PENETRATING ABDOMINAL TRAUMA:
GUIDELINES FOR ANTIBIOTIC PROPHYLAXIS

CINCINNATI--For the last quarter-century, it has been standard practice to administer antibiotics to patients with penetrating abdominal trauma because of the high incidence of infectious complications following such injuries. However, there has been little consensus regarding which antibiotic or combination of antibiotics should be given prophylactically--or the duration for which the drugs should be administered.

To address this problem, a panel of experts led by Fred A. Luchette, MD, has formulated evidence-based practice guidelines for prophylactic antibiotic administration following penetrating abdominal trauma.[1] As Dr. Luchette noted in an interview with PULMONARY REVIEWS, developments at the national health policy level, as well as managed care imperatives, suggest that clinical practice guidelines will play an increasingly prominent role in medicine.

"Such guidelines can contribute as an aid to clinical decision-making, a research tool, and an educational resource," said Dr. Luchette, associate professor of surgery at the University of Cincinnati Medical Center. "As managed care increasingly affects medicine, practitioners should feel compelled to establish recommended guidelines themselves rather than rely on outside special interests."

To prepare the guidelines, Dr. Luchette and his colleagues on the Eastern Association for the Surgery of Trauma (EAST) Practice Management Guidelines Work Group performed a MEDLINE search to identify articles on antibiotic administration in patients with penetrating abdominal wounds. They identified 55 English-language references published between 1976 and 1997; they also reviewed the bibliography of each article to check for additional references.

Of the 39 studies selected for evidentiary review, 32 pertained to comparisons of various antibiotic regimens; the remaining seven addressed pharmacokinetics and costs. (The other 16 references were review articles, case studies, or letters to the editor.) The selected articles were reviewed by five general surgeons and two pharmaceutical outcome researchers, who then collaborated to produce the guidelines.

Synthesizing these data, the EAST Group developed guidelines at three levels. "On level 1, the recommendation is convincingly justifiable based on available scientific information alone," explained Dr. Luchette. "Level 2 includes recommendations that are reasonably justifiable by available scientific evidence and strongly supported by expert critical care opinion. Level 3 consists of recommendations supported by available data but for which adequate scientific evidence is lacking."

RECOMMENDATIONS

The EAST Group's recommendations are as follows:

Level 1: Sufficient data exist to recommend a single preoperative dose of prophylactic antibiotics with broad-spectrum aerobic and anaerobic coverage as a standard of care for trauma patients sustaining penetrating abdominal wounds. Unless a hollow viscus injury is present, no further antibiotic administration is necessary.

Level 2: Sufficient data exist to recommend continuation of prophylactic antibiotics for no more than 24 hours if injury to any hollow viscus has occurred.

Level 3: Insufficient clinical data exist to provide meaningful guidelines for reducing infectious risks in trauma patients with hemorrhagic shock. However, some evidence suggests that antibiotic dosages may need to be altered in patients with hemodynamic shock. Vasoconstriction alters the normal distribution of antibiotics, resulting in reduced tissue penetration. As a consequence, it may be reasonable to increase the administered dose twofold or threefold and to repeat the dose after every 10th unit of blood product is transfused until there is no further blood loss. Once hemodynamic stability has been achieved, antibiotic administration should be continued. The agent chosen should have excellent activity against obligate and facultative anaerobic bacteria; the duration of treatment depends on the degree of wound contamination. Aminoglycosides have exhibited suboptimal activity in patients with serious injury, probably owing to altered pharmacokinetics or drug distribution.

ONE DRUG OR SEVERAL?

The EAST Group analyzed 10 studies and one meta-analysis that compared the effectiveness of single-agent versus combination therapy for penetrating wounds. In most cases, a penicillin derivative or cephalosporin was compared with an aminoglycoside combination. After reviewing the evidence, Dr. Luchette and his colleagues concluded that "single and combination therapy are equally effective in minimizing trauma-related infections after penetrating abdominal wounds." However, the panel was unable to determine whether any specific antibiotic was preferable to others.

Fewer studies evaluated the duration of treatment. Based on the available evidence, the panel recommended that antibiotics be given for at least 12 but no more than 24 hours, unless hemodynamic shock is present.

COST ANALYSIS

In addition to evaluating clinical parameters, Dr. Luchette and his associates assessed the financial implications of various treatment strategies. In particular, they examined studies that analyzed total costs (for the drug, laboratory tests, personnel time, and ancillary supplies). Only a few such studies are available. Nevertheless, they concluded that "single-agent therapy using a drug with aerobic and anaerobic coverage may be a cost-effective choice compared with the more traditional combination antibiotic regimen (gentamicin plus clindamycin)."

FUTURE DIRECTIONS

Acknowledging that the EAST Group's evidentiary study was somewhat limited in scope, Dr. Luchette suggested that future studies should be double-blind and should clearly define the criteria for trauma-related injuries. "The prospective, randomly assigned, double-blind study is the gold standard," he said. "Unfortunately, very few of these have been designed to evaluate the use of prophylactic antibiotics in penetrating abdominal trauma."

Dr. Luchette stressed the need to assess other risk factors, including those related to the drug (such as time to administration, half-life, and duration) and those related to the patient (such as the presence of shock and/or organ injuries). More studies need to investigate the interaction of hemodynamic status with volume of distribution. The specific organisms responsible for trauma-related infections also require further study.

In Dr. Luchette's view, the most significant guideline emerging from the EAST Group's study was that the administration of prophylactic antibiotics in penetrating abdominal trauma, while beneficial, in most cases should not be continued for more than 24 hours.

"Several of the studies we evaluated employed antibiotic prophylaxis for as long as five days, a practice which is clearly inadvisable based on our review of the literature," he said. "With increasing concerns about bacterial resistance, restricting antibiotics would seem to represent better practice than overusing these agents."

--Stanley Nelson

Reference
1. Luchette FA, Borzotta AP, Croce MA, et al. Practice management guidelines for prophylactic antibiotic use in penetrating abdominal trauma: the EAST Practice Management Guidelines Work Group. J Trauma. 2000;48:508-518.

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