PT, PTT and p l a t e l e t s . There were no s t a t i s t i c a l di f ferences between the two groups i n PT and PTT or length of time the catheters remained patent . The authors concluded that .25 U/mL heparin was s u f f i c i e n t to maintain catheter patency for up to three days. They suggested that another study comparing 1 U/mL heparin to sa l ine be done and any di f ferences be measured. C l i f t o n and colleagues (1991) compared the e f f i c a c y of sa l ine versus a higher than usual heparin concentrat ion for maintaining a r t e r i a l catheter patency i n 30 adult medical ICU pat i en t s . One group received a f lush so lu t ion of sa l ine and the other group received heparin 4 U/mL i n s a l i n e , both at a flow rate of 3 c c / h r . P la te l e t counts and PT were done p r i o r to catheter i n s e r t i o n , then 24, 48, 72, and 96 hours post catheter i n s e r t i o n . If any catheters were discontinued p r i o r to the 96 hours, the same blood tests were repeated. C l i f t o n and colleagues detected s t a t i s t i c a l l y s i g n i f i c a n t d i f ferences i n patency rates between the 2 groups. While there were no s i g n i f i c a n t changes i n p l a t e l e t counts or 44 prothrombin times i n e i ther of the two groups, the inves t igators reported that a concentration of 4 U/mL of heparin resu l ted i n a catheter s u r v i v a l rate of 86% at 96 hours, while catheters maintained with sa l ine had only a 52% s u r v i v a l rate a f ter 40 hours. The fact that the concentrat ion of heparin i n t h i s study was double that of any other study could have l a r g e l y contributed to the r e s u l t s . Catheter s u r v i v a l was not defined i n the study, however catheter occ lus ion was defined as the i n a b i l i t y to withdraw blood f r e e l y through the a r t e r i a l l i n e . No information was provided as to when a r t e r i a l catheters were removed. The authors found the use of sa l ine as a continuous f lush so lu t ion was associated with an increased frequency of catheter occ lus ion and malfunction compared to the f lush s o l u t i o n containing heparin. The strength of t h i s study was the double -b l ind randomized design. The information descr ib ing the subjects i n the sample was i n s u f f i c i e n t because no information was provided about the underlying medical condit ions which may have affected coagulat ion. They d i d not report PTTs e i ther which i s the test most profoundly af fected by heparin . The American Assoc ia t ion of C r i t i c a l Care Nurses (AACN), (1993) conducted a m u l t i - s i t e study, e n t i t l e d the Thunder Projec t , which evaluated the ef fects of heparinized and nonheparinized f lush solut ions on the patency of a r t e r i a l 45 pressure monitoring l i n e s . The major strength of t h i s study-was that 5139 pat ients from 198 f a c i l i t i e s were randomly assigned to double-bl inded treatment groups of heparinized and nonheparinized f lush so lut ions . The concentrations of heparin were not s p e c i f i e d . Data on the presence of acceptable square waveform and a r t e r i a l backflow were c o l l e c t e d at four hour i n t e r v a l s for up to 72 hours. The re su l t s of the study ind ica ted that a r t e r i a l pressure monitoring l i n e s maintained with heparinized f lush solut ions had a s i g n i f i c a n t l y greater p r o b a b i l i t y of remaining patent over time than l i n e s maintained with nonheparinized f lush so lu t ions . Because the sample was large , data on four other var iab le s could be analyzed to show that they s i g n i f i c a n t l y increase the p r o b a b i l i t y of the l ine s remaining patent: (a) the pat ient rece iv ing other anticoagulants or thrombolyt ics , (b) having a catheter longer than 2 inches, (c) using the femoral i n s e r t i o n s i t e , and (d) being of the male gender. This study concluded that chances for patency were greatest i n men with long femoral l i n e s who received other anticoagulants or thrombolytics and heparinized f lush so lu t ions . Because the sample s ize was large , th i s study could be regarded as the strongest study conducted to date. Unfortunately, there was l i m i t e d information about the type of f lush so lut ions used so the amount of heparin was not contro l l ed for i n the study. In add i t ion there were no coagulation tests measured. Further 46 weaknesses of the study were that a large number of the subjects had received anticoagulants and thrombolytic agents during the study period and a va r i e t y of a r t e r i a l catheter types were used. These confounding factors make i t d i f f i c u l t to compare the findings of t h i s study to others. Critique of Adult Studies In three of the six studies, the designs were double blinded and randomized (Oulette & Eisner, 1992; Bolgiano et a l . , 1990; C l i f t o n et a l . , 1991). Hook and colleagues (1987) and Hook (1988) used a convenience sample and the American Association of C r i t i c a l Care Nurses (1993) used a randomized design with a m u l t i - s i t e p a r t i c i p a t i o n . Random assignment strengthens the external v a l i d i t y of the study thus allowing for the findings to be applied to other populations. Some studies did report variables that could a f f e c t the outcome of the t r i a l . Only Bolginao and colleagues (1990), Butt and colleagues (1987), and C l i f t o n and colleagues (1991) provided information about catheter type. Bolgiano and colleagues (1990) and C l i f t o n and colleagues (1991) both chose the larger #20 gauge catheter which t h e o r e t i c a l l y allows for fr e e r blood flow to minimize the r i s k of c l o t formation. In the studies by Hook and colleagues (1987), Hook (1988), and Bolgiano and colleagues (1990) the a r t e r i a l catheters were i n s i t u for only 72 hours. The other two studies d i d not specify the duration of a r t e r i a l cannulation. 47 A l l s i x adult studies spec i f i ed outcome v a r i a b l e s . However only four studies measured p l a t e l e t counts (Hook et' a l . , 1987; Hook et a l . , 1988; Bolgiano, 1990; C l i f t o n et a l . , 1991) . Only Hook and colleagues (1987) and Hook (1988) recorded any observations of c lo t s on or i n the catheter at the time of catheter removal. Two studies used observable i n d i c a t o r s instead of coagulation factors for outcome var iab le s (Oulette & Eisner , 1992; American Assoc ia t ion of C r i t i c a l Care Nurse, 1993). Oulette & Eisner (1992) found a shorter catheter patency durat ion through observable outcome v a r i a b l e s , less accuracy of the a r t e r i a l pressure compared to the cuff blood pressures, and more frequent dampening of waveform patterns with sa l ine so lut ions . Several studies have been conducted which attempt to answer the question of what f lush so lu t ion i s best to maintain catheter patency (Johnstone, 1991), but the v a r i e t y of f l u s h so lut ions used i n the s ix adult studies c r i t i q u e d make i t d i f f i c u l t to compare the f indings . Hook and colleagues (1987) compared 2.5 U/mL of heparin i n a Ringer's Lactate s o l u t i o n to p l a i n Ringer's Lactate . Bolgiano and colleagues (1990) compared a small concentration of heparin (.25 U/mL) to the more usual 2 U/mL concentration of heparin i n an unspec i f i ed so lu t ion , but d id not use a non-heparinized s o l u t i o n . C l i f t o n et a l . (1991) compared a heparinized f lush of 4 U/mL to a sa l ine f lush at a flow rate of 3 mL/hr. Oulette and Ei sner 48 (1992) compared 2 U/mL of heparin to sa l ine but d i d not report the length of time for catheter patency. The American Assoc ia t ion of C r i t i c a l Care Nurses (1993) used heparinized f lush so lut ions but nei ther the concentration of heparin nor the so lu t ion was s p e c i f i e d . Of the s ix studies , two studies (Oulette and E i s n e r , 1992; Bolgiano et a l . , 1990) found heparin re su l t ed i n a greater degree of catheter patency. C l i f t o n and col leagues (1991) and the American Assoc ia t ion of C r i t i c a l Care Nurses, (1993) reported greater p r o b a b i l i t y of maintaining patency over 72 hours i f the f lush so lut ion was heparinized. Hook and colleagues (1987) and Hook (1988) both found no d i f ference i n patency rates with or without heparin i n the f lush s o l u t i o n . However, only Hook and colleagues (1987) had hourly manual f lushes of 3 cc of the non-heparinized f l u i d . This suggests that the f lush ing act ion may be the most c l i n i c a l l y s i g n i f i c a n t fac tor i n maintaining a r t e r i a l catheter .patency, and not the heparin. To date there i s i n s u f f i c i e n t data to support t h i s not ion. Descr ip t ion and C r i t i q u e of Paediatr ic Studies Butt and colleagues (1987) invest igated the e f fects of 1.0 U/mL and 5.0 U/mL of heparin and infus ion rates of 1 mL/hr and 2 mL/hr on a r t e r i a l catheter patency. A sample of 470 c h i l d r e n was studied but no information about the age or type of pat ient was reported. A #22 gauge catheter was inser ted 49 into the r a d i a l ar tery i n 81% of the subjects , l eaving 19% of the catheter s i t e s unspec i f ied . Results ind ica ted that durat ion of patency increased when the flow rate was 2 mL/hour rather than 1 mL/hour, and the heparin concentrat ion increased from 1 to 5 U/mL. Even though the sample was large , several d i f ferences l i m i t i t s comparison with the adult s tudies . In t h i s study a high concentration of heparin was compared to a low concentrat ion of heparin. Since no comparison was made with a nonheparinized f lush so lu t ion , th i s study does not give any further c l a r i t y to the heparin versus sa l ine debate for maintaining catheter patency. Furthermore, the 22 gauge catheter and the flow rates used i n th i s study were d i f f e r e n t than the adult s tudies . Rajani and colleagues (1979) completed a study of 62 infants i n an Intensive Care Un i t . The authors compared one group of 32 infants rece iv ing a f lush so lu t ion of heparin 1 U/mL to another group of 3 0 infants rece iv ing 0.9% NaCl as the f lush s o l u t i o n . Information was not ava i lab le on the type of catheter used. The u m b i l i c a l cord ar tery cannulated for t h i s study does not allow for comparison to the other s tudies . The authors d i d not speci fy which coagulation studies were used, but reported no s i g n i f i c a n t di f ferences i n test r e s u l t s between the heparinized and nonheparinized f lush so lu t ions . The authors found that the ha l f l i f e of catheter funct ion was seven days i n the heparinized group and two days i n the 50 nonheparinized group. Butt and colleagues (1987) found higher concentrations of heparin increased durat ion of catheter patency. Rajani and colleagues (1979) reported a greater p r o b a b i l i t y of maintaining patency over 72 hours i f the f lush so lu t ion was hepar in ized . The resu l t s of these paed ia tr i c studies (Butt et a l . , 1987; Rajani et a l . , 1979) suggest catheter patency i s enhanced by heparin i n the f lush s o l u t i o n . However, the r e s u l t s of these two studies cannot be compared to each other or the studies i n the adult populat ion because (a) the catheter s ize i s unspeci f ied or smaller, (b) the in fus ion rates d i f f e r e d , (c) the f lush solut ions d i f f e r e d i n heparin concentrat ion, and, most importantly (d) the ar tery s ize among in fants , c h i l d r e n and adults are p h y s i o l o g i c a l l y d i f f e r e n t . In summary, the many var iab les used i n each study made comparisons d i f f i c u l t . The sample types v a r i e d and included in fants , c h i l d r e n and adults i n both medical and s u r g i c a l intens ive care u n i t s . The f lush solut ions included sa l ine and Ringer 's lac ta te with various concentrations of heparin and no heparin . The infusions rates also v a r i e d . The catheter s izes ranged from 2 0 to 22 gauge and the cannulated a r t e r i e s d i f f e r e d due to the populat ion. Reasons why the catheters were discontinued were not spec i f i ed i n any of the s tudies . Outcome var iab le s were very d i f f erent and i n some cases not s p e c i f i e d . In the American Assoc ia t ion of C r i t i c a l Care 51 (1993) study di f ferences were found i n gender but no other study discussed gender as a v a r i a b l e . F i n a l l y , the length of time the catheters were i n s i t u were d i f f e r e n t . In conclus ion, while research examining a r t e r i a l catheter patency by comparing heparinized and non-heparinized f l u s h so lut ions shows a trend suggesting that some heparin i s required i n the f lush solut ions to maintain catheter patency, i t i s inconc lus ive . There remains a lack of consensus about what type of f lush so lu t ion i s most e f f ec t ive i n maintaining catheter patency while ensuring minimal impact on haemostasis. Since there i s i n s u f f i c i e n t evidence to conclude heparin i s abso lute ly necessary to maintain patency of a r t e r i a l catheters , numerous researchers have suggested that , t h i s p r a c t i c e needs to be challenged and tested (Johnstone, 1991; Hook et a l . , 1987 ) . Therefore, another study i s warranted to address the e f fects of various types of f lush so lu t ion on a r t e r i a l catheter patency. Summary An analys i s of the l i t e r a t u r e i n r e l a t i o n to the t h e o r e t i c a l framework was presented i n th i s chapter. The major components of haemostasis were reviewed. The inf luence of the a r t e r i a l catheter system and the e f fects of cardiac surgery on haemostasis were discussed. Research l i t e r a t u r e on various f lush solut ions was presented and c r i t i q u e d i n c l u d i n g both the strengths and weaknesses for each study. 52 CHAPTER THREE Methods Introduction The research design of th i s study, sample s e l ec t i on , data c o l l e c t i o n procedures, instruments for data c o l l e c t i o n , data ana lys i s , assumptions and l i m i t a t i o n s , and e t h i c a l considerat ions for the protect ion of human r ight s are described i n t h i s chapter. Research design A three group, double b l i n d experimental design with repeated measures was used to test the hypotheses (see Figure I I ) . Subjects were randomly assigned to one of 3 f lush so lu t ion groups. The solut ions inc luded: (a) heparin 2.0 U/mL i n 500 mL of sa l ine , (b) heparin 1.0 U/mL i n 500 mL of sa l ine , or (c) s a l i n e . The contro l group received heparin 2.0 U/mL f lush so lu t ion because i t i s the so lu t ion used rout ine ly i n the cardiac surgery intens ive care unit (CSICU) where the study was conducted. Heparin 1 U/mL was se lected because i t was h a l f the concentration of the contro l group i n comparison to sa l ine and was a common concentration of heparin reported i n the l i t e r a t u r e . The experimental groups rece ived e i ther the 1.0 U/mL of heparin or the sa l ine 53 Figure II Design of the Study Three group double b l i n d experimental design. Group #1 R C Xi Ol 02 03 Group #2 R El X2 Ol 02 03 Group #3 R E2 X3 Ol 02 03 Legend: R = Randomized subjects to one of three groups X = Treatment as the flush solution 0 = Observation of blood coagulation studies (PT, PTT, Platelets) Times Oi=on admission to the CSICU, 02=in f i r s t 24 hrs post-op day, 03=in 48 hours post-op. (Samples were drawn at 02 and/or 03) C = Control f l u s h solution 2.0 U/mL heparin E = Experimental f l u s h solutions Ei=1.0 U/mL heparin, E2= saline 54 f lush s o l u t i o n . An a r t e r i a l catheter was inser ted in to each pat ient i n the operating room just p r i o r to the surgery commencing and the f lush so lu t ion was begun at that time. The design allowed the inves t igator to test (a) whether there was a di f ference i n occ lus ion r i s k of the r a d i a l a r t e r i a l catheter among the f lush so lu t ions , and (b) whether there was a di f ference i n frequency of occ lus ion of the r a d i a l a r t e r i a l catheter among the f lush so lu t ions . In the o r i g i n a l research design, the blood sampling protoco l was based on the routine blood sampling protoco l of the CSICU. That protocol changed just p r i o r to the implementation of th i s study and therefore the study protoco l also had to be changed. Each subject was to have PT, PTT, and p l a t e l e t counts measured at four routine i n t e r v a l s : on admission to the CSICU, twice during the f i r s t 24 hours pos t -operat ive ly (as ordered by the phys i c ian ) , and then at 48 hours. The blood sampling protoco l was changed as a cost containment measure i n response to q u a l i t y improvement i n i t i a t i v e s . Unfortunately , th i s change i n protocol was beyond the i n v e s t i g a t o r ' s c o n t r o l . The change meant that blood 55 samples were obtained pos t -operat ive ly on admission to the CSICU, and then at 24 and/or 48 hours pos toperat ive ly . Sample . The o r i g i n a l p lan for the study was to have a sample s i ze of 30 p a r t i c i p a n t s randomly assigned to 3 groups. With a s ign i f i cance l e v e l at p= 0.05 and a medium ef fect s i ze of 0.5, a sample s ize of 30 can be expected to r e s u l t i n a power of 0.80 for a 5 part repeated measures study with 3 groups. This was ca lcu la ted using Pearson H a r t l y Power Tables (Dr. Boldt , personal communication, September 9, 1993). The sample s ize of 30 was re ta ined even though the test frequency changed to two or three blood values per subject . It i s acknowledged that the power to detect di f ferences was reduced by t h i s change. Subjects were drawn from pat ients admitted to the cardiac surgery intensive care uni t i n a large t e r t i a r y care h o s p i t a l i n Vancouver. Inclus ion c r i t e r i a for the subjects i n the study were: 1. f i r s t - t i m e coronary ar tery bypass graft surgery. 2. admitted to the cardiac surgery ICU pos toperat ive ly . 3. pat ients between the ages of 35 and 75 years . 56 4. no other chronic i l l n e s s other than coronary ar tery disease. 5. no known coagulation d i sorders . 6. pat ients had taken a c e t y l s a l i c y l i c ac id (ASA) p r i o r to h o s p i t a l admission. 7. cannulat ion with a #20 Tef lon r a d i a l ar t ery catheter p r i o r to surgery. 8. normal PT, PTT, and p l a t e l e t counts p r e - o p e r a t i v e l y . 9. able to understand E n g l i s h . Data C o l l e c t i o n Procedures The inves t igator v i s i t e d the pre-operat ive cardiac ward of the agency to explain the study to the nursing s t a f f and to answer questions regarding the study. The inves t iga tor requested the Head Nurse on the cardiac ward to i d e n t i f y pat ients meeting the i n c l u s i o n c r i t e r i a and to ask those pat ients i f they would be w i l l i n g to be approached by the inves t iga tor . The inves t iga tor explained the study to those p o t e n t i a l p a r t i c i p a n t s , reviewed the consent form, and requested the pat ient s ign the consent form i f he/she agreed to p a r t i c i p a t e . A f t e r obtaining consent, the researcher n o t i f i e d the pharmacist and the fol lowing procedure was fol lowed. Using a table of random numbers, the pharmacist assigned 57 each subject to e i ther one of the experimental groups or the contro l group. The pharmacist had the reference codes i d e n t i f y i n g the type of f lush so lu t ion each subject rece ived . Reference codes were sealed u n t i l the completion of the study. The code was to be broken only i f a subject was at r i s k from a coagulation d i sorder and i t was deemed necessary to i d e n t i f y the nature of h i s / h e r f l u s h s o l u t i o n . There was no need to break the code during the data c o l l e c t i o n per iod . The hosp i ta l pharmacy prepared a l l 3 0 f lush bags i n the three concentrations s t ipu la ted: heparin 2.0 U/mL, heparin 1.0 U/mL, and s a l i n e . Once consent was obtained and the operating time for the pat ient had been confirmed, the pharmacist prepared and l a b e l l e d the f lush bag with the reference code. The inves t igator de l i vered each designated f lush bag to the operating room where i t was given to the per fus ion i s t who then used the designated f lush bag as the a r t e r i a l f lush so lu t ion (see Appendix E ) . During the cardiac s u r g i c a l procedure the p a t i e n t ' s blood was f u l l y heparinized to prevent c l o t t i n g as i t flowed through the cardiopulmonary bypass machine. The longer the durat ion of surgery, the greater the length of 58 time the pa t i en t ' s blood was mixed with heparin. Once the surgery was completed, the anesthet ist administered an appropriate dose of protamine sulphate intravenously to reverse the act ion of heparin. A f t e r surgery, the pat ient was trans ferred to the CSICU and data c o l l e c t i o n began. It continued for 4 8 hours or u n t i l the catheter was removed, whichever came f i r s t . Each pat ient had blood drawn for the three coagulat ion tests (PT, PTT, and p l a t e l e t counts) on admission to the CSICU and at one or two rout ine i n t e r v a l s which occurred e i ther at 24 and/or 48 hours pos t -operat ive ly as ordered by the phys i c ian . The bedside nurse recorded the fol lowing information for each pat i ent : (a) demographic data, (b) each time the a r t e r i a l catheter was f lushed and the reason why, (c) the nature of any problems with the a r t e r i a l catheter, with date and time, (d) the time each blood coagulation test was done and the re su l t s of the tes t s , (e) reason (s) for the catheter removal, i f removed e a r l i e r than normal, and (f) i f any c l o t s were present i n or on the catheter t i p at the time of removal (see Appendix B) . The a r t e r i a l pressure waveform was assessed as an i n d i c a t o r of catheter patency. A paper recording of the 59 p a t i e n t ' s a r t e r i a l waveform was obtained at the time of admission and at every s h i f t change. The normal waveform for that pat ient was establ i shed on admission to CSICU. If , on admission, the waveform pattern appeared abnormal, i t s a c c e p t a b i l i t y was v e r b a l l y confirmed with the anaesthet i s t . At the beginning of each 12 hour s h i f t during the 48 hours of the study, a copy of the recording , with the subject 's code number, date and time, was attached to the data c o l l e c t i o n sheet to document the waveform pat tern . If the a r t e r i a l waveform pat tern changed during the s h i f t , the nurse obtained an a d d i t i o n a l waveform recording, mounted i t , and documented i t on the data c o l l e c t i o n form. The inves t igator p e r i o d i c a l l y reviewed the procedure for data c o l l e c t i o n to v e r i f y that the process was being fol lowed. For a l l subjects , the inves t iga tor was ava i l ab l e to the nursing s ta f f by phone, and for the f i r s t s i x subjects , the inves t igator was present at the time of the pa t i en t ' s admission to the CSICU to trouble shoot i f any problems arose. At the time of removal, the a r t e r i a l catheter was inspected for any c lo t s i n or on the catheter t i p . To decrease s u b j e c t i v i t y , two nurses, the bedside nurse and 60 one of f ive ass i s tant head nurses, performed the two-step assessment. The fol lowing procedure was used once the catheter was removed: f ive mLs of f lush so lu t ion were withdrawn from the i r r i g a t i o n system connected to the f l u s h bag and flushed through the catheter onto a gauze pad. The nurses observed for any c lo t s on the catheter , i n the lumen or on the gauze pad, and recorded the f indings on the data c o l l e c t i o n sheet. The a r t e r i a l catheters were removed within 4 8 hours of i n s e r t i o n which i s the usual protoca l i n the CSICU. However, i f there was any d i f f i c u l t y with the catheter , the p a t i e n t ' s phys ic ian was n o t i f i e d , and the catheter was removed i f so ordered. If the a r t e r i a l catheter was no longer required, i t was not replaced and the pat ient remained i n the study. If the a r t e r i a l catheter was s t i l l necessary and needed to be re inser ted , the fo l lowing procedure was to be followed: (a) the code would be broken and the pat ient would be removed from the study, (b) the catheter would be replaced, and (c) the rout ine f lush so lu t ion , heparin 2.0 U/mL, would be subst i tuted as the a r t e r i a l catheter f lush s o l u t i o n . However, no subjects were removed from the study. 61 Instruments for Data C o l l e c t i o n The instruments used to c o l l e c t data were ( a) laboratory equipment used to measure PT, PTT, and p l a t e l e t count, (b) bedside cardiac pressure monitors, paper graph recorder and transducers, and (c) the data c o l l e c t i o n too l designed by the inves t iga tor . Laboratory equipment The laboratory personnel tested a l l blood samples taken by the nurses i n the CSICU to determine the PT, PTT, and p l a t e l e t count. Standard equipment was used to obtain and measure the specimens. In order to ensure r e l i a b i l i t y of the study f indings , a l l t e chn ica l and laboratory instruments were checked for accuracy by s t a f f of the h o s p i t a l ' s biomedical department p r i o r to the study. Monitoring equipment The monitoring equipment consisted of eight i d e n t i c a l Marquette Tramscope 12E cardiac monitors which d isp layed the a r t e r i a l pressure waveform and d i g i t a l blood pressure. The monitors were checked by s t a f f of the biomedical department for accuracy p r i o r to the s t a r t of the data c o l l e c t i o n . The usual CSICU' protoco l was used to monitor a l l subjects . The standard a r t e r i a l catheter f lush system consisted of a Viggo-Spectramed Custom DTX K i t disposable transducer system connected to the bedside monitor. It included high-pressure tubing and an i n - l i n e f lush device for continuous and intermit tent f lush ing . The a r t e r i a l f lush systems were maintained according to the CSICU standards for a r t e r i a l monitoring (see Appendix A ) . Data C o l l e c t i o n Tool Study data were c o l l e c t e d by the CSICU nursing s t a f f u t i l i z i n g a data c o l l e c t i o n too l designed by the inves t iga tor (see Appendix B) . The too l included relevant demographic data per ta in ing to the pa t i en t , number of bypasses, length of time on the bypass pump, length of time of a r t e r i a l catheter placement, reasons for d i scont inuat ion of the catheter, and the presence of c l o t s on or i n the catheter t i p . If the catheter required f lush ing , space was ava i lab le for nurses to record the time and i n d i c a t i o n . Data regarding blood sampling and assessments of a r t e r i a l l i n e patency were a lso recorded on the data c o l l e c t i o n t o o l . Any catheter malfunctions were documented as wel l as methods used for troubleshooting and in tervent ion . 63 R e l i a b i l i t y & V a l i d i t y Ident i f i ed ind icators for occ lus ion r i s k and catheter patency were va l idated by a l i t e r a t u r e review and by discuss ions with s ix expert p r a c t i t i o n e r s from the CSICU, inc lud ing three nurses and three phys ic ians . Content v a l i d i t y for the c l i n i c a l ind ica tors of loss of catheter patency was provided by research conducted by Hook and colleagues (1987) . The method for evaluat ion of c l o t formation was derived from the work of Hanson, Grant, and Majors (1976). To help ensure that the procedures were performed as ou t l ined , the inves t igator used several s t ra teg i e s . P r i o r to data c o l l e c t i o n , the inves t igator discussed with a l l 40 nurses i n the CSICU. The purpose of the sessions was to expla in the ra t iona le for the study and to review the protoco l s , procedures, and recording of data on the data c o l l e c t i o n forms. Sample data c o l l e c t i o n forms were reviewed. A step-by-step out l ine was presented so that the s t a f f were aware of the data required at s p e c i f i c times, and of the procedure for checking for c l o t s on the catheter t i p s (see Appendix C) . Deta i led i n s t r u c t i o n was provided to the f ive ass is tant head nurses on how to perform the ro le as the second assessor for blood c l o t s 64 when catheters were removed. In order to ensure that data were c o l l e c t e d and recorded i n a consistent manner the data c o l l e c t o r s (CSICU nursing staff) were required to provide a return demonstration of the procedures required for t h i s study. As well, the investigator was present at the time of CSICU admission of the f i r s t s i x subjects to answer questions and to ensure that the necessary procedures were being followed. A l l the CSICU nurses were c e r t i f i e d in' performing a l l procedures required i n t h i s study. The new procedures for the s t a f f nurses at the bedside included the recording on the data c o l l e c t i o n forms and the procedure for checking for c l o t s when removing a r t e r i a l catheters. From the investigator's observations and a review of the data c o l l e c t i o n tools, i t was determined that a l l procedures were followed co r r e c t l y , except on four occasions where there were missing data. The missing data included: two patients had the admission a r t e r i a l waveform recording mounted on t h e i r charts but not on the data c o l l e c t i o n t o o l , and two other patients did not have the admission blood values recorded on the data c o l l e c t i o n forms. Retrospectively the investigator recovered missing data and retained 65 these patients for analysis for t h i s study. To confirm the nurses' interpretation of the pattern, the investigator reassessed a r t e r i a l waveform patterns on the recording obtained by the nurses on admission to the CSICU, at each s h i f t change and during any pattern change. P i l o t study A p i l o t study was conducted with four subjects who met the c r i t e r i a for sample selection. The purpose of the p i l o t study was to i d e n t i f y any problems associated with the procedures. Since no problems were encountered during the p i l o t study and no changes were made to the protocols, the data for these subjects were incorporated into the t o t a l sample, making the p i l o t study data part of the t o t a l research data base. Data Analysis Data were entered into a computer and analyses were performed using the s t a t i s t i c a l program SPSSX. Descriptive s t a t i s t i c s were used i n order to describe the c h a r a c t e r i s t i c s of the sample as well as the d i s t r i b u t i o n of each of the variables i n the study. To test hypothesis one about occlusion r i s k , data from each blood test and the presence of c l o t s on or i n the catheter t i p 66 at removal were analyzed separately using the Kruskal-Wallis procedure. To test hypothesis two regarding frequency of catheter occlusion, the Kruskal-Wallis procedure and the Mann-Whitney U-Wilcoxon Rank Sum W test were used to detect differences among the groups. Nonparametric procedures were used to test both hypotheses because the number of blood samples drawn was not equal among groups. More samples were drawn at d i f f e r e n t times, and less than ten samples per time period were c o l l e c t e d per group. Only on admission were there ten samples for each of the three groups. If differences were found among the three groups, i d e n t i f i c a t i o n as to where those differences occurred was made using the Mann-Whitney U Wilcoxon Rank Sum W te s t . Assumptions The following assumptions underlie the study: 1. A l l the instruments were accurate when cal i b r a t e d . 2 . The concentrations of the three f l u s h solutions prepared by pharmacy were as required; i e . , heparin 2 . 0 U/mL, heparin 1 . 0 U/mL, and saline. 3. There were no manufacturing defects i n the a r t e r i a l catheters, transducers and fl u s h systems. 67 Limitat ions The fo l lowing l i m i t a t i o n s re la te to the sample s i ze , length of time i n surgery and i n the CSICU, personnel involved, the procedure for i n s e r t i o n of a r t e r i a l catheters , and the number of data c o l l e c t o r s . These l i m i t a t i o n s influence the g e n e r a l i z a b i l i t y of the r e s u l t s . 1. The sample s ize was small , considering that subjects had 2 or 3 blood tests taken at various time po in t s . 2. The length of time pat ients spent i n surgery and i n the CSICU var i ed with the number of bypasses done, the p a t i e n t ' s condi t ion and also surgeon preference. These factors were not c o n t r o l l e d . 3. Differences i n catheter i n s e r t i o n techniques by various anaesthetists were not c o n t r o l l e d . 4. Because pat ients were t y p i c a l l y discharged wi th in 48 hours of admission to the CSICU, the f indings may not be general izable to other uni ts where catheters remain i n place longer. 5. Since there were a number of data c o l l e c t o r s involved, there may have been some di f ferences i n f lush ing procedures and data c o l l e c t i o n . Although educational sessions were conducted, there may have been v a r i a t i o n i n 68 how the protoco l was c a r r i e d out. Eth ics and Human Rights The study proposal was approved by: (a) the h o s p i t a l research committee and the hosp i ta l nursing research committee, and (b) the Un ivers i ty of B r i t i s h Columbia C l i n i c a l Screening Committee for Research and Other Studies Involving Human Subjects. The names of the p a r t i c i p a n t s and the hosp i ta l where the study was conducted were kept conf ident ia l (see Appendix D) . P a r t i c i p a t i o n i n the study was voluntary. A p a t i e n t ' s nursing care, medical treatment, and/or access to h o s p i t a l services were not jeopardized i f he/she refused to p a r t i c i p a t e i n the study or withdrew fo l lowing enrolment. Subjects' r igh t s were protected i n several ways. The Head Nurse on the cardiac ward of the se lected agency i n i t i a l l y approached p o t e n t i a l subjects who met the c r i t e r i a for the study to obtain permission for the inves t iga tor to approach them. The inves t iga tor then explained the study, reviewed the "Patient Informed Consent" (see Appendix D) , and requested the pat ients to s ign the consent form i f they agreed to p a r t i c i p a t e . Subject names d i d not appear on any of the data 6 9 c o l l e c t i o n too l s . The procedures used to monitor a r t e r i a l patency and care of a r t e r i a l catheters were consistent with a r t e r i a l catheter care procedures s t ipu la ted by h o s p i t a l p o l i c y . Standard procedures were used for obtaining a l l blood samples. The only dev iat ion from the standard procedure was the concentration of the f lush so lu t ion for the two experimental groups. No add i t i ona l blood samples were required for the study. C r i t i c a l care experts ( including nurses, pharmacists and physicians) agreed that the health of -a subject would not be at r i s k i f the patency of the a r t e r i a l catheter could not be maintained with the f lush s o l u t i o n . It was poss ib le , however, that the catheter might occlude and become non-funct ional , thus necess i ta t ing i t s removal. If t h i s d id occur, i t was the subject 's condi t ion that determined whether or not recannulat ion was necessary. I f any problem arose regarding coagulation for any pat i ent , the code was to be broken to determine which f l u s h so lu t ion the pat ient rece ived. This problem never arose during the study. Summary In th i s chapter the methods were descr ibed. 70 This involved the design, sample s e l ec t ion c r i t e r i a , procedures for data c o l l e c t i o n and data ana lys i s , and the measures used to protect the pa t i en t ' s r i g h t s . 71 CHAPTER FOUR Presentation and Discuss ion of Results Introduction This chapter consists of three sect ions . In the f i r s t sect ion the c h a r a c t e r i s t i c s of the sample are presented. The f indings for each of the hypotheses are described i n the second sect ion and f i n a l l y , the f indings are discussed. C h a r a c t e r i s t i c s of the Sample During the data c o l l e c t i o n per iod (May to June, 1994), 45 pat ients had coronary ar tery bypass graf t surgery for the f i r s t time at the hosp i ta l where the study was conducted. Five of these pat ients d i d not meet the c r i t e r i a for the study, therefore 40 pat ients were approached by the researcher to consider p a r t i c i p a t i o n i n the study. T h i r t y pat ients agreed to p a r t i c i p a t e . Of the 10 pat ients who preferred not to p a r t i c i p a t e , one pat ient dec l ined due to f ee l ing too anxious about the surgery, 3 others f e l t the research study was too r i s k y for them, and 5 pat ients d id not wish to p a r t i c i p a t e i n any research study. The other pat ient was already involved i n two other research studies and chose not to p a r t i c i p a t e . No pat ients withdrew from the study. 72 Socio-demographic C h a r a c t e r i s t i c s The sample consisted of 24 males and 6 females (n=3 0). Ages ranged from 44 to 76 years (M= 63.2, SD= 8.9) . There were no s i g n i f i c a n t di f ferences among the groups with regards to age. Table 2 out l ines the age d i s t r i b u t i o n of the sample i n r e l a t i o n to the groups. Table 2 Age D i s t r i b u t i o n of the Sample Age Flush Solut ion . Years Sal ine Heparin Heparin 1 U/mL 2 U/mL 40-49 0 1 2 50-59 2 2 1 60-69 7 4 4 70-79 1 3 3 Mean 64 .4 63 .2 62 .1 SD 5 .19 10 .41 10 . 81 Surg i ca l Status A l l of the pat ients i n th i s study were admitted for e l e c t i v e coronary ar tery bypass graft surgery. None had previous cardiac surgery. Four cardiac surgeons each operated on f ive to ten of the pat ients i n t h i s study. The number of coronary bypasses performed per pat ient v a r i e d from one to seven (M= 3.7, SD= 1.5) and the 73 Table 3 Duration of Pump and Clamp Times Variable Flush Solution Pump Time i n Hours/ Minutes per Patient Saline Heparin 1 U/mL Heparin 2 U/mL 0'30"-l'14" 1 5 2 1'15"-1'59" 8 4 6 2'00"-2'44" 1 0 1 2'45,,-3'29" 0 1 1 3'30"-4'14" 0 0 0 N 10 10 10 Mean 1' 42" 1'21"* 1' 44" SD(minutes) 21" 37" 34" Clamp Time i n Hours/ Minutes per Patient 0'00"-0'29" 0 1 1 0'30"-0'59" 3 7 3 1'00"-1'29" 6 0 2 1'30" -1'59" 1 1 2 2'00" - 2'29" 0 1 2 2'30"-2'59" 0 0 0 N 10 10 10 Mean 1' 13" 55" 1' 18" SD(minutes) 18" 31" 34" * S i g n i f i c a n t difference among groups p_=. 04 . Difference was between 1 U/ml heparin group and the other groups p_=.01. 74 majori ty of the pat ients had between two to four bypasses. There were no s i g n i f i c a n t di f ferences among the groups. The length of time pat ients were on the cardiopulmonary bypass pump ranged from 44 minutes(") to 3 hours (') (M= 96.06", SD= 32.54") (see Table 3) . There were s i g n i f i c a n t di f ferences i n time on the pump across the groups (H= 6.25, p_=.04). The sa l ine and the 2 U/mL heparin group had s i g n i f i c a n t l y longer pump times than the 1 U/mL heparin group (Z= -2.238, 2 - t a i l e d p_=.01). The v a r i a t i o n i n pump time may be re la ted to the fact that of the ten surgeries done by one surgeon, f ive of the ten pat ients were i n the 1 U/ml group. No other major di f ferences were noted for other surgeons. The length of time the aorta was cross-clamped during the coronary ar tery bypass surgery ranged from 25" to 2'14" (M= 68.5", SD= 9.8"). There were no s i g n i f i c a n t d i f ferences among groups re la ted to cross-c lamping. Time Catheter Ins i tu The length of time the a r t e r i a l catheter was i n s i t u ranged from 23'30" to 62'30" (M= 37'30", SD= 9'26"). In the sa l ine group, the durat ion of a r t e r i a l c a t h e t e r i z a t i o n ranged from 23'30" to 62'30". The ranges 75 i n the 1 and 2 U/mL of heparin group were from 24'15" to 45' and from 24' to 47'10". There were no s i g n i f i c a n t differences i n duration of cannulation across the groups (H=1.26, p=0.53) (see Table 4). Table 4 Time catheter i n s i t u per flush solution group Time i n Hours Saline Heparin 1 U/mL Heparin 2 U/mL 23'36"-26'30" 3 2 1 26'36"-29'30" 1 2 0 29'36"-32'30" 0 0 1 32'36"-35'30" 1 0 0 35'36"-38'30" 0 0 1 38'36"-41'30" 1 3 1 41'36"-44'30" 2 2 1 44'36"-47'30" 1 ' 1 5 47'36"-50'30" 0 0 0 50'36"-53'30" 0 0 0 53'36"-56'30" 0 0 0 56'36"-59'30" 0 0 0 59'36"-62'30" 1 0 0 Total 10 10 10 M 37' 36'10" 39'15" SD 12'17" 8' 11" 7' 55" Time Catheter Insitu The length of time the a r t e r i a l catheter was i n s i t u ranged from 23'30" to 62'30" (M= 37'30", SD= 9'26"). In the saline group, the duration of a r t e r i a l c atheterization ranged from 23'30" to 62'30". The ranges 76 i n the 1 and 2 U/mL of heparin group were from 24'15" to 45' and from 24' to 47'10". There were no s i g n i f i c a n t d i f ferences i n durat ion of cannulation across the groups (H=1.26, p_=0.53) . In summary, the groups were not s i g n i f i c a n t l y d i f f e r e n t i n terms of gender, age, and clamp time, however there was a di f ference i n the pump time. Pat ients i n the 1 U/mL heparin group were on the pump a s i g n i f i c a n t l y shorter time than those i n the other two groups (Z= -2.38, 2 - t a i l e d p_=. 01) . Findings Hypothesis 1: Differences i n Occlusion Risk The f i r s t hypothesis addressed the d i f ferences i n occ lus ion r i s k of the a r t e r i a l catheters . Coagulation studies were compared on admission to CSICU and at 24 hours and/or 48 hours postoperat ive ly . In add i t i on , observations made for the presence or absence of c l o t s i n and on the catheter immediately fo l lowing removal were compared. Prothrombin Time Table 5 d isplays the PT values for each f l u s h so lu t ion group at the three time per iods . Only at the time ofadmission to CSICU were there s i g n i f i c a n t © * No o T J CO CO H II H - H - 3 CD • LQ LQ OJ o p 3 h-1 T J H - H -OJ l-h l-h rt H - H - *-3 H - O. O CD OJ OJ II rt rt rt IT € CL Q_j i OJ H- H- H CD H i H i H i H i OJ rt CD CD Ul CD H H CQ CD CD co rt CD o O a CD CD CD cr 0 OJ OJ rt CQ 3 cr 0 cr 3 OJ CD LQ rt rt 55 LQ to CD H M> CD 0 OJ T J H tn a aw \ II oo 3 • h-1 o cr 0 cr • C CD H CD OJ LQ H O iH T J OJ rt cr CD o rt cr CD H LQ H O T J CD 3 C/J CD a OJ ^ L£> H CO H H to CTl LO tO to to 00 H H H CTi OJ H tO CTl O I I I H H H 00 CTl OJ ~ J h-1 LTI H- H! TJ 3 H - H 3 0 CQ CD rt OJ CD cr O — HI LQ 0 TJ 0 CD 3 H 3 CD C L — cr CQ H -CJ o LO to LT1 to Ln O - J U) Ul © o o tn o I—1 Ln OJ H o o Ln Ln co to ^ to H 'so O H -0 o o to H O H CO H O O - J O O OJ rt > o CL 3 O H -OJ CQ H CQ O H -a o C3 O TJ CC to •d o *i ^ CO CQ rr O TJ CC ^ TJ 0 ii co CO CO ft ft > 0 CL 3 O H -C0 CQ H CQ n H -a o 3 o TJ cn to T J o H J> CQ CO rt O TJ CC ^ TJ 0 w CO CD CO rt > CL O H -co co H CO a o C 3 O TJ CC to TJ 0 K iJ> CQ CD rt O TJ CC ^ TJ 0 H co CD CO ft 3 o H 3 OJ co OJ I—1 H -CJ CD 3 ir1 CC CD TJ OJ •i H -C 3 to 3 tr1 CC CD TJ 0) H H-C 3 to o o C L H3 CD CD rt CQ 0 >TJ rt co j- cr o CJ 78 d i f f e r e n c e s among t h e f l u s h s o l u t i o n g r o u p s ( H = 5 . 8 8 , P = . 0 5 ) . The t h e s a l i n e a n d t h e 2 U / m L h e p a r i n g r o u p h a d s i g n i f i c a n t l y l o n g e r P T s t h a n 1 U / m L g r o u p (Z= - 2 . 0 1 , 2 -t a i l e d p = . 0 4 ) . T h e means i n s e c o n d s (S) f o r t h e t o t a l s a m p l e f o r PT o n a d m i s s i o n , a t 24 a n d a t 48 h o u r s w e r e 1 3 . 4 3 S , 1 2 . 6 3 S a n d 1 3 . 1 2 S r e s p e c t i v e l y . The PT r a n g e d f r o m 1 1 . 2 S t o 1 6 . 9 S (M=13 .96) o n a d m i s s i o n , f r o m 1 1 . 4 S t o 1 4 . 2 S (M=12 .74 ) a t 24 h o u r s , a n d f r o m 1 1 . 4 S t o 1 4 . 1 S (M=12 .46 ) a t 4 8 h o u r s . I n t h e s a l i n e g r o u p , t h e PT r a n g e d f r o m 1 3 . 1 S t o 1 5 . 4 S o n a d m i s s i o n ( M = 1 4 . 3 1 ) , 1 2 . 3 S t o , 1 3 . 2 S a t 24 h o u r s ( M = 1 2 . 8 4 ) , a n d 1 1 . 4 S t o 1 4 . 1 S a t 48 h o u r s ( M = 1 2 . 6 0 ) . I n t h e 1 U / m L g r o u p , t h e PT r a n g e d f r o m 1 1 . 2 S t o 1 4 . 1 S o n a d m i s s i o n ( M = 1 3 . 2 0 ) , 1 1 . 4 S t o 1 4 . 2 S a t 24 h o u r s ( M = 1 2 . 8 6 ) , a n d 1 1 . 8 S t o 1 2 . 1 S a t 48 h o u r s ( M = 1 1 . 9 5 ) . I n t h e 2 U / m L g r o u p , t h e PT r a n g e d f r o m 1 3 . 5 S t o 1 6 . 9 S o n a d m i s s i o n ( M = 1 4 . 3 8 ) , 1 1 . 4 S t o 1 3 . 4 S a t 24 h o u r s ( M = 1 2 . 5 4 ) , a n d 1 2 . 3 S t o 1 2 . 9 S a t 4 8 h o u r s ( M = 1 2 . 5 3 ) . B e c a u s e c o a g u l a t i o n s t u d i e s w e r e n o t o r d e r e d f o r a l l s u b j e c t s , a l l s u b j e c t s w e r e n o t t e s t e d a t e a c h t i m e p e r i o d . F o r e x a m p l e , a t 48 h o u r s o n l y f r o m t w o t o s i x p a t i e n t s w e r e t e s t e d i n e a c h g r o u p . On a d m i s s i o n , 7 i n t h e s a l i n e , 5 i n t h e 1 U / m L , a n d 79 9 i n the 2 U/mL group had longer than normal PTs. At that time, there were therefore more pat ients i n the sa l ine and 2 U/mL heparin groups than i n the 1 U/mL heparin group who had values longer than normal. Only-one pat ient i n the 1 u/mL group at 24 hours and one i n the sa l ine group at 4 8 hours had prolonged although complete data on a l l pat ients at these times i s l a c k i n g . P a r t i a l Thromboplastin Times Table 6 d isplays the PTT values for each f lush group at the three time per iods . PTTs were not s i g n i f i c a n t l y d i f f e r e n t among the groups on admission (H=5.58, p_=0.06) , at 24 hours (H=0.44, p_=.80) and at 48 hours (H=4.49, p_=. 11) . The means for the t o t a l sample for PTT on admission, at 24 and at 48 hours were 32.06 S , 30.76 S and 30.3 S re spec t ive ly . The PTT ranged . from 25.1 S to 54.4 S (M=32.13) on admission, from 23.6 S to 35.4 S (M=30.73) at 24 hours, and from 26.7 S to 35.8 S (M=30.69) at 48 hours. A l l pat ients were not tested for the PTT at each time per iod . In the sa l ine group the PTT ranged from 25.7 S to 54.4 S on admission (M=33.85), from 29.9 S to 34.0 S at 24 hours (M= 31.36), and from 28.6 S to 32.0 S at 48 hours (M=30.66). In the 1 U/mL group the PTT © o CD T J PJ rt H -CD rt rf CD CD rt CD P-tu rt CT O rt tr to pj o. co tr o c to 3 o to O J M> CO CD O O O CD cn C D 3 ~j O J • O J VO • tO CO r-> O J CTl OJ r—' OJ • o on • o to • VO IX) • OJ tJ> O to • VO 00 • O <1 H tO • 00 VO • M> O . 0 8 H 0 J • O J H • O O O OJ • H vo OJ O OJ • to 0 J • to Ul (jl J> H> 0 J OJ to to O Ul O Ul O Ul o 0 o o o o o o 1 I I I I I I Ul J> J> OJ OJ to to rfs> VD >J> VO J> VO tl> VD VD VO VD VD VD VD P CQ CD CD M O O tO Ul tO O Ul O O O O tP» H O CTi O O O O 0 J 0 J O ® O O h-1 O tO -J O 00 to O O O t—1 0 J to to o o o o o to o O O O O J J > O J o O J O O O H 0 J 0 J O O O O H H H O CD CO rt rt > 0 O 3 n H -cn CD M CD O H -a o TJ TJ H, pj rt H -0J O TJ ffi u> T J O 4 00 CD CO rt rt > 0 O 3 O H -cn co M CD o K -a o 3 O TJ X to T J O I-! J> CD CQ rt O T J X T J .0 ^ CO CO CO rt rt > 0 0-3 O H -co co M CD n H -a o 3 O TJ ffi to T J 0 ri J> CD CD rt o T j m J > T J 0 ^ CO CO CD rt 0 ii 3 P> H -CD 3 tr1 CD T J P) 3 to 3 tr1 CD T J OJ LU i—1 0 o o. CD CD rt CO |0 T ] c c rt co H - tr 0 81 ranged from 25.1 S to 42.3 S on admission (M=29.49) , from 23.6 S to 35.4 S at 24 hours (M=29.77), and from 26.7 S to 2 9.3 S at 4 8 hours (M=28 .00K In the 2 U/mL group the PTT ranged from 26.8 S to 38.8 S on admission (M=33.05), from 26.6 S to 3 5.4 S at 24 hours (M=31.38), and from 29.8 S to 35.8 S at 48 hours (M=32.53). Of the 30 PTTs tested on admission, 23 were wi th in normal range and the remainder were prolonged. By 24 and 48 hours, the PTTs were normal for a l l 10 pat ients tested i n the sa l ine group. In the 1 U/mL group, one PTT was prolonged at admission and one at 24 hours but two PTTs were shorter than normal at 24 hours. In the 2 U/mL group, three PTTs were prolonged on admission, and one PTT was prolonged at both 24 and 4 8 hours. P l a t e l e t Counts Table 7 d isplays the p l a t e l e t counts for each f lush so lu t ion group at the three time per iods . There were no s i g n i f i c a n t di f ferences among the f lush so lu t ion groups on admission (H=5.00, p=0.08) and at 48 hours postoperat ive ly (H=0.06, p_=.97). However, there were s i g n i f i c a n t di f ferences at 24 hours (H=7.85, p_=.01) . The p l a t e l e t counts for the 1 U/mL heparin group were s i g n i f i c a n t l y higher (Z=-2.63, 2 - t a i l e d p= . 008) than for ZQ © O CD TJ rt H-CD Hi rt £ PJ CQ rt CD CQ rt CD DJ D Co H- H-HiLQ Hi 3 CD CD H) O CD Hi TJ H- Ml H i O o PJ H rt pj C 3 t r \ o o 3 3 rt MLQ tr H-LQ tO CD K IJ^ TJ Cd 3 H CL 3 0TJ CQ J>LQ CO H o tr c O TJ c PJ rt to »i> tr o HS CQ rt CTTJ CD II PJ DJ O rt CD rt o CQ H O (H TJ CQ TJ o o co CO D S CD PJ CQ ( O M H p in o ui Jr ui o o o Q o 3 i i tO tO H KD KD KD KD KD PJ CQ CD CD OJ • CO CO • H - J tO h-1 Ul to • OJ O • H 00 OJ H O J> • OJ tl> • H Ul H o to cn H Ul cn © O O O Ul o O H H ^ O OJ Oi • CO CO • to u> tO H Ul Ul • CTi O • OJ H O J> • Ul |J> • H Ul o to m to o co O H * > W O to O O H H O OJ H OJ OJ • to -4 • H H OJ H CO OJ • U> O • OJ O Ul H 00 |J> • ~J to • OJ o O O H tO Ul tO o H o cn o O H H O O. CQ > CO H- CL H 0 3 Hi H-CQ rt i 0 — O TJ O 0 M 3 r t — rt CD CQ I—1 CD rt O a O TJ £ to TJ 0 H CQ CD rt O TJ X TJ 0 H co CD CQ rt O CQ 0 rt 0 > DJ 3 H-CQ I O TJ X to TJ 0 H »J> CQ CQ rt O TJ TJ 0 co CO rt X H. CD O CD > CO H o. a H -0 m rt 0 3 H-co O TJ X to TJ 0 H CO CD rt O TJ X TJ 0 H co CO CD rt 25 o H 3 PJ co PJ 3 CD 3 tr1 X CD TJ PJ t i H-3 to 3 ir1 K CD TJ PJ t i w h-' 0 0 DJ Hi CD CO rt I—1 ill co co c rt H-0 3 83 the other two groups. The means for the sample for p l a t e l e t counts on admission to CSICU, at 24 and at 48 hours were 148.06 G/L, 142.05 G/L and 144.81 G/L respectively. The p l a t e l e t counts ranged from 91 to 279 G/L (M=148.06 G/L) on admission, from 100 to 221 G/L (M=142.05 G/L) at 24 hours, and from 86 to 220 G/L (M=144.81 G/L) at 48 hours. In the saline group, the p l a t e l e t counts ranged from 91 to 279 G/L on admission (M=143.70), from 115 to 142 G/L at 24 hours (M=123.80), and from 100 to 220 G/L at 48 hours (M=143.50) . In the 1 U/mL group, the p l a t e l e t counts ranged from 100 to 249 G/L on admission (M=168.40), from 129 to 201 G/L at 24 hours (M=156.12), and from 124 to 167 G/L at 48 hours (M=145.50). In the 2 U/mL group, the p l a t e l e t counts ranged from 95 to 206 G/L on admission (M=132.10), from 100 to 221 G/L at 24 hours (M=139.00), and from 86 to 202 G/L at 48 hours (M=147.00). As for the other coagulation studies, a l l patients were not tested at each time period. For example, at 48 hours, of the 10 subjects i n each group only 6 i n the saline group, 2 i n the 1 U/mL and 3 i n the 2 U/mL group had physician orders for testing. Fourteen patients had p l a t e l e t counts within normal 84 range, 2 to 7 pat ients i n each group had lower than normal counts and no one had counts higher than normal. Of the 20 pat ients tested at 24 hours, 14 p l a t e l e t counts were lower than normal, and of the 11 pat ients tested at 48 hours, 6 p l a t e l e t counts were lower than normal. The 1 U/mL group had fewer values that were below normal. No pat ient had higher than normal counts at any time. Clots In and On the Catheter Comparisons were made of the presence of c l o t s on and i n the catheter t i p at the time the catheter was removed. Of the 3 0 catheters, three catheters i n the sa l ine group had c l o t s . There were no c l o t s observed i n e i t h e r of the heparin groups. There were no s t a t i s t i c a l l y s i g n i f i c a n t di f ferences i n c l o t formation i n or on the catheter t i p across the three groups (H=1.85, p_=.39) . In summary, hypothesis one cannot be e n t i r e l y supported. The 1 U/mL group had shorter PT times on admission and s i g n i f i c a n t l y higher p l a t e l e t counts at 24 hours than the sa l ine and 2 U/mL groups. Otherwise there were no s i g n i f i c a n t d i f ferences . Although not s t a t i s t i c a l l y d i f f e r e n t , a f ind ing which i s noteworthy i s that 3 catheters i n the sa l ine group had c l o t s when 85 removed while there were no c lo t s i n the catheters for the other 2 groups. Hypothesis 2: Differences In Frequency Of Occlus ion The second hypothesis tested the di f ferences i n frequency of occ lus ion of the a r t e r i a l catheters . The three f lush so lu t ion groups were compared i n r e l a t i o n to the frequency of: d i f f i c u l t y f lush ing the catheter , d i f f i c u l t y a s p i r a t i n g blood from catheter, a r t e r i a l waveform pattern dampening, complete loss of a r t e r i a l waveform pattern and reasons why catheters were removed. In addi t ion the groups were compared i n terms of frequency of p o s i t i o n a l a r t e r i a l catheter occurrence, number of times the catheters were f lushed and reasons why the catheters were f lushed. Occurrences of D i f f i c u l t y Flushing There was one occasion when nurses had d i f f i c u l t y f lush ing the catheters of those rece iv ing the 1 and 2 U/mL heparin so lu t ion . There were 3 occasions where nurses had d i f f i c u l t y f lushing catheters i n the sa l ine group. In the 1 U/mL and 2 U/mL heparin groups there was 1 occasion each of d i f f i c u l t i e s (Table 8). 86 Occurrences of D i f f i c u l t y A s p i r a t i n g Blood From The Catheter Nurses had more d i f f i c u l t i e s a s p i r a t i n g blood from the catheter of pat ients i n the sa l ine group. There were s i g n i f i c a n t di f ferences across the groups (H=6.00, p_=.04) with the sa l ine group having more d i f f i c u l t i e s then the other two groups (Z= -1.93, 2 t a i l e d p_=.05) . D i f f i c u l t y was i d e n t i f i e d with a s p i r a t i n g blood from the catheter i n 5 pat ients i n the sa l ine group, 1 pat ient i n the 1 U/mL heparin group and 1 pat ient i n the 2 U/mL heparin group. D i f f i c u l t y occurred more than once for one pat ient i n the sa l ine group. Occurrences of Dampened A r t e r i a l Waveform There were no s i g n i f i c a n t di f ferences among groups i n r e l a t i o n to occurrence of dampened waveforms (H=1.02, p_=0.37) . In the sa l ine group there were 5 pat ients where d i f f i c u l t i e s were noted, 3 of whom had 2 occurrences of d i f f i c u l t y . In each of the 1 and 2 U/mL groups two pat ients had d i f f i c u l t i e s . Three of these had 1 occurrence and the other had 4 occurrences. Occurrences of Loss of A r t e r i a l Waveform Four pat ients i n the sa l ine f lush so lu t ion group experienced a loss of waveform. Two pat ients i n the 1.0 cn oo p- P -CQ CQ ts ts P - P -Mi Hi H - P -O PJ rt 0, &, P - P -Hi Hi Hi Hi CD CD P, P, CD CD n n CD CD cn tr 3 CD o rt 3 £ CQ CD CD ef-ts tr CD rt trcq CD H O CD C p) T J r—1 CD P -3 T J CD II PJ O H ^ CL • rt tr CD tr CD T J PJ P> P -t> Hi I—1 CD tr CQ H o C T J T J o L8 CJI O > * PJ 0 PJ CD < CD 3 T J U CD CD T J H- P -Hi CD P, Hi 0 0 ti PJ Hi H Hi CD rt P -3 0. H - O > ti C s; CQ r-1 rt PJ rt CD < P> CD M P - Hi 0 P) 0 0 r—1 H a-3 Tj O r—1 P-C Hi CD Hi tr P-H - o tl c CQ M rt to o to o a o T j P - O P Hi O Hi £ P P CD tl P -n I—' rt to to OJ to OJ 3 3 cr CD P> o Hi o o o d H P CD ti o CD CD T J CD P TJ PJ rt P -CD ts rt CD PQ CD tl O O ^ CD CD O Hi 0 Hi CD P) O tr o P 3 PJ CO pj I—1 p-ti CD CD T J P) P> P -tl to \S P. p-PJ cr M CD CQ « CD T J PJ P, P -ti I—1 CQ tr Co o I—1 rt p-0 tl 88 U/mL heparin f lush group and only 1 pat ient i n the 2.0 U/mL group experienced a loss of a r t e r i a l waveform. Again there were more d i f f i c u l t i e s associated with the sa l ine f lush so lu t ion than with the two other so lu t ions . There were no s i g n i f i c a n t d i f ferences , however, among the groups re la ted to loss of a r t e r i a l waveform (H=2.27, E=0 .3.2) . Reasons for catheter removal Five catheters i n the sa l ine group and nine catheters i n each of the heparin groups were removed because they were no longer needed. The remaining f i ve catheters i n the sa l ine group required removal because of the i n a b i l i t y to withdraw blood, i e . they were occluded. This s i t u a t i o n only occurred for 1 pat ient i n the 2 U/mL group and d id not occur at a l l for any pat ients i n the 1 ' U/mL group. The ^differences across groups were s i g n i f i c a n t with more pat ients i n the sa l ine group r e q u i r i n g t h e i r catheter to be removed because of occ lus ion than i n the 1 U/mL group (H=8.45, p= 0.01) . C l i n i c a l l y , th i s f ind ing was also s i g n i f i c a n t because a greater number of pat ients i n the sa l ine group versus the other two groups had t h e i r catheters removed because of occ lus ion (see Table 9) . For one pat ient i n the 1.0 U/mL 89 f lush group, the i n i t i a l catheter was removed because of a r t e r i a l spasm, a second catheter was inser ted , and subsequently removed by the pat ient himself . Table 9 Reasons for Catheter Removal Reasons for Catheter Removal Flush So lut ion Normal Sal ine 1 U/mL Heparin 2 U/mL Heparin Catheter no longer required 5 9 9 * I n a b i l i t y to withdraw blood 5 0 1 A r t e r i a l Spasm 0 1 0 TOTAL 10 10 10 * S i g n i f i c a n t di f ference among the groups p=.01. S i g n i f i c a n t d i f ference was between the sa l ine and the 1 U/mL group p=.01. T o t a l Number of Problems In addi t ion to comparing the var iab les i n d i v i d u a l l y , a comparison was made of the t o t a l occurrences of d i f f i c u l t i e s (the sum of d i f f i c u l t i e s f lu sh ing , a s p i r a t i n g , dampened waveform, and loss of a r t e r i a l waveform). There were no s i g n i f i c a n t d i f ferences among 90 the groups on th i s summed score (H=0.92, p_=.40). A d d i t i o n a l Findings A d d i t i o n a l f indings noted i n th i s study were r e l a t e d to f lush ing the a r t e r i a l catheters and p o s i t i o n a l catheters . Even though these f indings were not part of the hypotheses they d id contribute relevant information about maintaining catheter patency. Occurrences of Flushing of the A r t e r i a l Catheter There were no s i g n i f i c a n t di f ferences across the groups for the t o t a l number of times the catheters were f lushed (H=3.30, p_=.19) , or for f lushing required because of blood sampling (H=0.73, p_=.69), dampened waveform (H=3.30, p_=.19) and/or c a l i b r a t i o n (H=0.31, p_=.86) (see Table 10) . Catheters required f lushing an average of 15.7 times per pat ient (SD=6.2, range 6 to 30 times per p a t i e n t ) . The most frequent reason for f lushing the catheter was the need for blood sampling (M=12.7, SD=4.92, range 6-24 per p a t i e n t ) , followed by problems re la ted to dampened waveform (M=1.26, SD=2.30, range 0-10 per p a t i e n t ) , and l a s t , c a l i b r a t i o n of the catheter system (M=1.8, SD=2.65, range 0-11 per patient) . A r t e r i a l spasms and r e p o s i t i o n i n g of the arm (M=0.2, SD= 0.66, range 0-3 per 91 Table 10 Frequency of F l u s h i n g the A r t e r i a l Catheter Fl u s h S o l u t i o n Frequency of Catheter F l u s h i n g S a l i n e Heparin Heparin 1 U/mL 2 U/mL T o t a l Times Catheter Flushed 0-3 0 0 0 4-7 0 1 0 8-11 3 0 4 12-15 4 4 1 16-19 1 3 3 20-23 0 0 1 24-27 1 1 1 28-31 1 1 0 Mean 15 . 9 16 . 6 14 . 8 SD 7.24 6.22 5 . 65 Due to Blood Sampling 0-3 6 5 5 4-7 4 3 4 8-11 0 2 1 Mean SD 11.5 13 . 9 12 . 7 3 . 77 2 .42 5.29 Due t o Dampened Waveform 0-3 9 8 10 4-7 0 0 0 8-11 1 2 0 Mean 2 . 0 1.1. 0 . 7 SD 3 . 01 2 .42 1. 05 Due t o C a l i b r a t i o n 0-3 9 8 9 4-7 0 2 1 8-11 1 0 0 Mean SD 2.2 1. 8 1.4 3 .25 1. 75 1.57 TOTAL 10 10 10 92 patient) were other, although infrequent, reasons for f l u s h i n g . However, while nei ther occurred i n the 2 U/mL group there was 1 occurrence i n the sa l ine group and there were 2 occurrences i n the 1 U/mL group. Occurrences of P o s i t i o n a l Catheters There were no s i g n i f i c a n t di f ferences among the groups (H=2.34, p_=.31) re la ted to the occurrence of p o s i t i o n a l catheters . In the sa l ine f lush group, 5 pat ients had to have t h e i r wrist repos i t ioned i n order to prevent catheter occ lus ion with 2 pat ients each having 2 occurrences. This d i f f i c u l t y was also experienced by 2 pat ients i n the 1 U/mL f lush group and 4 pat ients i n the 2 U/mL f lush group, with 3 pat ients having one occurrence and 1 pat ient having 2 occurrences. The groups were not s i g n i f i c a n t l y d i f f erent on th i s v a r i a b l e . Summary In summary, hypothesis two was not f u l l y supported. Although there were no s i g n i f i c a n t di f ferences i n the frequncy of having d i f f i c u l t y ' f lushing the catheter , dampened waveform pattern, and complete loss of a r t e r i a l waveform pattern , the sa l ine group had s i g n i f i c a n t l y more d i f f i c u l t i e s a s p i r a t i n g blood from the catheter and more catheters requ ir ing removal because of occ lus ion . 93 Furthermore although not s t a t i s t i c a l l y d i f f e r e n t , the sa l ine group had more p o s i t i o n a l a r t e r i a l catheters , and required f lush ing more often. Discussion of Findings In t h i s sect ion the representativeness of the sample i s addressed and the f indings are examined i n r e l a t i o n to each of the hypotheses. The f indings for each hypothesis are discussed i n terms of the t h e o r e t i c a l framework, p r i o r research and other l i t e r a t u r e . Methodological issues are also addressed. Representativeness of the sample The sample i s representative of those i n d i v i d u a l s who have coronary ar tery bypass graft surgery i n B r i t i s h Columbia i n terms of gender and age. P r o v i n c i a l data from 1991 to 1994 indicated that more men than women by a r a t i o of 3.7:1 have coronary ar tery bypass surgery and that the mean age i s 63.8 (Prov inc ia l Cardiac Reg i s try , 1995). The age range of the 30 pat ients i n t h i s study was 45 to 75 years (M=63.2 years) . Twenty-four were males and 6 were females. The 3 f lush groups were equivalent i n terms of: age, gender, number of bypasses, clamp time, and durat ion of cannulat ion. Unfortunately, they were not equivalent i n 9 4 r e l a t i o n to pump time. The 1 U/mL heparin f lush group had s i g n i f i c a n t l y shorter pump times than the other two groups perhaps because one surgeon performed f ive of the ten operations i n th i s group and only ten surgeries i n t o t a l . Hypothesis 1 The f indings re la ted to occ lus ion r i s k as measured by coagulat ion fac tors : PT, PTT, and p l a t e l e t counts, and by presence of c l o t s on catheter t i p on removal were not d e f i n i t i v e i n showing one f lush so lu t ion to be super ior to another. The 1 U/mL group had shorter PTs on admission and higher p l a t e l e t s at 24 hours but groups were not s i g n i f i c a n t l y d i f f erent on coagulation studies throughout. Three catheters had c l o t s on catheter removal and they were a l l i n the sa l ine group. The fo l lowing reasons may expla in the f indings r e l a t e d to the PT and p l a t e l e t values: (a) the l i m i t e d number of coagulation tests done (b) the negative e f fects of the bypass pump; (c) the d i l u t i o n e f fects of the card iop leg ia f l u i d on coagulation fac tors ; (d) the amount of heparin that may s t i l l be i n the pa t i en t ' s body at the end of surgery and (e) the amount of heparin i n the f l u s h so lu t ions . Each of these reasons w i l l be discussed 95 separate ly . The power to i d e n t i f y di f ferences i n coagulat ion r e s u l t s (PT, PTT, and p la te le t s ) was diminished because fewer tests were done than o r i g i n a l l y planned. The r e s u l t i n g small number of tests done at 24 and 4 8 hours would have decreased the power to detect d i f f erences . The longer a pat ient i s on the bypass machine, the greater the r i s k to hemostasis because p l a t e l e t s and coagulat ion factors are consumed. The less time the blood i s exposed to the pump, the less damage would l i k e l y ensue (Thelan et a l . , 1990). The fact that the 1 U/mL group had the shorter pump times could expla in t h e i r more normal PT values and why t h e i r p l a t e l e t s were higher than those on the pump for longer (Wright and Shelton, 1993) . The length of surgery influences the amount of card iop leg ia f l u i d needed to keep the heart i n an arres ted s tate . Those pat ients who are on the pump longer receive more cardiopleg ia f l u i d ; coagulat ion factors become more d i l u t e d and so less l i k e l y to promote haemostasis. Because heparin i s infused into the blood i n the card iop leg ia bypass c i r c u i t , the longer a person i s on 96 the pump, the longer the exposure to heparin and i t s e f fec ts on some coagulation fac tors . Heparin concentrations are maintained at 300 to 400 u n i t s / k g of body weight, the amount usua l ly required to maintain an ac t iva ted c l o t t i n g time 4-6 times greater than normal (Holloway, 1993). Even though protamine sulphate i s administered to reverse the ef fects of heparin, i t i s not always completely e f f e c t i v e . Because the ha l f l i f e of heparin i s approximately 1.5 to 2 hours (Krogh, 1995), i t i s not uncommon to f i n d prolonged PTTs i n the f i r s t four to s ix hours a f ter admission to the CSICU, as was found i n t h i s study. There may have been some protec t ive e f fect from the heparin for the f i r s t s i x hours, but, beyond s ix hours, the ef fect of the heparin given during surgery would have worn of f . A f t e r s ix hours the coagulat ion re su l t s are therefore l i k e l y to re turn to normal l i m i t s as they d id i n th i s study. The amount of heparin i n the f lush so lu t ion may not be s u f f i c i e n t to influence coagulation fac tors . In a 48 hour per iod approximately 500 un i t s , inc lud ing 15 manual f lushes of 7 mL per f lush , are administered. This amount of heparin i s minimal and i s u n l i k e l y to have af fected coagulat ion re su l t s i n any major way. 97 The majority of problems with the catheters tended to occur i n the second 24 hour postoperative p e r i o d . There were more incidences of d i f f i c u l t y f lush ing the catheter, d i f f i c u l t y a s p i r a t i n g blood, dampened a r t e r i a l waveform, complete loss of a r t e r i a l waveform pat tern and more c l o t s on and i n the catheter t i p . The protec t ive e f fects of heparin remaining from surgery could have inf luenced the f indings r e s u l t i n g i n fewer d i f ferences among the groups during the f i r s t s i x hours. Furthermore, since the incidences of c l o t t i n g seems to be higher during the second 24 hour per iod , i t i s important that nurses continue to make close observations of the a r t e r i a l catheter to detect any signs of catheter occ lus ion . In other studies where coagulation factors were compared, there also were no s t a t i s t i c a l l y s i g n i f i c a n t d i f ferences between sa l ine and heparin groups. C l i f t o n and colleagues (1991) reported no s i g n i f i c a n t d i f ferences i n PTT and p l a t e l e t counts between the 4 U/mL heparin and sa l ine f lush groups done 24, 48, 72 and 96 hours post-i n s e r t i o n . Hook and colleagues (1987), Hook (1988), and Bolgiano and colleagues (1990) also reported no di f ferences for PT, PTT and p l a t e l e t counts at 72 hours. 98 Blood coagulation studies may not be the best way to determine which f lush so lu t ion i s more e f f e c t i v e . Although small amounts of heparin i n the f lush s o l u t i o n may not influence coagulation tes ts , heparin may be a fac tor i n whether there are c lo t s on or i n the catheter t i p at the time of removal, whether there are problems with catheter maintenance, and/or whether catheters w i l l require removal because of c l o t s . Clots i n and on the catheter at the time of removal may be a v a l i d i n d i c a t o r of occ lus ion r i s k . In th i s study, although there were no s t a t i s t i c a l l y s i g n i f i c a n t di f ferences among the groups, more pat ients i n the sa l ine f lush group had c l o t s than any other group. Only 3 other researchers reported information about c l o t s . Hook and colleagues (1987) found 2 c lo t s on the catheter t i p and another c l o t i n the catheter lumen i n the group that received Ringer 's lac ta te f lush so lu t ion . No catheters where .25 U/mL heparin f lush so lu t ion was used had c l o t s . Bolgiano and colleagues (1990) reported that , for catheters f lushed with heparinized so lut ions , only 2 catheters out of 104 c l o t t e d . In the present study, there were 3 pat ients i n the sa l ine group with c lo t s present on the catheter t i p compared to both of the heparin f lush groups which had no 99 c l o t s . Even though these f indings were not s t a t i s t i c a l l y -s i g n i f i c a n t , they do suggest a trend that the sa l ine group was more at r i s k for occ lus ion than the other two f lush groups. Hypotheses 2 There was a s i g n i f i c a n t l y greater incidence i n the sa l ine group of catheters requ ir ing removal because of occ lus ion . Five of the 10 catheters i n the sa l ine group had to be removed because blood could not be asp irated from them. Nurses car ing for pat ients i n the sa l ine group also reported greater frequency of d i f f i c u l t y a s p i r a t i n g the catheter . Although not s t a t i s t i c a l l y s i g n i f i c a n t , there were more problems regarding f lu sh ing , waveform dampening, loss of waveform pattern and p o s i t i o n a l catheters i n the sa l ine group. Comparing resu l t s to other s tudies , a l l p r i o r studies reported that d i f f i c u l t i e s which occurred with f lush ing catheters fol lowing blood sampling. No study reported on the t o t a l number of flushes or on the reasons why f lush ing occurred. Only Hook and colleagues (1987) and Hook (1988) re ferred to routine manual f lushes on an hourly bas i s . They d i d not provide any ra t iona l e for t h i s procedure. It i s unknown i f th i s procedure might 100 have inf luenced t h e i r re su l t s because the rout ine f lush ing ac t ion may have contributed to the prevention of c l o t formation. These authors concluded that there was no s i g n i f i c a n t d i f ference i n catheter patency between the heparinized and nonheparinized f lush so lu t ions . In terms of dampened waveform, Ouelette and Ei sner (1992) found that the sa l ine group i n t h e i r study a l so experienced more frequent dampening of waveforms. The authors also found that the sa l ine group had less accurate blood pressure readings v i a the a r t e r i a l catheter . Most studies described catheter patency i n terms of catheter s u r v i v a l time and reported longer s u r v i v a l time for the heparin f lushed catheters . C l i f t o n and colleagues (1991) reported that the 4 U/mL heparin group had a catheter s u r v i v a l rate of 86% at 96 hours compared with 52% s u r v i v a l rate at 40 hours for catheters maintained with s a l i n e . In th i s study, however, there were no di f ferences between the groups regarding catheter s u r v i v a l time with catheters surv iv ing a mean of 3 6 - 3 9 hours i n each group. In the two paed ia tr i c studies , Rajani and colleagues (1979) reported the ha l f l i f e of the catheter to be 7 101 days i n the 1 U/mL group and only two days i n the sa l ine group. They used no other ind ica tors of patency. Butt and colleagues (1987) also reported that when the concentrat ion of heparin was increased from 1 to 5 U/mL i n the f lush so lu t ion catheter, s u r v i v a l time was prolonged up to 7 days. Catheter s u r v i v a l was reported as only 2 days with the nonheparinized f lush so lu t ion group. In the present study, more catheters were removed i n the sa l ine group because of occ lus ion than i n the heparin groups. Although occ lus ion may not have been c i t e d as the reason catheters were removed i n other s tudies , only the American Assoc ia t ion of C r i t i c a l Care Nurses (1993) study reported less p r o b a b i l i t y of catheter occ lus ion with higher heparin concentrations. Butt and colleagues (1987) reported that a higher concentration of heparin, 5 U/mL, resu l ted i n prolonged catheter patency but no time frame was spec i f i ed . In the present study, ha l f of the catheters i n the sa l ine group were removed because they could not be asp ira ted . This f ind ing , although not s t a t i s t i c a l l y s i g n i f i c a n t , suggests that heparin may be required i n the f lush so lu t ion to maintain catheter patency (Rajani et a l . , 1979; Butt et a l . , 1987; C l i f t o n et a l . , 1991; 102 Ouelette & Eisner 1992; American Assoc ia t ion of C r i t i c a l Care Nurses (1993) . Although no studies reported d i f f i c u l t i e s with a s p i r a t i o n , there i s a trend that supports the notion that a r t e r i a l catheter patency i s at greater r i s k when maintained with nonheparinized f l u s h so lu t ions . An add i t i ona l f ind ing i n th i s study that i s worth not ing, was the ef fect of p o s i t i o n a l catheters . With a p o s i t i o n a l catheter, the rate of flow can be impaired thereby p o t e n t i a l l y increas ing the incidence of c l o t formation. Although p o s i t i o n a l catheters occurred more frequently i n the sa l ine group, there were no s t a t i s t i c a l d i f ferences . P o s i t i o n a l catheters may have increased the r i s k of dampened waveforms, i n a b i l i t y to asp irate blood from the catheter and necess i tated manual f lush ing to prevent catheter occ lus ion , however with the small sample s ize i t i s not poss ib le to c l a r i f y the e f fec ts of the p o s i t i o n a l catheters . Although coagulation factors may not have r e f l e c t e d major di f ferences among the groups, observable i n d i c a t o r s of occ lus ion and occ lus ion r i s k d id r e f l e c t the fact that catheters maintained with a sa l ine f lush so lu t ion had more d i f f i c u l t i e s than those maintained with heparin . The heparin groups had s i g n i f i c a n t l y fewer problems than 103 the sa l ine group regarding catheters r e q u i r i n g removal because of occ lus ion problems, with a s p i r a t i n g blood from the catheter and dampened waveforms. No d i f ference was apparent between the heparin groups on these i n d i c a t o r s . Although the 1 U/mL heparin f lush so lu t ion may have been s u f f i c i e n t to maintain patency, one must be hes i tant i n concluding that the 1 U/mL f lush was superior because the 1 U/mL group had shorter pump times and t h i s fac tor may have inf luenced the group's r i s k of occ lus ion and occurrences of occ lus ion . Only speculations may be made about the d i f ferences between the three f lush so lut ion groups. One reason for the d i f ference may be a t t r ibuted to the small sample s i z e . If the sample had been larger , perhaps a c l e a r e r trend may have appeared which might suggest which type of f lush so lu t ion that was most e f f ec t i ve . Further research may provide more conclusive r e s u l t s . Summary In t h i s chapter the f indings of the study have been presented and discussed. Research l i t e r a t u r e has been reviewed and compared to the f indings of t h i s study. 104 CHAPTER FIVE Summary, Conclusions, and Implications Introduction In t h i s chapter a summary of the study i s presented and major conclusions are out l ined . Implicat ions of t h i s study for nursing are presented. Summary This study was designed to compare the ef fect iveness of two concentrations of heparin, 2 U/mL and 1 U/mL, and one of normal sa l ine i n maintaining patency of r a d i a l ar t ery catheters . The study question arose from the r i s k of thrombocytopenia associated with.the use of heparin , as wel l as p r i o r research on the need for heparin to keep intermit tent intravenous catheters patent and from t h i s i n v e s t i g a t o r ' s observations that the type of f lush s o l u t i o n d i d not seem to af fect a r t e r i a l catheter patency. Since sa l ine had e f f e c t i v e l y maintained heparin lock patency i t was reasonable to expect sa l ine could a lso maintain patency of a r t e r i a l catheters . A review of the l i t e r a t u r e revealed that various types of f lush solut ions had been used for maintaining a r t e r i a l catheter patency. Six adult studies and two p a e d i a t r i c studies have been reported (Rajani et a l . , 105 1979; Butt et a l . , 1987; Hook et a l . , 1987; Hook, 1988; Bolgiano et a l . , 1990; C l i f t o n et a l . , 1991; the American Assoc ia t ion of C r i t i c a l Care Nurses, 1993). Hook and colleagues (1987) and Hook (1988) using a cardiac surgery-populat ion as t h e i r sample, were the only researchers who found no s i g n i f i c a n t di f ference i n catheter patency between heparinized and nonheparinized f lush so lu t ions . C l i f t o n et a l . , (1991) and the American Assoc ia t ion of C r i t i c a l Care Nurses (1993) found that the use of sa l ine as the f lush so lu t ion was associated with an increased frequency of catheter occ lus ion and malfunction compared to heparinized f lush so lut ions . Ouelette and Ei sner (1992) also found the sa l ine group had more observable d i f f i c u l t i e s with catheter patency and more frequent dampening of a r t e r i a l waveforms. Two p a e d i a t r i c studies a lso (Rajani et a l . , 1979, Butt et a l . , 1987) reported an increased frequency of catheter occ lus ion and malfunction with sa l ine f lush compared to heparinized f lush so lu t ions . Although most of these studies supported the not ion that heparin i s needed i n the f lush so lu t ion to maintain a r t e r i a l catheter patency, i t was not c l ear how much heparin may be required i n the f lush s o l u t i o n , because the type of comparison f lush so lu t ion v a r i e d , the 106 samples v a r i e d i n age and type of pat ient , and d i f f e r e n t outcome var iab le s were used to draw conclusions about catheter patency. The t h e o r e t i c a l framework for th i s study was based on factors in f luenc ing haemostasis: the degree of endothe l ia l damage; the rate and t u r b i d i t y of blood flow; and the presence of s u f f i c i e n t inherent coagulat ion f a c t o r s . By a f fec t ing each of these fac tors , the a r t e r i a l catheter system i s designed to minimize the r i s k of thrombosis. Heparin i n the f lush so lu t ion i s thought to i n h i b i t the funct ion of the coagulation factors i n haemostasis. In th i s study i t was hypothesized that when rout ine catheter care and continuous f lush ing with 3 mL/hr of e i ther heparin 2.0 U/mL, heparin 1.0 U/mL, or sa l ine f lush so lu t ion was provided there would be: (1) no d i f ference i n occ lus ion r i s k of subjects' r a d i a l a r t e r i a l catheters among f lush solut ions as ind icated by: prothrombin time, p a r t i a l thromboplastin time, p l a t e l e t count, and the presence of c lo t s i n the so lu t ion f lushed through the catheter and/or on the catheter t i p a f t er removal, and (2) no di f ference i n frequency of occ lus ion of subjects ' r a d i a l a r t e r i a l catheters among f l u s h 107 so lut ions as indicated by removal of the catheter for any of the fo l lowing reasons: (a) the i n a b i l i t y to f lush the catheter , (b) the i n a b i l i t y to aspirate blood from the catheter , and (c) loss of a r t e r i a l catheter waveform on the monitor. A three group, double-b l ind experimental design with repeated measures was used to test the hypotheses. A sample of 3 0 pat ients from one h o s p i t a l represented the general populat ion of pat ients having f i r s t time coronary ar tery bypass surgery i n B r i t i s h Columbia. A f t e r obta in ing consent, each subject was randomly assigned to e i t h e r one of the experimental groups or the contro l group. The f lush solut ions were prepared and dispensed by pharmacy. The inves t igator ensured that each assigned f lush bag was used as part of the a r t e r i a l system as soon as the r a d i a l a r t e r i a l catheter was inserted by the anaesthet ist at the beginning of surgery. A f t e r surgery, the pat ient was transferred to the CSICU and data c o l l e c t i o n began. It continued for 48 hours or u n t i l the catheter was removed, whichever came f i r s t . Each pat ient had blood drawn for three coagulat ion tests (PT, PTT, and p l a t e l e t count) on admission to the 108 CSICU and then at 24 and/or 48 hours pos t -operat ive ly as ordered by the phys ic ian . The fol lowing information was recorded for each pat ient : demographic data; a r t e r i a l waveform pattern at the time of admission and at every s h i f t change; the number of times the a r t e r i a l catheter was f lushed and the reason why; the nature, date and time of any problems occurring with the a r t e r i a l catheter , reason (s) for the catheter removal, and i f any c l o t s were present i n or on the catheter t i p at the time of removal. The f i r s t hypothesis for occ lus ion r i s k was tested by analys ing coagulation tests and frequency of c l o t s on or i n the catheter at the time of catheter removal. Analys i s indicated there were only two s t a t i s t i c a l l y s i g n i f i c a n t l y d i f f erent blood values . In the 1 U/mL f l u s h group, the PT on admission to the CSICU was s i g n i f i c a n t l y shorter and p l a t e l e t counts at 24 hours were s i g n i f i c a n t l y higher. Although not s t a t i s t i c a l l y s i g n i f i c a n t , the sa l ine group had a greater number of c l o t s i n and on the catheter t i p on removal compared to the heparinized groups. Hypothesis two was tested by r e l a t i n g the frequency of catheter occ lus ion to observable ind ica tors of occ lus ion . The only s i g n i f i c a n t f ind ing was that there 109 was d i f f i c u l t y a s p i r a t i n g blood from the catheters more frequently i n the sa l ine f lush group. There were no s i g n i f i c a n t di f ferences found among groups i n frequency of d i f f i c u l t y f lush ing the catheter, a r t e r i a l waveform pat tern dampening, or complete loss of a r t e r i a l waveform pat tern . A d d i t i o n a l f indings not included i n the hypothesis but of c l i n i c a l in teres t were the number of times the catheters were f lushed, the frequency of p o s i t i o n a l a r t e r i a l catheters , and reasons why the catheters were f lushed. The number of times the catheter needed to be f lushed was r e f l e c t i v e of common nursing prac t i ce s to ensure patency of the a r t e r i a l catheter and accuracy of the blood pressure readings. The reasons for the f l u s h were re la ted to blood sampling, dampened waveform and fo l lowing c a l i b r a t i o n . None of these f indings were s t a t i s t i c a l l y s i g n i f i c a n t but they were noted and observed c l i n i c a l l y . A r t e r i a l catheters are commonly inserted i n pa t i en t ' s r a d i a l a r t e r i e s and the natura l f l e x i n g ac t ion of the wrist bends the catheter thus r e q u i r i n g the wrist to be frequently repos i t ioned . The number of times the catheter was f lushed was mainly r e l a t e d to blood sampling. Flushing the catheter 110 fo l lowing blood sampling i s a necessary procedure to maintain catheter patency. The f indings might be inf luenced by: (1) the fact that pat ients blood work was only done at two points i n time, thereby decreasing the a b i l i t y to r e f l e c t trends, (2) the shorter bypass pump time of the 1 U/mL f l u s h group, (3) the d i l u t i o n of coagulation factors by the c a r d i o p l e g i a " f l u i d , and (4) the length of time heparin c i r c u l a t e s during surgery which may influence coagulat ion fac tor s . Conclusions The f indings do not f u l l y support the two hypotheses. Because the sample s ize was small and few coagulat ion tests were done, the resu l t s of t h i s study are not conclus ive . However, the resu l t s do suggest a trend. A r t e r i a l catheters maintained with a heparinized f lush so lu t ion seem to have a greater p r o b a b i l i t y of remaining patent over time than f lush so lut ions maintained without heparin. The heparin groups had s i g n i f i c a n t l y fewer c l i n i c a l problems than the sa l ine group, with fewer catheters r e qu ir ing removal because of occ lus ion , less problems with a s p i r a t i n g blood from the catheter and fewer dampened waveforms. Because the I l l r e s u l t s of the coagulation tests were not d e f i n i t i v e i t i s questionable how useful coagulation factors are i n p r e d i c t i n g occ lus ion r i s k . C l i n i c a l ind ica tors may be more useful i n determining frequency and r i s k of occ lus ion than coagulation tes t s . Implications for Nursing Pract ice One impl i ca t ion from th i s study i s that a r t e r i a l catheter f lush solut ions should continue to be maintained with 2 U/mL of heparin. The reason for t h i s i s because the r e s u l t s of the study were inconclus ive but the trend was i n favour of • a heparinized f lush s o l u t i o n . Unfortunately i t was unclear as to how much heparin i s required to maintain catheter patency. Another impl i ca t ion of th i s study was that nurses need to be aware of the s ign i f i cance of the length of time a pat ient i s on the bypass pump. Those pat ients who are i n surgery longer, could be at greater r i s k for bleeding i n i t i a l l y pos t -operat ive ly for the f i r s t s i x hours because t h e i r coagulation factors may be a l t e r e d due to the e f fects of being on the bypass pump. Nurses also need to be aware that coagulat ion studies are not the best ind ica tor of r i s k s of catheter occ lus ion: frequency of d i f f i c u l t y f lushing the catheter , 112 d i f f i c u l t y a s p i r a t i n g blood from the catheter, a r t e r i a l waveform pattern dampening, complete loss of a r t e r i a l waveform pattern , frequency of p o s i t i o n a l a r t e r i a l catheter occurrence, number of times the catheters are f lushed and reasons why the catheters are f lushed. These seem to be bet ter ind icators of catheter occ lus ion and therefore need to be assessed and recorded. The nurse must then r e c t i f y what nurses can do to decrease occ lus ion r i s k and prevent occ lus ion . Implications for Nursing Research Several suggestions for further research can be made based on the f indings of th i s study. Rep l i ca t ion of t h i s study using a larger sample to ensure s u f f i c i e n t s t a t i s t i c a l power to d i f f e r e n t i a t e between groups and to include several var iab les should be done. Because in frequent ly performed coagulation studies may not be conclusive i n i d e n t i f y i n g occ lus ion r i s k , c l i n i c a l observations may be better ind ica tors of catheter occ lus ion and should be included as outcome var iab le s and analyzed. Concluding Remarks Findings from th i s study do not support a change from the present prac t i ce of using 2 U/mL heparin f l u s h so lu t ion to using sa l ine f l u s h . Although coagulat ion tes ts ind icated no major di f ferences among the groups, the sa l ine group had more c lo t s and the highest number of catheters removed for occ lus ion problems. It remains to be seen whether a r t e r i a l catheters can be maintained without heparin for the f i r s t s i x hours. Findings suggest that catheter problems occurred p r i m a r i l y i n the second 24 hour per iod . This ra i ses the question, should nurses use two types of f lush solut ions to maintain catheter patency? 114 References American Assoc ia t ion of C r i t i c a l - C a r e Nurses (1993) . Evaluat ion of the e f fects of heparinized and nonheparinized f lush solut ions on the patency of a r t e r i a l pressure monitoring l i n e s : The AACN Thunder Project . American Assoc ia t ion of C r i t i c a l Care, 2(1), 3-15. Ashton, J . , Gibson, P . , & Summers, S. (1990). Ef fec t s of heparin versus sa l ine so lu t ion on intermit tent in fus ion device i r r i g a t i o n . Heart & Lung, 19(6), 608-612. Barnes, S. (1989). Rationale for subs t i tu t ing 0.9% sodium chlor ide i n j e c t i o n for heparin i n the maintenance of per iphera l indwel l ing intermit tent intravenous devices (heparin lock devices) . Unpublished manuscript. B a r r e t t , P . , & Lester , R. (1990). 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Paul 's H o s p i t a l , (1987). SI Reference handbook. Vancouver: St . Paul 's H o s p i t a l . Swerling, R. (1982). Normal sa l ine or d i l u t e heparin for heparin lock flush? Infusion, 6.(4), 123-4. Warkentin, T. & Kelton, J . (1990). Heparin and p l a t e l e t s . Haematology Oncology C l i n i c s of North America, 4(8) , 243-264 . Woods, S . , F r o e l i c h e r , E . , Halpenny, C , and Motzer, S . , (1995) . Cardiac Nursing, (3rd ed.) . P h i l a d e l p h i a : J . B . L ipp incot t Company. Wright, J . & Shelton, B. (1993) . Desk reference for c r i t i c a l care nurs ing. Boston: Jones and B a r t l e t t Publ i shers . Young, M . , Ehrenpreis , E . , Ehrenpreis , M . , & Kirshblum, S.(1989). Heparin-associated thrombocytopenia and thrombosis syndrome i n a r e h a b i l i t a t i o n p a t i e n t . Archives of Phys ica l Medicine and R e h a b i l i t a t i o n , 20 (6) , 468-470 . 122 APPENDIX A St . Paul 's Hospi ta l Po l i cy Management of A r t e r i a l Pressure Monitoring I. GENERAL INFORMATION A catheter is passed into an artery and connected to pressure monitoring tubing, a transducer and oscilloscope to monitor blood pressure continuously. A pressure bag and flush device is used to keep a heparinized saline solution flowing constantly through the catheter at a rate of approximately 2 ml/hr. This will keep the catheter patent without interfering with continuous monitoring. II. WAVE FORM COMPLICATIONS - Hemmorrhage - Thrombus or Embolus - Infection INSERTION AND MAINTENANCE OF THE CATHETER: Physician's Responsibilities: - Allen's Test for ulnar patency - insertion of the Arterial Catheter - ordering of blood pressure parameters - ordering of blood specimens - ordering removal of catheter Nursing Responsibilities: - assisting with insertion of the arterial catheter - establishing a continuous irrigation system according to procedure. - 2 - 123 - ensuring accuracy of the system - v a s c u l a r l i n e s are c a l i b r a t e d and double-checked w i t h c u f f pressures every four hours and prn. - maintenance of the i r r i g a t i o n system - mo n i t o r i n g of the a r t e r i a l pressure and i n s e r t i o n s i t e a c c o r d i n g to n u r s i n g standards - a p p l i c a t i o n , change, and documentation of d r e s s i n g a c c o r d i n g to procedure - withdraw! ; of blood specimens removal of a r t e r i a l c a t h e t e r - documentation R e s p i r a t o r y T h e r a p i s t ' s R e s p o n s i b i l i t i e s : - withdrawal of blood specimens (shared w i t h nursing) PRECAUTION: MEDICATIONS ARE NOT ADMINISTERED THROUGH AN ARTERIAL LINE A. INSERTION OF THE (ZATHKl'KR: Equipment: - pressure monitor - hemodynamic c a r t - pressure transducer and monitoring k i t - I.V. pole - transducer bracket - pressure bag - f l u s h bag - premixed heparin (1000 u n i t s i n 500 cc 0.9% Sodium C h l o r i d e ) - 20 ml p l a s t i c s y r i n g e - one rubber-tipped k e l l y f orcep c a t h e t e r - ask p h y s i c i a n f o r s i z e and type r e q u i r e d Procedure: 1. Turn pressure monitor on to warm up 2. F l u s h transducer and a l l t u b i n g w i t h h e p a r i n i z e d s a l i n e 3. Mount transducer on IV pole 4. Pass end of ext e n s i o n tubing to p h y s i c i a n to be attached to the a r t e r i a l c a t h e t e r . Squeeze f l u s h bar so th a t f l u i d i s f l o w i n g from tubing. 5. Squeeze f l u s h bar again to i r r i g a t e the catheter once i t i s attached. - 3 - 124 6. L e v e l transducer w i t h the r i g h t a t r i u m (use m i d - a x i l l a r y l i n e , 5th i n t e r c o s t a l as landmark). 7. Zero and c a l i b r a t e according to s p e c i f i c monitor's procedure. 8. Observe and record a r t e r i a l pressures. Double-check w i t h c u f f BP. 9. Dress area according to i n s e r t i o n s i t e : a) B r a c h i a l a r t e r y : i ) cleanse s i t e w i t h t i n c t u r e of h i b i t a n e 1:200 i i ) apply transparent adhesive d r e s s i n g i i i ) secure arm to padded armboard w i t h " K l i n g " , ensuring limb i s immobilized i v ) anchor stopcock to " K l i n g " d r e s s i n g w i t h waterproof tape - place waterproof tape under stopcock to p r o t e c t d r e s s i n g from contamination when withdrawing blood specimens b) R a d i a l a r t e r y : i ) cleanse s i t e w i t h t i n c t u r e of h i b i t a n e 1:200 i i ) apply transparent adhesive d r e s s i n g i i i ) place padded armboard on back of w r i s t and secure w i t h " K l i n g " . Ensure t h a t both ends or armboard are covered w i t h " K l i n g " and i t i s not able to s l i p out of p l a c e . NOTE: Place r o l l of " K l i n g " under w r i s t i f necessary to hyper-extend i v ) anchor stopcock to K l i n g d r e s s i n g w i t h waterproof tape - place waterproof tape under stopcock to p r o t e c t d r e s s i n g from contamination when withdrawing blood specimens - 4 - 125 c) Femoral a r t e r y : i ) cleanse w i t h t i n c t u r e of h i b i t a n e (1:200) i i ) apply t r a n s p a r e n t adhesive d r e s s i n g i i i ) anchor stopock and tu b i n g to s k i n w i t h water-proof tape d) D o r s a l i s pedis or p o s t e r i o r t i b i a l a r t e r y : i ) cleanse w i t h t i n c t u r e of h i b i t a n e (1:200) i i ) apply transparent adhesive d r e s s i n g i i i ) wrap tubing to ankle w i t h k l i n g d r e s s i n g i v ) anchor stopcock to k l i n g d r e s s i n g w i t h waterproof tape - place waterproof tape under stopcock to p r o t e c t d r e s s i n g from contamination when withdrawing blood specimens CAUTION: ENSURE THAT CANNULATED LIMB IS VISIBLE AT ALL TIMES TO DETECT POTENTIAL HEMMORRHAGE NOTE: Exception to Transparent adhesive Dressing: I f a r t e r i a l l i n e i s e s t a b l i s h e d v i a cutdown procedure then cutdown area w i l l i n i t i a l l y r e q u i r e d ry dr e s s i n g secured w i t h e l a s t o p l a s t tape. Use t r a n s -parent adhesive o n l y t o secure t u b i n g . Mark on e l a s t o p l a s t date and time d r e s s i n g a p p l i e d . Dressing must be removed and s i t e checked d a i l y . I f allergic to trans p a r e n t adhesive use dry dressingT - 5 - 126 b. maintenance of the irrigation system: 1. Trouble shooting: problem cause prevention treatment a) damped pressure Catheter t i p tracing against vessel wall P a r t i a l occlusion of t i p by c l o t C l o t t i n g i n stop-cock, transducer or tubing Leak i n pressure tubing A i r bubbles i n transducer or connector tubing Usually unavoidable Reposition catheter while observing wave form (physician) Continuous infusion Aspirate c l o t with under pressure of syringe and gently 1000 units heparin f l u s h with in 500 cc N.S. heparinized saline Carefully flush catheter after ^ blood withdrawal and re-establish I.V. drip. Tighten a l l con-nections when i n i t i a t i n g i r r i g a t i o n system Carefully flush transducer and tubing when setting up system and attaching to catheter Aspirate tubing with syringe (between patient and nearest stopcock). Flush transducer and tubing to a i r Tighten a l l connections Check system -a) flush transducer and d r i p tubing to atmosphere b) aspirate blood from tubing between patient and nearest stop cock Flush gently b) Abnormally high or low Change i n trans-ducer l e v e l Maintain patient i n Recheck patient and same position for transducer positions s e r i a l pressure Double check with measurements cuff BP Improper sequence of stopcock operation Use proper stop-cock sequence Flush transducer with I.V. solution; use proper sequence of turning stopcock to record pressure - 6 - 127 problem c) No pressure av a i l a b l e cause prevent ion treatment Transducer not open Follow routine, to patient Monitor settings incorrect, e.g. size, zero Check patient and systematic steps cuff B.P. Check for s e t t i n g up system - stop-cocks system and pressure check monitor measurement amplifier setup Hematoma a f t e r withdrawal of catheter Bleeding or oozing at puncture s i t e e) Decreased or absent pulse d i s t a l to puncture s i t e Spasm of artery f) Absent or dim- Thrombosis ot ished pulse artery d i s t a l to in s e r t i o n s i t e Maintain firm con- Continue to hold tinuous pressure on pressure to puncture s i t e during with-drawal of catheter and for at least ten minutes after withdrawal s i t e u n t i l oozing stops. Hold patient i n c r i t i c a l care area for 30 minutes following removal of catheter. Apply s t e r i l e gauze and Elastoplast f i r m l y over puncture s i t e , check r a d i a l pulse after placement to ensure adequate blood flow to arm. For femoral a r t e r i a l puncture s i t e s hold pressure 15 minutes Introduce a r t e r i a l needle cleanly,non -traumatically (physician) Inject lidocaine hydrochloride l o c a l l y at insertion s i t e and 10 mg into a r t e r i a l catheter (physician) A clean puncture i s less traumatic to the artery; check d i s t a l pulse a f t e r introduction of catheter; check d i s t a l pulse after application of dressing and hourly •thereafter. Ensure infusion of flush system Arteriotomy and Fogarty catheterization both d i s t a l l y and proximally from the puncture s i t e usually result i n return of pulse (physician) - 7 - 128 Dressing Change: a) Transparent adhesive d r e s s i n g may remain i n place as long as i t remains i n t a c t and the i n s e r t i o n s i t e remains f r e e of signs of inflammation. However, the " K l i n g " must be removed and the s i t e checked d a i l y to ensure: - the d r e s s i n g i s i n t a c t • - the s i t e i s c l e a n and f r e e from moisture and d r i e d blood - the catheter and connection are secure I f the s i t e i s f r e e of inflammation and n e c r o s i s and the transparent adhesive i s i n t a c t , reapply the padded board and k l i n g b) .Document according to n u r s i n g standards Withdrawal of blood samples: remove s o l i d cap from stopcock c l o s e s t to p a t i e n t place cap on a l c o h o l swab to maintain s t e r i l i t y cleanse p o r t w i t h a l c o h o l swab a t t a c h 3 ml s y r i n g e to atmosphere p o r t open 3-way stopcock to p a t i e n t and atmosphere p o r t s withdraw 3 ml of blood f o r d i s c a r d t u r n o f f stopcock to p a t i e n t a t t a c h a p p r o p r i a t e s y r i n g e f o r blood sample to atmosphere port open stopcock to p a t i e n t and atmosphere p o r t s and withdraw s u f f i c i e n t amount of blood f o r sample (s) r e t u r n stopcock t o i n - l i n e p o s i t i o n ensure t h a t there are no a i r bubbles i n tubing and squeeze f l u s h bar g e n t l y to c l e a r blood from l i n e open stopcock to atmosphere and o f f to p a t i e n t squeeze f l u s h bar to i r r i g a t e atmosphere port r e t u r n stopcock t o i n - l i n e p o s i t i o n - 8 - 129 o) swab stopcock with alcohol swab p) replace s t e r i l e s o l i d cap on atmosphere port ' q) observe d r i p chamber to ensure that f l u s h bar has closed r) ensure that there i s an appropriate pressure t r a c i n g on the o s c i l l o s c o p e s) document according to nursing standards PRECAUTIONS: Ensure f l u s h bar i s not stuck i n the "open" p o s i t i o n (I.V. would infuse r a p i d l y ) . I f bar s t i c k s , clamp o f f tubing and replace system. I f blood has backed up l i n e and a c l o t i s suspected, as p i r a t e the tubing before the l i n e i s flushed. C . TRANSPORT OF THE PATIENT WITH A PRESSURE MONITORING SYSTEM INTACT: Attach p a t i e n t to a s u i t a b l e portable monitor and continue pressure monitoring during transport. D. DISCONTINUATION OF THE SYSTEM: 1. Removal of the l i n e An a r t e r i a l l i n e should remain i n s i t u no longer than 7 days. C r i t e r i a : - there must be a physician's order - ensure second R.N. has been a l e r t e d when l i n e i s going to be removed a) Indwelling catheter in s e r t e d v i a cutdown and sutured i n place: Equipment: s c a l p e l blade instrument set t i n c t u r e of hibitane (clear) 2 or 3 packets of 4 x 4 s t e r i l e gauze 3" E l a s t o p l a s t adhesive bag f o r garbage - 9 - 130 Procedure: i ) remove d r e s s i n g i i ) cleanse area w i t h t i n c t u r e of h i b i t a n e i i i ) cut r e t a i n i n g suture w i t h s c a l p e l i v ) p l a c e a f o l d e d 4 x 4 gauze over the a r t e r i a l s i t e . (Do not use a bulky d r e s s i n g as t h i s prevents f i r m , d i r e c t p r e s s u r e ) . v) remove a r t e r i a l l i n e keeping continuous d i r e c t pressure on the s i t e f o r a minimum of 10 minutes and always u n t i l there i s no s i g n of bleeding.' T h i s can take up to 30 mins. v i ) when there i s no s i g n of b l e e d i n g , apply a pressure d r e s s i n g c o n s i s t i n g of a f o l d e d 4 x 4 gauze and a p i e c e of 3" E l a s t o p l a s t . v i i ) check the a r t e r i a l l i n e to ensure t h a t the e n t i r e c a t h e t e r has been removed. N o t i f y p h y s i c i a n i f c a t h e t e r not i n t a c t . v i i i ) document the procedure, n o t i n g the c o n d i t i o n of the i n c i s i o n or puncture s i t e i x ) monitor p u l s e , c o l o u r , warmth, movement and s e n s a t i o n of limb below s i t e f o l l o w i n g the procedure, document and report any s i g n of ischemia to the p h y s i c i a n x) disconnect pressure monitoring k i t from monitor cable and d i s c a r d b) Catheter i n s e r t e d by puncture: Equipment: s c a l p e l blade instrument set t i n c t u r e of h i b i t a n e ( c l e a r ) 2 or 3 packets of 4 x 4 s t e r i l e gauze 3" E l a s t o p l a s t adhesive bag f o r garbage Procedure: i ) remove d r e s s i n g - 10 - 1 3 1 i i ) cleanse area w i t h t i n c t u r e of h i b i t a n e i i i ) cut r e t a i n i n g suture w i t h s c a l p e l i v place a f o l d e d 4 x 4 gauze over the a r t e r i a l s i t e . (Do not use a bulky d r e s s i n g as t h i s prevents f i r m , d i r e c t p r e s s u r e ) . v) remove a r t e r i a l l i n e keeping continuous d i r e c t pressure on the s i t e f o r a minimum of 10 minutes and always u n t i l there i s no s i g n of b l e e d i n g . This can take up to 30 mins. v i ) when there i s no s i g n of b l e e d i n g , apply a pressure d r e s s i n g c o n s i s t i n g of a f o l d e d 4 x 4 gauze and a piece of 3" E l a s t o p l a s t . v i i ) check the a r t e r i a l l i n e to ensure t h a t the e n t i r e c a t h e t e r has been removed. N o t i f y p h y s i c i a n i f cath e t e r not i n t a c t . v i i i ) document the procedure, n o t i n g the c o n d i t i o n o f the i n c i s i o n or puncture s i t e i x ) monitor p u l s e , c o l o u r , warmth, movement and sen s a t i o n o f l i m b below s i t e f o l l o w i n g the procedure, document and report any s i g n of ischemia to the p h y s i c i a n x) disconnect pressure m o n i t o r i n g k i t from monitor cable and d i s c a r d REMOVAL OF FEMORAL LINE Pressure should be a p p l i e d above s k i n puncture s i t e . Pressure should be a p p l i e d across i n g u i n a l crease w i t h s i d e of hand. PRECAUTION: P a t i e n t i s to remain i n the c r i t i c a l care area f o r 30 minutes f o l l o w i n g removal o f the c a t h e t e r . 2. Capping a r t e r i a l l i n e : (see Management of a Capped A r t e r i a l L i n e , S e c t i o n A . 2 ) Revised October, 1990 CCPOL-1/17 APPENDIX B Data C o l l e c t i o n Tools PT #: PT HOSPITAL #: FLUSH BAG LETTER: GENDER: MALE FEMALE AGE: SURGEON: # OF BYPASS GRAFTS: d m y ADMISSION TO HOSPITAL: DATE: / / / TIME BYPASS PUMP TIME: CROSS CLAMP TIME: RADIAL ARTERY LINE ESTABLISHED: DATE: / / / TIME RADIAL ARTERY LINE DISCONTINUED: DATE: / / / TIME d m y ADMISSION TO CSICU: DATE: / / / TIME d m y DISCHARGE FROM CSICU: DATE: I I I TIME 133 Reason and Frequency of Flushing the A r t e r i a l Catheter Code # 1) Indicate the time of f lush ing . 2) Check ( ) the appropriate box to indicate reason for f l u s h i n g . Date Time I n i t i a l s Post Blood Sample Dampened Wave form C a l i b r a t i o n Other ** If you have any problem with f lushing of the catheter please document t h i s on the "Radial A r t e r i a l Catheter Problems" data c o l l e c t i o n sheet. 134 Blood Work Results Code# Time Interval Post-operative Admit Hours Hours Hours Day 1 Day 2 Time 0600 0600 PT PTT P l a t e l e t s Radia l A r t e r i a l Catheter Problems Indicate Y = Yes N = No Date Time Date Time Date Time Date Time Date Time Unable to f lush catheter . Unable to aspirate blood. Dampened pat tern . Complete loss of pa t tern . P o s i t i o n a l catheter . Other: RADIAL ARTERIAL LINE DISCONTINUED: REASON CLOTS PRESENT ON CATHETER TIP: YES / NO # 1 3 5 Appendix C Ef fec t s of f lush solut ions on r a d i a l ar tery catheter patency. Guidel ines for nurses p a r t i c i p a t i n g i n the data c o l l e c t i o n A l l pat ients w i l l be admitted to the CSICU fo l lowing coronary ar tery bypass surgery. The pat ients w i l l have a r a d i a l a r t e r i a l catheter i n s i t u , connected to the standard a r t e r i a l f lush system. Follow the standards of care for a r t e r i a l monitoring as per hosp i ta l procedure. The f lush so lu t ion bag w i l l be coded by pharmacy and marked with a number. Follow these steps with every CABG pat ient who i s admitted to CSICU and i s i n the a r t e r i a l f lush s o l u t i o n study: Normal routine 1. Connect the a r t e r i a l l i n e f lush system to the a r t e r i a l catheter, assess the waveform pattern for accuracy and mount a waveform s t r i p on the data c o l l e c t i o n form with the pa t i en t ' s code name found on the a r t e r i a l f lush bag (as preassigned by pharmacy). 2. Send blood samples at the time of admission inc lud ing the PT, PTT, and p l a t e l e t s . Repeat these blood samples as ordered up to twice i n the f i r s t 24 hours pos t -operat ive ly , then at 0600 on day one and day two pos t -operat ive ly . Record the blood re su l t s on the data 136 c o l l e c t i o n sheet. 3. Attach a s t r i p of the a r t e r i a l waveform pat tern at the s tar t of each s h i f t . 4. Complete the demographic data sheet i n the f i r s t four hours fol lowing the pa t i en t ' s admission. The information which needs to be recorded on the data c o l l e c t i o n form includes: the pa t i en t ' s h o s p i t a l number, p a t i e n t ' s code number, gender, age, surgeon, # of bypass g r a f t s , admission to h o s p i t a l , pump and clamp times, t o t a l blood loss i n OR, admission date and time to CSICU, date and time the a r t e r i a l l i n e was inser ted . 5. Record each time the r a d i a l a r t e r i a l catheter i s f lushed inc lud ing the date, time and reasons / ind icat ions for the f lush on the data c o l l e c t i o n sheet. 6. The assessment for c lo t s requires a double check u t i l i z i n g the ass i s tant head nurse. There are two parts to t h i s assessment. F i r s t , assess for c l o t s , us ing a syringe aspirate 5 cc of blood back from the a r t e r i a l catheter stopcock and gently empty the syringe contents onto a gauze pad. Both nurses need to observe for any signs of a c l o t on the gauze. Second, remove the catheter 137 and both nurses observe to see i f there are any c l o t s present on the catheter. Record a l l f indings on the data c o l l e c t i o n sheet. 7. Record the date, time, and reason the a r t e r i a l catheter i s removed on the data c o l l e c t i o n form. Problems with the catheter 8. Record any problems with the r a d i a l a r t e r i a l catheter inc lud ing the date and time and the s p e c i f i c problem on the data c o l l e c t i o n sheet. 9. If changes i n the a r t e r i a l waveform pat tern occur, the nurse w i l l take an add i t i ona l waveform s t r i p , mounted i t on the form and document i t on the data c o l l e c t i o n form. 138 APPENDIX D Informed Consent T i t l e : Test ing whether heparin i n the f lush so lu t ion i s needed to keep r a d i a l ar tery catheters open. Investigator: Bernice Budz, R . N . , M.S .N. Student You have been asked to p a r t i c i p a t e i n a research study. Your surgeon i s aware of your p o t e n t i a l p a r t i c i p a t i o n but p a r t i c i p a t i o n i s voluntary and i s e n t i r e l y up to you. Purpose Pat ients who have coronary ar tery bypass surgery have a very small tube or catheter rout ine ly inserted into the r a d i a l a r t e r y which i s located on the lower aspect of the arm. This catheter helps us monitor your blood pressure on.an ongoing bas is and to e a s i l y take blood samples as required . To keep t h i s tube open, i t must be flushed with an intravenous f l u i d s o l u t i o n , usua l ly c a l l e d the f lush s o l u t i o n . This f l u s h so lu t ion contains a small amount of heparin which i s be l i eved to help prevent the blood from c l o t t i n g i n the tube. Although i t was be l ieved heparin was necessary to prevent c l o t s from forming, studies have i d e n t i f i e d that for other types of catheters , the a d d i t i o n a l heparin was not necessary. This study w i l l inves t igate whether or not these tubes remain open just as wel l when so lut ions have less heparin than i s current ly used or no heparin . 139 Procedures You w i l l be randomly assigned by the pharmacist ( l ike toss ing a coin) to have your catheter flushed with one of three so lu t ions , e i t h e r a so lu t ion with the amount of heparin normally used at t h i s h o s p i t a l , or a so lu t ion with less than the usual amount, or a so lu t ion with no heparin. Following the regular h o s p i t a l procedure your blood w i l l be tested for i t s a b i l i t y to c l o t at least 4 times over the f i r s t 48 hours a f ter your surgery. No a d d i t i o n a l blood work from what occurs normally i s therefore required for your p a r t i c i p a t i o n i n th i s study. As w e l l , rout ine procedures w i l l be done as usual to assess and care for your a r t e r i a l catheter . The blood work done as a routine part of your post operat ive care w i l l be used to assess the e f fects of the three d i f f e r e n t types of so lut ions . Risks and Benefits There i s no serious r i s k to you to be i n t h i s study. Although i t i s poss ib le that your catheter may c l o t more e a s i l y i f you get the sa l ine f lush so lu t ion or the so lut ion with the reduced heparin concentrat ion, evidence from studies that compared f l u s h so lut ions used for venous catheters indicated no more l i k e l i h o o d of c l o t t i n g for these solut ions than for the so lu t ion that contained the regular amount of heparin. In add i t ion , s ince the amount of heparin rout ine ly i n the f l u i d i s smal l , the d i f ference between the normal so lu t ion and the other two so lut ions i s minimal and i t i s u n l i k e l y that c lo t s w i l l form i n the tube. In fac t , p o t e n t i a l benefi ts of not get t ing heparin are that i t 1 4 1 I have read the above information and I have had the opportunity to ask questions to help me understand what my p a r t i c i p a t i o n would invo lve . I f r e e l y consent to p a r t i c i p a t e i n the study and acknowledge rece ipt of a copy of the consent form. Signature of the Part i c ipant Date Signature of the Witness Date 142 Appendix E Research Study by Bernice Budz E f f e c t s of flu s h solutions on r a d i a l artery catheter patency. Information for Perfus ion is t s A f t e r obtaining pat ient consent the researcher w i l l n o t i f y the Pharmacist and the fol lowing procedure w i l l be fol lowed. A randomized process (using the table of random numbers) w i l l be used to i d e n t i f y each group composed of 10 subjects who w i l l receive e i t h e r the f lush so lu t ion containing heparin 2.0 units /mL, or heparin 1.0 units /mL, or 0.9% s a l i n e . The pharmacist, alone, w i l l have the reference codes i d e n t i f y i n g the type of f lush so lu t ion each subject rece ives . Reference codes w i l l be sealed u n t i l the completion of the study. However, the code w i l l be broken i f a s i t u a t i o n ar i ses whereby the heal th of a subject i s at r i s k from a coagulation disorder and i t i s e s s en t ia l to i d e n t i f y the contents of h i s / h e r f lush s o l u t i o n . The h o s p i t a l pharmacy w i l l prepare f lush bags i n the concentrations s t i p u l a t e d for each of the three groups; heparin 2.0 units /mL, heparin 1.0 units /mL, and 0.9% s a l i n e . The 30 f lush bags w i l l then be coded and sent to the operating room where they w i l l be i n i t i a t e d as the f lush so lut ion once the p a t i e n t ' s r a d i a l a r t e r i a l catheter has been inserted . Af ter the pat ient has had surgery and has been admitted to the CSICU the data c o l l e c t i o n process w i l l begin. It w i l l continue for 48 hours or u n t i l the catheter i s removed, whatever comes f i r s t . The per fus ion i s t s i n the operating room w i l l be responsible 143 to hang the f i r s t f lush so lut ion bag and w i l l a lso be in s t ruc ted about the study. They w i l l be informed as to what f lush bag they are to hang for the a r t e r i a l l i n e system on each pat ient based on randomization of the f lush so lut ions . If you have any questions please c a l l Bernice at ext. 2118 or 2190. * Note: There must be a separate f lush bag for the a r t e r i a l l i n e and the Swan Gantz f lush l i n e . 

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