Isoflurane anesthesia causes a transient alteration in nocturnal sleep

Nocturnal sleep was studied in eight healthy young volunteers before and after isoflurane anesthesia. All night polysomnographic recordings were obtained for seven consecutive nights from approximately 2300 to 0700 h. On the morning after the third night each subject was anesthetized with isoflurane 1.1 MAC for approximately 3 h. The stages and indices of nocturnal sleep were calculated for each night of study according to standard criteria. The effects of anesthesia on nocturnal sleep were confined to the first postanesthetic night. Slow wave sleep (Stages 3 and 4) was moderately suppressed from 16 +/- 1% to 6 +/- 1%, and Stage 2 sleep reciprocally increased from 52 +/- 2% to 60 +/- 2% (mean +/- SEM, P less than 0.05). There were no detectable changes in the sleep onset latency, the total quantity of sleep, or the proportion of rapid eye movement (REM) sleep. Anesthesia was followed by daytime napping in six of the eight volunteers. Nocturnal sleep was similar in the subjects who napped and those who did not. It is concluded that anesthesia with isoflurane leads to a modest and a transient change in the architecture of nocturnal sleep.