Timing of tracheal intubation: monitoring the orbicularis oculi, the adductor pollicis or use a stopwatch?

Abstract

The most suitable time for tracheal intubation, following vecuronium 0.1 mg kg⁻¹, was estimated in 120 patients. The trachea was intubated at cessation of the visually observed response of the orbicularis oculi muscle to facial nerve stimulation (group 1; n = 30), or of the manually detected response of the adductor pollicis to ulnar nerve stimulation (group 2; n = 30), or after waiting 3 min (group 3; n = 30), or 4 min (group 4; n = 30). There were no significant differences in intubation scores between the four groups of patients. Loss of response to train-of-four stimulation occurred significantly sooner in group 1 (orbicularis oculi) than in group 2 (adductor pollicis) P = 0.021). However, intubating conditions were poor in four patients (14%) in group 1, compared with none in group 2 and one in groups 3 and 4, respectively. Thus, contrary to expectations, the cessation of the response of the orbicularis oculi muscle did not guarantee good or even satisfactory intubating conditions. The results suggest that in fit adult patients it is as good to wait 3 min after injection of vecuronium 0.1 mg kg⁻¹ before tracheal intubation, as to use a nerve stimulator.