Repeated Preoperative Intranasal Administration of Insulin Decreases the Incidence of Postoperative Delirium in Elderly Patients Undergoing Laparoscopic Radical Gastrointestinal Surgery: A Randomized, Placebo-Controlled, Double-Blinded Clinical Study

Study Objectives: This study aimed to investigate the effects of repeated preoperative intranasal administration of insulin on the incidence of postoperative delirium (POD) and the levels of serum pro-inflammatory markers in elderly patients undergoing laparoscopic radical gastrointestinal surgery. Design: Prospective, randomized, double-blinded, placebo-controlled clinical study. Setting: General Hospital of Western Theater Command from August 2019 to December 2019. Patients: Ninety elderly patients underwent laparoscopic radical gastrointestinal tumor resections under general anesthesia. Interventions: Patients were randomly divided into a control group (0.5 mL saline administered intranasally) or an insulin group (20 U/0.5 mL insulin administered intranasally) for 2 days prior to surgery, with 45 patients in each group. Measurements: The incidence of delirium was measured at postoperative day 1 (T2), day 3 (T3), and day 5 (T4) using the Confusion Assessment Method for the intensive care unit (CAM-ICU). Plasma levels of interleukin (IL)-1 beta, IL-6, and tumor necrosis factor (TNF)-alpha were measured at T0 (before insulin or saline administration), T1 (at the end of surgery), T2, T3, and T4 by enzyme-linked immunosorbent assay. Main Results: Compared with the control group, the insulin group demonstrated a decreased POD incidence (12.5% vs. 47.5%, p = 0.001) within 5 days after surgery. The incidence of POD was significantly lower in the Ins group than in the Con group at T2 (12.5% vs. 32.5%, p = 0.032) and at T3 (2.5% vs. 20%, p = 0.034). The incidence of POD decreased in both groups over time and was similar at T4 (0% vs 10%, p = 0.116). Compared with the baseline value at T0, serum TNF-alpha, IL-6 and IL-1 beta concentrations increased significantly at T1-4 (p < 0.05). Compared with the control group at the same time point, the expression levels of TNF-alpha, IL-6 and IL-1 beta in group I at T2 and T3 were significantly reduced (p < 0.05). The incidence rates of adverse events were similar in the two groups. Conclusions: Repeated preoperative intranasal administration of insulin prevented the occurrence of delirium after laparoscopic radical gastrointestinal surgery in elderly patients and reduced TNF-alpha, IL-1 beta, and IL-6 levels.