Necrotizing Soft Tissue Infections

Necrotizing Soft Tissue Infections is a topic covered in the 5-Minute Emergency Consult.

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Basics

Description

  • Necrotizing soft tissue infections (NSTI) are infections of any layer of the skin associated with necrotizing changes
    • Usually spreads rapidly along tissue planes
  • Characterized by:
    • Widespread fascial and muscle necrosis with relative sparing of the skin
    • High mortality
    • Systemic toxicity
  • Crepitant anaerobic cellulitis:
    • Necrotic soft tissue infection with abundant connective tissue gas
  • Progressive bacterial gangrene:
    • Slowly progressive erosion affecting the total thickness of skin but not involving deep fascia
  • Nonclostridial myonecrosis (synergistic necrotizing cellulitis):
    • Aggressive soft tissue infection of skin, muscle, SC tissue, and fascia
  • Fournier gangrene:
    • Mixed aerobic–anaerobic soft tissue necrotizing fasciitis of the skin of the scrotum and penis in men and the vulvar and perianal skin in women
  • Necrotizing fasciitis:
    • Progressive, rapidly spreading infection with extensive dissection and necrosis of the superficial and deep fascia
  • Accounts for 500–1,500 cases per year in US
  • Often difficult to recognize
  • Incidence increases with:
    • Age
    • Smoking
    • Chronic systemic disease:
      • Diabetes
      • Obesity
      • Peripheral vascular disease
      • Alcohol abuse
      • IV drug use
  • 24–34% mortality
  • Also high morbidity:
    • Amputations
    • Renal failure

Etiology

  • Conditions that lead to the development of NSTIs:
    • Local tissue trauma with bacterial invasion
    • Local ischemia and reduced host defenses:
      • More frequently in diabetics, alcoholics, immunosuppressed patients, IV drug users, and patients with peripheral vascular disease
  • Type I NSTI:
    • Polymicrobial
    • Anaerobic and aerobic
    • Include Fournier gangrene and Ludwig angina
    • After surgical procedures
    • Existing diabetes, peripheral vascular disease, chronic kidney disease, alcohol abuse
      • Compromised immune system
    • Represent 80% of NSTIs
    • Strep species are most common aerobes
      • Also staph, enterococci, and gram-negative rods
    • Bacteroides are most common anaerobes
  • Type II NSTI:
    • Monomicrobial
    • Typically aerobic Streptococcus
    • Often young, healthy patients
    • Most common cause of “flesh eating” disease
    • Methicillin-resistant Staphylococcus aureus (MRSA) species are becoming more common
  • Type III NSTI
    • Least common NSTI (<5%)
    • Rapidly progressive
    • Clostridial myonecrosis is an example
    • Usually following penetrating wounds or crush injuries
    • Also can be seen after black tar heroin injection, skin popping, intestinal surgery, obstetrical complications
  • Bacteria involved include:
    • Group A β2-hemolytic streptococcus (GABHS)
    • Group B streptococcus
    • Staphylococci
    • Enterococci
    • Bacillus
    • Pseudomonas
    • Escherichia coli
    • Proteus
    • Klebsiella
    • Enterobacter
    • Bacteroides
    • Pasteurella multocida
    • Clostridium sp.
    • Vibrio sp.
    • Aeromonas sp.
    • Fungi

Pediatric Considerations
  • Neonates: Omphalitis and circumcision are predisposing factors.
  • Risk factors for children:
    • Chronic illness
    • Surgery
    • Recent varicella infection (58-fold increased risk of GABHS NSTI)
    • Congenital and acquired immunodeficiencies

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Citation

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TY - ELEC T1 - Necrotizing Soft Tissue Infections ID - 307316 Y1 - 2016 PB - 5-Minute Emergency Consult UR - https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307316/all/Necrotizing_Soft_Tissue_Infections ER -