Skip to main content Accessibility help
  • Print publication year: 2015
  • Online publication date: April 2015

109 - Postoperative wound infections

from Part XIV - Infections related to surgery and trauma


Postoperative wound infection is the archetypal surgical infection because it follows a surgical procedure and requires surgical intervention for resolution. As with many infections, best results are obtained by prompt diagnosis and treatment, which is facilitated by understanding the risk factors. The most obvious factor influencing risk of infection is the density of bacterial contamination of the incision. This was recognized several decades ago in the wound classification system that divides all surgical wounds into the following four categories: clean, clean-contaminated, contaminated, and dirty. Clean wounds result from an elective procedure without break in technique that does not involve any area of the body other than skin normally colonized by resident bacteria. Clean-contaminated wounds result from a procedure such as elective bowel resection that intentionally opens the gastrointestinal (GI) tract or other colonized region such as the female genital tract but does not result in grossly visible spill of contents during the procedure. Contaminated procedures are those with gross spill from the GI tract or trauma and emergency procedures in which a wound has been created without normal antisepsis and sterile technique. A dirty wound is one that results from an operation in an area of active infection or previous bowel injury and leak. Among these categories, infection risk ranges historically, before modern understanding and practice of perioperative antibiotic prophylaxis, from 2% for clean wounds to 30% to 40% for dirty wounds when the skin is closed primarily.

Studies done many decades ago demonstrate that essentially all surgical incisions, even in clean operations, have some bacteria in the wound at the end of the procedure. Clinicians have recognized that the nature of host defenses and the extent to which the operative procedure or pre-existing disease impairs these defenses also influences the risk of wound infection. Modern wound classifications that include underlying risk as well as the risk of bacterial contamination predict infection more accurately. The most widely used system now assigns one point each for wound classification of contaminated or dirty, an operation lasting longer than the 75th percentile for that procedure, and an American Society of Anesthesiology (ASA) physical status classification of 3 or 4. In this system, the risk of postoperative wound infection for patients with risk points of 0, 1, 2, or 3 is 1.5%, 2.9%, 6.8%, and 13.0%, respectively (Table 109.1). These data reflect modern use of perioperative prophylactic antibiotics, as discussed in Chapter 114, Surgical prophylaxis. Efforts at the Centers for Disease Control and Prevention (CDC) are currently trying to develop more precise procedure-specific risk predictions for surgical site infections, but are in very preliminary stages.

Suggested reading
Culver, DH, Horan, TC, Gaynes, RP, et al. Surgical wound infection rates by wound class, operative procedure, and patient risk index. National Nosocomial Infections Surveillance System. Am J Med. 1991;91(3B):152S–157S.
Dellinger, EP. Approach to the patient with postoperative fever. In: Gorbach, SL, Bartlett, JG, Blacklow, NR, eds. Infectious Diseases, 3rd edn. Philadelphia, PA: Lippincott Williams & Wilkins; 2004:817–823.
Dellinger, EP. Surgical infections. In: Mulholland, MW, Lillemoe, KD, Doherty, GM, Maier, RV, Upchurch, GR, eds. Greenfield's Surgery: Scientific Principles and Practice, 4th edn. Philadelphia, PA: Lippincott Williams & Wilkins; 2005:163–177.
Garibaldi, RA, Brodine, S, Matsumiya, S, et al. Evidence for the non-infectious etiology of early postoperative fever. Infect Control. 1985;6:273–277.
Horan, TC, Gaynes, RP, Martone, WJ, et al. CDC definitions of nosocomial surgical site infections, 1992: a modification of CDC definitions of surgical wound infections. Am J Infect Control. 1992;20:271–274.
Miller, LG, Perdreau-Remington, F, Rieg, G, et al. Necrotizing fasciitis caused by community-associated methicillin-resistant Staphylococcus aureus in Los Angeles. N Engl J Med. 2005;352:1445–1453.
Mu, Y, Edwards, JR, Horan, TC, Berrios-Torres, SI, Fridkin, SK. Improving risk-adjusted measures of surgical site infection for the national healthcare safety network. Infect Control Hosp Epidemiol. 2011;32:970–986.
National Academy of Sciences, National Research Council, et al. Postoperative wound infections: the influence of ultraviolet irradiation on the operating room and of various other factors. Ann Surg. 1964;160(Suppl 2):1.
Paydar, KZ, Hansen, SL, Charlebois, ED, Harris, HW, Young, DM. Inappropriate antibiotic use in soft tissue infections. Arch Surg. 2006; 141:850–854; discussion 855–856.
Stevens, DL, Bisno, AL, Chambers, HF, et al. Practice guidelines for the diagnosis and management of skin and soft-tissue infections. 2014 update by the Infectious Diseases Society of America. Clin Infect Dis. 2014;59:e10–52.