Necrotizing fasciitis
Background
- Rapidly progressive, life-threatening infection involving fascia and subcutaneous tissue
- Mortality: 20-40% even with treatment; increases with delayed diagnosis[1]
- Early surgical exploration and debridement are the most important prognostic factors
- Gas formation is NOT required for diagnosis; absence of gas on imaging does NOT rule out NF[2]
Types
- Type I (Polymicrobial): mixed aerobic/anaerobic organisms; most common overall
- Typically in diabetics, immunocompromised, post-surgical patients
- Abdominal wall, perineum (Fournier gangrene)
- Type II (Monomicrobial): Group A Streptococcus (most common) or Staphylococcus aureus
- Can occur in young, healthy patients
- Extremities most common site
- Type III (Gas gangrene): Clostridium perfringens (myonecrosis)
- Extremely rapid progression; crepitus common
- Type IV: Fungal (immunocompromised, trauma)
Risk Factors
- Diabetes (most common comorbidity), IV drug use, obesity
- Immunosuppression (HIV, malignancy, chronic steroids)
- Recent surgery or traumatic wounds
- Peripheral vascular disease, chronic renal failure, cirrhosis
- NSAIDs (may mask early symptoms and promote GAS virulence)
Clinical Features
- Pain out of proportion to exam (most important early clinical clue)
- However: some patients present with "la belle indifference" (painless) — ischemic insensate tissue[3]
- Erythema without sharp margins (unlike erysipelas)
- Rapidly progressive swelling and induration
- Hemorrhagic bullae (violaceous/dusky bullae)
- Skin anesthesia (destruction of superficial cutaneous nerves — late but specific)
- Crepitus (type I infections; absent in many cases)
- Skip lesions (areas of normal-appearing skin between involved areas)
- Lymphangitis and lymphadenopathy are ABSENT (fascia lacks lymphatic drainage)[4]
- Systemic toxicity: fever, tachycardia, shock, DIC
Differential Diagnosis
- Cellulitis (most common misdiagnosis — cellulitis improves with antibiotics; NF does not)
- DVT
- Compartment syndrome
- Pyomyositis
- Gas gangrene without fasciitis
- Erysipelas
Template:Skin and soft tissue infection DDX
Evaluation
Labs
- CBC: leukocytosis (or leukopenia in severe sepsis)
- BMP: creatinine (AKI), sodium <135 (associated with NF)
- CRP: >150 mg/L
- Lactate: elevated (tissue ischemia)
- CK: may be elevated (myonecrosis)
- Blood cultures, wound cultures
- Coagulation studies (DIC screening)
LRINEC Score[5]
- Has NOT been prospectively validated
- Score ≥6: PPV 92% for NF
- 10% of patients with score <6 still had NF — low score does NOT rule out NF
- CRP ≥150 (+4), WBC 15-25 (+1) / >25 (+2), Hgb 11-13.5 (+1) / <11 (+2), Na <135 (+2), Cr >1.6 (+2), Glucose >180 (+1)
HUCLA Criteria[6]
- WBC >15.4 OR Na <135: associated with NF
- PPV 26%, NPV 99% — useful to rule out NF, not confirm it
Imaging
- Should NOT delay surgical exploration if clinical suspicion is high
- CT (study of choice if imaging obtained): soft tissue gas, fascial thickening, fluid collections, fat stranding
- MRI: T2 fascial/subcutaneous edema (very sensitive but time-consuming)
- Bedside US: thickened fascia, subcutaneous fluid, subcutaneous emphysema; limited by gas artifact[7]
- Absence of gas on imaging does NOT exclude NF
Definitive Diagnosis
- Surgical exploration is the ONLY way to definitively diagnose NF
- Findings: grayish necrotic fascia, lack of tissue resistance to blunt dissection, "dishwater" pus, thrombosed vessels
Management
Surgical
- Emergent surgical exploration and debridement — the single most important intervention
- Indicated if: severe pain, systemic toxicity, elevated CK, clinical suspicion with or without imaging findings
- Repeat debridement (planned "second look") typically at 24-48 hours
- Average: 3-4 debridements before wound management
- Delay in surgery increases mortality by approximately 9x
Antibiotics
- Must cover gram-positives (including MRSA), gram-negatives, AND anaerobes
- Empiric regimen:
- Piperacillin-tazobactam 4.5g IV q6h (or meropenem 1g IV q8h)
- + Vancomycin 25-30 mg/kg IV loading dose (or linezolid 600 mg IV q12h) — MRSA coverage
- + Clindamycin 900 mg IV q8h — suppresses toxin production (especially GAS exotoxins)[8]
- Clindamycin should be included in all regimens regardless of other antibiotics
Supportive Care
- Aggressive IV fluid resuscitation
- Vasopressors for septic shock
- Serial lactate monitoring
- Blood products for DIC
- ICU admission
IVIG
- Consider for streptococcal toxic shock syndrome associated with NF (controversial)
Disposition
- ICU admission for all patients
- Surgery consult in ED for any suspected case
- Serial debridements as needed
- Wound management: VAC therapy, skin grafting after infection controlled
Calculators
Template:LRINEC Score Calculator
See Also
References
- ↑ Hakkarainen TW et al. Necrotizing soft tissue infections: review and current concepts. Curr Probl Surg. 2014;51(8):344-72. PMID 25069713
- ↑ Misiakos EP et al. Current concepts in the management of necrotizing fasciitis. Front Surg. 2014;1:36. PMID 25593960
- ↑ TheHealthScience. Emergent Management of Necrotizing Soft Tissue Skin Infections. 2013.
- ↑ Seal DV. Necrotizing fasciitis. Curr Opin Infect Dis. 2001;14(2):127-32. PMID 11979122
- ↑ Wong CH, et al. The LRINEC score: a tool for distinguishing necrotizing fasciitis from other soft tissue infections. Crit Care Med. 2004;32(7):1535-1541. PMID 15241098
- ↑ Wall DB et al. A simple model to help distinguish NF from non-NF soft tissue infection. J Am Coll Surg. 2000;191(3):227-31. PMID 10989895
- ↑ Core Ultrasound: Soft Tissue. https://www.coreultrasound.com/sti/
- ↑ Stevens DL, et al. Practice guidelines for the diagnosis and management of SSTI: 2014 update by IDSA. Clin Infect Dis. 2014;59(2):e10-e52. PMID 24973422
- Golger A, et al. Mortality in patients with necrotizing fasciitis. Plast Reconstr Surg. 2007;119(6):1803-7. PMID 17440360
- Puvanendran R et al. Necrotizing fasciitis. Can Fam Physician. 2009;55(10):981-987. PMID 19826154
- Anaya DA, Dellinger EP. Necrotizing soft-tissue infection: diagnosis and management. Clin Infect Dis. 2007;44(5):705-710. PMID 17278065