Comparison of sedation with midazolam and ketamine: effects on airway muscle activity

Male patients, aged 27-74 yr, without hypertension or overt cardiovascular disease were premedicated with temazepam 20 mg orally and allocated randomly to receive sedation with either midazolam (12 patients) in a dose sufficient to provide light sedation (retained response to loud voice) or ketamine 1 mg kg-1 (11 patients). Median midazolam dose was 0.08 (interquartile range 0.02) mg kg-1. The activity of the muscles of the tongue, anterior neck and scalene group was measured with surface electrodes and compared with the awake state. Muscle activity decreased significantly after midazolam in each group of muscles, to median values of 42%, 28% and 33%, respectively, of awake values. Airway obstruction occurred in 10 of 12 patients and during obstruction muscle activity increased significantly to 69%, 73% and 52% of awake values, but in all cases this was insufficient to overcome the obstruction. After ketamine, activity did not change significantly and there were no episodes of airway obstruction. Phasic muscle activity was noted after sedation in 11 subjects but there was no difference in the incidence between the two groups (midazolam, six patients; ketamine, five patients).