The effect of a preoperative oral nutritional supplement on postoperative insulin resistance in rectal cancer patients

Results: Insulin resistance (IR) after major surgery is associated with postoperative complications. Preoperative immune‐enhancing nutritional supplements reduce postoperative infectious complication, but whether they improve insulin sensitivity (IS) in the postoperative state is unknown. We performed a double blind randomized controlled pilot study to evaluate the effect of a preoperative oral nutritional supplement (ONS), containing carbohydrates, anti‐oxidants and glutamine, on postoperative glucose metabolism in rectal cancer patients. ONS (group A) or placebo (B) was given approximately 15, 11 and 4 hrs before surgery. Subjects were studied in the week prior to surgery and one day after surgery in the basal state and during a two‐step hyperinsulinemic euglycemic clamp using a stable isotope. Basal endogenous glucose production (EGP) and hepatic and peripheral (rate of disappearance, Rd) IS were measured. Data are given as median (range). We included eight patients in each group (both groups 5 male/3 female; age A: 63 [53‐69] vs. B: 61 [49‐79] yrs; BMI A: 25 [21‐28] vs. B: 27 [23‐31] kg/m2). Glucoregulatory hormones were not significantly different during all clamps. Glucose metabolism in the preoperative state was comparable between the groups (basal EGP A: 12.1 [9.3‐14] vs. B: 11.3 [10‐13] mumol/kg/min, p=0.36.; insulin‐mediated suppression of EGP A: 53.2 [30‐62] vs. B: 39.4 [21‐66] %, p=0.42; Rd A: 37.2 [19‐50] vs. B: 29.2 [16‐35] mumol/kg/min, p=0.07). In the postoperative state, basal EGP did not differ within and between groups. Surgery induced no reduction in hepatic IS (EGP B: 27 [11‐56] %, pre. vs. post. p=0.25), but it induced a reduction in peripheral IS (Rd B: 15.0 [13‐19] mumol/kg/min, pre. vs. post. p=0.04). Only surgery‐induced peripheral IR differed between the groups (Rd A: 21.5 [14‐28] vs. B: 15.0 [13‐19] mumol/kg/min, p=0.04). We conclude that rectal surgery induces profound peripheral IR. The preoperative ONS improved surgery‐induced peripheral IR, but had no effect on hepatic IS. Further research is required to evaluate if this results in lower postoperative morbidity and mortality rates.