Necrotizing Soft Tissue Infection

Aka: Necrotizing Soft Tissue Infection, Necrotizing Fasciitis, Fournier's Gangrene

1. Definitions
   1. Necrotizing Fasciitis
      1. Rapidly prgressive, deep subcutaneous infection
   2. Fournier's Gangrene
      1. Massive infection and swelling of Scrotum and penis
      2. Extends into perineum or abdominal wall, and legs
2. Pathophysiology
   1. Infection spreads between fascia and SQ tissue
   2. Fibrous bands prevent infectious spread
      1. Present in head and distal extremities
      2. Lacking in trunk and proximal extremities
3. Risk factors
   1. Age over 50 years
   2. Malnutrition
      1. Hypoalbuminemia
      2. Alcoholism
   3. Immunocompromised state
      1. Cancer
      2. Corticosteroid use
   4. Poor vascular supply
      1. Peripheral Vascular Disease
      2. Diabetes Mellitus
   5. Skin Trauma
      1. Burn Injury
      2. Trauma
      3. Intravenous Drug Abuse
      4. Recent surgery
      5. Alcohol Abuse
   6. Miscellaneous risk factors
      1. Obesity
   7. Break in Gastrointestinal or Genitourinary mucosa
      1. Colon Cancer
      2. Diverticula
      3. Hemorrhoids or Anal Fissure
      4. Urethral tear
4. Symptoms and Signs progression (in order of occurrence)
   1. Pain
   2. Unexplained fever
   3. Swelling
   4. Brawny edema and tenderness
   5. Dark red induration
   6. Bullae filled with blue or purple fluid
   7. Skin friable, bluish, maroon, or black
   8. Extensive thrombosis of dermal blood vessels
   9. Extension to deep fascia leads to brown-gray appearance
   10. Rapid spread along fascial planes, veins and lymph
   11. Toxicity, shock, and multi-organ failure
5. Signs: Distribution
   1. Extremities (53%)
   2. Perineum or buttocks (20%)
   3. Trunk (18%)
   4. Head and neck (9%)
   5. References
      1. Bosshardt (1996) Arch Surg 131:846-52
6. Etiologies
   1. Polymicrobial - Mixed aerobic and Anaerobic Bacteria
      1. Break in Gastrointestinal or Genitourinary mucosa
      2. Fournier's Gangrene
      3. Comorbid conditions associated with mixed infection
         1. Diabetes Mellitus
         2. Peripheral Vascular Disease
   2. Group A Streptococcus (Streptococcus Pyogenes)
      1. Begins deep at non-penetrating minor trauma
      2. Contusion seeded by transient bacteremia
      3. Gas production only if mixed infection
      4. Severe toxicity, renal Impairment may precede shock
      5. Myositis in 20-40% cases
         1. Creatine Phosphokinase (CPK) is markedly elevated
      6. Mortality: 20-50% despite Penicillin
   3. Other bacterial causes
      1. Staphylococcus aureus
      2. Clostridium perfringens
         1. Hyperbaric Oxygen treatment may help in Gas Gangrene
7. Diagnosis: Findings Suggestive of Necrotizing Fasciitis
   1. Fever (Temperature over 100.4 F)
   2. Soft tissue erythema, edema and severe pain
   3. Vessicles or Bullae
      1. Bullae become violaceous after 4-5 days
      2. Skin then becomes necrosis
   4. Crepitation is only variably present
8. Diagnosis: Definitive
   1. Deep tissie biposy with culture and Gram Stain
9. Labs
   1. Complete Blood Count
      1. White Blood Cell count over 14,000 per mm3
      2. Hemoglobin less than 10 mg/dl
      3. Platelet Count <150,000 per mm3
   2. Serum Electrolytes
      1. Serum Sodium under 135 meq/L
      2. Blood Urea Nitrogen 15 mg/dl
      3. Serum Calcium under 8.4 mg/dl
   3. Coagulation Studies
      1. Prothrombin Time (PT) prolonged
      2. Partial Thromboplastin Time (aPTT) prolonged
   4. Arterial Blood Gas
      1. Arterial pH < 7.35
10. Differential Diagnosis
    1. See Skin Infection (Pyoderma)
    2. Cellulitis
    3. Erysipelas
    4. Toxic shock syndrome
    5. Necrotizing Insect Bite (e.g. Brown Recluse Spider)
11. Management: Surgical exploration to fascia and muscle
    1. Early exploration within 12 hours is critical
    2. Observe for
       1. Necrotizing Fasciitis
       2. Myositis
       3. Gangrene
    3. Technique
       1. Visualize deep structures
       2. Remove necrotic materials
       3. Reduce compartment pressure
       4. Send material for Gram Stain and Culture
12. Management: Empiric
    1. Combination Regimen (3 drug therapy)
       1. Anaerobe coverage
          1. Clindamycin 600-800mg IV q8h or
          2. Flagyl 750mg q6h
       2. Gram Positive coverage
          1. Ampicillin or
          2. Penicillin
       3. Gram Negative coverage
          1. Gentamicin 1.0-1.5 mg/kg q8h (after 2mg/kg load)
    2. Single agent regimen
       1. Ceftriaxone 2 g IV every 12 hours
       2. Ampicillin-Sulbactam (Unasyn) 2-3g IV q6h
       3. Ticarcillin-Clavulanate (Timentin)
       4. Piperacillin-Tazobactam (Zosyn)
    3. Combination for Penicillin allergic patient
       1. Vancomycin and
       2. Gentamicin or Aztreonam
    4. Alernative combination protocol
       1. Ceftazidime (Fortaz) and
       2. Clindamycin or Metronidazole
    5. Other measures
       1. Maximize nutritional status
13. Prognosis
    1. Mortality: 25% (up to 70% in those who develop Sepsis)
14. References
    1. Elliott (2000) Am J Surg 179:361-6
    2. Headley (2003) Am Fam Physician 68(2):323-8
    3. Usatine (2010) Am Fam Physician 82(7): 773-80
    4. Wall (2000) J Am Coll Surg 191:227-31