I. INTRODUCTION

Healthcare-associated infections (HAIs) are a major source of morbidity and mortality in the United States. In acute care hospitals in the United States, on any given day, about 1 patient out of 25 carries some form of HAI, and more than half of HAIs occur outside of the intensive care unit. These HAIs include surgical site infections (SSIs), catheter-associated urinary tract infections (CAUTIs), central line-associated bloodstream infections (CLABSIs), and ventilator-associated pneumonia (VAP). The most frequent organisms causing HAIs are coagulase-negative staphylococci, Staphylococcus aureus, Enterococcus species, Candida species, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Enterobacter species, Acinetobacter baumannii, and Klebsiella oxytoca. Of concern, up to 16% of HAIs are caused by antimicrobial-resistant pathogens, the most common being methicillin-resistant S. aureus (MRSA), vancomycin-resistant Enterococcus faecium (VRE), extended-spectrum β-lactamases and carbapenem-resistant pathogens. The detection, prevention, and reduction of HAIs are a top priority of hospital infection control programs and governmental agencies such as the Centers for Disease Control and Prevention (CDC).

II. SURGICAL SITE INFECTIONS

Careful attention to sterile surgical technique and the appropriate timing and dosing of perioperative antibiotics remain the most important measures in preventing SSIs, which is the most common nosocomial infection among postoperative patients.

A. Definition

The CDC defines SSI as an infection that occurs at or near a surgical site within 30 days of the surgical procedure, or within 90 days if hardware was implanted. The site can be incisional (superficial or deep) or related to the organ/space and involve any part of the anatomy that may have been incised, shifted, or manipulated during the procedure.

B. Diagnosis of SSI

The diagnosis of SSI can be made from any of the following criteria: purulent drainage from operative site, positive culture obtained from surgical site that was closed primarily, the surgeon’s diagnosis of infection, or a surgical site that requires reopening.

C. Classification of Wounds

Classification of wounds based on the definition from the CDC National Healthcare Safety Network and Healthcare Infection Control Practice Advisory Committee:

1. Clean wounds arise from operations done electively and atraumatically, neither with no inflammation or break in sterile technique. In addition, the respiratory, biliary, gastrointestinal (GI), nor genitourinary (GU) tracts were entered during the procedure. These wounds are associated with a less than 2% risk of infection.

2. Clean-contaminated wounds are from urgent or emergent cases in which the respiratory, biliary, GI or GU tracts were entered electively with minimal spillage of contents, and without encountering urine or bile. There is a less than 4% risk of infection.

3. Contaminated wounds are from procedures in which there was gross spillage from the GI tract, infected bile or urine was encountered, there was a major break in sterile technique, penetrating trauma <4 hours old, or chronic, open wounds that are to be grafted or covered. There is an approximately 20% risk of infection.

4. Dirty wounds arise from operations in which there was purulent inflammation (i.e., an abscess). In addition, this encompasses preoperative perforation of the respiratory, biliary, GI or GU tract, or penetrating trauma >4 hours old. These wounds carry an approximately 40% risk of infection.

D. Risk Factors for the Development of SSI

1. Systemic factors: diabetes, steroid use, age, obesity, malnutrition, recent surgery, massive transfusion, and American Society of Anesthesiologists physical status class 3 or 4.

a. Local factors: foreign body, electrocautery, epinephrine injection, prior irradiation, wound drains, and hair removal with razor (preferable to remove hair using depilatory or clippers).

E. Prevention of SSI

1. Perioperative considerations

Hair should be removed only if necessary and done immediately before the operation, preferably with electric clippers. Serum blood glucose should be controlled perioperatively. Hyperglycemia (>200 mg/dL) has been associated with increased SSI risk. Normothermia should be maintained intraoperatively and postoperatively, because a core temperature of <36° Celsius is associated with increased SSI risk.

2. Operating rooms should be maintained with a positive pressure relative to corridors and adjacent areas to prevent airflow from the “less clean” areas. There should be a minimum of 15 air changes per hour, of which at least 3 should be fresh air. Operating room doors should be kept closed, except as needed for passage of equipment, personnel, and the patient.

3. Selection of the appropriate perioperative antibiotic requires consideration of the most likely involved pathogen and ability for adequate tissue penetration at the site of surgery.

a. Antibiotics should be dosed within 60 minutes prior to incision in order to achieve the appropriate tissue concentration. In the case of antibiotics with longer infusion times, such as vancomycin or fluoroquinolones, doses should be given within 60 to 120 minutes prior to the incision.

1. Organisms by wound type. The predominant organisms seen in clean cases are skin flora, including streptococcal species, Staphylococcus aureus, and coagulase-negative staphylococci. The predominant organisms seen in clean-contaminated cases: gram-negative rods, enterococci, and skin flora, as above. Finally, in the case of procedures that involve entering a viscus, organisms reflect the flora of that viscus or nearby mucosal surfaces, and infections are usually polymicrobial.

2. For a list of common types of organisms by surgical site, see Table 39.1.

3. Cefazolin is the most widely used perioperative antibiotic with proven efficacy for antimicrobial prophylaxis. It is safe, carries a low cost, possesses a desirable duration of action, and is effective
against streptococci, methicillin-sensitive staphylococci, and some gram-negative organisms. Alternatives to penicillins include vancomycin and clindamycin. However, in these cases, antimicrobials with activity against gram-negative organisms must sometimes be added (i.e., gentamicin, fluoroquinolones, or aztreonam).

b. An additional dose should be considered if the procedure lasts for greater than 3 hours, for longer than two half-lives of the drug, or there is more than 1,500 mL of blood loss. Special consideration should be taken in situations where the half-life may be shortened (i.e., extensive burns) or prolonged (i.e., renal insufficiency). Further dose adjustments and weight-based dosing must be employed in obese patients.

c. The use of perioperative antibiotics is considered prophylaxis for clean and clean-contaminated cases. The use of antimicrobial agents is considered therapeutic treatment of the presumed infection in contaminated and dirty cases.

d. Duration of antimicrobial prophylaxis should be less than 24 hours.

4. Staphylococcus aureus decolonization

Patients colonized with MRSA have an increased risk for SSI with MRSA compared with noncarriers. There lacks a consensus regarding decolonization of patients with known MRSA, because some studies have shown it to be neither beneficial nor cost-effective. However, certain high-risk surgical subgroups (e.g., cardiac surgery, joint replacements, or spinal procedures involving implants) may benefit from decolonization. Decolonization methods in past clinical trials have varied and include intranasal mupirocin with or without the addition of chlorhexidine bathing.