[Comparison of the effect of isoflurane and that of sevoflurane on hepatic circulation and oxygen metabolism during acute hypoxia in dogs].

Hepatic oxygen delivery, consumption and the hepatic energy charge were assessed in twenty-five mongrel dogs inhaling isoflurane (ISO) or sevoflurane (SEV) associated with graded hypoxic gas mixtures (FI02 0.21 to 0.08). Hepatic blood flow was measured using electromagnetic flowmetry: hepatic oxygen delivery and consumption were calculated from hepatic arterial, portal venous and hepatic venous blood. The hepatic energy charge was assessed by measuring arterial ketone body ratio (AKBR), which is considered to be an indicator of mitochondrial energy charge level. There was no significant differences in mean arterial pressure (MAP), cardiac output (CO) and systemic vascular resistance (SVR) between the ISO group and the SEV group at any FIO2 level. In the ISO group, portal venous blood flow (PVBF) was maintained well, but a compensatory increase of hepatic arterial blood flow (HABF) was significantly smaller in the ISO group compared with the SEV group. As the result of changes of HABF and PVBF, there was no significant difference in total hepatic blood flow (THBF) between the two groups at FIO2 0.21-0.10. However, THBF tended to decrease at FIO2 0.08 relatively more in the SEV group compared with the ISO group. AKBR gradually decreased with development of hypoxia, approaching the critical level of 0.4 in both groups but there was no significant difference between the two groups. The serum catecholamine levels, epinephrine and norepinephrine increased in both groups only at FIO2 0.08. Results of the present study suggest that ISO maintained PVBF well and SEV maintained HABF well, respectively at mild to moderate hypoxia. Both ISO and SEV could suppress the exaggerated reaction to hypoxic hypoxemia, and maintain hepatic circulation and hepatic oxygen metabolism at mild to moderate hypoxia, although CA level increased and energy charge were seriously depressed at FIO2 0.08 in both groups. In conclusion, ISO and SEV could sustain hepatic circulation and oxygen metabolism in better condition than with halothane demonstrated in our previous study.