Necrotizing fasciitis is a subset of the aggressive skin and soft tissue infections (SSTIs) that cause necrosis of the muscle fascia and subcutaneous tissues. This infection typically travels along the fascial plane, which has a poor blood supply, leaving the overlying tissues initially unaffected, potentially delaying diagnosis and surgical intervention. The infectious process can rapidly spread causing infection of the fascia, peri-fascial planes, and cause secondary infection of the overlying and underlying skin, soft tissue, and muscle.
Necrotizing fasciitis is typically an acute process occurring rapidly over several days. It is a direct sequela of bacterial infection introduced through a break in the skin’s integrity in approximately 80% of all cases. Gram-positive cocci specifically strains of Staphylococcus aureus and Streptococci are responsible for the majority of these single site source infections. Polymicrobial infections occur as well because of a combination of gram-negative and anaerobic involvement.
The infection rapidly transits the muscle fascia. After several days the overlying skin, which appears unaffected initially, will transition to an erythematous, reddish-purple to bluish-gray hue. The texture of the skin will become indurated, swollen, shiny, and feel warm in temperature. At this stage, the skin is exquisitely tender to palpation and can also be painful out of proportion to presenting symptoms. Skin breakdown will begin in 3 to 5 days and is accompanied by bullae and cutaneous gangrene. Pain is reduced in the affected area secondary to thrombosed small vessels and destruction of the superficial nerves in the subcutaneous tissues. Advanced stages of the infection are characterized by systemic symptoms such as fever, tachycardia, and sepsis.
Tissue obtained from the operating room after debridement will usually show extensive superficial fascial necrosis. The majority of small and medium-size blood vessels will be thrombosed. Aggregates of neutrophils will be observed in the fascia and subcutaneous tissues. Small vessel vasculitis and extensive fat necrosis will also be evident. All the glands in the dermis and subcutaneous tissues will be necrotic as well. Gram stain will show clusters of various types of microorganisms.
Necrotizing infections are more commonly present with excruciating pain out of proportion to presenting symptoms and systemic septic signs than non-necrotizing infections.
Physical findings of necrotizing soft tissue infections may include tenderness to palpation beyond the erythematous border, crepitus, and cellulitis. The presence of bullae, ecchymotic changes to the skin, and dysesthesia or paresthesia should also be treated as a necrotizing infection.
Any rapidly progressing skin or soft tissue infection should be managed aggressively due to the difficulty in differentiating non-necrotizing from necrotizing skin and soft tissue infections.
The Laboratory Risk Indicator for Necrotizing Infection (LRINEC) Score was developed in a 2004 report to distinguish NSTIs from other severe soft tissue infections. The scoring system is hinged on abnormalities in six independent variables:
C-reactive protein, mg/L
Total white cell count (WBC), cells/mm
A score of six has a positive predictive value of 92% and negative predictive value of 96%. A score of eight or greater represents a 75% risk of a necrotizing infection.
Diagnosis of NSTIs is still primarily a clinical one. Imaging may be useful in providing data when the diagnosis is uncertain. The most common plain film finding is similar to cellulitis with increased soft tissue thickness and opacity. Computed tomography (CT) has greater sensitivity than plain film in identifying necrotizing soft tissue infections.
These patients are extremely ill and should be transferred immediately to the intensive care unit. The sepsis causes refractory hypotension and diffuse capillary leak. Thus the patient will need aggressive resuscitation with fluids and use of inotropes to maintain blood pressure. The patient must be kept NPO (nothing by mouth) until seen by the surgeon. Nutrition is vital but only after surgery has been completed. Enteral feedings should be started as soon as the patient is hemodynamically stable. The enteral feedings may help offset the massive negative protein balance that occurs as a result of catabolism.
Key concepts for treatment/management of skin and soft-tissue infections are:
Early diagnosis and differentiation between necrotizing and non-necrotizing SSTIs
The early launch of appropriate empiric antibacterial coverage (wide-spectrum)
Adequate control of infection sources such as aggressive surgical intervention for abscess drainage and debridement of necrotizing soft tissue infections (NSTIs)
Identification of infection-causing pathogen and applicable adjustment of antimicrobial coverage.
Antimicrobial therapy of necrotizing fasciitis is as follows:
The treatment of necrotizing fasciitis is surgery and no time should be wasted calling for a surgical consult. The earlier the surgery is undertaken the better the outcome.
The surgery requires extensive, wide debridement of all necrotic tissues. In some cases, a second-look surgery may also be required. Early surgery may help minimize tissue loss and eliminate the need for amputation of a gangrenous extremity. With wide debridement, the wounds need to be left open and are packed with wet gauze. Daily dressing changes are mandatory. As long as the necrotic tissue is removed, the patient's recovery is faster. A great deal of surgical judgment is required when faced with normal appearing tissue which is not frankly necrotic. In most cases, if there is any doubt about viability, the tissues should be removed. In most cases, hemodynamic stability is restored once the necrotic tissue and pus are removed. The patient should be kept intubated and monitored in a critical care unit. In some patients, daily surgical debridement may be required. During the surgery, meticulous attention should be paid to hemostasis.
Once all the necrotic tissue is removed and there is evidence of granulation tissue, the plastic surgeon should be consulted. In most cases, primary closure is not possible and hence the plastic surgeon may be required to reconstruct the soft tissues and close the wound with a muscle flap. If there is no adequate natural skin available for a skin graft, then one may need to use artificial skin.
Another method of treatment includes the use of hyperbaric oxygenation. While the literature does suggest this modality can be used, most of these patients are in the intensive care unit attached to a variety of medical equipment, thus making the journey to the hyperbaric oxygen therapy facility difficult. For small wounds, hyperbaric oxygen therapy may be effective, but for large wounds, there is no evidence that this therapy improves healing or prolongs life. Finally, it should be noted that hyperbaric oxygen therapy is an adjunctive treatment and not a substitute for surgical debridement.
Necrotizing fasciitis is a life-threatening disorder which carries a mortality ranging from 20% to 80%. Risk factors for adverse outcomes include advanced age, resistant organism, delay in therapy, multiorgan failure, and infection site.
Necrotizing is a life-threatening disorder with a very high mortality rate. Any delay in diagnosis or treatment usually results in a poor outcome. The disorder is best managed by a team of healthcare professionals that includes a urologist, general surgeon, an infectious disease expert, intensivist, nephrologist, and radiologist. The role of the nurse and pharmacist is also of critical importance. The nurse is often the first to recognize that the patient is critically ill or in pain. The patient should be kept NPO, hydrated and immediately covered with broad-spectrum antibiotics. The pharmacist should check cultures and ensure that the right antibiotics are used to cover the offending organism. The stoma nurse should be consulted because many of these patients also need a fecal diversion to prevent contamination of the perineum. These patients are best managed in the ICU until signs of toxicity diminish. Only through a systemic approach with close collaboration can the mortality of this condition be lowered. (Level V)
Necrotizing fasciitis is a serious disorder that carries a mortality rate of anywhere from 30-90%. The mortality ultimately depends on patient age, type of organism, the speed of diagnosis and treatment and patient comorbidity. The worst prognosis is in patients with specific streptococcal strains. Other factors that adversely affect prognosis include loss of consciousness, respiratory distress, renal failure, and ARDs. Survival is best for patients who have an immediate radical debridement, hydration, and broad-spectrum antibiotics. Even after treatment, survivors of the disorder tend to have a shorter lifespan than age-matched controls. (Level V)
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