Objective To compare the effects of general anesthesia and spinal anesthesia on the incidence of postoperative cognitive dysfunction in elderly patients undergoing lower extremity orthopedic surgery.

Methods 65 elderly patients who underwent elective lower extremity orthopedic surgery in Zhongshan Hospital, Fudan University from April 1, 2016 to March 30, 2017 were enrolled. Patients were randomized into general anesthesia group (GA group, n=31) or spinal anesthesia group (SB group, n=34). Cognitive function was assessed with three neuropsychological tests: mini-mental state examination (MMSE), Montreal cognitive assessment (MoCA) and trail making test (TMT). Each patient was assessed for 4 times: the day before the operation, 3 h after the operation, 24 h after the operation, before discharge. 14 in-hospital patients for diabetes were also assessed for 3 times with the same interval as control group. Patients were monitored with cerebral oximetry and bispectral index (BIS) intraoperatively. During the whole operation, the value of BIS was maintained between 40-60 for general anesthesia patients under intravenous anesthesia. BIS value was 70-80 for spinal anesthesia patients with propofol. The cerebral oximetry fell by no more than 20% of the base value.

Results At 3 h after the operation, POCD was detected in 9.7% (95%CI 0-20.1%) of patients in the GA group and 2.9% (95% CI 0-8.5%) of patients in the SB group, the difference was not statistically significant (P=0.272). At 24 h after the operation, POCD was diagnosed in 3.2%(95%CI 0-9.4%) of patients in the GA group and 0% of patients in the SB group, the difference was not statistically significant (P=0.477). No statistic significance was found in any neuropsychological tests before discharge.

Conclusions Compared with spinal anesthesia, general anesthesia may result in the temporary deficit of cognition which could reverse before discharge.