Comparison of the adductor pollicis, orbicularis oculi, and corrugator supercilii as indicators of adequacy of muscle relaxation for tracheal intubation.

ABSTRACT

BACKGROUND: The purpose of this study was to verify which muscle among the adductor pollicis (AP), orbicularis oculi (OO), and corrugator supercilii (CS) is a better predictor of optimal intubating conditions after administration of rocuronium. METHODS: In this prospective trial, 201 patients were randomized into six groups to receive rocuronium at a dose of 0.6 or 1.0 mg kg(-1) during propofol-remifentanil-nitrous oxide anaesthesia. The tracheal intubation was performed after maximal neuromuscular block by acceleromyography at the thumb (AP), the eyelid (OO), and the superciliary arch (CS). The onset time, intubating conditions, peak vital signs, and bispectral index were assessed. RESULTS: The onset time of rocuronium in the OO and CS muscle was significantly shorter than in the AP muscle (P<0.001), but excellent intubating conditions were significantly increased in the AP (87%) and the CS (77%) compared with the OO (32%) after a dose of 0.6 mg kg(-1) of rocuronium (P<0.05). CONCLUSIONS: After administration of rocuronium, twitch monitoring at the OO allows a faster intubation but is associated with an unacceptable incidence of inadequate intubating conditions. Excellent intubating conditions are observed most frequently with AP monitoring but with the longest delay before intubation is attempted. Monitoring of the CS allows intubation earlier than that of AP with fewer patients having excellent but no patients having inadequate intubating conditions.