Diagnosis: Gas Gangrene

A CT scan with contrast of the patient's left arm showed significant subcutaneous air consistent with diagnosis of acute soft tissue necrotizing fasciitis of the left upper extremity. The patient was started on IV antibiotic therapy including Vancomycin, Zosyn and Clindamycin and an emergent surgical consult was obtained. The patient was rushed to the OR where the diagnosis of necrotizing fasciitis was confirmed.

In the OR the patient underwent extensive excision of skin and subcutaneous tissue with a total area of 220 cm^2 of soft tissue removed. Intra-operative cultures grew Clostridium perfringens susceptible to multiple antibiotics. The patient's antibiotics were tailored to IV Zosyn monotherapy and he did well post-operatively. The patient was discharged in stable condition on hospital day 10 with in-home health wound care services. 

Necrotizing Fasciitis - Rapid Fire 

• Type 1 nec fasc = polymicrobial (most cases) 
• diabetics 
• immunocompromised 

• Type 2 nec fasc = single organsim  
• group A beta-hemolytic strep (most common) aka "flesh-eating bacteria"
• other bugs: Staph aureus, Enterococci, Enterobacteriaceae 
• anaerobes: Bacteroides, Clostridium

• Caused by direct extension from skin in 80% of cases 

• Exotoxins destroy tissue, contribute to shock, cause intravascular hemolysis and DIC

• Fournier's gangrene = nec fasc of perineum
• polymicrobial
• urgent urology consult because infection is rapidly progressive 

• Gas gangrene = clostridial myonecrosis
• crepitus on exam though nonspecific
• traumatic form (more common, think war wounds) 
• spontaneous form (rare) 

• History may include: 
• penetrating trauma
• recent surgery
• IV drug use
• childbirth 

• Presentation
• initial symptoms can be vague (malaise, fever, myalgias, nausea, diarrhea) 
• may appear as simple cellulitis but with pain out of proportion
• skin eventually turns violaceous and ecchymotic (late finding)
• hemorrhagic bulla (late finding)  
• classic "wooden-hard" subcutaneous tissue = deep tissue inflammation

• Lab findings
• hyponatremia and leukocytosis are suggestive but nonsensitive/nonspecific

• Diagnosis 
• for ED MD diagnosis must be clinical 
• pain out of proportion, crepitus, free air on imaging, leukocytosis, etc
• intra-operative evidence of deep tissue infection necessary for official diagnosis

• Management
• urgent surgical consult if suspected
• antibiotic therapy 
• broad-spectrum beta-lactam --> Zosyn, Unasyn, Cefepime
• Vancomycin --> MRSA coverage
• Clindamycin --> disrupts group-A strep exotoxin production 
• definitive management is surgical (fasciotomies, repeated debridement)
• efficacy of hyperbaric oxygen therapy is unclear  

• 20% mortality rate means you can make a difference

References: 

Rosen's Emergency Medicine Concepts and Clinical Practice, 8th Ed, 2014, Chapter 137: Skin and Soft Tissue Infections by Daniel J. Palin and Denise Nassisi