Myocardial Metabolism and Oxygenation in Man Awake and during Halothane Anesthesia

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Abstract
Cardiac catheters were placed in 7 healthy conscious patients so that aortic and left ventricular pressures (and the derivative), cardiac output (thermodilution) and myocardial blood flow (Ar washin) could be measured. Blood was drawn for measurement of arterial blood-gas and arterial and coronary venous O2, glucose, lactate, pyruvate and fatty acid values. After induction of anesthesia by inhalation of halothane, the measurements were made during administration of low (0.70%) and high (1.54%) end-tidal halothane concentrations. Myocardial function decreased in a dose-related fashion without a change in heart rate. Myocardial blood flow and oxygen consumption were depressed in a similar manner. Myocardial O2 extraction decreased and lactate did not change; apparently myocardial oxygenation was adequate. The heart rate-systolic blood pressure product correlated poorly with myocardial O2 consumption. Systolic blood pressure and the contractile performance index [dP/dt/IP] were better correlated with myocardial O2 consumption, but the value of the coefficient was still low. Without significant changes in heart rate, systolic blood pressure is the best correlate of myocardial O2 consumption in healthy man during the myocardial depression produced by halothane.