Dose-response of rocuronium bromide in children anesthetized with propofol: a comparison with succinylcholine.

Background: The aim of this study was to determine the potency of rocuronium during propofol/fentanyl/N2O anesthesia in children and to compare the time course of action of rocuronium at doses of two and three times the ED95 with that of succinylcholine.

Methods: Rocuronium (120, 160, 200, or 240 microg/kg) was administered to 48 children aged 2-10 yr. Neuromuscular block was assessed by monitoring the electromyographic response of the adductor digiti minimi to supramaximal stimulation of the ulnar nerve at 2 Hz for 2 s every 10 s. Potency was determined by log-probit transformation and least-squares linear regression analysis of dose and response. In a second group of 30 children, the onset and recovery profile of rocuronium at doses of two and three times the ED95 was compared with that of succinylcholine (2 mg/kg).

Results: Values for ED50 and ED95 were 210 +/- 24 and 404 +/- 135 microg/kg, respectively. The time to 90% neuromuscular block after 1.2 mg/kg rocuronium (three times the ED95), 33 +/- 5 s (mean +/- SD), did not differ significantly from that after succinylcholine, at 30 +/- 7 s; however, both were significantly less than that after 0.8 mg/kg rocuronium, 46 +/- 8 s (P < 0.05). The time to 25% recovery from 1.2 microg/kg rocuronium, 41 +/- 13 min, was approximately 50% greater than that after 0.8 mg/kg, at 27 +/- 6 min (P < 0.001), and eight times greater than that after succinylcholine, at 5.2 +/- 1.9 min (P < 0.001).

Conclusions: Both 1.2 mg/kg rocuronium (three times the ED95) and 2 mg/kg succinylcholine provide 90% neuromuscular block within 45 s in 95% of children. The present dose-response data support the use of rocuronium at a dose of 1.2 mg/kg when rapid onset and intermediate-duration neuromuscular block are needed in children.