Comparison of equipotent doses of non-depolarizing muscle relaxants in children.

The neuromuscular effects of equipotent doses of non-depolarizing muscle relaxants used for endotracheal intubation were studied in 27 children anesthetized with thiopental, nitrous oxide/oxygen, and narcotic. Equipotent doses of d-tubocurarine (0.8 mg/kg), metocurine (0.5 mg/kg), and pancuronium (0.13 mg/kg) were used. At these doses conditions for intubation were satisfactory in all children and the twitch was completely abolished in 26 of the 27 patients. The twitch height recovered to 5% of control values in 54 +/- 6 minutes, and 29 +/- 2 minutes later recovered to 25% of control values. The time from injection of the drug to maximum effect, the conditions for intubation, and recovery times among the three drugs were not significantly different. Train-of-four values correlated (p less than 0.001) with the twitch heights. When the twitch height at 0.1 Hz was 21% of control values, only three contractions were detected following train-of-stimulation. At 14% of control twitch height, two contractions were detected; at 7% of control twitch height, one contraction was detected. The most frequent reason for administering an incremental dose of relaxant was the beginning of respiratory movements, corresponding to a twitch height of 24% of control values (train-of-four 3%). The second most common reason was unsatisfactory abdominal wall relaxation (twitch height 31% of control values, train-of-four 11%.