EPIDEMIOLOGY AND RISK FACTORS FOR SURGICAL SITE INFECTIONS
It is estimated that over 40 million surgical procedures are performed every year in the United States. Surgical site infections (Table 55-1) complicate approximately 2% to 5% of these procedures, representing 38% of nosocomial infections occurring in surgical patients. Risk factors for surgical site infections (SSIs) can be classified as either patient-related factors or surgical factors, and can be stratified into modifiable, potentially modifiable, and nonmodifiable risk factors. Modifiable risk factors include elective operations in the presence of associated infections, prolonged preoperative hospital stays, seromas, dead space, foreign bodies, and routine drain use, among others, and can be improved with the use of good surgical practice and specific preventive strategies. Nonmodifiable risk factors are most commonly patient-related and have an important effect on the incidence of SSI for each individual patient. The wound class (Table 55-2) is a relatively good predictor of SSI and has traditionally been used to estimate the risk of SSI and as a benchmark for comparisons between institutions. However, with the better recent understanding of SSI and its multifactorial risk factors, more sophisticated predictive scores, such as the National Nosocomial Infection Surveillance (NNIS) score, have been developed to better estimate the risk of SSI for each individual patient, after considering the interaction between different risk factors (Table 55-3). Specific preventive measures have been identified and are used to decrease the risk of SSI. These include minimizing the presence of microorganisms with prophylactic antibiotics and optimizing the patient’s ability to fight those still present at the surgical site during the perioperative period.
Patient risk factors for surgical site infections may include obesity, diabetes mellitus, older age, malnutrition, prolonged hospital stay prior to surgery, active infection at another site, cancer, immunosuppression, and tissue ischemia due to irradiation or vascular disease. Although some of these risk factors may not be reversible, hospitalists taking care of preoperative patients should optimize glycemic control and nutritional status, and encourage smoking cessation.
TABLE 55-1Criteria for SSI |Favorite Table|Download (.pdf) TABLE 55-1 Criteria for SSI
|Classification ||Definition |
|Superficial incisional || |
Within 30 d postoperatively
Involves skin or subcutaneous tissue of the incision and at least one of the following:
Purulent drainage from the superficial incision
Organism isolated from an aseptically obtained culture of fluid or tissue from the superficial incision
At least one of the following signs or symptoms of infection: pain or tenderness, localized swelling, redness, or heat and incision is deliberately opened by surgeon and is culture-positive or not cultured
Diagnosis by surgeon or attending physician
|Deep incisional |
Within 30 d if no implant in place; within 1 y if implant
Involves deep soft tissues and at least 1 of the following:
Purulent drainage from the deep incision but not from the organ/space component
Deep incision spontaneously dehisces or is deliberately opened and is culture-positive ...