The Influence of Anaesthetics on Systemic Vascular Resistance During Cardiopulmonary Bypass

The influence of various anaesthetic techniques was studied during total cardiopulmonary bypass with a disc oxygenator, high flow perfusion and mild hypothermia. Data were obtained from 52 adult patients undergoing corrective surgery for congenital or acquired heart disease. The material was randomly divided in two groups with 28 and 24 patients, respectively. Before perfusion, the same anaesthetic technique was applied to all patients. During perfusion, halothane was vapourized into the oxygenator at concentrations of 1.0-1.5% in group I. In group II, no halothane was used but 5-10 mg diazepam was supplied into the oxygenator at the beginning of bypass. To both groups small amounts of fentanyl were given during bypass. There were no significant differences in mean perfusion time and perfusion blood flow between the groups. Systemic vascular resistance increased in both groups during cardiopulmonary bypass and hypothermia. In group I, a significant increase did not occur until after 60 minutes (13%), whereas in group II a significant increase occurred as early as after 40 minutes with a maximum after 60 minutes (25%). Data for base excess demonstrated a significant fall after 30-40 minutes of perfusion in group II, but no significant changes in group I. It is concluded that halothane exerts a beneficial vasodilatory action during cardiopulmonary bypass and hypothermia and the hazards of local reduction in organic blood flow are eliminated, since an adequate perfusion pressure and flow are maintained by the heart-lung machine.