Interrupted time series analysis of the impact of a bundle on surgical site infections after colon surgery

Background: Surgical site infections (SSIs) are monitored in Italy through a national surveillance system. A 4-element bundle was introduced in 2012, consisting of: appropriate preoperative shower and hair removal, perioperative normothermia, and antibiotic prophylaxis. The aim of this study was to evaluate the effect of the intervention on SSI rates after colon surgery. Methods: A retrospective cohort study was conducted between 2008 and 2019 in 29 hospitals of northern Italy. An interrupted time series analysis (ITSA) was modeled to assess the bundle's impact on SSI trends. Logistic regression was performed to identify predictors of SSI among procedures performed in the postintervention period, comparing full and partial bundle compliance. Results: Data of 5487 colon surgery procedures were collected (1243 preintervention and 4244 postintervention). The ITSA identified a significant change in the monthly postintervention SSI trend of −0.19% and a change in level of −2.09%. A significant protective effect of full bundle compliance compared to partial bundle compliance (OR 0.74, P.043) was found, whereas the single effect of the bundle elements was nonsignificant. Conclusions: Results of this study suggest this relatively simple bundle protocol is effective in reducing SSI risk.