Onset and recovery of neuromuscular blockade after two doses of rocuronium in children

Study Objective: To determine if 450 μg/kg (1.5 times the ED 95) of rocuronium would result in a comparable onset with a shorter duration of action when compared with 600 μg/kg (2 times the ED 95). Design: Randomized, single-blind study. Setting: Teaching hospital. Patients: 85 ASA physical status I and II children ages 2 through 12, undergoing elective surgery with an inhalation induction using halothane. Interventions: Group 1 received 600 μg/kg rocuronium, and Group 2 received 450 μg/kg rocuronium. Measurements and Main Results: The two groups were compared using a Student’s t-test, with p < 0.05 significant. The time of onset, or time to 95% suppression of neuromuscular twitch with standard errors, was 140 ± 13 seconds (range 46 to 365 sec) in Group 1 and 148 ± 13 seconds (range 82 to 345 sec) in Group 2 (NS = not significant). The times to 25% return of twitch from baseline (T 25) in Groups 1 and 2 were 28 ± 1.5 minutes (range 14 to 45 min) and 26 ± 1.6 minutes (range 10 to 55 min), respectively (NS). The differences between these two doses in onset of, and recovery from, block were not found to be statistically significant. The results, however, excluded 5% of the higher dose group and 31% of the lower dose group who did not achieve 95% suppression of twitch. Time to maximal suppression of neuromuscular blockade, however, was not statistically significant for the 85 patients with a time of 270 ± 28 seconds (range 91 to 605 sec) with a mean maximal suppression of 98.7% in Group 1 and 313 ± 25 seconds (range 91 to 899 sec) with a mean maximal suppression of 93.1% in Group 2. Conclusion: The two doses of rocuronium did not differ statistically in onset or duration. Rocuronium at 600 μg/kg offers more reliability than 450 μg/kg in achieving adequate muscle relaxation, and the lower dose may result in a significantly large number of patients who may have inadequate intubating conditions.