Fig. 1
Necrotizing fasciitis of the upper limb in an immunocompromised adolescent. Note the swelling of the more proximal limb well beyond the dorsal hand erythema (Courtesy of Allan Peljovich, MD)
With continued progression, necrotizing fasciitis may lead to hypovolemic shock organ failure and finally death.
Laboratory Data
As is the case with a patient being evaluated for a presumed cellulitis, CBC with differential, standard electrolyte chemistry, ESR, and CRP should be assessed. Elevated CRP (>150 mg/dl), white blood cell (WBC) count (>15/mm3), serum creatinine (>1.6 mg/dl), serum glucose (>180 mg/dl), as well as decreased serum Hemoglobin (<13.5 g/dl) and serum sodium (<135 mmol/L) were found to be independent predictors of necrotizing fasciitis compared to severe soft tissue infections. In addition, hemoglobin <11 g/dl and WBC count >25/mm3 even more strongly predict the diagnosis of necrotizing fasciitis. Thrombocytopenia, though not highly sensitive for necrotizing fasciitis, is highly specific to the diagnosis.
The LRINEC (laboratory risk indicator for necrotizing fasciitis) is a scoring system developed to predict the presence of necrotizing fasciitis. A total score of 6 should prompt significant suspicion of the diagnosis, whereas a score >8 strongly predicts the diagnosis (Table 1; Wong et al. 2003) .
Table 1
The LRINEC (laboratory risk indicator for necrotizing fasciitis) is a scoring system developed to predict the presence of necrotizing fasciitis
Parameter (units) | Value | Score |
|---|---|---|
C-reactive protein (mg/L) | <150 | 0 |
>150 | 4 | |
WBC count (per mmõ) | <15 | 0 |
15–25 | 1 | |
>25 | 2 | |
Hemoglobin (g/dL) | >13.5 | 0 |
11–13.5 | 1 | |
<11 | 2 | |
Serum sodium (mmol/L) | >135 | 0 |
<135 | 2 | |
Creatinine (mg/dl) | <1.6 | 0 |
>1.6 | 2 | |
Glucose (mg/dL) | <180 | 0 |
>180 | 1 |
Imaging
Despite advances in imaging over previous decades, the diagnosis of necrotizing fasciitis is a decidedly clinical diagnosis. While the presence of subcutaneous gas on plain radiographs or computed tomography (CT) strongly suggests a necrotizing infection, this finding is present in less than 20 % of patients with the diagnosis. Multiple abscesses and thickened edematous fascia can be seen on imaging as well.
Magnetic resonance imaging (MRI) is the most sensitive imaging modality for the diagnosis of necrotizing fasciitis. Thickened fascia and the presence of gas in the soft tissues are identified readily on the various MR imaging formats. Despite the potential utility of imaging studies to more conclusively confirm the diagnosis of necrotizing fasciitis, it is imperative that time not be wasted in definitively treating these patients. The benefits of the imaging studies must be weighed against the considerable expense of time when treating a critically ill patient.
Treatment of Necrotizing Fasciitis
Multiple authors share the same conclusion that the single most important factor influencing mortality among necrotizing fasciitis patients is time from admission or diagnosis to first surgical debridement. Based upon several studies, the initial 24-h period is the optimal window of time during which initial surgical management should occur. Delayed initial debridement, increased body surface area involved, immune deficiency, and comorbid medical conditions (renal, pulmonary, cardiac, and vascular disease) are all predictors of the increasing rates of mortality.
Medical Therapy
Management of patients with suspected necrotizing fasciitis includes close monitoring of hemodynamic status, continued volume resuscitation, and broad-spectrum IV antibiotic therapy. Particularly in areas with high MRSA prevalence, vancomycin is the first choice agent to treat Gram (+) infections. Group A beta-hemolytic streptococcus infections are often managed with IV penicillin with or without concomitant clindamycin. High-dose penicillin is indicated in cases of limb trauma occurring in farm or barnyard environments, due to the risk of clostridial infection. Despite their effectiveness against Gram-negative pathogens, the use of fluoroquinolones is contraindicated in children.
Specific antibiotic protocols are often determined based upon drug-resistance patterns and regionally varied strains of bacteria and are beyond the scope of this chapter. It is suggested that colleagues with particular expertise in this area, such as infectious disease specialists, are involved in the care of these patients.
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