Influence of acute normovolemic hemodilution on the potency and time course of action of rocuronium in rabbits

ABSTRACT

BACKGROUND: We performed this study to evaluate the potency and time course of rocuronium-induced neuromuscular block following moderate or severe acute normovolemic hemodilution (ANH) in rabbits. METHODS: Forty five rabbits were randomly assigned to the control (C) group, the moderate ANH (M) group, or the severe ANH (S) group. After stabilization of sevoflurane anesthesia, ANH was achieved by drainage of arterial blood and an intravenous infusion of 6% hydroxyethyl starch, during which hematocrit (Hct) decreased to 26.2 ± 2.5% in the M group and 17.6 ± 2.2% in the S group. We determined dose-response relationships of rocuronium in the three groups and created a time course of the action of 0.6 mg/kg rocuronium. RESULTS: The 50% effective dose (ED50) for rocuronium was 45% and 50% lower in the M and S groups, respectively, than in the C group (50.9 ± 6.3 µg/kg) (P < 0.001). The onset time after 0.6 mg/kg rocuronium was faster in the ANH groups compared with the C group (P < 0.001). The duration of neuromuscular block was prolonged by 38% and 43% in the M and S groups, respectively, compared with the C group (49.1 ± 6.9 min) (P < 0.001). CONCLUSIONS: ANH resulted in high potency, rapid onset, and prolonged duration of rocuronium. However, the severity of ANH did not alter the potency and duration of action of rocuronium.