Comparative metabolic effects of halothane and enflurane in rat heart cell culture

The effects of halothane and enflurane on the oxygen consumption rates and substrate utilization by beating and nonbeating rat heart myocytes in cell culture were compared. Halothane, on an equal dose and equal MAC (minimum alveolar concentration producing immobilization of 50% of subjects) basis, was significantly more effective than enflurane in reducing total myocyte oxygen consumption and contractile rate. The greater effect of halothane on oxygen consumption was not due entirely to its effect on myocyte contractile rate, since quiescent (nonbeating) cells and cells rendered nonbeating by large doses of halothane also showed greater reductions in oxygen consumption than with large doses of enflurane. Both halothane and enflurane reduced glucose and palmitic acid metabolism by myocytes when compared with controls. However, there were no significant differences between halothane or enflurane with regard to glucose metabolism. Halothane was significantly more effective than enflurane in reducing cellular palmitic acid metabolism. Although palmitic acid uptake by myocytes was reduced to the same extent by both anesthetics when compared with control uptake values, halothane reduced myocyte uptake of glucose to a greater degree than enflurane. The results of this study indicate that halothane is a more potent myocardial metabolic depressant than enflurane.