Sleep arousal after lower abdominal surgery and relation to recovery from respiratory obstruction

Hypoxemic episodes occur during sleep after abdominal surgery, possibly caused by airway obstruction. The authors found arousals from sleep more often than respiratory disturbances, so they related changes in sleep state (short arousals from sleep and longer periods of wakening) to the sudden increase in respiratory flow that indicates relief from complete or partial respiratory obstruction.

Sleep state and nasal flow were studied in 16 patients receiving patient-controlled morphine and oxygen by facemask on the night after routine gynecologic surgery. Traces were analyzed separately for sleep events and for sudden increases in respiratory flow. The authors noted sleep events (arousals from sleep and transition from sleep to wake) that occurred within 12 s of relief of obstruction.

Sleep quality was poor, with only stage 2 sleep in most patients. Median sleep duration was 70% of the study period, with 15 arousals and 6 awakenings per hour of sleep. Only 30% of arousals and awakenings were associated with relief of obstruction. Relief of obstruction also occurred without arousal from sleep, with a median frequency of 38 (30-62) in each night. Relief of obstruction was more frequently associated with arousal from sleep after benzodiazepine premedication (33% vs. 28%; P = 0.012), but this allocation was not randomized.

Arousals from sleep are frequent after abdominal surgery and mostly not related to respiratory disturbance. Relief of respiratory obstruction can occur during sleep without sleep arousal and during wakefulness.