Gas Gangrene

This rare condition is caused by local infection with the anaerobic, spore-forming, gram-positive, rod-shaped bacillus Clostridium perfringens or another clostridial species. It occurs in devitalized tissues and results from compromised arterial circulation after trauma or surgery. The usual incubation period is 1 to 4 days but can vary from 3 hours to 6 weeks or longer.

Gas gangrene carries a high mortality unless therapy begins immediately. With prompt treatment, 80% of patients with gas gangrene of the extremities survive; the prognosis is poorer for gas gangrene in other sites, such as the abdominal wall or the bowel.

Causes

The organism most often responsible, C. perjringens, is a normal inhabitant of the GI and female genitourinary tracts; it's also prevalent in soil. Transmission occurs when the organism enters the body during trauma or surgery.

Because C. perfringens is anaerobic, gas gangrene occurs most frequently in deep wounds, especially those in which tissue necrosis further reduces the oxygen supply. When C. perfringens invades soft tissues, it produces thrombosis of regional blood vessels, tissue necrosis, and localized edema. Such necrosis releases both carbon dioxide and hydrogen subcutaneously, producing interstitial gas bubbles.

Gas gangrene occurs most commonly in the extremities and in abdominal wounds and less often in the uterus.

Signs and symptoms

Gas gangrene produces severe pain in the infected area. Initially, the area is swollen and pale, but eventually turns red, then bronze, and finally blackish green. Large blisters often form. Gas bubbles may be visible in the blister fluid or may be felt under the skin. The odor of any wound drainage is described as sweet or mousy, unlike the putrid odor typical of other anaerobic infections.

As the infection progresses, the person becomes sweaty and very anxious; vomiting may also occur. Fever , rapid heart rate, rapid breathing, altered mental state, loss of appetite, diarrhea , vomiting, and vascular collapse may also occur if the bacterial toxins are allowed to spread in the bloodstream. Gas gangrene can be a life-threatening condition and should receive prompt medical attention

Diagnostic tests

Several tests confirm the diagnosis. Anaerobic cultures of wound drainage show C. perjringens; a Gram stain of wound drainage discloses large, grampositive, rod-shaped bacteria; X-rays reveal gas in tissues; and blood studies show leukocytosis and, later, hemolysis.

Treatment

Appropriate treatment includes careful observation for signs of myositis and cellulitis. The patient needs immediate treatment if these signs appear and immediate wide surgical excision of all affected tissues and necrotic muscle in myositis. Delayed or inadequate surgical excision is fatal.

The patient also needs I.V. administration of antibiotics and, after adequate debridement, hyperbaric oxygenation, if available. For 1 to 3 hours every 6 to 8 hours, the patient is placed in a hyperbaric chamber and exposed to pressures designed to increase oxygen tension and prevent multiplication of the anaerobic Clostridia. Surgery may take place within the hyperbaric chamber if the chamber is large enough.

Prevention

Clean any skin injury thoroughly. Watch for signs of infection (such as redness, pain, drainage, or swelling around a wound), and consult your health care provider promptly if these occur.

Penetrating abdominal wounds should be surgically explored and drained, any tears in the intestinal walls closed, and antibiotic treatment begun early. Patients undergoing elective intestinal surgery should receive preventive antibiotic therapy. Use of antibiotics prior to and directly following surgery has been shown to significantly reduce the rate of infection from 20-30% to 4-8%.