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Definition

Gangrene is the death of tissue caused by the lack of blood supply.

Description

The severity of gangrene is wide-ranging. It can affect a minuscule skin area or a finger or toe, or even an entire limb such as an arm, a foot, or a leg. Gangrene is usually classified into two categories, dry gangrene and wet gangrene.

Dry gangrene

Dry gangrene occurs when a portion of bodily tissue dies because its blood supply has been decreased or completely cut off. This type of gangrene will not spread to other healthy tissue, and infection is not present. It is usually a slow process, with the affected area gradually becoming cold, discolored, and eventually totally black. Shrinkage and withering away of the affected tissue occurs as the tissue dies.

Wet gangrene

Dry and wet gangrene are two terms often applied to different phases of the same death of tissue. Wet gangrene (also called moist gangrene) occurs when dry gangrene becomes infected, often due to injury, and the infection causes the tissue to die.

In the United States, approximately 50% of moist gangrene cases are the result of a severe traumatic injury; 40% occur following surgery. Car and industrial accidents, crush injuries, and gunshot wounds are the most common traumatic causes. Because of prompt surgical management of wounds with the removal of dead tissue, the incidence of gangrene from trauma has significantly diminished. Surgeries involving the bile ducts or intestine are the most frequent procedures causing gangrene. Approximately two-thirds of cases affect the extremities, and the remaining one-third involve the abdominal wall.

One particularly dangerous type of wet gangrene is termed gas gangrene, or myonecrosis. This particular type is caused by the infection of injured tissue or surgical wounds from the Clostridium species of bacteria, an especially virulent pathogen. In anaerobic conditions, that is, conditions in which oxygen levels are low, Clostridium can rapidly produce poisonous substances called toxins that cause tissue to die. Four of the Clostridium toxins, Alpha, Beta, Epsilon, and Iota, are capable of causing death.

Gas gangrene differs from other wet gangrenes because it is more involved with muscle than skin tissue. Not only do the toxins manufactured by Clostridium cause the death of tissue, but they also destroy blood cells, constrict blood vessels, thus decreasing circulation, and damage blood vessels so that they leak. Fortunately, in peacetime, and with improvements in medical care, gas gangrene is not a frequently occurring phenomenon. (It occurs in only between one and three thousand people in the United States each year.) However, in the past, in wartime, gas gangrene has killed literally millions.

Causes and symptoms

Dry gangrene

Some of the most common causes of dry gangrene include:

• arterial obstruction, or occlusion of an artery, caused by arteriosclerosis, diabetes mellitus, AIDS or blood clot
• severe blunt trauma to a part of the body causing damage and therefore obstruction of an artery

• frostbite, which occurs when tissue becomes so cold that it is literally deprived of blood and therefore oxygen, and dies
• diseases that affect the blood vessels, and especially the arteries, such as Buerger's disease or Raynaud's disease
• traumatic occurrences such as crushing injuries, fractures, burns, and even injections given into skin or muscle

Wet gangrene

Causative organisms for wet gangrene infection include:

• Streptococcus
• Staphylococcus

A serious but rare form of infection with Group A Streptococcus can impede blood flow and, if untreated, can progress to gangrene caused by chemical reaction. This type of gangrene is more commonly called necrotizing fasciitis, or infection of the skin and tissues directly beneath the skin.

Gas gangrene, the most serious form of wet gangrene, often is caused by Clostridium bacteria, which are normal inhabitants of the gastrointestinal, respiratory, and female genital tracts. They often infect thigh amputation wounds, especially in those individuals who have lost control of their bowel function (incontinence). Gangrene, incontinence, and debility are often combined in patients with diabetes, and it is in the amputation stumps of diabetic patients that gas gangrene often occurs.

Areas of either dry or moist gangrene are initially characterized by a red line on the skin that marks the border of the affected tissues. The onset of dry gangrene is normally characterized by dull, aching pain at the site. The skin usually develops an abnormal, unhealthyappearing pallor and is cold to the touch. As tissues begin to die, dry gangrene may continue to cause some pain; but it may go unnoticed, especially in the elderly or in those individuals with diminished sensation to the affected area. As more tissue dies, its color changes to brown, and finally purplish-black. This dead tissue will gradually separate from the healthy tissue and fall off.

Gas gangrene has a dramatically sudden, rapid onset. It is frequently first noticed as a marked swelling and either a pallid or brownish-red colored area surrounding the wound site. The borders of the infected site can expand literally within minutes. Symptoms of gas gangrene include:

• edema, or swelling, at the injury site that expands quickly
• pain in the area surrounding the skin injury
• crepitus, a bubbly, crackling sound often heard upon palpation
• pallor at the injury site, then increasingly dusky discoloration
• low-grade to moderate temperature elevation
• tachycardia, or increased heart rate
• diaphoresis, or clammy, sweaty skin
• formation of blisters filled with rust-colored fluid
• wound drainage, foul-smelling and rusty or bloody in appearance
• in severe cases, shock (Symptoms of shock include generalized pallor, hypotension, rapid pulse, and cold hands and feet.)

Diagnosis

A diagnosis of gangrene is based on a combination of the patient history, a physical examination, and the results of blood and other laboratory tests. A physician will look for a history of recent trauma, surgery, cancer, or chronic disease. Blood tests will be used to determine whether infection is present and determine the extent to which an infection has spread.

A sample of drainage from a wound, possibly obtained through surgical exploration, may be cultured with oxygen (aerobic) and without oxygen (anaerobic) to identify the microorganism causing the infection and to aid in determining which antibiotic will be most effective. A gangrenous sample will contain few if any white blood cells and, when stained (with Gram stain) and examined under the microscope, will show the presence of purple (Gram-positive) rod-shaped bacteria.

X ray studies and more sophisticated imaging techniques, such as computed tomography scans (CT) or magnetic resonance imaging (MRI), may be helpful in making a diagnosis, since gas accumulation and muscle death (myonecrosis) may be visible. These techniques, however, are not sufficient alone to provide an accurate diagnosis of gangrene.

Precise diagnosis of gas gangrene often requires surgical exploration of the wound. During such a procedure, the exposed muscle may appear pale, beefy-red, or in the most advanced stages, black. If infected, the muscle will fail to contract with stimulation, and the cut surface will not bleed.

Treatment

Gas gangrene is a potentially lethal condition requiring immediate action. It is recommended that anyone having any or all of the symptoms of gas gangrene contact a health provider immediately. Generally, once a diagnosis of gas gangrene is made, infected, gangrenous tissue must be removed surgically. To assure its complete removal, it is often necessary to remove all tissue surrounding the infection or even to amputate a portion of the body. Aggressive use of antibiotics, usually intravenously to start, is also begun as soon as possible. Pain medication will also usually be necessary.

Areas of dry gangrene that remain free from infection (aseptic) in the extremities are most often left to wither and fall off. Treatments applied to the wound externally (topically) are generally not effective without adequate blood supply to support wound healing. Assessment by a vascular surgeon, along with x rays to determine blood supply and circulation to the effected area, can help determine whether surgical intervention would be beneficial.

Once the causative organism has been identified, moist gangrene requires the prompt initiation of intravenous, intramuscular, and/or topical broad-spectrum antibiotic therapy. In addition, the infected tissue must be removed surgically (debridement), and amputation of the affected extremity may be necessary. Pain medications (analgesics) are prescribed to control discomfort. Intravenous fluids and, occasionally, blood transfusions are indicated to counteract shock and replenish red blood cells and electrolytes. Adequate hydration and nutrition are vital to wound healing.

Although still controversial, some cases of gangrene are treated by administering oxygen under pressure greater than that of the atmosphere (hyperbaric) to the patient in a specially designed chamber. The theory behind using hyperbaric oxygen is that more oxygen will dissolve in the patient's bloodstream, and therefore more oxygen will be delivered to the gangrenous areas. By providing optimal oxygenation, the body's ability to fight off the bacterial infection is believed to be improved, and there is a direct toxic effect on the bacteria that thrive in an oxygen-free environment. Some studies have shown that the use of hyperbaric oxygen produces marked pain relief, reduces the number of amputations required, and reduces the extent of surgical debridement required. Patients receiving hyperbaric oxygen treatments must be monitored closely for evidence of oxygen toxicity. Symptoms of this toxicity include slow heart rate; profuse sweating; ringing in the ears; shortness of breath; nausea and vomiting; twitching of the lips, cheeks, eyelids, nose; and convulsions.

The emotional needs of the patient suffering from gangrene are also a large component of treatment. The individual with gangrene should be offered moral support, along with an opportunity to share questions and concerns about changes in body image. In addition, particularly in cases where amputation is required, physical, vocational, and rehabilitation therapy will also be required.

Prognosis

Except in cases where the infection has been allowed to spread through the blood stream, as in the case of severe gas gangrene, prognosis for survival is generally favorable. Anaerobic wound infection can progress quickly from initial injury to gas gangrene and the spread of the infection to the blood stream within one to two days. Between 20 and 25% of gas gangrene victims do not survive. If recognized and treated early, however, approximately 80% of patients survive, and only 15 to 20% require any form of amputation. Unfortunately, the individual with dry gangrene most often has multiple other health problems that complicate recovery, and it is usually these health problems that can prove fatal.

Health care team roles

• In most cases, gangrene is discovered while the patient is still in a healthcare facility following trauma, surgery, or treatment of serious medical conditions. A diagnosis of gangrene is generally made by a primary care physician or surgeon.
• Both registered nurses (RNs) and licensed practical nurses (LPNs) must complete a prescribed course in nursing and pass a state examination. RNs typically have a degree in nursing. Both RNs and LPNs care for patients afflicted by gangrene both in general hospitals, homes, or other healthcare facilities. Good nursing care and observation are primary requirements. These will include taking vital signs, monitoring surgical wounds or injuries for signs and symptoms of infection, providing aseptic (germ-free) treatment to wounds and injuries, collecting specimens of wound drainage to be tested, and making all efforts necessary to keep the patient as comfortable as possible. Education about the underlying cause of the gangrene (diabetes, infection, etc.) is an important aspect of caring for these patients.

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KEY TERMS

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Aerobic—A type of organism that grows and thrives only in environments containing oxygen.

Anaerobic—A type of organism that grows and thrives in an oxygen-free environment.

Arteriosclerosis—Build-up of fatty plaques within the arteries that can lead to the obstruction of blood flow.

Aseptic—Without contamination with bacteria or other microorganisms.

Crepitus—A crackling sound.

Gram stain—A staining procedure used to visualize and classify bacteria. The Gram stain procedure allows the identification of purple (Gram-positive) organisms and red (Gram-negative) organisms.

Hyperbaric oxygen—Medical treatment in which oxygen is administered in specially designed chambers under pressures greater than that of the atmosphere in order to treat specific medical conditions.

Incontinence—A condition characterized by the inability to control urination or bowel functions.

Myonecrosis—The destruction or death of muscle tissue.

Sepsis—The spreading of an infection in the bloodstream.

Thrombosis—The formation of a blood clot in a vein or artery that may obstruct local blood flow; or may dislodge, travel downstream, and obstruct blood flow at a remote location.

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• Clinical laboratory scientists have specialized training and must pass a state examination. They do the necessary tests on wound drainage specimens to determine the organism involved in the infection.
• Radiologic technologists have specialized training and must pass a state examination. They take X rays and other tests to visualize and monitor the course of the gangrene.
• Physical therapists must complete a prescribed course and pass a state examination in order to be licensed. Typically they have a degree. Physical therapists work with patients that have sustained an amputation because of gangrene to maintain and maximize mobility in walking, wheelchair use, and transferring (from wheelchair to toilet or from standing to sitting, for example). The physical therapist advises on such mobility aids as wheelchairs, braces, and canes.
• Social workers have a degree in social work. A social worker may help coordinate services and ease the transition out of the hospital back into the home or extended care facility, if necessary. Social workers may help counsel the patient and the family during the difficult rehabilitation period.
• Occupational therapists must complete a prescribed course and pass a state examination in order to be licensed. Typically they have a degree. They help people disabled after an amputation or loss of function caused by gangrene to relearn necessary functions needed to carry out normal activities of daily living such as bathing, dressing, and preparing meals.

All healthcare team members need to be aware that the person with gangrene, and possibly an amputation, and the family members who may care at home for the person will need to learn an entirely new set of skills and adaptations. Both the patient and family often experience stress, anxiety, and depression. Both may need teaching regarding both physical and mental symptoms that often follow gangrene or amputation, and the family may need to be taught how to deliver necessary care. For the patient with gangrene, finding other individuals or a support group composed of people that have had similar illness or injury can be one of the most important steps in the rehabilitation process.

Prevention

Patients with diabetes or severe arteriosclerosis need to take particular care of their hands and feet because of the risk of infection associated with even a minor injury. Education about proper foot care is vital. Diminished blood flow as a result of narrowed vessels will not lessen the body's defenses against invading bacteria. Measures taken towards the reestablishment of circulation are recommended whenever possible. Any abrasion, break in the skin, or infected tissue should be cared for immediately. Any dying or infected skin must be removed promptly to prevent the spread of bacteria.

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 between 4 and 8%.

Joan M. Schonbeck