What is gangrene?

Causes and Symptoms

Gangrene involves tissue death (necrosis) due to lack of blood flow or bacterial infection. There are three main types of gangrene: dry gangrene, wet gangrene, and gas gangrene. Dry gangrene
refers to necrosis caused by blood flow interruption without bacterial infection, as from diseases such as diabetes and atherosclerosis that impair the circulatory system. Dry gangrene affects the extremities, most commonly the toes and feet, and presents as dry, shriveled, purplish or blackened skin that looks like it has been mummified. Wet gangrene and gas gangrene, on the other hand, are both caused by bacterial infections. Wet gangrene can be caused by a variety of bacteria that infect damaged tissue following an injury or trauma, such as bedsores or frostbite. The infected tissue can blister or swell and emit a foul-smelling discharge. Wet gangrene is more dangerous than dry gangrene because of the risk of sepsis, or infection spreading to the whole rest of the body, often resulting in death. Gas gangrene is a specific kind of bacterial infection, usually Clostridium perfringens but sometimes Clostridium septicum, that affects deep muscle tissue. It is generally the result of trauma or surgery, although it can occur spontaneously. The infection begins deep beneath the skin, but eventually large patches of skin can turn dark purple and develop large dark blisters. The disease is known for its quick progression, muscle and tissue death, gas production, and, ultimately, sepsis. Not every infected wound will progress to wet or gas gangrene; they occur only if there is sufficient tissue death, as the dead tissue provides an excellent environment for the bacteria to grow and flourish.

With gas gangrene that is the result of surgery or trauma, bacteria enter the body through an opening in the skin. When the involved tissue becomes compromised because of a lack of blood, infection occurs and the process of necrosis begins. Spontaneous gas gangrene occurs when the bacteria spread from the gastrointestinal tract (stomach and intestines) in people with colon
cancer. When there is a small tear in the gastrointestinal tract, the bacteria enter the bloodstream and spread to the muscles. Spontaneous gas gangrene is caused by Clostridium septicum. C. septicum is different from C. perfringens because it can survive and grow in conditions that are aerobic. In both types of gas gangrene, the real cause of the associated problems are the exotoxins that are released. These exotoxins destroy cells, resulting in tissue death that can also affect the heart muscle.

Treatment and Therapy

The usual treatment for gangrene is the removal of dead and dying tissue (a procedure called abridgement), usually surgically, to improve the healing of surrounding tissue. Sometimes skin grafts may be used to repair the damaged area. However, if the damage is too extensive, amputation of the affected digits or limb may be required. In the case of gangrene caused by bacterial infection, an immediate course of intravenous antibiotics is also pursued. Blood thinners may also be administered to prevent blood clots. Gas gangrene is an infectious disease emergency, and the patient should be evaluated immediately. An additional treatment for gas gangrene is a procedure called hyperbaric oxygen therapy, in which the patient is placed in a small chamber that is filled with oxygen at greater than normal atmospheric pressure. This forces more oxygen into the blood, which is detrimental to the growth of Clostridium septicum, because it is an anaerobic bacterium, meaning it thrives in the absence of oxygen.

To prevent gangrene, early wound care is mandatory. The use of antibiotics to prevent infection is also important in the care of a patient who has sustained trauma. Once the diagnosis of gangrene has been made, aggressive management that includes cutting away the dead tissue, managing the basic life support parameters, antibiotics, and surgery if needed, will improve the prognosis. Therefore, the mainstay of treatment is early identification and aggressive treatment.

Bibliography

Carson-DeWitt, Rosalyn. "Gangrene." Health Library, September 30, 2012.

Folstad, Steven G. “Soft Tissue Infections.” In Emergency Medicine: A Comprehensive Study Guide, edited by Judith E. Tintinalli. 6th ed. New York: McGraw-Hill, 2004.

"Gangrene." Mayo Clinic, August 10, 2011.

"Gangrene." MedlinePlus, August 24, 2011.

Urschel, John D. “Necrotizing Soft Tissue Infections.” Postgraduate Medical Journal 75 (November, 1999): 645–649.

Wong, Jason K., et al. “Gas Gangrene.” http://www .emedicine.com/emerg/topic211.htm.