Association Between the Risk of Surgical Site Infection and Surgical Volume in Hospitals Participating in the Nosocomial Infection Surveillance Network of South-Eastern France

Background: The mortality and complication rates of many surgical procedures are inversely related to surgical volume. However, the few studies focusing on the association between surgical site infection (SSI) risk and hospital surgical volume have reported conflicting results.

Objective: To determine if SSI risk is associated with surgical volume in hospitals in the south-east of France.

Methods: An epidemiological survey was conducted based on data from an SSI surveillance network between 1995 and 2007. Each patient undergoing a urinary or a digestive surgical procedure during the last quarter of each year was included. Surgical volume, calculated for each procedure, was defined as the number of procedures conducted in the surgical unit during the last quarter and was categorised in three groups: 1) > 30, 2) 16 to 30, and 3) ≤ 15. Risk factors (RF) of SSI were collected. A multivariate logistic regression analysis was performed by surgical procedure to identify if surgical volume was an independent RF of SSI. Confounders included in the model were the National Nosocomial Infection Surveillance (NNIS) risk index category, age, gender, multiple surgical procedures, celiosurgery, emergency surgery, ambulatory surgery, pre-operative hospitalisation duration, year and hospital type.

Results: Prospective surveillance identified 118 SSI after 2,952 operations (attack rate (AR) = 4.0 %) in urology surgery and 419 SSI after 16,491 operations (AR = 2.5 %) in digestive surgery. A low surgical volume was not associated with SSI risk for colostomy, appendectomy, and prostatectomy, but was an independent RF of SSI for cholecystectomy (adjusted odds ratio for group 2 [aOR₂] 1.56, 95% confidence interval [CI] 0.55–4.39; aOR for group 3 [aOR₃] 2.98, 95% CI 1.09–8.19) and lower urinary tract surgery (aOR₂ 1.51, 95% CI 0.64–3.56; aOR₃ 2.37, 95% CI 1.15–4.87). A non significant trend was observed for hernia surgery (aOR₂ 1.81, 95% CI 0.89–3.67; aOR₃ 2.24, 95% CI 0.98–5.12).

Conclusions: Undergoing cholecystectomy, lower urinary tract surgery, or hernia surgery in a surgical unit with a low volume of procedures increases the patient’s risk of SSI. Patients should consider these findings in selecting a hospital to carry out these procedures.  Although different possible explanations exist for these findings, in the context of the drive for economies, these kinds of results could nevertheless be used by health policy makers to decide to set up high-volume surgical units at regional level for some specific procedures.