Cerebral metabolism during cross-circulation in experimental hepatic failure in the pig

The effect of hepatic assistance on cerebral metabolism was evaluated in a series using cross-circulation, anticipating increased efficiency of hepatic support. The experimental model for liver failure was pigs with totally devascularized liver. Cross-circulation with a normal sibling pig, cross-circulation with inflow in the donor directly into the portal vein and cross-perfusion with isolated perfused liver starting 20 h after elimination of liver function in the recipient and lasting for 3 h did not increase survival. Before cross-circulation in these three groups, the cerebral flow and oxygen uptake were decreased; during the cross-circulation a significant but temporary increase was found. In experiments with early and prolonged perfusion with isolated perfused liver no changes in cerebral flow, oxygen or glucose uptake were found, and these variables were still normal 6 h after termination of the perfusion. The survival time was significantly increased. In the control group a significant rise in blood and CSF ammonia was found with a mean CSF/blood ratio of 0.92. After cross-circulation, the CSF/blood ratio was 0.52 and 0.62, respectively, indicating a proportionally greater elimination of ammonia from the cerebrospinal fluid than from the blood. Cross-circulation did not significantly change the alpha-ketoglutarate, glutamate or glutamine CSF concentrations. After prolonged cross-perfusion, the ammonia blood/CSF ratio was 0.24. It is concluded that by extended extracorporeal hepatic assistance it is possible to increase survival and to prevent changes in cerebral metabolism and ammonia accumulating in the cerebrospinal fluid.