Gas Gangrene of Extremity Flashcards
True/False: Most cases of gas gangrene are caused by clostridial species.
False - multiple, nonclostridial infections, including staph and strep, make up more than half the cases
What is the most common cause of gas accumulation within a wound?
Direct injection at the time of injury
What is the mortality of gas gangrene?
15-70%
What is the key to treatment of gas gangrene?
- Rapid diagnosis, 2. Early broad spectrum antibiosis, 3. Supportive Care, 4. Early debridement
Along with colonization and release of exotoxins, what more is needed for clostridial species to cause gas gangrene?
Low oxygen tension in tissues, secondary to either tissue injury or chronic low blood flow, as found in diabetes or surgical devascularization
What exotoxin is the most lethal?
alpha toxin (phospholipase C), which causes profound shock via direct cardiotoxicity, hemolysis, increased capillary permeability, and leukocyte dysfunction
What malignancy has been associated with gas gangrene?
Metastatic Colorectal Carcinoma
Why does C. perfringens thrive in low oxygen states?
It is a facultative anaerobe - growth and exotoxin activity arrests at 100% oxygen.
What injuries predispose to gas gangrene?
Crush, MVAs, open fractures, wounds involving large muscle mass, high velocity missiles, and iatrogenic
What are the cutaneous findings of gas gangrene?
Pain out of proportion to exam, crepitus, edema, skin bronzing/necrosis, and hemorrhagic bullae
What diagnostic tests are necessary to evaluate a wound for gas gangrene?
None - it is a clinical diagnosis
What are the first treatment steps in dealing with gas gangrene?
Aggressive medical therapy - resuscitation, broad spectrum antibiotics, possible transfusion (with evidence of exotemic hemolysis or coagulopathy)
What first line antibiosis is recommended in clostridial gas gangrene?
High dose Penicillin G
What first line antibiosis is recommended in non-clostridial gas gangrene?
Triple therapy - Penicillin, Tobramycin, and Clindamycin (for example)
True/False: Antibiotics and incision/drainage may be sufficient in treating gas gangrene.
False - surgical debridement is the only effective management
Along with close hemodynamic monitoring, what is a necessary part of post operative care in gas gangrene?
Wound hygiene - wet to dry dressing changes or VAC acceptable; plastic surgery consult may advised
What potential benefits are there to negative pressure wound therapy?
- Removal of excess fluids, 2. Increased local blood flow, 3. Decreased bacterial counts
What are the reported benefits of hyperbaric oxygen therapy in dealing with gas gangrene?
Possible decreased mortality and decreased duration of antibiotic therapy (controversial - shown only in dogs)
What is the proposed beneficial mechanism of action of hyperbaric oxygen in gas gangrene?
Inhibition of alpha toxin, inhibition of bacterial replication, and improved tissue oxygenation
What conditions predispose to nonclostridial gangrene?
Diabetes, chronic vascular compromise, radiation, cholecystitis, and following appendectomy
What are the most common isolates from nonclostridial gangrene wounds?
beta hemolytic strep, S. aureus, Streptococcus, Bacteroides, Peptostreptococcus, and aerobic coliform bacteria. Candida and Mucormycosis have been cultured in diabetics.
What waterborne bacteria cause gas gangrene?
Aeromonas hydrophilia (gram negative rod from leech bites) and Vibrio vulnificus (gram negative from marine environment); both traditionally cause gastroenteritis, but may cause gas gangrene if they enter the skin
