What is gas gangrene?
Gas gangrene describes a situation where bacteria from damaged or traumatised muscle or soft tissue, invades healthy adjacent muscle. The infection originates in a wound contaminated with bacteria from the Clostridia family.
The other name for gas gangrene is clostridial myonecrosis, which refers to the breakdown of the muscle tissue by a process of necrosis. Necrosis is the death of some or all the cells in an organ or tissue, in this case muscle.
What causes gas gangrene?
Eighty percent of cases of gas gangrene are caused by the bacterium Clostridium perfringens, while C. novyi, C. septicum and C. histolyticum cause most of the other cases.
What are the risk factors for gas gangrene?
The incidence of gas gangrene is quite low despite the fact that more than 30% of deep wounds are infected with clostridia species.
Gas gangrene occurs in a situation of trauma to muscle, particularly deep, lacerating wounds. Wounds that are particularly susceptible to gas gangrene are shrapnel wounds, particularly when deep muscle is involved. In non-military situations, gas gangrene can develop after trauma, surgery or intramuscular injection.
The trauma need not be severe, but the wound must be deep, necrotic and without any communication to the surface of the body.
What are the symptoms and signs of gas gangrene?
The incubation period is usually short – almost always less than three days and often less than 24 hours.
Typically, gas gangrene begins with the sudden appearance of pain in the region of the wound. Once established, the pain steadily increases in severity, but remains confined to the infected area. It spreads only if the infection spreads.
Soon after the pain develops, local swelling and oedema (excessive accumulation of fluid in the tissues) starts. This is accompanied by a thin, often bloody, fluid discharge.
The patient often develops a very fast heartbeat (tachycardia). There may be very little elevation in temperature.
Gas is usually not obvious at this stage and may not appear at all. The fluid leaking from the wound is often frothy.
The skin is taut, white, often marbled with blue and cooler than normal.
The symptoms progress rapidly. Swelling, oedema and blood poisoning (toxaemia) increase. A profuse fluid discharge appears, which may have a sweetish smell.
At surgery, the muscle is characteristically pale, oedematous, and does not contract when probed with a scalpel. It appears beefy red and dead and can progress to become black, crumbly (friable) and gangrenous.
In untreated cases, as the local wound progresses, the skin becomes bronzed. Blisters appear, become filled with dark red fluid and are accompanied by patches of gangrene on the skin. Gas appears in the later stages.
The patient suffers from a drop in blood pressure and kidney failure. Untreated patients eventually become delirious, lapse into a coma and die as a result of blood poisoning.
How is gas gangrene diagnosed?
Diagnosis must be based mainly on clinical findings. Because so many wounds are contaminated with clostridia without gas gangrene developing, the mere presence of these bacteria does not make the diagnosis.
In the presence of clinical signs of gas gangrene, bacterial cultures should be obtained from blood and wound fluids to find out to which antibiotics the infection is sensitive.
X-rays can sometimes be helpful by showing gas in the tissues, although this is not necessarily due to clostridia since other anaerobic bacteria also produce gas.
The definitive diagnosis of gas gangrene is made by a frozen section biopsy of muscle. A biopsy of the muscle is taken. It is then frozen and placed in a special instrument that produces microscopically fine slices, which are examined under a microscope.
How is gas gangrene treated?
The main treatment is through surgery. The necrotic tissue must be removed completely and the wound drained of fluid.
A broad-spectrum antibiotic is started in severe cases while waiting for the antibiotic sensitivities from the cultures.
Most gas gangrene is susceptible to penicillin, but other antibiotics used are chloramphenicol, clindamycin, the newer cephalosporins and aminoglycocides.
Localised skin and soft tissue infection can be managed by removing dead muscle rather than by using antibiotics. Drugs are required when the process extends into adjacent tissue, or when fever and signs of sepsis in the rest of the body are present.
When to see your doctor
If you have a penetrating wound with lacerations to muscle you should always seek medical help, particularly if the wound starts to become very painful.
(Reviewed by Prof. Don du Toit, University of Stellenbosch)
The information provided in this article was correct at the time of publishing. At Mediclinic we endeavour to provide our patients and readers with accurate and reliable information, which is why we continually review and update our content. However, due to the dynamic nature of clinical information and medicine, some information may from time to time become outdated prior to revision.