Necrotizing fasciitis (NF) is a deep-seated infection of the subcutaneous tissue that progresses rapidly along fascial planes with severe systemic toxicity and 20-40% mortality. NF leads to progressive destruction of fascia, subcutaneous fat, and muscles, usually with resulting necrosis of the overlying skin. Bacteria enter the skin through a cut or scratch; the most common offenders are Group A streptococcus (Streptococcus pyogenes), Staphylococcus aureus, Clostridium perfringens, Bacteroides fragilis, Aeromonas hydrophila, and Klebsiella. NF is classified into four major categories: Type 1 is polymicrobial involving at least one anaerobe with or without a facultative anaerobe (a microorganism that can live and grow with or without molecular oxygen) and is localized on the trunk, abdomen, or perineum; Type 2 is monomicrobial, usually caused by group A beta hemolytic streptococci and/or other streptococci or staphylococci and occurs on the extremities. Type 3 is monomicrobial usually involving Clostridium or Gram-negative bacteria and is associated with crush injuries or surgical wounds, causing crepitus in the wound and subcutaneous gas. Type 4 in caused by fungal infection, usually Candida spp, and is rare, aggressive, and usually on immune-suppressed patients.1 In all types, the bacteria release toxins that produce an exotoxin which in turn activates T cells. This process produces increased cytokines that lead to severe systemic symptoms known as toxic shock syndrome, which can be fatal if the initial necrosis is not immediately controlled.
Risk factors for NF include IV drug use, diabetes, renal failure, pulmonary diseases, liver cirrhosis, peripheral vascular disease, obesity, malnutrition, and drug abuse. A 50% mortality rate is associated with any combination of three or more risk factors. The exception to this is the pediatric population in which NF is rare, but may occur in healthy children following minor lesions that become infected.
Clinical Presentation NF is frequently preceded by a minor skin trauma that serves as a portal for the causative bacteria. This is followed by a sequence of the following clinical manifestations:
- Low-grade fever
- Pain, usually out of proportion to the initial clinical findings
- Swelling with massive, “sausage-like” edema
- Erythema with bullous skin changes
- Lack of adenopathy, misses immune recognition
- Skin necrosis with hypoesthesia or anesthesia
- Striking indifference to one’s clinical state
- Toxic-shock appearance with rapid demise
- Cellulitis—all of the signs of NF may not be present initially, leading to an early misdiagnosis of cellulitis.
- Gas gangrene
Medical Management Medical management includes appropriate antibiotics, aggressive and immediate surgical debridement of all infected subcutaneous and dermal tissue (the saying is that the patient goes straight from the ER to the OR), and medical stabilization as needed. Adjunctive hyperbaric oxygen therapy may be beneficial in promoting healing after all infected tissue is removed.
Wound Management Wound management depends on the extent of surgical debridement, as well as the amount and quality of the residual soft tissue. If there is concern about continued infection, antimicrobial dressings are used, for example, Nano crystalline silver, half or quarter strength Dakin solution (unless there is granulation tissue), or acetic acid washes for pseudomonas. Once the wounds are more than 70% clean, negative pressure wound therapy is useful to facilitate wound contraction and angiogenesis in preparation for skin grafts or flaps. Pain management during wound care is essential, as well as nutritional supplements for adequate caloric and protein intake. If the wounds are extensive, physical and occupational therapies are needed to optimize strength, range of motion, and function.
In summary, the most important aspects of treating NF are timely diagnosis of the infection, immediate surgical debridement, meticulous wound care, and rehabilitation during and after wound healing.
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