This study was aimed at clarifying the usefulness of the arterial ketone body ratio (AKBR), which reflects hepatic mitochondrial redox state and closely correlates with hepatic energy production, for understanding the degree of hepatic mitochondrial damage and the extent of the deterioration in hepatic energy metabolism during or shortly after hemorrhagic shock. Changes in the AKBR of 33 trauma victims who were admitted to our institute in hemorrhagic shock with a systolic pressure lower than 70 mmHg were measured until the patient recovered with the restoration of AKBR to the normal range (> or = 1.0) or until the patient died. During hemorrhagic shock the AKBRs were highly decreased, indicating deteriorated hepatic function. With successive fluid resuscitation the AKBR quickly recovered in 15 surviving patients from an initial value of 0.26 +/- 0.03 toward normal within hours, indicating that hepatic mitochondria are functioning normally. The AKBR recovered to a normal value of 1.10 +/- 0.06 on day 2 (p < 0.001). In 18 expired patients, AKBR did not recover to normal range, even though some of the patients recovered from the shock state. On the other hand, AST, ALT, LDH, and prothrombin time on day 2 were not significantly different from the values on admission, and the changes during the interval were not unidirectional even in the surviving patients, providing no information on the current functional state of the liver. Measurement of AKBR during and shortly after hemorrhagic shock provides timely and accurate information about liver function.