Surgical Site Infection: Conditional Influence of Surgery Duration and ASA Classification in Major Procedures

ABSTRACT

Surgical site infection (SSI) is a major complication in surgical patients. This study aimed to investigate predictors of SSI in cardiac, neurological and orthopaedic surgeries. A total of 28,803 procedures (2015–2021) were analysed. Predictive variables included age, sex, ASA score, wound classification, operative duration and preoperative stay. Logistic regression was applied. Overall SSI rate was 7.2% (2062 cases): 47% neurological, 39% cardiac and 15% orthopaedic. Infected patients had longer preoperative stays (median 6 [IQR: 2–13] vs. 3 days [IQR: 1–9], p  < 0.001), extended operative times (median difference: 70 min, 95% CI: 60–79, p  < 0.001), and prolonged hospitalizations (median difference: 14 days, 95% CI: 14–15, p  < 0.001). Mortality was higher among infected patients (15% vs. 8.2%). Despite lower SSI incidence, orthopaedic patients had a 3.0‐fold increase in median stay and 5.3‐fold increased odds of death. A significant duration × ASA (> 3) interaction indicated that SSI risk increased with surgical time in high‐severity patients. Model adequacy was confirmed by the Hosmer–Lemeshow test ( p  = 0.481). Higher ASA scores, prolonged surgeries, and extended preoperative stays are significant contributors to SSI risk in major procedures.