Haemodynamic and plasma vasopressin responses with high-dose fentanyl anaesthesia during aorto-coronary bypass operations.

Twelve male patients were given high dose fentanyl (75-100 microgram.kg-1) anaesthesia with oxygen during elective aorto-coronary bypass operations, and their haemodynamic and vasopressin responses were determined during induction, sternotomy, cardiopulmonary bypass, post-bypass and recovery periods. For comparison, a group of 12 male patients were anaesthetized with morphine, halothane 0.5 per cent, nitrous oxide and oxygen, and were similarly studied. Significant alterations in haemodynamics included increased mean arterial pressure after sternotomy in the fentanyl group, increased heart rate in both groups, increased systemic vascular resistance after sternotomy only in the halothane group, and decreased left ventricular stroke work index in both groups following induction, bypass, and during the recovery periods. Plasma vasopressin levels increased significantly in both groups during the bypass period, but returned to baseline levels following bypass. Serum sodium and osmolality did not change significantly, and urinary sodium and potassium excretion rose with the progress of the operation in both groups. A positive correlation was found between mean arterial pressure and vasopressin only in the halothane group. Systemic vascular resistance was correlated to vasopressin levels in both groups. Vasopressin response in both groups was similar, with significant but relatively low increases in levels during cardiopulmonary bypass. Fentanyl-oxygen anaesthesia did not provide haemodynamic stability in eight of 12 patients.