The relationship between postoperative cognitive dysfunction and the depth of sedation with propofol during spinal anesthesia in elderly patients

ABSTRACT

BACKGROUND: Postoperative cognitive dysfunction (POCD) is a common perioperative complication. The definitive causes of POCD have not been identified, but depth of anesthesia or sedation has been reported to influence POCD. The purpose of the present study was to assess the possible effect of the level of sedation on POCD at 1 week after surgery under spinal anesthesia in elderly patients. METHODS: We included 48 patients aged over 60 years, who were scheduled for elective knee and hip joint surgery under spinal anesthesia. Those patients were randomly allocated to one of the 2 groups deep sedation group and light sedation group. The depth of sedation was monitored by entropy and observer's assessment of alertness/sedation (OAA/S) score. Cognitive function was assessed by 5 neurocognitive tests before and at 1 week after surgery. A postoperative deficit was defined as a postoperative decrement to preoperative score greater than 1 standard deviation on any test. A patient whose postoperative performance deteriorated by 1 or more standard deviations on 2 or more tests was classified as having experienced POCD. RESULTS: POCD occurred in 7 patients (28%) in the deep sedation group and in 4 patients (17.4%) in the light sedation group. The incidence of the POCD was not significantly different between the 2 groups. CONCLUSIONS: We were unable to detect a significant association between the depth of sedation and the presence of POCD at 1 week after surgery under spinal anesthesia.