Comparison of Morning Operation and Evening Operation on Postoperative Sleep Quality and Pain Under General Anesthesia： A Randomized Controlled Trial

General anesthesia is a medically induced state of low reactivity consciousness involving amnesia, immobility, unconsciousness, and analgesia, which is similar to natural sleep. Its aim is to create a state of sensory deprivation to induce a lack of motor reaction to stimuli and to obtain an explicit amnesia. Some studies found that general anesthesia as an independent risk factor could result in a desynchronization of the circadian time structure and cause postoperative sleep disorders characterized by reduced rapid eye movement (REM) and slow wave sleep (SWS), which have significant deleterious impacts on postoperative outcomes, such as postoperative fatigue, severe anxiety and depression, emotional detachment and delirium, and even pain sensitivity or postoperative pain of patients.Several studies also indicated that circadian rhythms existed in human and controlled by a main internal central clock, the suprachiasmatic nuclei, located in the anterior hypothalamus, which produce and regulate biological rhythms such as sleep arousal, hormones and metabolism could also affect the dose of general anesthesics, which lead to different postoperative recoveries and may have different effects on postoperative sleep quality. Previous studies proved that postoperative sleep disturbances and poor sleep quality are associated with higher postoperative pain, changes in behavior and poor emotional well-being, which could further aggravate postoperative sleep quality. At present, there are few studies which are about the effect of circadian rhythm for different timing of surgery on intraoperative anesthestic requirement, postoperative sleep quality and pain under general anesthesia.