The influence of vasopressin and epinephrine on hepatic energy metabolism in the state of brain death was assessed by measuring arterial ketone body ratio (AKBR) and hepatic energy charge (EC) in brain-dead dogs. Mean arterial blood pressure (MABP) was significantly decreased from 125.5 +/- 5.5 to 53.4 +/- 1.7 mmHg after complete brain death (P less than 0.01). In the control group AKBR and EC were maintained at near the normal values thereafter, despite marked hypotension. Combined administration of vasopressin and epinephrine sustained AKBR normally and improved MABP above 90 mmHg (P less than 0.01). EC was also maintained within the normal range at 5 hr after initiation of administration of the drugs. By contrast, vasopressin or epinephrine alone maintained AKBR and EC at near the normal values, but improved MABP just slightly to around 60 mmHg (P less than 0.01). As for the volume control, the urinary output was significantly smaller in the vasopressin and epinephrine-treated group than in the control group (P less than 0.05). It is suggested that combined administration of vasopressin and epinephrine has a synergistic effect in improving the hemodynamics and maintenance of the energy status of the liver. This regimen is recommended as a good one for maintaining potential liver donors in the state of brain death.