Objective:To evaluate the effect of repeated intranasal insulin on postoperative delirium (POD) in elderly patients undergoing general anesthesia.Methods:Seventy elderly patients, aged ≥65 yr, with body mass index ≤28 kg/m 2, of American Society of Anesthesiologists physical statusⅠ-Ⅲ, undergoing elective radical gastrectomy for gastric cancer under general anesthesia, were divided into 2 groups ( n=35 each) according to the random number table method: control group (group C) and insulin group (group I). In group C, normal saline 0.5 ml was administered intranasally twice a day from 2 days before surgery until the day of surgery.In group I, insulin 20 U (0.5 ml) was administered intranasally twice a day from 2 days before surgery until the day of surgery.The regional tissue oxygen saturation (rSO 2) was measured after entering the operating room (T 0), at intubation (T 1), at 1, 2 and 3 h after the start of operation (T 2-4), at the end of surgery (T 5) and at extubation (T 6). The insulin allergic reactions, nasal irritation and hypoglycemic reactions were recorded after intranasal administration of insulin or normal saline within 2 days before operation.The blood glucose concentrations were measured at T 0, T 3 and T 5.The occurrence of POD within 3 days after operation was recorded. Results:Compared with group C, the incidence of POD was significantly decreased within 3 days after operation, and the rSO 2 was increased at T 1-6 in group I ( P<0.05). The rSO 2 was significantly higher at T 1-6 than at T 0 in two groups ( P<0.05). There were no significant changes in blood glucose concentrations at T 0, T 3 and T 5 between the two groups ( P>0.05). No insulin allergic reactions, nasal irritation and hypoglycemic reactions occurred in two groups ( P>0.05). Conclusion:Repeated intranasal administration of insulin can increase the rSO 2 during operation and decrease the occurrence of POD in elderly patients undergoing radical gastrectomy for gastric cancer.