Necrotizing soft tissue infection

Definition

Necrotizing soft-tissue infection is a severe type of tissue infection that can involve the skin, subcutaneous fat, the muscle sheath (fascia), and the muscle. It can cause gangrene, tissue death, systemic disease, and death.

Causes, incidence, and risk factors

Necrotizing subcutaneous infection or fasciitis can be caused by a variety of bacteria including oxygen-using bacteria (aerobic) or oxygen-avoiding bacteria (anaerobic). A very severe and usually fatal fasciitis is caused by a deadly species of streptococcus called "flesh-eating bacteria" by the press.

This type of infection develops when bacteria enter the body, usually through a minor skin injury or abrasion. The bacteria begin to grow and release toxins that:

• Directly kill tissue
• Interfere with the blood flow to the tissue
• Digest materials in the tissue, which rapidly spreads the bacteria
• Cause widespread effects, such as shock

Infection may begin as a small reddish painful spot or bump on the skin. This quickly changes to a painful bronzed or purplish patch that expands rapidly. The center may become black and dead (necrotic). The skin may break open. Visible expansion of the infection may occur in less than an hour.

Symptoms may include fever, sweating, chills, nausea, dizziness, profound weakness, and finally shock. Without treatment death can occur rapidly.

Symptoms

• Severe pain in the area
• Swelling in the area
• Discoloration in the area
  • May appear reddened, bronzed, bruised, or purple (purpuric)
  • Progresses to dusky, dark color
• Bleeding into the skin
• Visibly dead (necrotic) tissue
• Patchy skin color
• Skin breaks (open wound)
• Skin around the wound feels hot and looks reddened, raised, or discolored (inflamed)
• Oozing fluid ranging from yellowish-clear or yellowish-bloody to puslike
• Fever
• General ill feeling

Signs and tests

The appearance of the skin and underlying tissues, and the presence of gangrene (black or dead tissue) indicates a necrotizing soft tissue infection. Imaging tests, such as CT scans, are sometimes helpful.

Often a patient will be diagnosed in the operating room by a surgeon. A gram stain and culture of drainage or tissue from the area may find which bacteria is causing the infection.

Treatment

Powerful, broad-spectrum antibiotics must be given immediately through a vein (IV). This is an attempt to control the infection by quickly raising the blood levels of the antibiotic. Surgery is required to open and drain infected areas and remove dead tissue.

Skin grafts may be required after the infection is cleared. If the infection is in a limb and cannot be contained or controlled, amputation of the limb may be considered. Sometimes pooled immunoglobulins (antibodies) are given by vein to help fight the infection.

If the organism is determined to be an oxygen-avoiding bacteria (anaerobe), the patient may be placed in a hyperbaric oxygen chamber, a device in which the patient is given 100% oxygen at several atmospheres of pressure.

Expectations (prognosis)

Outcomes are variable. The type of infecting organism, rate of spread, susceptibility to antibiotics, and the timing of diagnosis all contribute to the final outcome.

Scarring and deformity are common with this type of disease. Fatalities are high even with aggressive treatment and powerful antibiotics. Untreated, the infection invariably spreads and causes death.

Complications

• Local spread of infection, progressive tissue damage
• Systemic spread of infection, sepsis, shock
• Scarring and disfigurement
• Functional loss of a limb
• Death

Calling your health care provider

This disorder is severe and may be life-threatening, so consult your health care provider immediately.

Call your health care provider if signs of infection occur around a skin injury: pain, swelling, redness, drainage of pus or blood, fever, or other similar symptoms.

Prevention

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

Illustrations

Necrobiosis lipoidica diabeticorum - abdomen

Necrobiosis lipoidica diabeticorum - leg

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