Primary outcome
critically ill
CRITICALLY ILL
Primary outcome was the subjective sleep quality at surgery night, assessed by the Chinese version Richards Campbell Sleep Questionnaire (RCSQ) at 07:00–09:00 on postoperative first morning [The RCSQ involves five domains including sleep depth, sleep latency, awakenings, returning to sleep, and overall sleep quality. Each domain is assessed by using a 100-mm visual analog scale with higher scores indicating better sleep. Overall RCSQ sleep score is defined as the mean value of above five domains and classified into four groups: very poor sleep with scores of 1–25, poor sleep with scores of 26–50, good sleep with scores of 51–75, and very good sleep with scores of 76–100. Although originally designed for critically ill patients in intensive care unit, the RCSQ has also been used among general surgical patients [