Necrotizing Fasciitis

Key Features

Essentials of Diagnosis

• A rapidly spreading infection involving the fascia of deep muscle

• Areas that are often affected

  • An extremity

  • Head and neck

  • Perinanal area or genital area ("Fournier gangrene")

• Skin or blunt trauma injury may precede the infection

• Patients who are more susceptible are

  • Immunosuppressed

  • Diabetic

  • At extremes of age (elderly or neonates)

  • Affected by liver disease

General Considerations

• Distinguishing necrotizing fasciitis from necrotizing myositis may be difficult as skeletal muscle and fascia are involved in both syndromes

• Necrotizing fasciitis

  • Most often monomicrobial

  • Usual causative agent is Streptococcus pyogenes (Group A beta-hemolytic streptococci)

  • Can also be caused by other streptococcal species, and occasionally by Staphylococcus aureus

  • Infections can be polymicrobial (mixed aerobic and anaerobic bacteria)

  • A history of exposure to brackish water or marine life should raise suspicion for Vibrio vulnificans or Aeromonas species

  • Patients with burn injuries are susceptible to Pseudomonas species

• Necrotizing myositis

  • Often caused by Clostridia species (clostridial myonecrosis or "gas gangrene")

Clinical Findings

• Presentation is similar to severe cellulitis

• Rapid progression

• Systemic toxicity

• Severe pain

• Pain often subsides as nerves are destroyed

• Multiorgan failure is common as infection progresses

Diagnosis

Laboratory Findings

• Elevated white blood cell count, erythrocyte sedimentation rate and C-reactive protein

• Elevated creatine kinase may indicate muscle involvement

• Blood, wound, and tissue cultures should be obtained

• Histologic specimens may demonstrate

  • Extensive tissue destruction

  • Thrombosis of blood vessels

  • Bacteria spreading along fascial planes

Imaging

• CT or MRI of the affected area may show gas in tissues or fascial plane infection

• Imaging may also appear normal, so rely on clinical suspicion and surgical evaluation

Treatment

Medications

• Antibiotic therapy should then be tailored to culture results

• Broad-spectrum antibiotic therapy

  • Should be initiated whenever the diagnosis is suspected

  • Should cover aerobic and anaerobic organisms

  • Initial therapy for patients with normal kidney function typically consists of

    • Intravenous therapy with a carbapenem (meropenem 2 g every 8 hours or imipenem 1 g every 6 hours) or piperacillin-tazobactam 4.5 g every 6 hours plus an agent with activity against methicillin-resistant S aureus (vancomycin, linezolid or daptomycin) plus clindamycin for its antitoxin and other effects against toxin-producing strains of streptococci and staphylococci

• Patients with exposure histories that suggest less common etiologies should have additional therapy targeted to those organisms

• Intravenous immunoglobulin for streptococcal necrotizing soft tissue infections

  • Dose: 1 g/kg on day 1, followed by 0.5 g/kg on days 2 and 3

  • Has been shown to reduce mortality when added to surgical and antibiotic therapy

Surgery

• Early and extensive debridement is essential for survival

• Surgical evaluation ...