[Effects of fentanyl on hepatic circulation and hepatic oxygen metabolism in dogs].

Hepatic circulation, oxygen metabolism and energy charge level were assessed in 12 mongrel dogs (10.6 +/- 0.9 kg) during cumulative administrations of fentanyl 3, 10, and 30 micrograms.kg-1 i.v., under air-1% isoflurane anesthesia. Hepatic blood flow was measured with electromagnetic flowmeters. Hepatic oxygen delivery and consumption were calculated from measured hepatic blood flow and oxygen content in hepatic arterial, portal venous and hepatic venous blood. Hepatic energy charge was assessed by measuring the arterial ketone body ratio (AKBR), which is considered to be an indicator of mitochondrial energy charge level. Hepatic blood flow and oxygen metabolism did not change after administration of 3 micrograms.kg-1 of fentanyl, but mean arterial blood pressure, cardiac output, hepatic arterial blood flow, portal venous blood flow and hepatic oxygen delivery were significantly suppressed by 30 micrograms.kg-1 of fentanyl. Hepatic oxygen consumption and AKBR were well maintained by spontaneous rises in hepatic oxygen uptake ratio. However, these results suggest that the significant decrease of hepatic oxygen delivery during administration of 30 micrograms.kg-1 of fentanyl could be exacerbated by combination with hypoxemia or hypoperfusion of the liver, and this might be followed by hepatic dysfunction.