Ventricular Function During Halothane Anesthesia in Closed Chest Dog

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Abstract
Determination of left and right ventricular stroke work were obtained in 15 non-operated dogs under local anesthesia before, during and after halothane anes-thesia. Depression of myocardial contractility as indicated by % changes in slopes of the ventricular function curves was directly related to the inspired concentration of halothane. Per cent changes in the slopes of the left ventricular function curves with 0.5, 1.0, 1.5 and 2.0% halothane were -3, -13, -51, and -89 respectively. Changes in the right ventricular function curves were similar to those of the left Myocardial O2 consumption as determined by tension-time index was also reduced. The decrease of ventricular stroke work paralleled the decrease of tension-time Index in relation to the inspired concentration of halothane. These results tend to support the concept that the mechanical efficiency of the heart is not altered and that the ventricles operate at different functional levels during various concentrations of halothane anesthesia in the presence of a decrease in myocardial contractility.