Risk Factors for Surgical Site Infection in Patients Undergoing Sacral Nerve Modulation Therapy

Abstract

The aim of this study was to identify risk factors for surgical site infection in patients undergoing sacral nerve modulation (SNM) surgery. We conducted a retrospective cohort analysis of 290 patients undergoing a total of 669 SNM procedures between 2002 and 2012 by 2 fellowship-trained female pelvic medicine and reconstructive surgery attending physicians at the University of California-Irvine Medical Center. Infection was defined as a charted abnormal examination finding at the implantation site (erythema, induration, purulent discharge) resulting in prescription of antibiotics, hospitalization, or explantation. We extracted information from the medical record regarding possible risk factors for infection including age, body mass index, immunosuppression (diabetes mellitus, chronic steroid use, smoker, chemotherapy), number of procedures per patient, and number of days between stages 1 and 2. In addition, we compared infection rates before and after 2008 when a clinical practice change was made with the implementation of home chlorhexidine washing (CHW) prior to SNM surgery. Thirty infections occurred, 25 of which were managed with oral antibiotics. Nine required intravenous antibiotics, and 11 required removal of the implanted device. Three patients experienced infection on 2 separate occasions. Seventeen infections had culture data available. Nine of the patients who underwent explantation had wound cultures positive for methicillin-resistant Staphylococcus aureus.Thirteen of the 26 patients who developed infection had medical histories significant for immunosuppression. Three patients developed late-onset abscess formation at 234, 257, and 687 days after stage 2, respectively. The median time between the most recent SNM procedure and development of infection was 14 days (range, 6-88 days).Body mass index and immunosuppression were significant predictors of infection, whereas age, parity, indication for procedure, and number of days between stages 1 and 2 were not found to be independent predictors. Three hundred twenty-three procedures were performed prior to and 346 procedures were performed after institution of home CHW. Twenty-four (80%) of the 30 reported infections were prior to CHW, whereas only 6 infections (20%) occurred after this change in practice. Prior to institution of CHW, the infection rate was 7.4%, and after institution of CHW, it was 1.7% (P = 0.002). Of the 83 patients with compliance data available for CHW use, 71 reported using CHW, whereas 12 reported not using CHW. Surgical site infection is a significant risk of SNM surgery, although our infection rate is lower than previously reported. Chlorhexidine washing appears to reduce the risk of infection in this population. Because the majority of infections requiring explantation were methicillin-resistant S. aureus positive, prophylactic treatment for this organism should be considered as an additional strategy to reduce infection. Body mass index and immunosuppression appear to be independent risk factors for infection.