Neuromuscular effects of rapacuronium in pediatric patients during nitrousoxide-halothane anesthesia: comparison with mivacurium

Purpose: To describe neuromuscular effects of rapacuronium in pediatric pat ients during N2O-halothane anesthesia and compare them with mivacurium in c hildren. Methods: 103 pediatric patients. seven days - 12 yr, received rapacuronium or mivacurium during N2O-halothane anesthesia. Onset and recovery of block were measured using EMG (Datex). Block was compared between groups based on drug treatment and age. Children < two years received I or 2 mg.kg(-1) rap acuronium: 2 - 12 yr received either 2 mg.kg(-1) or 3 mg.kg(-1) rapacuroniu m, or 0.2 mg.kg(-1) mivacurium. Results: There were no differences in onset( 1.7 +/- 1.8 min) or maximum bl ock (T1 2.4 +/- 8%) among neonates, infants, and toddlers after either dose of rapacuronium. There was no difference between I and 2 mg.kg(-1) of rapa curonium block at 60 sec. Train-of-four ratio (T4/T1) > 0.7 occurred later after 2 mg.kg(-1) than 1 mg.kg(-1) in these patients (P < 0.05). There was no difference in T25 among neonates, infants and toddlers for I mg.kg(-1) o r 2 mg.kg(-1) doses. Rapacuronium, 3 mg.kg(-1), produced maximum block 1.5 min earlier than did mivacurium, 0.2 mg.kg(-)1 (P < 0.001). There was no di fference in block at 60 sec. maximum block or time to maximum block between 2 and 3 mg.kg(-1) rapacuronium for children > two years of age. Maximum bl ock occurred 1.0 +/- 0.5 min after 2 or 3 mg.kg(-1) when T1 was 0.2 +/- 1.1 % of baseline. T25 and T4/T1 > 0.7 occurred 10 to 11 min later after this d ose of rapacuronium than after mivacurium. Conclusion: Rapacuronium produces block earlier than mivacurium, Recovery f rom rapacuronium block is dose related and slower than that following mivac urium during halothane anesthesia.