Gas gangrene

Section: Skin and soft tissue Sub-section: Skin infections and breakdown Curriculum: Curriculum, page 53

Definition

• Clostridial mуοոесrоѕis (gas gaոgrеne) is a life-threatening muscle infection that develops either contiguously from an area of trauma or hematogenously from the gastrointestinal tract with muscle seeding
  • Rapidly progressive and limb/life threatening
  • Deepest necrotizing soft tissue infection
  • Hallmarks are severe myonecrosis with gas production and sepsis

Types

• Two major presentations
  • Taumatic gas gaոgrеոе is most commonly caused by Clostridium perfringens
  • Spontaneous gaոgrеոе is most commonly caused by Clostridium septicum.

Incidence

• 1,000 cases per year in US

Pathology

• Caused by
  • Spore-forming Clostridial species
  • 7 species, C. perfringens 80-95%
    • Gram +ve, spore forming anaerobic bacilli
  • Found in soil, GI and female GU
• Produce over ten exotoxins
  • Exotoxin - Alpha toxin
    • Direct cardiodepressant
    • Secondarily effects tissue breakdown
• Mechanisms of infection:
  • Direct inoculation (open wound)
  • Haematogenous spread

Clinical Presentation

• Incubation < 3 days
• Pain out of proportion to physical findings
• “Heaviness” of affected part
• Oedema and crepitus (later findings)
• Bronze/brownish
  • With malodorous serosanginous d/c, bullae may be present
• Low grade fever, tachycardia
• Confusion, irritability, or sensorium changes
• Ulcer – Meleney’s – Burrowing Ulcer

Investigations

• Labs:
  • Metabolic acidosis, leucocytosis, anaemia, thrombocytopenia, coagulopathy
  • Myoglobinuria
  • Liver/kidney dysfunction
• Gram Stain:
  • Pleomorphic gram-positive bacilli with or without spores
• Radiologic studies may demonstrate gas

Management

• Resuscitation: crystalloid, plasma, packed cells
• Antibiotics:
  • Penicillin G (24 m units IV divided) + Clindamycin (900 mg IV q8h)
  • Ceftriaxone and erythromycin alternatives
• Mixed infections require aminoglycosides, PCNase resistant PCN’s or vancomycin
• Tetanus as indicated
• Surgery: Debridement is mainstay
• Hyperbaric oxygen: After debridement

Non-Clostridial Myonecrosis

• Mixed - aerobic & anaerobic
• Presentation, evaluation & treatment similar to Clostridial sp
  • Pain not as pronounced, delay in presentation
• Broad-spectrum coverage: Meropenem or Imipenem
  • Vancomycin, clindamycin in PCN allergic
• Early debridement & HBO