Necrotizing Soft Tissue Infection

Description: Family Practice Notebook Necrotizing Soft Tissue Infection Necrotizing Fasciitis Fournier's Gangrene Definitions Necrotizing Fasciitis Deep subcutaneous infection Fournier's Gangrene Massive infection and swelling of scrotum and penis Extends into perineum or abdominal wall, and legs Pathophysiology Infection spreads between fascia and SQ tissue Fibrous bands prevent infectious spread Present in head and distal extremities Lacking in trunk and proximal extremities Risk factors Age over 50 years Malnutrition Hypoalbuminemia Alcoholism Immunocompromised state Cancer Corticosteroid use Poor vascular supply Peripheral Vascular Disease Diabetes Mellitus Skin trauma Burn Injury Trauma Intravenous Drug Abuse Recent surgery Miscellaneous risk factors Obesity Break in Gastrointestinal or Genitourinary mucosa Colon Cancer Diverticula Hemorrhoids or Anal Fissure Urethral tear Symptoms and Signs progression (in order of occurrence) Pain and Unexplained fever Swelling Brawny edema and tenderness Dark red induration Bullae filled with blue or purple fluid Skin friable, bluish, maroon, or black Extensive thrombosis of dermal blood vessels Extension to deep fascia leads to brown-gray appearance Rapid spread along fascial planes, veins and lymph Toxicity, shock, and multi-organ failure Signs: Distribution Extremities (53%) Perineum or buttocks (20%) Trunk (18%) Head and neck (9%) References Bosshardt (1996) Arch Surg 131:846-52 Etiologies Group A Streptococcus (Streptococcus Pyogenes) Begins deep at non-penetrating minor trauma Contusion seeded by transient bacteremia Gas production only if mixed infection Severe toxicity, renal Impairment may precede shock Myositis in 20-40% cases Creatine Phosphokinase (CPK) is markedly elevated Mortality: 20-50% despite Penicillin Mixed aerobic and Anaerobic Bacteria Break in Gastrointestinal or Genitourinary mucosa Fournier's Gangrene Comorbid conditions associated with mixed infection Diabetes Mellitus Peripheral Vascular Disease Staphylococcus aureus Clostridium perfringens Hyperbaric Oxygen treatment may help in Gas Gangrene Diagnosis: Findings Suggestive of Necrotizing Fasciitis Fever (Temperature over 100.4 F) Soft tissue erythema, edema and severe pain Vessicles, Bullae or Necrosis Crepitation is only variably present Labs Complete Blood Count White Blood Cell count over 16,300 per mm3 Hemoglobin less than 10 mg/dl Platelet Count <150,000 per mm3 Serum Electrolytes Serum Sodium under 135 meq/L Serum Calcium under 8.4 mg/dl Coagulation Studies Prothrombin Time (PT) prolonged Partial Thromboplastin Time (aPTT) prolonged Arterial Blood Gas Arterial pH <7.35 Differential Diagnosis See Skin Infection (Pyoderma) Cellulitis Erysipelas Necrotizing Insect Bite (e.g. Brown Recluse Spider) Management: Surgical exploration to fascia and muscle Early exploration within 12 hours is critical Observe for Necrotizing fasciitis Myositis Gangrene Technique Visualize deep structures Remove necrotic materials Reduce compartment pressure Send material for Gram Stain and Culture Management: Empiric Combination Regimen (3 drug therapy) Anaerobe coverage Clindamycin 600-800mg IV q8h or Flagyl 750mg q6h Gram Positive coverage Ampicillin or Penicillin Gram Negative coverage Gentamicin 1.0-1.5 mg/kg q8h (after 2mg/kg load) Single agent regimen Ceftriaxone 2 g IV every 12 hours Ampicillin-Sulbactam (Unasyn) 2-3g IV q6h Ticarcillin-Clavulanate (Timentin) Piperacillin-Tazobactam (Zosyn) Combination for Penicillin allergic patient Vancomycin and Gentamicin or Aztreonam Alernative combination protocol Ceftazidime (Fortaz) and Clindamycin or Metronidazole Other measures Maximize nutritional status References Elliott (2000) Am J Surg 179:361-6 Headley (2003) Am Fam Physician 68(2):323-8 Wall (2000) J Am Coll Surg 191:227-31