Perioperative diabetes related complications in patients undergoing major surgery are associated with the duration of gastrointestinal and orthopaedic surgery.

Background: Diabetes mellitus (DM) is a common chronic condition among surgical patients. It is associated with increased perioperative morbidity and mortality. Realworld data on the clinical predictors of postoperative complications in diabetic patients undergoing major surgery are limited. This study aimed to characterise perioperative outcomes and identify independent predictors of 28day postoperative complications. Methods: A retrospective cohort study at a single UK tertiary hospital. Adult patients with a known diagnosis of type 1 or type 2 diabetes mellitus who underwent major procedures under general anaesthesia between January 2020 and September 2025 were identified through electronic patient records (EPR). The primary outcome was any postoperative complication within 28 days. We used multivariable logistic regression to identify independent predictors of complications, adjusting for age, sex, ASA grade, surgical category, admission urgency, operative duration, diabetes type, HbA1c, and socioeconomic deprivation (Index of Multiple Deprivation [IMD]). Results: We screened 2623 patients and included 267; we analysed 267 patients (260 with outcome data). The 28day postoperative complication rate was 23.1% (46/199) among those with outcome data. Infection was the most common complication. In multivariate analysis, surgical duration was the only independent predictor of complications (adjusted odds ratio [aOR], 1.71; 95% CI, 1.16 to 2.51; p=0.007). Other variables were not associated with complications. Conclusions: In this study of patients with DM undergoing major surgery, operative duration was the only modifiable independent predictor of 28-day postoperative complications. Socioeconomic deprivation and preoperative HbA1c were not independently associated with outcomes, suggesting that standardised perioperative care pathways may attenuate these effects.