Animal studies have shown that halothane decreases total hepatic blood flow (THBF) by reducing both arterial (HABF) and portal (PVBF) inflow, whereas isoflurane appears to preserve them. In this study we assessed the effect of halothane and isoflurane on HABF and PVBF in surgical patients by using the pulsed Doppler technique. A validation study was conducted in six cynomolgus monkeys to compare the values of THBF obtained by the pulsed Doppler and indocyanine green clearance methods. Subsequently, six patients (ASA status I and II) undergoing elective open cholecystectomy were studied after surgery by using implanted pulsed Doppler probes. THBF and liver flow partition were compared during 1% halothane and 1.5% isoflurane (end-tidal concentrations). In the animal study, there was good agreement between the techniques (Bland and Altmann representation). In flunitrazepam-anesthetized patients, THBF was 1120 +/- 284 mL/min. Compared with this baseline and for a similar mean arterial blood pressure decrease (10%), THBF was maintained with isoflurane, whereas it decreased by 36% (P < 0.05) under halothane. With isoflurane, PVBF increased (25%; P = 0.067) with a maintained HABF. With halothane, both PVBF (-44%; P < 0.05) and HABF (-20%; P < 0.05) were reduced. Halothane acted mainly as a vasoconstrictor of the hepatic circulation, whereas isoflurane was a vasodilator, confirming the beneficial effect of isoflurane on hepatic oxygen supply.
Implications: Volatile anesthetics may alter liver circulation with serious adverse effects. Using implanted pulsed Doppler probes in six anesthetized patients, we showed that halothane acted mainly as a vasoconstrictor of the liver vascular bed, whereas isoflurane was a vasodilator, confirming the beneficial effect of isoflurane on liver oxygen supply.