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Cardiac performance and metabolism during coronary artery bypass graft surgery
103 CARDIAC PERFORMANCE AND METABOLISM DURING CORONARY ARTERY BYPASS A Comparison of fentanyl/propofol with GRAFT SURGERY. fentanyl/enflurane anaesthesia. S M Underwood, S W Davies, R 0 Feneck, R K Walesby Departments of Anaesthesia, Cardiology and Cardiothoracic Surgery The London Chest Hospital, Bonner Road, LONDON El, UK
INTRODUCTION Patients presenting for CABG surgery are at risk from myocardial ischaemia and infarction, thus anaesthetic techniques which keep this risk to a minimum are essential (1). Previous work has suggested that an opiate based technique supplemented by volatile anaesthetics may best achieve this end (2). We have chosen to compare the effects of fentanyl/ enflurane (E) anaesthesia with fentanyl/propofol (P) anaesthesia on myocardial performance and metabolism before bypass. PATIENTS AND METHODS 20 patients scheduled for elective CABG who gave written informed consent were studied. The trial had received local ethical committee approval. All patients received their routine antianginal medication on the morning of surgery, and premeditation with oral benzodiazepine and i.m. opiate. Monitoring was established with pulmonary artery, radial artery and thermodilution coronary sinus catheters. Lead II ECG was displayed and V5 was recorded using a Holter monitor. Anaesthesia was induced with fentanyl 20 wg/kg and pancuronium 0.1 mg/kg to establish neuromuscular blockade. Mechanical ventilation was provided with 50% 0 /N . Patients were randomly allocated ?o deceive either: (P) propofol 6 mg/kg/hr for up to 10 mins, then halved and adjusted as desired (mean dose 2.8 mg/kg/hr) or (E) enflurane 0.8% inspired concentration for 10 minutes, reduced to 0.6% and adjusted as desired (mean insp cone 0.7%). Measurements were made before induction (baseline), after intubation and after sternotomy. Individual episodes of hypertension (systolic BP> 120% baseline) were treated with boluses of glyceryl trinitrate (GTN) i.v. Data were analysed by Freidmann a-way analysis of variance, Wilcoxon matched-pairs signed-ranks and Mann-Whitney tests as appropriate.
RESULTS Patient data and baseline haemodynamic analysis confirm comparability between the groups. During the study there were no significant differences in haemodynamics between the groups. Following intubation, both groups showed a rise in heart rate (HR) and cardiac index. Systemic vascular resistance (SVR) fell after intubation then increased during surgery. 5 patients receiving E and 3 receiving P required single bolus doses of GTN. Stroke index was unchanged after intubation but fell during surgery as SVR increased. Right atria1 and pulmonary capillary wedge pressures remained unchanged with both E and P; pulmonary artery pressure increased after intubation then fell following either E or P. Regional and global coronary blood flow (CBF) were maintained in both groups as were MvO and lactate extraction ratio. However; instances of lactate production were seen. One patient receiving E showed an increase in CBF and Mv02 during surgery and coronary sinus lactate production suggesting simple myocardial oxygen imbalance. Halter monitoring confirmed ischaemia but not perioperative infarction. One patient receiving P showed an increase in regional CBF and MvO regional lactate production but no E&'changes at any time. DISCUSSION Previous work suggests that increased HR is an important cause of perioperative ischaemia (1). Our data suggest that increased SVR may also adversely affect myocardial oxygen balance. Previous data show that E is a useful adjunct to fentanyl for CABG surgery (2). We believe our data suggest that P in the manner described is an acceptable alternative. REFERENCES 1. Slogoff S, Keats AS. Does perioperative myocardial ischemia lead to postoperative myocardial infarction? Anesthesiology 1985; 62: 107-114 2. Moffitt EA, Sethna DH. The coronary circulation and myocardial oxygenation in coronary disease: effects of anesthesia. Anesth Analg 1986; 65: 395-410
INTRODUCTION Patients presenting for CABG surgery are at risk from myocardial ischaemia and infarction, thus anaesthetic techniques which keep this risk to a minimum are essential (1). Previous work has suggested that an opiate based technique supplemented by volatile anaesthetics may best achieve this end (2). We have chosen to compare the effects of fentanyl/ enflurane (E) anaesthesia with fentanyl/propofol (P) anaesthesia on myocardial performance and metabolism before bypass. PATIENTS AND METHODS 20 patients scheduled for elective CABG who gave written informed consent were studied. The trial had received local ethical committee approval. All patients received their routine antianginal medication on the morning of surgery, and premeditation with oral benzodiazepine and i.m. opiate. Monitoring was established with pulmonary artery, radial artery and thermodilution coronary sinus catheters. Lead II ECG was displayed and V5 was recorded using a Holter monitor. Anaesthesia was induced with fentanyl 20 wg/kg and pancuronium 0.1 mg/kg to establish neuromuscular blockade. Mechanical ventilation was provided with 50% 0 /N . Patients were randomly allocated ?o deceive either: (P) propofol 6 mg/kg/hr for up to 10 mins, then halved and adjusted as desired (mean dose 2.8 mg/kg/hr) or (E) enflurane 0.8% inspired concentration for 10 minutes, reduced to 0.6% and adjusted as desired (mean insp cone 0.7%). Measurements were made before induction (baseline), after intubation and after sternotomy. Individual episodes of hypertension (systolic BP> 120% baseline) were treated with boluses of glyceryl trinitrate (GTN) i.v. Data were analysed by Freidmann a-way analysis of variance, Wilcoxon matched-pairs signed-ranks and Mann-Whitney tests as appropriate.
RESULTS Patient data and baseline haemodynamic analysis confirm comparability between the groups. During the study there were no significant differences in haemodynamics between the groups. Following intubation, both groups showed a rise in heart rate (HR) and cardiac index. Systemic vascular resistance (SVR) fell after intubation then increased during surgery. 5 patients receiving E and 3 receiving P required single bolus doses of GTN. Stroke index was unchanged after intubation but fell during surgery as SVR increased. Right atria1 and pulmonary capillary wedge pressures remained unchanged with both E and P; pulmonary artery pressure increased after intubation then fell following either E or P. Regional and global coronary blood flow (CBF) were maintained in both groups as were MvO and lactate extraction ratio. However; instances of lactate production were seen. One patient receiving E showed an increase in CBF and Mv02 during surgery and coronary sinus lactate production suggesting simple myocardial oxygen imbalance. Halter monitoring confirmed ischaemia but not perioperative infarction. One patient receiving P showed an increase in regional CBF and MvO regional lactate production but no E&'changes at any time. DISCUSSION Previous work suggests that increased HR is an important cause of perioperative ischaemia (1). Our data suggest that increased SVR may also adversely affect myocardial oxygen balance. Previous data show that E is a useful adjunct to fentanyl for CABG surgery (2). We believe our data suggest that P in the manner described is an acceptable alternative. REFERENCES 1. Slogoff S, Keats AS. Does perioperative myocardial ischemia lead to postoperative myocardial infarction? Anesthesiology 1985; 62: 107-114 2. Moffitt EA, Sethna DH. The coronary circulation and myocardial oxygenation in coronary disease: effects of anesthesia. Anesth Analg 1986; 65: 395-410