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Introduction
  • Definition
    • also called clostridial myonecrosis
  • Epidemiology
    • demographics
      • male:female ratio
        • no sexual predilection
    • location
      • buttocks, thigh, perineum
    • risk factors
      • posttraumatic (associated with C perfringens)
        • car accidents (most common)
        • crush injuries
        • gunshot wounds with foreign bodies
        • burns and frostbite
        • IV drug abuse
      • postoperative
        • bowel resection or perforation
        • biliary surgery
        • premature wound closure
      • spontaneous
        • colon cancer (associated with C. septicum)
        • neutropenia
  • Pathophysiology
    • Clostridial species 
      • Clostridium perfringens (most common), Clostridium novyi, Clostridium septicum 
      • found in soil and gut flora
      • gram-positive obligate anaerobic spore-forming rods that produce exotoxins (e.g. C. perfringens alpha toxin)  
        • causes muscle necrosis and vessel thrombosis 
        • can cause hemolysis and shock
      • incubation period <24h
      • gas produced by fermentation of glucose
        • main component is nitrogen 
    • other bacteria include E. coli, Pseudomonas aeruginosa, Proteus species, Klebsiella pneumoniae
  • Prognosis
    • overall 25% mortality 
    • 50% mortality if bacteremic
    • 100% mortality if treatment is delayed
    • poorer prognosis for older patients with comorbidities
Presentation
  • History
    • recent surgery to GI or biliary tract
  • Symptoms
    • triad 
      • sudden progressive pain out of proportion to injury
        • from thrombotic occlusion of large vessels
      • tachycardia not explained by fever
      • feeling of impending doom
  • Physical exam
    • sweet smelling odor
    • swelling, edema, discoloration and ecchymosis
    • blebs and hemorrhagic bullae
    • "dishwater pus" discharge
    • crepitus
    • altered mental status
Imaging
  • Radiographs
    • findings
      • linear streaks of gas in soft tissues  
Studies
  • Labs
    • Elevated LDH
    • Elevated WBC
    • Metabolic acidosis and renal failure
  • Histology
    • Gram stain reveals Gram-positive bacilli  
    • absence of neutrophils  
      • lack of acute inflammatory response is hallmark of gas gangrene
  • Culture
    • blood culture rarely grows Clostridial species
Differentials
  • Necrotizing fasciitis  
Treatment
  • Nonoperative
    • high dose IV antibiotics
      • 1st line is penicillin G and clindamycin 
      • alternative treatment is erythromycin, tetracycline or ceftriaxone
        • clindamycin and tetracycline inhibit toxin synthesis
    • hyperbaric O2
      • indications
        • useful adjunct
      • outcomes
        • effectiveness of HBO2 is inconclusive
  • Operative
    • radical surgical debridement with fasciotomies
      • indications
        • 1st line treatment is surgical
Complications
  • Shock
  • Renal failure
    • both mediated by TNF alpha, IL-1, IL-6
 

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