Comparison of fentanyl and halothane as supplement to nitrous-oxide-oxygen anaesthesia for coronary artery surgery.

Twenty unselected patients suffering from incapacitating angina, in spite of medication with nitrates, beta-blockers and calcium antagonists, were studied before and during coronary artery bypass surgery. Fentanyl or halothane was randomly used in combination with nitrous oxide for maintenance of anaesthesia in order to compare the haemodynamic response to surgery and cardiopulmonary bypass with these two anaesthetic regimens. Systemic and pulmonary artery pressure were kept within normal limits with the aid of volume replacement and/or nitroprusside. The haemodynamic response to surgery and bypass was benign and almost identical in the two groups. Cardiac index increased markedly after bypass (P less than 0.02-0.001) from 2.0 to 3.0 1 X min-1 X m-2 due to an increase in heart rate with no change in stroke index (40 ml X m-2). Oxygen delivery remained unchanged at 17 mmol X min-1 X m-2 in spite of a marked reduction in blood erythrocyte volume fraction (B-EVF), from 38% before bypass to 24% after bypass (P less than 0.001). Oxygen uptake remained unchanged until the end of surgery and did not differ between the groups. Systemic vascular resistance, corrected for the change in viscosity due to the altered B-EVF, was unchanged during the study. No difference was observed between the groups in the relation between pulmonary artery diastolic pressure and left ventricular stroke work index or stroke index, either before or at the end of cardiopulmonary bypass when the patients were transfused from the oxygenator.