Gas gangrene

Gas gangrene (also known as clostridial myonecrosis) is a life-threatening necrotizing soft tissue infection commonly caused by the rapid proliferation and spread of Clostridium perfringens from a contaminated wound. The clinical picture includes excruciating muscle pain, edema with subsequent skin discoloration (red-purple to black) and gas production. Crepitus, as well as a feathering pattern of gas in soft tissue imaging, are generally present. Without treatment, gas gangrene is fatal in almost 100% of cases. Surgical debridement in combination with antibiotic therapy reduces this figure by half.

• Pathogen
  • Clostridium perfringens (> 80% of cases): a gram-positive, obligate anaerobic, spore-forming bacterium
  • Less common: C. septicum, C. histolyticum
• Path of infection: wounds with compromised blood supply create an optimal anaerobic environment for the proliferation of C. perfringens → necrosis that progresses within 24–36 hours
  • Septic surgical wounds or procedures (e.g., bowel and biliary tract surgery, septic abortion) ^[1]
  • Deep, penetrating wounds (e.g., knife, gunshot)
  • Open fractures

Ubiquitous C. perfringens spores contaminate a wound → bacterial reproduction under anaerobic conditions → ↑ secretion of exotoxins, especially C. perfringens alpha-toxin (a phospholipase lecithinase) → degradation of phospholipids → tissue destruction (myonecrosis), inhibition of leukocyte function, and gas production → gas separation into healthy tissue → further colonization and more local tissue destruction → further exacerbation of anaerobic conditions by the development of edema

• Incubation period: hours to days
• Local signs and symptoms
  • Excruciating muscle pain
  • Massive edema with skin discoloration that progresses from bronze to red-purple to black and overlying bullae
  • Sweet and foul-smelling or nonodorous discharge produced by anaerobic metabolic products
  • Crepitus; : Palpation reveals crackling of the skin due to gas production (skin emphysema)
  • Spreading infection (see “Classic signs of inflammation”)
• Systemic toxicity ^[1]
  • Can progress to systemic infection within a few hours
  • Early signs
    • Fever
    • Tachycardia
    • Altered mental status
  • Late signs
    • Shock
    • Multi-organ failure
    • Hemolytic anemia
    • ARDS
    • Kidney and liver failure

Gas gangrene is a medical emergency that can rapidly progress to multiorgan failure.

Perfringens perforates: C. perfringens causes gas gangrene that leads to severe tissue damage.

Spontaneous gas gangrene

• Pathogen: most commonly caused by C. septicum
• Etiology: : typically a complication of an underlying disease, e.g., malignancy (e.g., colon carcinoma), diabetes, or immunosuppression
• Pathophysiology: : Bacteria from the gastrointestinal tract spread hematogenously (due to, e.g., a gastrointestinal lesion or adenocarcinoma of the colon) and reach the muscle tissue.
• Clinical features, diagnosis, and treatment: same as gas gangrene caused by C. perfringens (see sections below)

• Imaging: Radiography, CT, or MRI typically show a characteristic feathering pattern of the soft tissue.
• Laboratory tests
  • Gram staining: large, gram-positive rods
  • Wound culture: double zone of hemolysis on blood agar
  • Blood cultures
  • PCR or ELISA for detection of toxin in wound material (not widely available)
• Surgical exploration
  • Affected muscle does not bleed or contract, and may be pale or discolored red-purple to black.
  • Histopathological findings of biopsy ^[1]
    • Myonecrosis and destruction of surrounding degenerative tissue (muscle, skin fat, subcutaneous tissue)
    • Presence of pathogens; without inflammatory infiltrate

• Necrotizing fasciitis
• Vibrio vulnificus infection; : may occur after an open wound is exposed to seawater contaminated with V. vulnificus
• Group A streptococcal infection
• Rhabdomyolysis ^[1][2]
• Pyomyositis

The differential diagnoses listed here are not exhaustive.

The most important steps of management are immediate surgical debridement and antibiotic therapy. Patients should receive supportive therapy and intensive care.

• Surgical exploration and debridement: If applicable, amputation of the affected extremity may be necessary.
• Antibiotic therapy: penicillin plus clindamycin or tetracycline
• Assessment of compartment pressure if compartment syndrome is suspected
• Hyperbaric oxygenation use is controversial.
• Tetanus toxoid if indicated

References:^[1]

• Mortality rate ^[3]
  • Untreated: ∼ 100%
  • With appropriate treatment: 20–30%