Risk Factors for Superficial vs Deep/Organ-Space Surgical Site Infections Implications for Quality Improvement Initiatives

IMPORTANCE Surgical site infections (SSIs) are the focus of numerous quality improvement initiatives because they are a common and costly cause of potentially preventable patient morbidity. Superficial and deep/organ-space SSIs differ in terms of anatomical location and clinical severity. OBJECTIVE To identify risk factors that are uniquely predictive of superficial vs deep/organ-space SSIs occurring after colectomy procedures. DESIGN Retrospective cohort study. SETTING American College of Surgeons National Surgical Quality Improvement Program. PARTICIPANTS Patients undergoing colectomy procedures in 2011 were identified by Current Procedural Terminology codes. INTERVENTION Colectomy procedures. MAIN OUTCOMES AND MEASURES We compared rates of superficial SSI and deep/organ-space SSI associated with perioperative variables of interest: demographics; preoperative clinical severity, risk factors, and comorbidities and variables related to the hospitalization or procedure. Hierarchical multivariable logistic regression models were developed to identify risk-adjusted predictors of each SSI type. RESULTS Among 27 011 patients identified from 305 hospitals, 6.2% developed a superficial SSI and 4.7% developed a deep/organ-space SSI. Risk factors common to the occurrence of both SSI types were identified: open surgery (vs laparoscopic) and current smoker. Risk factors with differential effects on each SSI type included specific postoperative diagnoses, disseminated cancer, and irradiation therapy, which were all associated with increased odds of deep/organ-space SSI only. The graded relationship between increasing body mass index and SSI occurrence appeared to be stronger for superficial SSI. CONCLUSIONS AND RELEVANCE Risk factors for superficial SSI and deep/organ-space SSI vary in terms of magnitude and significance, suggesting that these SSI types are somewhat different disease processes. Groups interested in preventing SSIs might improve success by considering these SSI types independently for root-cause analyses and development of best practices and interventions.