Gangrene

The scenario most frequently called to mind by the word gangrene is of an extremely rapidly progressing disorder, classically affecting a leg wounded in battle, and resulting in a blackening of the limb which leads either to death of the individual or amputation of the limb to save that person's life. In fact, this scenario (courtesy of all those old war movies on late at night) is due to a very specific form of gangrene called "gas gangrene." Gas gangrene is a wound infection caused most frequently by the bacteria Clostridium perfringens, spores of which are present in soil. Individuals who suffer bullet wounds during the course of battle are very likely to have had these wounds contaminated with dirt or with shreds of their own clothing. This introduces the bacteria C. perfringens (or certain other clostridia cousins), into the wound. Some types of extreme injury in civilian life can also result in C. perfringens infection. Because C. perfringens bacteria sometimes reside within the gallbladder, spillage of gallbladder contents during surgery can result in gas gangrene of the abdominal muscles.

C. perfringens causes much of its effect due to its ability to produce toxins, or poisons. In fact, C. perfringens is a close cousin to the bacteria which cause tetanus (C. tetani) and botulism food poisoning (C. botulinum). These bacteria also produce their effects through the production of toxins.

Gas gangrene receives its name from another characteristic of the C. perfringens bacteria. These bacteria ferment (breakdown) certain chemical components of muscle, giving off gas in the process. During examination of the affected area, one can actually feel bubbles of gas which have risen up just under the layers of skin.

C. perfringens bacteria multiply so quickly that gas gangrene can develop in just a matter of hours. An individual with gas gangrene will note severe pain at the wound site, with increasing swelling of the area. The wound will begin to give off a watery, sometimes frothy fluid which has a unique sweet odor, probably due to the digestion of muscle carbohydrate by the bacteria. As muscle breakdown progresses, the muscle feels cooler and appears paler than normal. The muscle feels softer and more liquid, as the bacterial toxins actually work to liquefy it. Ultimately, the area turns a deep blue-black, the classic color of gangrenous tissue. Low blood pressure, kidney failure, and a state of shock (severely decreased blood circulation to all major organ systems) may set in. Survival time for an individual with untreated gas gangrene can be as short as a single day.

Diagnosis is by examination of tissue under a microscope, where the clostridia can be definitively identified. Certainly, gas gangrene has enough unique characteristics to allow a high level of suspicion based just on the appearance of the wound and the presence of gas as noted by the examiner's hand or as revealed by x ray of the area.

Treatment of gas gangrene is with massive doses of antibiotics, in particular Penicillin G. Surgical removal of infected tissue, with a wide margin around it, is necessary to halt the spread of infection, and gangrenous limbs may require amputation.

A fascinating type of treatment for gas gangrene is hyperbaric oxygen therapy (HBO). HBO involves placing an individual in a completely closed, carefully pressurized space, within which the patient will breathe 100% oxygen (as opposed to the 21% oxygen present in normal room air). This high level of oxygen reaches the tissues, where it slows the multiplication of the bacteria, inactivates toxin, and decreases further toxin production.