• Patient Safety Primer
  • Last Updated: June 2018

Surgical Site Infections


According to data from AHRQ, more than 10 million patients undergo surgical procedures as inpatients each year, accounting for over one-fourth of all hospital stays. The most common types of inpatient surgical procedures include cesarean section, orthopedic procedures (hip and knee replacement, hip fracture repair), neurosurgical procedures (spinal fusion and laminectomy), and intraabdominal procedures (cholecystectomy and colorectal resections). Increasing numbers of patients also undergo surgery at ambulatory surgery centers (facilities specifically designed for certain types of surgery after which the patient can be discharged home directly).

Surgical site infection (SSI)—defined by the Centers for Disease Control and Prevention (CDC) as infection related to an operative procedure that occurs at or near the surgical incision within 30 days of the procedure, or within 90 days if prosthetic material is implanted at surgery—is among the most common preventable complication after surgery. SSIs occur in 2% to 4% of all patients undergoing inpatient surgical procedures. Although most infections are treatable with antibiotics, SSIs remain a significant cause of morbidity and mortality after surgery. They are the leading cause of readmissions to the hospital following surgery, and approximately 3% of patients who contract an SSI will die as a consequence. Although SSIs are less common following ambulatory surgery than after inpatient procedures, they are a frequent source of morbidity in these patients as well.

Risk factors for SSI include patient factors (such as age, tobacco use, diabetes, and malnutrition) and procedure-specific risk factors (including emergency surgery and the degree of bacterial contamination of the surgical wound at the time of the procedure). While many of these risk factors are not modifiable, the majority of SSIs are considered preventable, and recent advances have improved our insights as to how hospitals can systematically prevent these infections. This Primer will provide an overview of the prevention of SSI, with a focus on system-level interventions. Information on other types of health care–associated infections (HAIs) may be found in the Health Care–Associated Infections Primer.

Prevention of Surgical Site Infections

Accurate measurement can be a challenge in patient safety, but prevention of SSIs (and HAIs in general) has benefited from the development of standard metrics that allow for tracking of infection rates over time and comparison of infection rates between facilities. The CDC's National Healthcare Safety Network (NHSN) has developed standards for SSI measurement. These definitions are also used by the National Surgical Quality Improvement Program (NSQIP), although NSQIP uses slightly different methods of surveillance for infections. Both the NHSN and NSQIP definitions are widely used for both quality improvement and research purposes. The CDC has also developed guidelines (last updated in 2017) summarizing the evidence for clinical interventions to prevent SSI; the World Health Organization also issued SSI prevention guidelines in 2016. Adherence to these clinical standards (for example, administration of appropriate antimicrobial prophylaxis) is routinely tracked in the form of process measures that, if adhered to, should reduce the incidence of SSI.

However, as with many other quality problems, implementing the recommended methods as standard practice and sustaining the use of preventive interventions has been challenging. Many organizations have been able to achieve sustained reductions in SSIs, and AHRQ has led notable efforts to encourage dissemination and implementation of SSI prevention strategies. Key elements of organizational interventions to prevent SSIs (and HAIs in general) include improving safety culture, the use of robust data tracking and feedback mechanisms, and utilizing checklists or evidence-based bundles.

The comprehensive unit-based safety program (CUSP) has been demonstrated to be an instrumental approach to driving reductions in SSI. CUSP emphasizes improving safety culture through a continuous process of identifying and learning from errors, improving teamwork, and engaging staff at all levels in safety efforts. The AHRQ Safety Program for Surgery used the CUSP model and implementation science approaches to improve adherence to evidence-based SSI prevention practices in 197 hospitals. Participating hospitals implemented the CUSP with mentorship from a national project team, used either the NHSN or NSQIP method to measure and feed back SSI rates to frontline personnel regularly, and participated in collaborative learning experiences. The intervention was associated with a significant reduction in SSI rates at participating hospitals, accompanied by improvement in perceived safety culture. Ethnographic analysis of the intervention found that active engagement from senior leadership and creation of a nonpunitive environment were crucial success factors. AHRQ has created toolkits for both hospitals and ambulatory surgery centers that contain guides and instructional modules for implementing CUSP principles and methods for promoting safe surgery.

Surgical safety checklists are tools to standardize safety assessment and improve teamwork and communication in surgical care, and also generally include specific steps to reduce SSI risk (for example, ensuring that preoperative antimicrobial prophylaxis has been administered at the appropriate time). The evidence base around checklists is summarized in the Checklists Primer. Although checklists are effective at preventing intraoperative and postoperative complications, real-world implementation remains a challenge, and there is no clear evidence that checklists alone can prevent SSIs. The AHRQ Safety Program for Surgery used a multicomponent intervention designed to improve safety culture in order to promote consistent use of the World Health Organization surgical safety checklist, and additionally to promote SSI prevention. The project did not use an explicit bundle of interventions focused on SSI, recognizing the limitations in the evidence base for SSI prevention and the fact that defects in safety systems leading to SSI may differ between hospitals. Bundled interventions may be an important part of overall institutional approaches to preventing SSIs, but the specific components of the bundle will likely vary across institutions. Another project, the AHRQ Safety Program for Improving Surgical Care and Recovery is an ongoing collaborative program to enhance the recovery of surgical patients. This project aims to address multiple types of patient harm, including SSI and other harms, in an integrated way throughout the surgical care pathway.

Current Context

SSI prevention is a high-priority goal for health care organizations. The Joint Commission includes use of guidelines to prevent SSI as one of its National Patient Safety Goals for hospitals and ambulatory surgery centers. The Centers for Medicare and Medicaid Services require hospitals to report SSI rates, which are publicly disseminated (along with other surgical quality measures) on its Hospital Compare website.

Efforts to prevent surgical site infections have been effective. Data from AHRQ's Partnership for Patients initiative indicates that the national rate of SSI decreased by 16% between 2010 and 2015, translating into significant benefits for patients (including many lives saved), as well as significant cost savings.

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