Objective To evaluate the effect of general anesthesia under the guidance of bispectral index (BIS) on postoperative fatigue syndrome (POFS) in elderly patients undergoing laparoscopic resection of gastrointestinal tumor. Methods A total of 90 patients of both sexes, aged 65-80 yr, with body mass index of 18-25 kg/m2 , of American Society of Anesthesiology physical status I -M, undergoing elective laparoscopic resection of gastrointestinal tumor, were divided into 3 groups (n = 30 each) using a random number table method; control group (C group...