Necrotizing Soft Tissue Infection (NSTI)

Necrotizing Soft Tissue Infection (NSTI)

David Ray Velez, MD

Table of Contents

Definitions
Classification and Microbiology
Risk Factors
Diagnosis
Treatment

Definitions

Necrotizing Soft Tissue Infection (NSTI): Necrotizing Infection of the Skin and Soft Tissue

Necrotizing Cellulitis: NSTI of the Skin (Sparing Fascia and Deep Muscle Compartments)

Necrotizing Fasciitis: NSTI of the Fascia

  • Spreads Along Fascia Deep to the Subcutaneous Tissue
  • Poor Blood Supply Along the Fascial Planes Allows More Rapid Spread of Bacteria Before Skin Changes are Seen

Necrotizing Myositis: (Non-Clostridial) NSTI Extending to the Deep Muscle Compartments

Clostridial Myonecrosis (Gas Gangrene): Clostridial NSTI Extending to the Deep Muscle Compartments

Fournier’s Gangrene: NSTI of the Perineum

Fulminant NSTI of the Arm 1

Fournier’s Gangrene 2

Classification and Microbiology

Classification

  • Clostridial Infection
  • Non-Clostridial Infection

Clostridial Infection

  • Clostridium perfringens – Most Common in Traumatic Gas Gangrene
  • Clostridium septicum – Most Common in Non-Traumatic Gas Gangrene
    • *Note: Often Associated with Underlying Malignancy
  • *Usually Associated with Myonecrosis

Non-Clostridial Infection

  • Type I: Polymicrobial – Most Common (75%)
  • Type II: Monomicrobial
    • Group A Streptococcus – Most Common Monomicrobial Organism
    • Staphylococcus aureus (MSSA and MRSA)
  • Type III: Marine Bacteria (Vibrio)
  • Type IV: Fungal (Candida)

Risk Factors

Risk Factors

  • Trauma
  • IV Drug Abuse
  • Surgery
  • Obesity
  • Alcoholism
  • Immunosuppression (Diabetes, Cirrhosis, HIV)
  • Mucosal Brach (Hemorrhoids, Rectal Fissure)
  • Malignancy
  • Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) – Debated Association

Diagnosis

Presentation

  • Severe Pain (Out-of-Proportion)
  • Cellulitis and Erythema (Without Sharp Margins)
    • Deeper Infections May Not Have Superficial Cellulitis
  • Edema
  • Bullae or Ecchymosis
  • Visible Skin Necrosis
  • Crepitus – From Anaerobic Production of Nitrogen and Hydrogen, Not Readily Absorbed by Tissue
  • Hypoesthesia (Decreased Sensation) – Late Finding from Small Blood Vessel Thrombosis and Superficial Nerve Destruction
  • Fever
  • Murky Gray (“Dishwater”) Fluid Drainage

Diagnosis

  • Diagnosis is Clinical and Only Confirmed by Surgical Exploration
  • Radiology Findings: Soft Tissue Gas, Fluid Collections, and Inflammatory Change
    • CT Scan is the Best Initial Imaging
  • Labs:
    • Elevated WBC and CRP
    • Decreased Sodium
    • Elevated Creatinine (AKI)
    • Hyperglycemia

Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) Score

  • Interpretation/Chance of NSTI:
    • Low Risk (0-5 Points): < 50%
    • Intermediate Risk (6-7 Points): 50-75%
    • High Risk (8-13 Points): > 75%
  • *Specific but Poor Sensitivity – Should Not Be Used to Rule Out
  • *Note: CRP ≥ 150 Has the Strongest Predictive Value (+4)

Soft Tissue Gas on CT 3

Soft Tissue Gas on XR

  CRP WBC Hgb Na Cr Glu
0 < 150 < 15 > 13.5 ≥ 135 ≤ 1.6 ≤ 180
+1 15-25 11-13.5 > 180
+2 > 25 < 11 < 135 > 1.6
+4 ≥ 150

Treatment

Primary Management: Emergent Aggressive Surgical Debridement and Broad-Spectrum Antibiotics

  • Rapidly Progresses with High Mortality (25%)

Surgical Debridement

  • Aggressive Surgical Debridement Emergently
  • Serial Wet-to-Dry Dressing Changes (May Consider Using Dakin’s Solution)
  • May Require Repeat Debridement Every 1-2 Days
  • Can Cause Significant Disfigurement and Disability
  • Extremities May Require Amputation

Empiric Antibiotics

  • Empiric Antibiotic Regimen: Piperacillin-Tazobactam or Carbapenem Plus Vancomycin and Clindamycin
  • Broad-Spectrum Coverage:
    • Piperacillin-Tazobactam (Zosyn)
    • Meropenem (Merrem)
    • Ertapenem (Invanz)
    • Imipenem
  • MRSA Coverage:
    • Vancomycin – Most Common
    • Daptomycin – Not for Pneumonia (Inactivated by Lung Surfactant)
    • Linezolid – Not for Bacteremia or Endocarditis
  • Clindamycin
    • Use to Inhibit Ribosomal Exotoxin Synthesis
    • Reduces the Production of Panton-Valentine Leucocidin (PVL) in Staphylococcus aureus
  • *Deescalate Based on Intraoperative Cultures

Adjunct Therapies

  • Hyperbaric Oxygen Therapy (HBOT)
    • May Have Reduced Morbidity and Mortality but Controversial and Data is Not Clear
    • Not Readily Availability at Most Institutions
  • Intravenous Immunoglobulin (IVIG)
    • May Consider IVIG for Group A Streptococcus (S. pyogenes) to Bind Exotoxin if Not Responding to Other Measures – Based Largely on Management of Toxic Shock Syndrome
  • Plasmapheresis
  • Diverting Colostomy
    • Consider for Severe Perineal Infections
    • *Controversial Use

Aggressive Surgical Debridement 4

References

  1. Adigun IA, Nasir AA, Aderibigbe AB. Fulminant necrotizing fasciitis following the use of herbal concoction: a case report. J Med Case Rep. 2010 Oct 19;4:326. (License: CC BY-2.0)
  2. Heiner JD, Eng KD, Bialowas TA, Devita D. Fournier’s Gangrene due to Masturbation in an Otherwise Healthy Male. Case Rep Emerg Med. 2012;2012:154025. (License: CC BY-3.0)
  3. Spadaro S, Berselli A, Marangoni E, Romanello A, Colamussi MV, Ragazzi R, Zardi S, Volta CA. Aeromonas sobria necrotizing fasciitis and sepsis in an immunocompromised patient: a case report and review of the literature. J Med Case Rep. 2014 Sep 22;8:315. (License: CC BY-4.0)
  4. Meyer Ganz O, Gumener R, Gervaz P, Schwartz J, Pittet-Cuénod B. Management of unusual genital lymphedema complication after Fournier’s gangrene: a case report. BMC Surg. 2012 Dec 23;12:26. (License: CC BY-2.0)