Der Anaesthesist
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The cardiocirculatory responses to equianaesthetic concentrations (MAC 0.5 and MAC 1.0 plus 67% N2O) of halothane, methoxyflurane, enflurane and isoflurane were studied in a total of 35 closed-chest dogs during ventilation controlled to produce normocapnia. Each anaesthetic produced a dose-related decrease in mean arterial pressure and in values reflecting cardiac function. These included cardiac output, stroke volume, left ventricular max dp/dt and ejection fraction. ⋯ Parallel with the depression in cardiac performance and blood pressure as two of the main predictors of energy demand, myocardial oxygen consumption was found to be significantly reduced by each of the anaesthetics. The ratio of the external work of the left ventricle to its oxygen consumption indicated that myocardial efficiency deterioated. The clinical implications are discussed.