Clinical Pearls & Morning Reports
Necrotizing infections occur after traumatic injuries, minor penetrating skin injuries, nonpenetrating injuries, and obstetrical and gynecologic procedures, as well as in postsurgical and immunocompromised patients. For patients with aggressive soft-tissue infection or those with mild infection plus evidence of systemic toxicity, prompt surgical exploration is extremely important for three reasons: to determine the extent of infection, to assess the need for débridement or amputation, and to obtain specimens for Gram’s staining and culture. Read the latest Case of the Massachussetts General Hospital.
Q: What is the difference between necrotizing fasciitis type I and type II?
A: Necrotizing fasciitis type I is a polymicrobial infection involving aerobic and anaerobic organisms. Predisposing factors include diabetic or decubitus ulcers, hemorrhoids, rectal fissures, episiotomies, and colonic or urologic surgery or gynecologic procedures. Necrotizing fasciitis type II is a monomicrobial infection. Among gram-positive organisms, group A streptococcus remains the most common pathogen, followed by methicillin-resistant Staphylococcus aureus. Unlike type I infections, type II infections may occur in persons without any underlying illness.
Q: Is there a link between nonsteroidal antiinflammatory drugs (NSAIDs) and group A streptococcal necrotizing fasciitis?
A: In the 1980s, an association between the use of NSAIDs and the development of group A streptococcal necrotizing fasciitis was proposed. Proponents recognized that NSAIDs can suppress critical neutrophil functions and augment the production of tumor necrosis factor α, a key mediator of septic shock. Other people argued that NSAIDs merely mask the signs and symptoms of developing infection, delaying diagnosis and treatment. Numerous clinical and epidemiologic studies have investigated, but not resolved, this issue.
A: Early diagnosis of necrotizing infections may be confounded by numerous factors. Physicians must be aware of these potential pitfalls, because delays in diagnosis and treatment have dire consequences. In approximately 50% of patients with group A streptococcal necrotizing fasciitis or myonecrosis, infection initiates deep in the soft tissues, without a portal of entry, often at sites of nonpenetrating trauma (muscle strain or bruise). Initially, only fever and crescendo pain (rapid pain escalation sufficiently severe to require ketorolac or narcotics) may be present, and such pain prompts patients to seek urgent medical care. Malaise, myalgias, diarrhea, and anorexia may also be present in the first 24 hours. Since cutaneous manifestations are absent initially, the infection is often misdiagnosed or the correct diagnosis, delayed, and as a result, the mortality exceeds 70%. Erroneous diagnoses include severe muscle strain and deep-vein thrombophlebitis; because of the associated gastrointestinal manifestations, food poisoning may also be diagnosed in error.
A: A review of 57 studies performed between 1997 and 2003 concluded that hyperbaric oxygen is not useful for the treatment of necrotizing fasciitis, a finding that is similar to the results of other studies. In contrast, a significant survival benefit of hyperbaric oxygen in necrotizing fasciitis was documented in recent studies from the United States and Australia. Recently, a study has been initiated to evaluate the effect of hyperbaric oxygen on inflammatory and vasoactive biomarkers in necrotizing infections. Meanwhile, its benefits remain controversial. The rationale for using intravenous immune globulin (IVIG) in patients with necrotizing fasciitis is based on its ability to neutralize extracellular toxins that mediate pathogenesis. Clinical studies suggesting that there are benefits to IVIG have had serious limitations. In view of these limitations and the lack of data from definitive double-blind, controlled studies, the Infectious Diseases Society of America does not recommend IVIG for necrotizing group A streptococcal infections. Though IVIG has its advocates, a consensus supporting its use has not been reached.