summary Necrotizing Fasciitis is a life-threatening bacterial soft tissue infection that spreads along soft tissue planes rapidly. Diagnosis is made clinically with the presence of skin discoloration, bullae, palpable crepitus and calculation of the LRINEC score. Emergent frozen section can help confirm diagnosis in early cases. Treatment is emergent radical debridement of all devitalized tissues with broad-spectrum IV antibiotics. Epidemiology Risk factors immune suppression diabetes AIDS cancer obesity bacterial introduction IV drug use hypodermic therapeutic injections insect bites skin abrasions abdominal and perineal surgery Etiology Associated conditions cellulitis overlying cellulitis may or may not be present Classification Necrotizing Fasciitis Classification Type Organism Characteristics Type 1 Polymicrobial Typically 4-5 aerobic and anaerobics pecies cultured: Non-Group A Strep Anaerobes including Clostridia Facultative anaerobes Enterobacteria Synergistic virulence between organisms Most common (80-90%) Seen in immunosuppressed (diabetics and cancer patients) Postop abdominal and perineal infections Type 2 Monomicrobial Group A β-hemolytic Streptococci is most common organism isolated 5% of cases Seen in healthy patients Extremities Type 3 Marine Vibrio vulnificus (gram negative rods) Marine exposure Type 4 Fungal Presentation Symptoms early localized abscess or cellulitis with rapid progression minimal swelling no trauma or discoloration late findings severe pain high fever, chills and rigors tachycardia Physical exam skin bullae discoloration ischemic patches cutaneous gangrene swelling, edema dermal induration and erythema subcutaneous emphysema (gas producing organisms) Imaging Radiographs not required for diagnosis or treatment Studies Biopsy indications emergent frozen section can confirm diagnosis in early cases technique take 1x1x1cm tissue sample can be performed at bedside or in operating room surgical intervention should not be delayed to obtain histological findings necrosis of fascial layer microorganisms within fascial layer PMN infiltration fibrinous thrombi in arteries and veins and necrosis of arterial and venous walls LRINEC Scoring system score > 6 has PPV of 92% of having necrotizing fasciitis CRP (mg/L) ≥150: 4 points WBC count (×103/mm3) <15: 0 points 15–25: 1 point >25: 2 points Hemoglobin (g/dL) >13.5: 0 points 11–13.5: 1 point <11: 2 points Sodium (mmol/L) <135: 2 points Creatinine (umol/L) >141: 2 points Glucose (mmol/L) >10: 1 point Differentials Gas gangrene Treatment Operative emergent radical debridement and broad-spectrum IV antibiotics indications whenever suspicion for necrotizing fasciitis antibiotics initial antibiotics start empirically with penicillin, clindamycin, metronidazole, and an aminoglycoside clindamycin has been shown to reduce odds of limb amputation definitive antibiotics penicillin G for strep or clostridium imipenem or doripenem or meropenem for polymicrobial add vancomycin or daptomycin if MRSA suspected technique hemodynamic monitoring with systemic resuscitation is critical hyperbaric oxygen chamber if anaerobic organism identified operative findings liquefied subcutaneous fat dishwater pus muscle necrosis venous thrombosis amputation indications low threshold for amputation when life threatening Prognosis Life threatening infection mortality rate of 32% mortality correlates with time to surgical intervention