Does anaesthesia cause postoperative cognitive dysfunction? A randomised study of regional versus general anaesthesia in 438 elderly patients

Background: Postoperative cognitive dysfunction (POCD) is a common complication after cardiac and major non-cardiac surgery with general anaesthesia in the elderly. We hypothesized that the incidence of POCD would be less with regional anaesthesia rather than general. Methods: We included patients aged over 60 years undergoing major non-cardiac surgery. After giving written informed consent, patients were randomly allocated to general or regional anaesthesia. Cognitive function was assessed using four neuropsychological tests undertaken preoperatively and at 7 days and 3 months postoperatively. POCD was defined as a combined Z score >1.96 or a Z score >1.96 in two or more test parameters. Results: At 7 days, POCD was found in 37/188 patients (19.7%, [14.3-26.1%]) after general anaesthesia and in 22/176 (12.5%, [8.0-18.3%]) after regional anaesthesia, P=0.06. After 3 months, POCD was present in 25/175 patients (14.3%, [9.5-20.4%]) after general anaesthesia vs. 23/165 (13.9%, [9.0-20.2%]) after regional anaesthesia, P=0.93. The incidence of POCD after 1 week was significantly greater after general anaesthesia when we excluded patients who did not receive the allocated anaesthetic: 33/156 (21.2%[15.0-28.4%]) vs. 20/158 (12.7%[7.9-18.9%]) (P=0.04). Mortality was significantly greater after general anaesthesia (4/217 vs. 0/211 (P<0.05)). Conclusions: No significant difference was found in the incidence of cognitive dysfunction 3 months after either general or regional anaesthesia in elderly patients. Thus, there seems to be no causative relationship between general anaesthesia and long-term POCD. Regional anaesthesia may decrease mortality and the incidence of POCD early after surgery.