questions 5

Necrotizing Fasciitis

Topic updated on 10/17/17 8:35pm

Snapshot
  • A 45-year-old woman presents to the emergency department for severe pain of her left foot. She states that this has never happened before. Her symptom is accompanied by fever and generalized myalgias. Medical history is significant for type II diabetes mellitus. On physical exam, there is exquisite tenderness to palpation, erythema, palpable crepitus, and tense bullae. Surgery is immediately consulted.
Introduction
  • Clinical definition
    • infection of the superficial fascia that is life-threatening
  • Epidemiology
    • risk factors
      • diabetes mellitus
      • chronic corticosteroid use
      • alcohol abuse
      • injection drug use
  • Etiology
    • polymicrobial infection
      • most common (70-80%)
      • contains aerobic and anaerobic organisms
        • aerobes
          • Streptococcus spp. (most common)
        • anaerobes
          • Bacteroides spp.
          • Peptostreptococcus spp. 
    • monomicrobial infection
      • most commonly caused by group A Streptococcus
  • Pathogenesis
    • inciting infection at tissue site can be accomplished via
      • hematogenous spread
      • direct inoculation
    • the infection rapidly spreads leading to
      • vascular occlusion → ischemia and necrosis
      • crepitus in cases of gas forming organisms (e.g., Clostridium) and anaerobic organisms
  • Prognosis
    • increased mortality and risk of amputation
Presentation
  • Symptoms
    • severe pain
      • out of proportion of superficial findings of the affected area
    • fever
  • Physical exam
    • tenderness to palpation
    • palpable crepitus
      • secondary to methane and CO2 production
    • erythema
    • bullae, blisters, or ulcers
    • cutaneous necrosis
    • progression of disease despite antibiotic treatment
Imaging
  • Magnetic resonance imaging (MRI)
    • indication
      • can be helpful to determine the extent of the infection
        • however, it must not delay antibiotics and surgical debridement
Studies
  • Labs
    • ↑↑ C-reactive protein
    • ↑ creatine kinase
    • ↑ white blood cell count (BUN) and blood urea nitrogen (BUN)
  • Intraoperative studies
    • Gram stain and culture
    • biopsy
  • Diagnostic criteria
    • based on clinical suspicion and confirmed intraoperatively with surgical debridement
      • labs or imaging do not override clinical judgement
Differential 
  • Cellulitis
  • Staphylococcus scalded skin syndrome
  • Gas gangrene
Treatment
  • Management approach
    • prompt surgical debridement is the mainstay of treatment along with antibiotic treatment
  • Medical
    • intravenous empiric antibiotics
      • indication
        • a treatment component of necrotizing fasciitis directed against likely organisms
          • e.g., antibiotics that target group A Streptococcus, gram-negative organisms, anaerobes, and methicillin-resistant Staphylococcus aureus (MRSA)
      • drugs
        • meropenem or piperacillin-tazobactam and vancomycin or linezolid
          • meropenem or piperacillin-tazobactam covers
            • group A Streptococcus
            • gram-negative organisms
            • anaerobes
          • vancomycin or linezolid covers
            • MRSA
        • penicillin and clindamycin
          • treatment of choice for known group A Streptococcus necrotizing fasciitis
  • Operative
    • surgical debridement
      • indication
        • a necessary component of treatment that also confirms the diagnosis
Complications
  • Streptococcal toxic shock syndrome
  • Compartment syndrome
  • Myositis
  • Muscle necrosis


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Qbank (1 Questions)

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(M2.DM.5) A 27-year-old man comes to the emergency department complaining of extreme pain in his left calf. He is a surfer and cut his leg on a reef over the weekend. He says he cleaned the wound himself and bandaged it, but has been having worsening pain. On exam, T is 101.8 F, HR is 108 bpm, RR 18 rpm, and BP 115/75 mmHg. The man's leg is exquisitely tender and shown in Image A. You note crepitus on palpation. Which of the following is most appropriate next step? Topic Review Topic
FIGURES: A          

1. Watchful waiting
2. Wound culture for directed antibiotic treatment
3. Empiric antibiotic coverage
4. Empiric antibiotic coverage and surgical debridement
5. Amputation

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