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

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.

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).

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).

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.