Effect of a bolus dose of midazolam on the auditory evoked response in humans

We have studied the effect of a bolus dose of midazolam on the auditory evoked response (AER) of the electroencephalogram (EEG) in nine patients. We measured the AER in the awake patient, at the point of loss of the eyelash reflex and when airway support was required. The eyelash reflex was lost at mean 1.78 (SD 0.5) min after administration of the midazolam bolus dose. Time to airway support in the seven patients who required it was 2.74 (1.26) min. Mean Nb latency in awake patients was 44.3 ms (95% CI 41.9-46.9) which was significantly shorter than Nb latency at the clinical end-points (P<0.001). When the eyelash reflex was lost, Mb latency was 55.7 ms (95% CI 51.4-60.3) and when airway support was needed, it was 50.9 ms (95% CI 48.6-53.2). We conclude that loss of consciousness after midazolam was associated with an increase in mean Nb latency.