Necrotising Fasciitis

Definition

Rare but very severe bacterial infection of deep fascia with secondary necrosis of soft tissue (e.g. muscle, skin).

Aetiology

Type I – Polymicrobial

· Mixed aerobic and anaerobic bacteria

Type II - Monomicrobial

· Group A Streptococcus (e.g. Streptococcus pyogenes)

· Staphylococcus aureus (commonly MRSA)

Pathogenesis

Trauma causing the breaking of skin (e.g. surgery, cut, scratch) allows bacteria to enter body. The bacteria colonises soft tissue and spreads in the fascial plane, releasing toxins which destroy the soft tissue. Certain toxins can cause systemic effects (e.g. renal failure, septic shock).

Signs and Symptoms

Symptoms start at site of infection – intense pain in excess of that expected with visual inspection. Signs of inflammation apparent – redness, swelling, heat. Spread of infection leads to a rapidly growing bronze- or purple-coloured patch. Within an hour, the skin may break open and exudation may occur.

Generalised signs and symptoms: malaise, fever, sweating, chills, nausea, dizziness, weakness, shock.

Without treatment, death can occur rapidly (73% untreated mortality rate).

Investigations

CT scan to view extent of necrosis.

Culture to confirm bacteria and determine antibiotic use.

Management

Before culture results, presumptive broad-spectrum aggressive intravenous antibiotic therapy. Intravenous donor antibodies. Targeted antibiotic therapy after identification of pathogenic bacteria.

Surgery to drain infected areas and debridement of necrotic tissue. Consider amputation if infection cannot be controlled. Skin grafting after infection cessation.

Hyperbaric oxygen therapy if bacteria is anaerobic.

Prognosis

Scarring and deformity common.

High death rate even with aggressive treatment.

Complications

Local progressive tissue damage, systemic infection (sepsis, shock), scarring and disfiguration, functional limb loss, death.

Prevention

Proper asepsis following penetrative trauma and surgical incisions.