UBC Theses and Dissertations

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UBC Theses and Dissertations

Advisory system for administration of Phenylephrine following spinal anesthesia for cesarean section Fung, Parry


Phenylephrine is a drug used at British Columbia Women's Hospital, Vancouver British Columbia to treat maternal hypotension induced by spinal anesthesia for Cesarean Section. Hypotension can cause serious fetus hypoxia, therefore maternal blood pressure must be kept above a minimum level. Phenylephrine dosage is mainly determined in a heuristic manner by the anesthesiologist's experience and observation. Since an overdose of phenylephrine can result in maternal bradycardia and hypertension, an advisory system is developed to recommend the optimal dosage of phenylephrine that ensures an appropriate blood pressure response. Data was collected from patients undergoing Cesarean Section at the British Columbia Women's Hospital for drug response modeling. Preliminary results indicated that the quality of noninvasive blood pressure measurement by the existing cuff sphygmomanometry was a prominent source of model uncertainty. Therefore an algorithm that improves the resolution of the blood pressure measurement using pulse transit time, the travelling time of a pulse wave between two sites, was developed and is presented in this thesis. The refined blood pressure reading was used for patient modeling. Separating phenylephrine's blood pressure response from the spinal anesthesia's is the main challenge for this system identification. Various techniques are discussed and validated in Chapter 3. The advisory system based on the results of Chapter 3 was then developed. When hypotension occurs, the advisory model predictive controller recommends an adequate phenylephrine dose according to the identified internal patient model. The design, tuning and online adaptation of the system are illustrated in Chapter 4. Chapter 5 concludes this thesis and points towards future research in this field.

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