Effect of different depths of anesthesia on postoperative cognitive function in laparoscopic patients: a randomized clinical trial

Objective: Postoperative cognitive dysfunction (POCD) is caused by many factors. This work was conducted to investigate the effect of different depths of anesthesia during combined intravenous-inhalational anesthesia on postoperative cognitive function in young and middle-aged laparoscopic patients. Methods: A total of 192 patients scheduled for gynecologic laparoscopic operations were randomly divided into three groups. Anesthesia was maintained with inhalation of sevoflurane and infusion of remifentanil, which was adjusted to maintain bispectral index (BIS) at 30 < BIS <= 40 in Group I, 40 < BIS <= 50 in Group II and 50 < BIS <= 60 in Group III. The Mini-Mental State Examination (MMSE) and Trail-Making Test (TMT) were used to assess cognitive function on the day before anesthesia and the day after surgery. Results: There were no significant differences in age, body mass index, educational level and surgery time. On the day before anesthesia, the average MMSE scores and TMT completion times in the three groups were not significantly different. On the day after surgery, Group II had a significantly higher average MMSE score (29.00 +/- 0.89) than Group I (28.36 +/- 1.42, p = 0.010) and Group III (28.45 +/- 1.27, p = 0.035) and lower TMT completion time (33.68 +/- 10.34) than Group I (39.45 +/- 13.99, p = 0.027) and Group III (39.50 +/- 12.50, p = 0.026). Conclusion: These results indicated that the depth of anesthesia, 405BIS <= 50, under combined intravenous-inhalational anesthesia yielded milder influence on postoperative cognitive function in young and middle-aged laparoscopic patients.