Necrotizing Fasciitis

Definition

• Infection and necrosis of superficial fascia, subcutaneous fat. and deep fascia (necrosis of arteries and nerves in subcutaneous fat gangrene)

• Fournier s gangrene: necrotizing fasciitis of the male genitalia (used by some to describe involvement of male or female perineum)

Epidemiology

• T risk in diabetes. PVD, alcohol abuse. IVDA. immunosuppression, cirrhosis

• Can also affect healthy individuals

Microbiology

• Group I (often after abd/perineal surgery): polymicrobial (anaerobe * facultative anaerobe

• GNR); often with DM. PVD and other comorbidities.

• Group II (extremities): Strep pyogenes • Staph: often healthy w/o obvious portal of entry, up to half have toxic shock syndrome (TSS)

• Group III: marine Vibrio infection

Clinical manifestations

• Most common sites: extremities, abdominal wall, and perineum, but can occur anywhere

• Cellulitic skin as with poorly defined margins rapid spread systemic toxicity

• Pain out of proportion to degree of apparent cellulitis; skin hypcresthetic and later anesthetic

• Bullae formation (serous — hemorrhagic); darkening of skin to bluish-gray -» I cutaneous gangrene crepitus or radiographically visible gas

Diagnostic signs

• Need high degree of clinical suspicion because of nonspecific physical exam

• Aspiration of necrotic center; blood cultures; Gram stain; ✓ CK for tissue necrosis

• Imaging studies: plain radiographs — soft tissue gas; CT — extent of infection, soft tissue gas; MRI best tissue contrast

• Clinical diagnosis enough to initiate urgent surgical exploration | Treatment

• Definitive treatment is surgical debridement of necrotic tissue and fasciotomy

• Type I: breadth of GNR coverage determined by host, prev hosp. prev Rx and initial

Gram stain; eg. carbapenem or [3rd gen ceph + amp • (clinda or metronidazole)]

• Type II: PCN • clindamycin. If community-acquired MRSA a consideration. + vanco.

If TSS. add high dose IVIG.

• Hyperbaric oxygen: useful adjunct, but should not delay definitive surgical treatment

Prognosis

• Generally fatal if untreated; reported mortality 20-50%

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