BACKGROUND: Rocuronium has been reported to develop a rapid onset of action and may be suitable as a component of a rapid-sequence intubation. The purpose of this study was to compare the onset of rocuronium at the adductor pollicis and the larynx and to determine the time suitable for intubation.

METHODS: Fifteen ASA physical status 1 and 2 adult patients were studied. Anesthesia was induced and maintained with propofol and alfentanil. The recurrent laryngeal nerve was stimulated superficially and movement of the vocal cords were recorded on video tape by using a fiberoptic bronchoscope passed via a laryngeal mask airway. Neuromuscular function was recorded at the adductor pollicis by using mechanosensor. After the administration of rocuronium 0.9 mg.kg_-1, the times to loss of fourth twitch response in train -of - four stimulation at the larynx and hand were observed.

RESULTS: The times to loss of fourth twitch response in train-of-four stimulation at the larynx and hand are 47.3 ± 12.8 sec and 70 ± 13.6 sec respectively.

CONCLUSIONS: Video imaging may be a useful research technique for estimating the neuromuscular blockade at the larynx and showing the onset time of rocuronium is significantly faster at the larynx than hand.