Pharmacodynamics of high-dose vecuronium in children during balanced anesthesia.

To compare the speed of onset, intubating conditions, duration of action, and recovery from neuromuscular blockade with vecuronium to those with succinylcholine, 40 ASA physical status 1 or 2 children (ages 2-9 yr) were studied during N2O-O2-opioid anesthesia. Each child was randomly assigned to receive a bolus dose of one of the following muscle relaxants: succinylcholine 2.0 mg/kg (n = 10), vecuronium 0.1 mg/kg (n = 10), vecuronium 0.2 mg/kg (n = 10), or vecuronium 0.4 mg/kg (n = 10). The evoked electromyogram of the abductor digiti minimi to train-of-four stimulation was monitored. We found that with succinylcholine, the time to 95% twitch depression (speed of onset, mean +/- SD), 24 +/- 7 s, was significantly less than that with each dose of vecuronium: 0.1 mg/kg, 83 +/- 21 s; 0.2 mg/kg, 58 +/- 17 s; and 0.4 mg/kg, 39 +/- 11 s, respectively (P less than 0.05). The time to laryngoscopy and intubation did not differ significantly between succinylcholine (48 +/- 10 s) and vecuronium 0.4 mg/kg (57 +/- 13 s); however, both were significantly less than than with vecuronium 0.1 and 0.2 mg/kg (P less than 0.005). The intubating conditions were excellent in 100% of patients. The duration of action was least with succinylcholine (5.7 +/- 1.5 min) and increased with increasing doses of vecuronium: 0.1 mg/kg, 23.9 +/- 5.1 min; 0.2 mg/kg, 55.2 +/- 11.6 min; and 0.4 mg/kg, 74.6 +/- 9.9 min, respectively (P less than 0.001). The recovery index was most rapid with succinylcholine (1.6 +/- 0.4 min) and was slowest with vecuronium 0.4 mg/kg (22.6 +/- 2.1 min) (P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)