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Introduction
  • Necrotizing fasciitis is a life threatening infection that spreads along soft tissue planes
  • Risk factors
    • immune suppression
      • diabetes
      • AIDS
      • cancer
    • bacterial introduction
      • IV drug use
      • hypodermic therapeutic injections
      • insect bites
      • skin abrasions
      • abdominal and perineal surgery
    • other host factors
      • obesity
  • Associated conditions
    • cellulitis
      • overlying cellulitis may or may not be present
  • Prognosis
    • life threatening infection
      • mortality rate of 32%
      • mortality correlates with time to surgical intervention
Classification
 
 Necrotizing Fasciitis Classification
Type Organism Characteristics
Type 1 q Polymicrobial
Typical 4-5 aerobic and anaerobic species cultured:
• non-Group A Strep
• anaerobes including Clostridia
• facultative anaerobes
• enterobacteria
• Synergistic virulence between organisms
 • Most common (80-90%)
 • Seen in immunosuppressed (diabetics and cancer patients)
 • Postop abdominal and perineal infections
Type 2  Monomicrobial
• Group A β-hemolytic Streptococci is most common organism isolated
 • 5% of cases
 • Seen in healthy patients
 • Extremities
Type 3 Marine Vibrio vulnificus
(gram negative rods)
 • Marine exposure
Type 4 MRSA  
 
Presentation
  • Symptoms
    • early
      • localized abscess or cellulitis with rapid progression
      • minimal swelling
      • no trauma or discoloration
    • late findings
      • severe pain
      • high fever, chills and rigors
      • tachycardia
  • Physical exam      
    • skin bullae
    • discoloration 
      • ischemic patches
      • cutaneous gangrene
    • swelling, edema
    • dermal induration and erythema
    • subcutaneous emphysema (gas producing organisms)
Imaging
  • Radiographs
    • not required for diagnosis or treatment
Differentials
  • Gas gangrene 
Studies
  • Biopsy 
    • indications
      • emergent frozen section can confirm diagnosis in early cases 
    • technique
      • take 1x1x1cm tissue sample
      • can be performed at bedside or in operating room
      • surgical intervention should not be delayed to obtain
    • histological findings
      • necrosis of fascial layer
      • microorganisms within fascial layer
      • PMN infiltration
      • fibrinous thrombi in arteries and veins and necrosis of arterial and venous walls
  • LRINEC Scoring system
    • score > 6 has PPV of 92% of having necrotizing fasciitis
      • CRP (mg/L) 
        • ≥150: 4 points
      • WBC count (×103/mm3)
        • <15: 0 points
        • 15–25: 1 point
        • >25: 2 points
      • Hemoglobin (g/dL)
        • >13.5: 0 points
        • 11–13.5: 1 point
        • <11: 2 points
      • Sodium (mmol/L)
        • <135: 2 points
      • Creatinine (umol/L)
        • >141: 2 points
      • Glucose (mmol/L)
        • >10: 1 point
Treatment
  • Operative
    • emergency radical debridement with broad-spectrum IV antibiotics post q 
      • indications
        • whenever suspicion for necrotizing fasciitis
      • operative findings
        • liquefied subcutaneous fat
        • dishwater pus
        • muscle necrosis
        • venous thrombosis
      • technique
        • hemodynamic monitoring with systemic resuscitation is critical
        • hyperbaric oxygen chamber if anaerobic organism identified
      • antibiotics
        • initial antibiotics
          • start empirically with penicillin, clindamycin, metronidazole, and an aminoglycoside
        • definitive antibiotics
          • penicillin G
            • for strep or clostridium
          • imipenem or doripenem or meropenem
            • for polymicrobial
          • add vancomycin or daptomycin
            • if MRSA suspected
    • amputation
      • indications
        • low threshold for amputation when life threatening
 

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