Dose-dependent depression of cardiac function and metabolism by halothane in swine (Sus scrofa)

Abstract

Halothane depresses myocardial blood flow and metabolism in the dog, but no studies in man have been published. However, the coronary circulation of the pig is remarkably similar to that of man. The authors investigated the effects of halothane nitrous oxide anesthesia on cardiac function and metabolism in piglets. Thermodilution cardiac output, catheter-tip-manometer measurement of left ventricular function, electromagnetic flowmeter measurement of coronary blood flow, and blood and tissue measurements of gases and metabolites were made during 0.04 (control), 0.46 (low concentration) and 1.04 (high concentration) per cent halothane vaporized in nitrous oxide, 60% : oxygen, 40%. Compared with control, the low concentration decreased cardiac output (CO) by 10%, left ventricular systolic pressure (LVSP) by 30%, peak contractile element velocity (V(max)) by 34%, coronary blood flow (CBF) by 36%, and cardiac oxygen uptake (V(O2)) by 55%. Compared with control, the high concentration decreased CO by 32%, LVSP and V(max) by 53%, CBF by 63% and V(O2) by 62%. This indicates that the dose-related depression in left ventricular function produced by halothane was accompanied by equivalent decreases in coronary blood flow and oxygen consumption. There was minimal evidence of anaerobic metabolism in these depressed ventricles. Tissue levels of the high-energy phosphates, adenosinetriphosphate and creatine phosphate, and glycogen were unchanged. It is concluded that changes in cardiac oxygenation and metabolism in the pig during halothane anesthesia result from the changes in ventricular function.