We measured lymphocyte energy charge (LEC) in septic patients after hepatectomy to clarify the energy metabolism of lymphocytes in relation to arterial ketone body ratio (AKBR) reflecting the hepatic mitochondrial redox potential. Sixteen patients with AKBR above 0.7 (state A) tolerated their operations well without postoperative infectious episodes and their LEC (0.895 +/- 0.005, mean +/- SEM) was significantly (p < 0.001) higher than that (0.841 +/- 0.010) of 9 patients with AKBR from 0.7 to 0.4 (state B). Four of the 9 state B patients had multiple organ failure (MOF) with sepsis as a trigger. AKBR in 7 of 9 state B patients decreased and remained below 0.4 (state C). These state C patients showed significantly reduced LEC (0.781 +/- 0.024; p < 0.001, p < 0.05, compared with that in states A and B, respectively) and finally died of MOF with septic state. These results suggest that the severe and prolonged impairment of energy metabolism in the liver may be accompanied with the metabolic derangement of lymphocytes.