Influences of cardiopulmonary bypass and fentanyl anesthesia on hepatic circulation and oxygen metabolism in beagles

Decreases in hepatic blood flow (HBF) have been reported in patients and in animal experiments during cardiopulmonary bypass (CPB). We examined changes in HBF and hepatic oxygen metabolism during CPB in 16 beagles anesthetized with fentanyl. Hepatic arterial blood flow (HABF) and portal venous blood flow (PVBF) were measured by using an electromagnetic flowmeter before and during normothermic and hypothermic CPB with 10 mu g.kg(-1).h(-1) (F-10 group; n = 8) or 50 mu g.kg(-1).h(-1) (F-50 group; n = 8) of fentanyl anesthesia. CPB was conducted with membrane oxygenation and a nonpulsatile pump flow of 2.4 L.m(-2).min(-1). Hepatic oxygen delivery (HDO2) and consumption (HVO2) were calculated from HBF and oxygen content in arterial, portal venous, and hepatic venous blood. HABF did not change during normothermic CPB in the F-10 group, but it decreased significantly during hypothermic CPB in both groups, especially the F-50 group. During CPB, PVBF and total HBF deceased significantly in both groups-more so with the larger dose of fentanyl-whereas HDO2 decreased significantly because the arterial and port venous blood oxygen levels decreased. The HVO2 was stable in the F-10 group but was significantly depressed during CPB in the F-50 group. Our results indicate that during hypothermic nonpulsatile CPB larger doses of fentanyl are associated with reduced HBF and impaired HDO2 and HVO2. Implications: Hepatic dysfunction after cardiopulmonary bypass (CPB) has been frequently reported and could be partly attributed to hepatic circulatory disturbance during CPB. We found that, in beagles, large doses of fentanyl were associated with greater decreases in hepatic blood flow and hepatic oxygen metabolism during hypothermic CPB than smaller doses of fentanyl.