The impact of pre-operative oral carbohydrate loading on peri-operative outcomes: A systematic review and meta-analysis of randomised controlled trials.

Background and Aims: Pre-operative oral carbohydrate loading is widely adopted in enhanced recovery after surgery protocols, yet its clinical benefits remain uncertain. This review aimed to determine the effect of pre-operative oral carbohydrate loading on the incidence of post-operative nausea and vomiting (PONV) and other peri-operative outcomes in surgical patients. Methods: MEDLINE, EMBASE, and CENTRAL databases were systematically searched from database inception to 31 August 2025. Randomised controlled trials examining the effects of pre-operative oral carbohydrate loading with conventional fasting or placebo in adult patients were included. Results: Ninety-eight trials involving 9,824 patients were included. The main pooled analysis showed lower incidence of PONV with oral carbohydrate loading prior to surgery [risk ratio (RR) 0.74, 95% confidence interval (CI) 0.58-0.94, Conclusion: Pre-operative oral carbohydrate loading may reduce PONV. However, this benefit was not confirmed in the sensitivity analysis restricted to low-risk bias studies. It also reduces pre-operative hunger and thirst, post-operative pain, and the length of hospital stay, although the certainty of evidence for these outcomes is low. The absolute effect sizes for post-operative pain and length of stay were small and of uncertain clinical importance. These findings should be interpreted with caution due to substantial heterogeneity, publication bias, and lower certainty of evidence.