BACKGROUND: Though the mivacurium is the short acting nondepolarizing neuromuscular blocking agent, the action duration of it is not prospected in condition of hepatic failure owing to its being metabolized by serum cholinesterase and other esterase produced in liver. The purpose of this study is to evaluate neuromuscular effect of the mivacurium in cats with acute hepatic failure. METHODS: Six cats administrated only mivacurium are the control group, and six cats with acute hepatic failure by galactosamine hydrochloride are the experimental group. The force of the anterior tibialis muscle in response to supramaximal common peroneal nerve stimulations were recorded, the time intervals from mivacurium administration to attain 100% twitch depression (onset time), from mivacurium administration to recovery of 25% twitch tension (duration) and from 25% to 75% of twitch recovery (recovery index) were compared between the control group and the experimental group. RESULTS: In experimental group, SGOT and SGPT prior to administration of galatosamine were 28.8+/-5.6 (IU/L) and 43.0+/-7.9 (IU/L), respectively, SGOT and SGPT in acute hepatic failure were 5004.0+/-8113.2 (IU/L) and 3763.0+/-5416.4 (IU/L), respectively, and there were significant differences between the control group and the experimental group. The action duration{47.6+/-18.0 (min)} and the recovery time{7.7+/-3.7 (min)} of mivacurium in the experimental group were more prolonged than the action duration{21.9+/-5.0 (min)} and the recovery time{4.4+/-0.7 (min)} of mivacurium in the control group. CONCLUSIONS: These results indicate that the hepatic failure can prolong the action duration and the recovery index of mivacurium, but the other factors affecting the action of mivacurium must be studied.