Necrotizing soft tissue infections

Skin and soft tissue infections (SSTIs) encompass a variety of pathological conditions ranging from simple superficial infections to severe necrotizing soft tissue infections.

Necrotizing soft tissue infections (NSTIs) are potentially life-threatening infections of any layer of the soft tissue compartment associated with widespread necrosis and systemic toxicity. NSTIs may involve dermal and subcutaneous components (necrotizing cellulitis), fascial component (necrotizing fasciitis), and muscular components (necrotizing myositis) either singularly or in combination.

Fournier’s gangrene is a rapidly progressive, variant of necrotizing fasciitis involving the external genitalia and perineum. Due to the complexity of fascial planes, this infection may extend up to the abdominal wall, down into the thigh, into the perirectal and gluteal spaces, and occasionally, into the retroperitoneum.

Successful management of NSTIs involves:

Prompt recognition,

Timely surgical debridement or drainage,

Resuscitation and

Appropriate antibiotic therapy.

Surgical debridement must be aggressive to halt progression of infection. Cultures of infected fluid and tissues should be obtained during the initial surgical debridement and the results used to tailor specific antibiotic management.

Radical surgical debridement of the entire affected area should be performed, continuing the debridement into the healthy-looking tissue.

In the setting of Fournier’s gangrene, diverting colostomy has been demonstrated to improve the outcome and the need for fecal diversion depends upon severity of the disease. It helps in decreasing sepsis by minimizing bacterial load in the perineal wound thus controlling infection. Diverting colostomy does not eliminate the necessity of multiple debridements, nor reduces the number of these procedures.

Any patient with extensive necrosis or who is considered to have not be adequately debrided at the initial operation should be returned to the operating room in 24–48 hours for a second look. Further debridement should be repeated until the infection is controlled.

Early appropriate empiric coverage against suspected pathogens should be initiated, based upon the clinical setting for patients with NSTI Patients whose clinical setting or gram stain suggests rapidly progressive infection potentiated by exotoxins from Gram positive pathogens (S. pyogenes, CA-MRSA, Clostridial species), treatment with antimicrobial agents should be combined with antiribosomal agents (clindamycin or linezolid). Patients who present with rapidly progressive infections with gram stains of tissue demonstrating gram negative pathogens (Aeromonas sp., Eikenella, Vibrio sp) should be treated with antiribosomal agents targeting gram negative pathogens (tetracyclines). Appropriate empiric coverage against MRSA should be immediately initiated in patients with necrotizing soft tissue infection.

Since it is impossible to exclude with certainty a polymicrobial necrotizing infection, an aggressive broad-spectrum empiric antimicrobial therapy should initially be selected to cover gram-positive, gram-negative, and anaerobic organisms until culture-specific results and sensitivities are available.

Early detection of severe sepsis and prompt aggressive treatment of the underlying organ dysfunction is an essential component of improving outcome of critical ill patients. Deep soft tissue infections may present with a fulminant course and may be associated with great morbidity and high case-fatality rates, especially when they occur in conjunction with toxic shock syndrome. After initial debridement, and early antimicrobial therapy, patients require early intensive care for haemodynamic and metabolic support. Patients may loss fluids, proteins and electrolytes from a large surgical wound. In addition hypotension is caused by vasodilation induced by the systemic inflammatory response syndrome to infection. Fluid resuscitation and analgesia are the mainstays of support for patients with advanced sepsis usually combined with vasoactive amines associated with mechanic ventilation. The aggressive nature of these infections should lead to a collaboration among all professionals involved.