Necrotizing fasciitis

Background

Necrotizing fasciitis is a rare, rapidly progressive infection primarily involving the fascia and subcutaneous tissue. It is perhaps the most severe form of soft tissue infection and is potentially limb and life threatening. Early recognition and aggressive debridement of all necrotic fascia and subcutaneous tissue aremajor prognostic determinants, and delay increases mortality.

Risk Factors

• DM
• Drug use
• Obesity
• Immunosuppression
• Recent surgery
• Traumatic wounds

Clinical Features

Nectrotizing fasciitis

• Skin exam
  • Erythema (without sharp margins)
  • Exquisitely tender (pain out of proportion to exam)
  • Skip lesions
  • Hemorrhagic bullae (violaceous bullae)
    • May be preceded by skin anesthesia (destruction of superficial nerves)
  • Crepitus (in type I infections)
• Swelling/edema may produce compartment syndrome
• Constitutional
  • Fever
  • Tachycardia
  • Systemic toxicity

Work-Up

• CBC
• Chem
• PT/PTT/INR
• CK
• Lactate

Diagnosis

CT of necrotizing fasciitis

• Surgical exploration is the ONLY way to definitively establish the diagnosis of necrotizing infection
• Imaging
  • Should not delay surgical exploration
  • CT is study of choice

HUCLA NF vs Non-NF Criteria (Wall et al)

• Retrospective study discovered:
  • WBC count >15.4(x10³/mm³) OR Na <135(mmol/L)
  • Associated with NF and combo of both increased likelihood of NF
  • PPV 26%/NPV 99%
• Good tool to R/O NF, not a good tool for confirming presence of NF
  • Helps distinguish NF from non-NF infection, when classic 'hard' signs of NF are absent

Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) Score (Wong et al)

• May use to risk stratify patients p/w signs of cellulitis to determine likelihood of necrotizing fasciitis
• Useful in context of a diagnosed or strongly suspected severe soft-tissue infxn
• Score based on: CRP, WBC, Hb, Na, Cr, Glucose
• Score > 6 has PPV of 92% and NPV of 96% for necrotizing fasciitis
  • Be aware LRINEC score has not been prospectively validated, index of suspicion is key

1. CRP (mg/L) ≥150: 4 pts
2. WBC count (x10³/mm³):
   1. <15: 0 pts
   2. 15-25: 1 pt
   3. >25: 2 pts
3. Hb (g/dL):
   1. >13.5: 0 pts
   2. 11-13.5: 1 pt
   3. <11: 2 pts
4. Na (mmol/L) <135: 2 pts
5. Cr (mg/dL) >1.6: 2 pts
6. glucose (mg/dL) >180: 1 pt

Differential Diagnosis

Skin and Soft Tissue Infection

• Cellulitis
  • Hand cellulitis
  • Facial cellulitis
  • Orbital cellulitis
• Erysipelas
• Lymphangitis
• Folliculitis
• Hidradenitis suppurativa
• Skin abscess
  • Anorectal abscess
  • Bartholin gland abscess
  • Pilonidal abscess
  • Scrotal abscess
• Necrotizing soft tissue infections
  • Necrotizing fasciitis
  • Necrotizing myositis
  • Necrotizing cellulitis
  • Fournier's gangrene
• Mycobacterium marinum

Look-A-Likes

• Sporotrichosis
• Osteomyelitis
• Deep venous thrombosis
• Pyomyositis
• Purple glove syndrome
• Tuberculosis (tuberculous inflammation of the skin)

Treatment

• Surgical exploration and debridement
  • Indicated in setting of severe pain, toxicity, fever, elevated CK (w/ or w/o radiographic evidence)
• Antibiotics
  • Must cover Gram +/- and anaerobes (esp GAS and clostridium)
  • Piperacillin-Tazobactam 3.375-4.5g q6hr AND clindamycin 600-900mg q8hr AND vancomycin 1gm IV q12hr

Disposition

Admit/OR

See Also

• Necrotizing Soft Tissue Infections