Enflurane depresses myocardial function, perfusion, and metabolism in the dog

Trained dogs with chronically implanted catheters and left ventricular (LV) pressure transducers were anesthetized with 2.3 per cent (1 + MAC) and 3.6 per cent enflurane. Left ventricular function and metabolism were studied while the dogs were awake and during exposure to the two anesthetic concentrations. Enflurane depressed LV function in a dose-dependent fashion. Myocardial blood flow and oxygenation mirrored the functional changes. Myocardial oxygen extraction decreased and lactate extraction increased to the myocardium. Low concentrations of halothane in the same dogs on different days had similar effects. However, 2 MAC halothane resembled 1.6 MAC enflurane, suggesting that the cardiovascular dose-effect curve for enflurane is steeper than that for halothane. Both anesthetics produce dose-dependent negative inotropic effects in the intact dog, accompanied by equivalent decreases in cardiac oxygen demand. Contrary to previous suggestions, enflurane appears to be at least at depressant to the dog heart as halothane.