What Is Gangrene?
Gangrene (“necrotizing soft tissue infection”) is body tissue death from loss of blood supply and, with it, oxygenation. It falls into three major categories:
- Dry gangrene: tissue dries and falls off. This is most commonly seen at the arterial tree terminal points where arterioles are small, such as the ends of the fingers or toes
- Wet gangrene: tissue becomes edematous and blisters form
- Gas gangrene: tissue demonstrates gas bubbles produced by bacteria
Causes of Gangrene
- Peripheral vascular disease, such as that seen in diabetes
- Burns (thermal or chemical)
- Smoking. Nicotine is a powerful vasoconstrictor, which negatively impacts everything from normal tissue oxygenation to impaired healing
- Crush injuries
- Traumatic injuries in which the blood supply to repaired tissue is not successfully re-established, as in reattachment of severed digits or limbs
- Infection that progressed to necrosis (cell death). Sources include breaches in the GI tract, urethral mucosa, oropharynx mucosa after surgery, and dental infection
Signs and Symptoms
- Erythema (redness)
- Edema (swelling)
- Crepitus (crackling sound in the tissue when pressed)
- Overt necrosis or ecchymosis (deep bruised appearance)
The endpoint of necrotizing infections is loss of the areas involved. Amputation above the gangrene may be necessary ultimately. Loss of areas due to separating off, as in dry gangrene, can cause spontaneous loss without surgical intervention, although surgical intervention will be necessary.
Prior to this, gangrene wound management mandates strategies that are implemented to prevent getting to this endpoint.
How Is Gangrene Diagnosed?
Gangrene is a progression to a climax in an incessant infectious process. The diagnosis is typically obvious by inspection and it is based on the type of tissue infected:
- Necrotizing cellulitis (soft tissue–fat, skin)
- Necrotizing fasciitis (fascia–deep soft tissues)
- Necrotizing myositis (muscle)
These different three layers exist in tissue planes which offer paths for the rapid spread of the infection, which is the cause of it often getting out of control even to the point of death.
Soft Tissue Gangrene
Necrotizing cellulitis is usually caused by Clostridium species or a mix of several bacteria. This does not extend deeper to the fascia or deep muscles, so although there is usually crepitus, there usually is not severe pain or swelling.
Necrotizing fasciitis is infection of the deeper tissues such as the fascia–the tough, fibrous tissue that overlies muscle. This layer is a poorly vascularized layer which lacks the full complement of immune defenses. This disadvantage, along with its extensive tissue expanse that facilitates spread, makes it particularly difficult to treat. The usual infectious organism is an anaerobic bacterium alone or in combination with other anaerobes.
Streptococcus aureus may be the infectious agent, whose exotoxins can produce toxic shock syndrome, shock, organ failure, and death.
Gangrenous involvement of the muscle is usually due to group A Streptococcus or other resistant Streptococci. When the organism is Clostridium, this can be the very destructive and virulent Clostridial myonecrosis (also called “gas gangrene”).
Management of Gangrene
Management and treatment of gangrene wounds requires an aggressive protocol of:
- Wound care
Whenever there is suspicion of gangrene (necrosis of tissue), aggressive surgical exploration is needed to confirm the diagnosis.
This procedure also allows an initial therapy, due to its debridement of necrotic tissue. A “second-look” surgery should be done a day later. Eventually, there may be necessary 3-4 debridement procedures, which is the average.
Antibiotics should begin as early as possible, even before any cultures identify the infectious organism(s) or before the sensitivities to antibiotics associated with those organisms are determined. Pending these cultures and their sensitivity results, there should be antibiotic coverage for gram-negative and gram-positive organisms and both aerobic and anaerobic bacteria, as well as antibiotics that treat resistant organisms such as methicillin-resistant Staphylococcus aureus (MRSA). Once the cultures are completed and sensitivities assessed, these results can fine-tune the antibiotic therapy.
A gangrenous wound should not be closed until all necrotic areas are clear (absent) and the tissue is well-vascularized. In the interval, covering should be done to protect the open wound from exposure to more pathogens and to keep it moist.
Prevention of Gangrene Wounds
Gangrene (necrosis) of tissue is a complication, not an initial condition that can be prevented. On-going risk factors that make it more likely, if ordinarily addressable infections begin, should be mitigated–smoking and circulatory compromise. For diabetics, this means strict glycemic control and immediate, aggressive identification and management of bedsores and pressure ulcers over bony prominences.
Prevention in the Patient with a Gangrene Wound
Those conditions that promote necrosis in infected tissues should be addressed in the often frustrating task of defeating gangrene before there is any more loss of tissue. This strategy is implemented while aggressively treating the gangrene (necrosis of tissue, fascia, and/or muscle) with persistent surgical debridement of necrotic tissue and rational antibiotic coverage.
During any phase of therapy–early or later–good nutrition is critical for re-establishment of tissue integrity that otherwise might fail with the progressive necrosis.
Anything that may negatively impact circulation, such as smoking or illicit use of sympathomimetics such as cocaine or methamphetamines, should be discontinued immediately as a life-and-death decision.
Prevention in Close Contacts of the Patient with a Gangrene Wound
Besides the patient him- or herself, any close contact with the afflicted patient is at risk of becoming a secondary case when group A Streptococcus is involved. For these individuals, prophylactic antibiotics are prudent if they are at increased risk due to diabetes or immunosuppression (chemotherapy, transplant patients, HIV).