Clinical and Metabolic Effects of Preoperative Carbohydrate Loading Before Colorectal Surgery: An Updated Systematic Review and Meta-Analysis of Randomized Controlled Trials

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Abstract

BACKGROUND & AIMS: To evaluate the effects of abbreviated preoperative fasting using carbohydrate-containing beverages compared with traditional fasting or placebo in patients undergoing colorectal surgery, expanding upon prior meta-analyses with an updated and more comprehensive evidence base. METHODS: PubMed, Embase, and the Cochrane Central Register of Controlled Trials were systematically searched for randomized controlled trials (RCTs) comparing patients receiving preoperative carbohydrate-containing beverages with those undergoing conventional fasting or placebo. Main endpoints were plasma insulin and blood glucose levels at operating room admission and 24 h postoperatively. Secondary outcomes included length of hospital stay (LOS), time to first defecation, postoperative ileus, and patient-reported postoperative symptoms such as nausea, vomiting, anxiety, hunger, and thirst. Analyses were conducted in R software (v4.5.2) using a random-effects model, with calculation of mean difference (MD) and 95% confidence interval (CI). Certainty of evidence was assessed using the GRADE approach, and meta-regression was performed to evaluate the surgical approach as a potential moderator of outcomes. RESULTS: Twenty trials including 1387 patients met the inclusion criteria; 49% received a preoperative oral carbohydrate-containing beverage. No significant differences were observed in plasma insulin levels at operating room admission (MD -0.19 μUI/mL; 95% CI -1.44 to 1.07; p = 0.59) or at 24 h postoperatively (MD -3.63 μUI/mL; 95% CI -10.49 to 3.23; p = 0.19). Blood glucose levels were also similar at operating room admission (MD 2.71 mg/dl; 95% CI -10.96 to 16.39; p = 0.61) and at 24 h postoperatively (MD -8.58 mg/dl; 95% CI -35.57 to 18.40; p = 0.41). LOS (MD -1.71 days; 95% CI -2.64 to -0.78; p = 0.0015) and time to first defecation (MD -0.95 days; 95% CI -1.72 to -0.19; p = 0.02) were reduced in the carbohydrate group. CONCLUSION: Although preoperative CHO beverages did not significantly affect plasma insulin or blood glucose levels at operating room admission or 24 h postoperatively, they were associated with statistically significantly reduced LOS and earlier gastrointestinal recovery, confirmed to be independent of surgical approach by meta-regression, without increasing postoperative complications. PROSPERO REGISTRATION NUMBER: CRD420261286419.

Abstract as published, via PubMed.