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Updated: Sep 6 2024

Necrotizing Fasciitis

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  • summary
    • Necrotizing Fasciitis is a life-threatening bacterial soft tissue infection that spreads along soft tissue planes rapidly.
    • Diagnosis is made clinically with the presence of skin discoloration, bullae, palpable crepitus and calculation of the LRINEC score. Emergent frozen section can help confirm diagnosis in early cases.
    • Treatment is emergent radical debridement of all devitalized tissues with broad-spectrum IV antibiotics.
  • Epidemiology
    • Risk factors
      • immune suppression
        • diabetes
        • AIDS
        • cancer
        • obesity
      • bacterial introduction
        • IV drug use
        • hypodermic therapeutic injections
        • insect bites
        • skin abrasions
        • abdominal and perineal surgery
  • Etiology
    • Associated conditions
      • cellulitis
        • overlying cellulitis may or may not be present
  • Classification
      • Necrotizing Fasciitis Classification
      • Type
      • Organism
      • Characteristics
      • Polymicrobial
      • Typically 4-5 aerobic and anaerobics pecies 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
      • 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
      • Fungal
  • 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
  • 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
  • Differentials
    • Gas gangrene
  • Treatment
    • Operative
      • emergent radical debridement and broad-spectrum IV antibiotics
        • indications
          • whenever suspicion for necrotizing fasciitis
        • antibiotics
          • initial antibiotics
            • start empirically with penicillin, clindamycin, metronidazole, and an aminoglycoside
              • clindamycin has been shown to reduce odds of limb amputation
          • definitive antibiotics
            • penicillin G
              • for strep or clostridium
            • imipenem or doripenem or meropenem
              • for polymicrobial
            • add vancomycin or daptomycin
              • if MRSA suspected
        • technique
          • hemodynamic monitoring with systemic resuscitation is critical
          • hyperbaric oxygen chamber if anaerobic organism identified
          • operative findings
            • liquefied subcutaneous fat
            • dishwater pus
            • muscle necrosis
            • venous thrombosis
      • amputation
        • indications
          • low threshold for amputation when life threatening
  • Prognosis
    • Life threatening infection
      • mortality rate of 32%
        • vasopressor requirements outside of operative anesthesia shown to be the strongest predictor for mortality
      • mortality correlates with time to surgical intervention
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