Pathophysiology
1) most common cause – Clostridia perfringens toxins (hyaluronidase, necrotizing toxin, and lecithinase) 2) other causal Clostridia organisms are C. septicum and C. histolyticum 3) occurs most commonly in setting of other cocci and gram-negative organisms 4) C. perfringens spores germinate to active microorganisms that ferment carbohydrates (which produces the gas) 5) usually occurs after penetrating wound with muscle laceration and interruption of blood supply and contamination with soil 6) incubation period is usually 24-48 h but occasionally can be years later if latent spores in wound germinate
Signs and Symptoms
1) sudden onset of pain in affected area 2) swelling 3) edema 4) thin watery exudate that changes to frothy, foul-smelling exudate as disease progresses 5) skin is white and tense with blue streaks in it initially and then turns bronzed with red bullae on it in later stages 6) muscle is pale whitish gray (“dirty dishwasher tissue”) initially and then turning to black in later stages 7) tachycardia 8) fever 9) hypotension and shock 10) crepitus in tissue (this is a rather later finding) 11) mental status is unaffected until the very end stages of disease.
Characteristic Test Findings
Laboratory – 1) Gram stain of wound exudate shows may gram-positive rods 2) hemolysis
Histology/Gross Pathology
C. perfringens is a large, anaerobic, spore-forming, encapsulated, nonmotile, gram-positive rod
Associated Conditions
1) severe clostridial infections can occur after instrument abortions with unclean devices Nontraumatic cases occur in – 2) gastrointestinal malignancy 3) abdominal radiation treatments 4) diverticulosis
Treatment
1) emergent, wide debridement 2) hyperbaric oxygen 3) penicillin and clindamycin or cefoxitin and clindamycin
Tips for USMLE
1) although not a hard-and-fast rule, gas gangrene is more commonly associated with a “messy” wound than with a “clean” through and through bullet or knife wound 2) think gas gangrene if a soldier receives a shrapnel wound in the leg while in battle: it is 36 hours before he can be airlifted to a hospital; he is awake and alert when he enters the hospital; he has a fever of 101.1 F; he is hypotensive; his wound does not show crepitus; the skin is whitish with blue streaks; underlying muscle is gray and does not contract when stimulated; the wound discharge is thin and has a foul smell but is not frankly purulent.
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