Masseter muscle is a better predictor of good intubating conditions than adductor pollicis after the administration of rocuronium in adults. We compared the onset of rocuronium at the masseter muscle to that at the adductor pollicis to determine which is the more suitable predictor of good intubating conditions using rocuronium in children.

Fifty children aged from 1 to 6 years old, were anesthetized with thiopental sodium and sevoflurane. The ulnar nerve was stimulated to monitor the relaxation of the adductor pollicis, and the mandibular nerve for monitoring masseter muscle relaxation. Rocuronium 0.6 mg/kg was administered. We measured the time to maximal blckade of the masseter muscle (M-0%). We recorded the percentage of relaxation of the adductor pollicis (AP-%) at M-0% and the time of the maximal blockade of the adductor pollicis (AP-0%), from the administration of rocuronium. Endotracheal intubation was started when the masseter muscle contraction was maximally blocked.

M-0% occurred at 37.4 ± 15.4 s, and AP-% was 32.4 ± 32.2% at M-0%. AP-0% occurred at 54.8 ± 19.0 s. The time gap between M-0% and AP-0% was 16.8 ± 18.3 s. Intubation was at 64.4 ± 19.4 s from the administration of rocuronium.

The time gap between M-0% and AP-0% was very short in children. Therefore, the monitoring of muscle relaxation on masseter muscle is not straightforward, and therefore, not advised.