Inhalational anesthetics produce differential effects on hepatic blood flow and oxygenation that may impact hepatocellular function and drug clearance. In this investigation, the effects of sevoflurane on hepatic blood flow and oxygenation were compared with those of enflurane, halothane, and isoflurane in ten chronically instrumented greyhound dogs. Each dog randomly received enflurane, halothane, isoflurane, and sevoflurane, each at 1.0, 1.5, and 2.0 MAC concentrations. Mean arterial blood pressure and cardiac output decreased in a dose-dependent fashion during all four anesthetics studied. Heart rate increased compared to control during enflurane, isoflurane, and sevoflurane anesthesia and did not change during halothane anesthesia. Hepatic arterial blood flow and portal venous blood flow were measured by chronically implanted electromagnetic flow probes. Hepatic O2 delivery and consumption were calculated after hepatic arterial, portal venous, and hepatic venous blood gas analysis. Hepatic arterial blood flow was maintained with sevoflurane and isoflurane. Halothane and enflurane reduced hepatic arterial blood flow during all anesthetic levels compared to control (P < 0.05), with marked reductions occurring with 1.5 and 2.0 MAC halothane concomitant with an increase in hepatic arterial vascular resistance. Portal venous blood flow was reduced with isoflurane and sevoflurane at 1.5 and 2.0 MAC. A somewhat greater reduction in portal venous blood flow occurred during 2.0 MAC sevoflurane (P < 0.05 compared to control and 1.0 MAC values for sevoflurane). Enflurane reduced portal venous blood flow at 1.0, 1.5, and 2.0 MAC compared to control. Halothane produced the greatest reduction in portal venous blood flow (P < 0.05 compared to sevoflurane). Hepatic O2 delivery during 1.5 and 2.0 MAC halothane exposure was reduced compared to results obtained with sevoflurane and isoflurane (P < 0.05). Hepatic O2 extraction showed no significant increase at any anesthetic MAC level other than 2.0 MAC for halothane and sevoflurane. Increases in O2 extraction were due to large reductions in O2 delivery with halothane and a moderate reduction in O2 delivery with sevoflurane not accompanied by a further reduction in O2 consumption. The authors conclude that sevoflurane at concentrations less than 2.0 MAC preserves hepatic arterial blood flow, total hepatic O2 delivery, and the O2 delivery-to-consumption ratio. Halothane produces the greatest reductions in hepatic arterial and portal venous blood flow.
