Objective To evaluate the sensitivity of arterial ketone body ratio as an indicator for multiple organ failure.Materials and methods The experimental model of multiple organ failure was made in adult and old rats by hypoperfusion-induced hemorrhagic shock. After blood sampling, the arterial acetoacetate, β-hydroxybutyrate, total ketone body, ALT, AST, BUN, creatinine at 2, 4, 8 hr in hypoperfusion were examined to compare the differences of ketone body ratio and organ failure between adult and old rats. Hepatic and mitochondrial metabolism were assessed by comparing ketone body ratios (AcAc/β-OHB) and free NAD+/NADH ratios. Results Ketone body ratio in old rats at 2, 4, 8 hr after the induction of hemorrhagic shock decreased from 0.68 to 0.31, 0.27 and 0.22, respectively. In adult rats, it decreased from 1.12 to 0.17, 0.12 and 0.09, respectively. Changes of ketone body ratio in the adult group were larger than in the elderly group ( P ＜ 0.001). The development of multiple organ failure is associated with the time of hemorrhagic shock development. Conclusions There was a different ketone body ratio between multiple organ failure in the elderly (MOFE) and multiple organ failure (MOF) in general adults. Ketone body ratio is a better indicator than ALT and AST in reflecting hepatic function in the early status of MOF. (J Geriatr Cardiol 2004;1(2) :125-128. )