1. The effect of cross-circulation on hepatic encephalopathy (evaluated by electroencephalography; EEG) induced by hepatectomy in the rat was examined.
2. Systemic-systemic cross-circulation induced improvement of the altered EEG in only two out of seven liverless rats when the exchange-flow rate was 6.4 ml min−1 kg body wt.−1, and in all seven liverless rats when the exchange-flow rate was 14.0 ml min−1 kg body wt.−1; the difference is statistically significant (P = 0.011).
3. Systemic-portal cross-circulation (systemic blood from the liverless rat being infused into the portal vein of the normal rat) induced improvement of the altered EEG in all seven liverless rats although the exchange-flow rate was only 6.4 ml min−1 kg body wt.−1
4. It is concluded (a) that a certain level of exchange-flow rate is required for cross-circulation to be efficient, and (b) that, for the same exchange-flow rate, systemic-portal cross-circulation is more efficient than systemic-systemic cross-circulation.