Necrotising fasciitis

• Necrotising fasciitis (NF) is a rare but life-threatening infection involving any layer of the deep soft tissue compartments (i.e. dermis, subcutaneous tissue, fascia or muscle).
• Aetiology:

  • Occurs when organisms migrate from subcutaneous tissue along fascial planes
  • Although muscle is typically spared by the organisms themselves, necrosis of muscle tissue can still occur because of compartment syndrome
  • Wide range of causative organisms - group A streptococcus, gram-negative organisms (Vibrio spp and Aeromonas hydrophilia - seawater contamination), fungal infection
  • In many cases the cause is polymicrobial
• Risk factors:

  • Skin injury - bites, trauma
  • Impaired immunity
  • IV drug use
• Typical symptoms:

  • Pain which is out of proportion to the clinical findings
  • Skin discolouration
  • Skin blistering
  • Fever
  • Malaise
• Clinical exam:

  • Local pain, swelling and erythema
  • Poorly defined margins with pain extending beyond the margins of erythema
  • Crepitus on palpation of the skin
  • Offensive discharge which may have a typical 'dishwater' appearance (grey, murky)
  • Oedema - which may be tense
  • Bullae
• Systemic features:

  • Fever
  • Hypotension and tachycardia
• Lab investigations:

  • FBC - significantly raised WCC
  • U&Es - hyponatraemia
  • CRP - elevated
  • CK - elevated if muscle involvement
  • Lactate - elevated
  • Blood cultures
  • Coagulation screen, and group and save as part of pre-op work up
• Microbiological investigations:

  • Blood cultures
  • Wound swabs
  • Debrided tissue gram-stain and culture
• Imaging:

  • Although imaging can be useful, should not delay emergency surgical management
  • CT - may reveal gas produced by the organisms and help assess the extent of spread
• Bedside finger test sometimes performed by plastic surgeons:

  1. Small incision is made down to the fascia under local anaesthetic
  2. Tissue is probed with a sterile gloved finger

  • Findings associated with NF = absence of bleeding, purulent pus and lack of normal tissue resistance to blunt dissection
• Diagnosis:

  • Necrotising fasciitis is a clinical diagnosis, but investigations can help inform further medical and surgical management.
• Medical management:

  • ABCDE assessment - treat issues such as haemodynamic instability
  • IV broad-spectrum antibiotics
• Surgical management:

  • Urgent surgical debridement is required to remove the infected tissue in the hope of halting further spread of the infection to surrounding tissue
  • After initial debridement, the wound is monitored and may require further debridement until the infection is controlled
• Types of NF depend on the organism:

  • Type I - more than one type of bacteria involved
  • Type II - due to streptococcus and staphylococcus
  • Type III - gas gangrene often due to clostridium
  • Other/type IV - marine organisms and fungal infections
• The bacteria multiply and release toxins and enzymes that result in thrombosis in the blood vessels. The result is the destruction of the soft tissues and fascia.
• •In children, type II necrotising fasciitis may complicate chickenpox.

  •Other causes in children include omphalitis, necrotising enterocolitis.