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The evidence-based way to prevent wound infections

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Are some CDC recommendations more equal than others?



Of 72 different ways to prevent surgical site infections, 49 are backed by enough confirmatory science to merit the CDC’s strongest recommendation for use in all hospitals. (The 23 other measures in the CDC advisory have not been or cannot be as thoroughly studied.)

How can we apply all possible precautions to every patient wheeled into the OR? The CDC’s Guideline for Prevention of Surgical Site Infections (formerly termed wound infections) advocates “a systematic but realistic approach” based on the evidence, coupled with awareness that risk of surgical site infection is influenced by characteristics of the patient, operation, personnel, and hospital.

This article reviews key evidence behind a number of the most strongly recommended measures, such as optimal regimens for prophylactic antibiotics, and some of the recommendations for which equally rigorous evidence is lacking.

The CDC’s Guideline ranks its recommendations according to 4 levels of evidence. A total of 49 recommendations meet the most rigorous evidence standards, and therefore are “strongly recommended for all hospitals.” (See How strong is the evidence?.)

Many of our infection prevention routines, of course, have been standard ever since Joseph Lister introduced the principles of antisepsis in the late 1860s. Technically, however, some standard infection prevention routines are based on a strong theoretical rationale along with suggestive though not confirmatory science.

By necessity, narrowly defined patient populations and ethical and logistical issues will always limit our ability to obtain confirmatory scientific answers to some questions. For example, wearing gloves vs not wearing gloves fits into that category. Likewise, the evidence on preoperative nutritional support for the sole purpose of preventing SSI does not meet the criteria for the best evidence category, “1A.” Yet, nutrition therapy is among the CDC’s recommendations, albeit the evidence behind it falls into the “NR” category, “no recommendation; unresolved issue.”

The CDC’s exhaustive guideline identifies 21 characteristics of patients and operations that influence a patient’s risk of surgical site infection (TABLE 1), and recommends prevention tactics that are backed by evidence (See CDC Advisory).

The CDC’s recommendations are grouped into these sections:

1. Preoperative preparation of the patient, hand/forearm antisepsis for surgical team members, management of infected or colonized surgical personnel, and antimicrobial prophylaxis.

2. Intraoperative ventilation, cleaning and disinfection of environmental surfaces, microbiologic sampling, sterilization of surgical instruments, surgical attire and drapes, asepsis, and surgical technique.

3. Postoperative incision care.

4. Surveillance.


21 factors that influence risk of surgical site infection

1 Age
2 Nutritional status
3 Diabetes
4 Smoking
5 Obesity
6 Coexistent infections at remote body site
7 Colonization with microorganisms
8 Altered immune response
9 Length of preoperative stay
10 Duration of surgical scrub
11 Skin antisepsis
12 Preoperative shaving
13 Duration of operation
14 Antimicrobial prophylaxis
15 Operating room ventilation
16 Inadequate sterilization of instruments
17 Foreign material in the surgical site
18 Surgical drains
19 Poor hemostasis
20 Failure to obliterate dead space
21 Tissue trauma
Source: Reference 1.

Preparing The Patient

Preoperative risk factors

Infection prevention begins with considering the preoperative risk factors of the patient’s condition.

Not all risk factors for surgical site infections can be modified (age, for example), but we should correct whatever we can before scheduling elective surgery.

Minimizing smoking improves postoperative SSI outcomes(EVIDENCE CATEGORY IB).

Weight loss before surgery has not been clearly correlated with improved SSI outcomes (EVIDENCE CATEGORY NR). However, body mass index may influence surgical complication rates, perhaps acting as a surrogate for technical difficulty or impaired wound-healing capacity.2,3

Nutritionis being recognized as a key determinant in outcomes, but reports have not established how preoperative parenteral or enteral nutrition influences SSI outcome (NO RECOMMENDATION).4,5

Antisepsis in the surgical field

The microbial source for most SSI is the patient’s endogenous flora, and the operative field determines the type of flora that will be encountered.

Normal skin flora consist mostly of gram-positive aerobes.

Antiseptic showering before surgery significantly reduces resident skin flora (EVIDENCE CATEGORY IB). Multiple showers with chlorhexidine have been shown to reduce resident bacteria up to 9-fold, but whether that reduces SSI rates is unclear.6

Prophylactic eradication of nasal Staph colonization (NO RECOMMENDATION). Recent attention has focused on microbial colonization with resistant organisms—and Staphylococcus aureus colonization of nares in cardiac surgery patients was found to be a major independent risk factor for surgical site infection.


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