Necrotizing fasciitis
Background
Risk Factors
- DM
- Drug use
- Obesity
- Immunosuppression
- Recent surgery
- Traumatic wounds
Clinical Features
- 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
- 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
- CRP (mg/L) ≥150: 4 pts
- WBC count (x103/mm3):
- <15: 0 pts
- 15-25: 1 pt
- >25: 2 pts
- Hb (g/dL):
- >13.5: 0 pts
- 11-13.5: 1 pt
- <11: 2 pts
- Na (mmol/L) <135: 2 pts
- Cr (mg/dL) >1.6: 2 pts
- glucose (mg/dL) >180: 1 pt
Differential Diagnosis
Skin and Soft Tissue Infection
- Cellulitis
- Erysipelas
- Lymphangitis
- Folliculitis
- Hidradenitis suppurativa
- Skin abscess
- Necrotizing soft tissue infections
- 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)
- Abx
- 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