The influence of two inhalational anesthetics, isoflurane and sevoflurane, on the end-systolic pressure-volume relations (ESPVR) of the left ventricle (LV) in situ was investigated in open-chest dogs anesthetized with α-chloralose. The LV volume was measured by a conductance catheter while the LV pressure was measured by a tipmicromanometer. The end-systolic elastance (Ees) of the LV was calculated as the slope of ESPVR which was elicited when the inferior vena cava was transiently occluded. The dogs were randomly assigned to two groups, receiving either 1.3% and 2.6% isoflurane (n=6) or 2.3% and 4.6% sevoflurane (n=6), which are equivalent to 1 and 2 MAC of isoflurane or sevoflurane, respectively. Both isoflurane and sevoflurane produced dose-dependent decreases in the cardiac output to a similar degree. Isoflurane and sevoflurane caused equivalent decreases in Ees of 23% and 16% at 1 MAC, and 48% and 41% at 2 MAC, respectively. Dobutamine 3 μg·kg-1·min-1 produced a simultaneous restoration of Ees and recovery of the cardiac output at 1 and 2 MAC of both isoflurane and sevoflurane. We thus conclude that the depressant effect of sevoflurane on cardiac contractility is almost identical to that of isoflurane in the dog, and they are both reversed by the use of a low dose of dobutamine.
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