Preoperative oral carbohydrate administration in adult elective surgery: protocol heterogeneity, regional practice patterns and evidence gaps–a scoping review

Objective This scoping review aimed to map the extent, characteristics and distribution of evidence on preoperative oral carbohydrate administration in adult elective surgical patients. Specifically, we sought to describe publication trends, regional practice patterns, surgical populations, intervention protocols, outcome domains and evidence gaps, thereby informing future standardization and individualized implementation within ERAS pathways. Methods Following the Arksey and O’Malley framework for scoping reviews, we searched eight Chinese and English databases including CNKI, Wanfang, PubMed, and Web of Science, to collect original studies published from 2015 to September 2025 on preoperative oral carbohydrate intake. Studies were screened and data extracted according to predetermined inclusion and exclusion criteria, followed by descriptive analysis. Results Eighty-two studies were included, comprising 76 randomized controlled trials and 6 non-randomized studies. Most studies were conducted in China and other Asian settings, and more than two-thirds were published after 2020. The commonly reported regimen involved 200–400 mL of a carbohydrate-containing clear fluid administered 2–3 h before surgery, although formulation, dose, timing and control conditions varied substantially across studies. Outcomes were mapped into five domains: metabolic responses, patient comfort, inflammatory or stress markers, clinical recovery and safety. Most included studies reported favorable metabolic or comfort-related findings; however, evidence was concentrated in single-center trials, short-term outcomes and relatively low-risk elective surgical populations. Conclusion Current literature suggests that preoperative oral carbohydrate administration is a widely studied and feasible component of ERAS pathways, but the evidence base remains heterogeneous in intervention protocols, outcome definitions and population coverage. Future multicenter studies should standardize reporting, include higher-risk populations such as older adults, frail patients and patients with diabetes, and assess long-term functional and patient-centered outcomes. Systematic review registration https://osf.io/9rd68/