Necrotising infections of the skin and soft tissues

Invasive infections of the soft tissues: skin, subcutaneous tissue, superficial or deep fascia, muscles. They include necrotising cellulitis, necrotising fasciitis, myonecrosis, gas gangrene, etc.

Clinical presentation depends on the causative organism and the stage of progression. Group A streptococcus is frequently isolated, as are Staphylococcus aureus, enterobacteriaceae and anaerobic bacteria including Clostridium sp.

Delay in treatment of a minor wound or certain types of wounds (gunshot wounds or stabbings, open fractures or non-sterile intramuscular injections/circumcisions) or certain infections (varicella or omphalitis), favours the development of a necrotising infection. Patient risk factors include immunosuppression, diabetes, malnutrition and advanced age.

A necrotising infection is a surgical emergency and has a high mortality rate.

Clinical features

• Initial signs and symptoms include erythema, oedema and pain disproportionate to appearance of infection. Location depends on the portal of entry. It may be difficult to differentiate necrotising infections from nonnecrotising infections (see Erysipelas and cellulitis, Chapter 4). Systemic signs of infection (fever, tachycardia etc.) may be present.
• Lesions progress rapidly despite antibiotic therapy, with the development of the typical signs of a necrotizing infection: haemorrhagic blisters and necrosis (cold bluish or blackish hypoaesthetic macules).
• Signs of late infection: crepitus on palpation and fetid odour (gas gangrene) with signs of severe systemic infection (see Shock, Chapter 1).

Laboratory

• If available, the following tests can help identify an early necrotising infection: white blood cell count > 15 000/mm³ or < 4000/mm³; serum creatinine > 141 micromol/litre; serum glucose > 10 mmol/litre (180 mg/dl) or < 3.3 mmol/litre (60 mg/dl). However, normal results do not exclude a necrotising infection.
• Obtain specimens for bacterial culture in the operating room and blood cultures if possible. 

Paraclinical investigations

Radiography: may demonstrate gas in muscles or along the fascia planes. Can rule out foreign body, osteomyelitis or osteosarcoma.

Treatment

Prompt surgical management accompanied by IV antibiotic therapy is essential to reduce the high mortality. Refer immediately to a surgeon. Start resuscitation if necessary (see Shock, Chapter 1).

• Emergency surgical treatment:
  • Debridement, drainage, wide excision of necrotic tissue and rapid amputation if necessary.
  • Surgical re-evaluation within 24 to 36 hours to check for eventual progression of the necrosis and need for further debridement.

• IV antibiotic therapy for at least 14 days or more depending on clinical response:
  cloxacillin + ceftriaxone + clindamycin or amoxicillin/clavulanic acid + clindamycin. For doses, see below.

cloxacillin IV infusion (60 minutes) a Citation a. Cloxacillin powder for injection should be reconstituted in 4 ml of water for injection. Then dilute each dose of cloxacillin in 5 ml/kg of 0.9% sodium chloride or 5% glucose in children less than 20 kg and in a bag of 100 ml of 0.9% sodium chloride or 5% glucose in children 20 kg and over and in adults.
Children < 40 kg: 50 mg/kg every 6 hours
Children ≥ 40 kg and adults: 3 g every 6 hours

ceftriaxone slow IV (3 minutes) or IV infusion (30 minutes) b Citation b. For administration by IV route, ceftriaxone powder should to be reconstituted in water for injection only. For administration by IV infusion, dilute each dose of ceftriaxone in 5 ml/kg of 0.9% sodium chloride or 5% glucose in children less than 20 kg and in a bag of 100 ml of 0.9% sodium chloride or 5% glucose in children 20 kg and over and in adults.
Children 1 month and over: 100 mg/kg once daily
Adults: 2 g once daily

clindamycin IV infusion (30 minutes) c Citation c. Dilute each dose of clindamycin in 5 ml/kg of 0.9% sodium chloride or 5% glucose in children less than 20 kg and in a bag of 100 ml of 0.9% sodium chloride or 5% glucose in children 20 kg and over and in adults.
Neonates 0 to 7 days (< 2 kg): 5 mg/kg every 12 hours
Neonates 0 to 7 days (≥ 2 kg): 5 mg/kg every 8 hours
Neonates 8 days to < 1 month (< 2 kg): 5 mg/kg every 8 hours
Neonates 8 days to < 1 month (≥ 2 kg): 10 mg/kg every 8 hours
Children 1 month and over: 10 to 13 mg/kg every 8 hours (max. 2700 mg daily)
Adults: 900 mg every 8 hours

amoxicillin/clavulanic acid (co-amoxiclav) slow IV injection (3 minutes) or IV infusion (30 minutes) d Citation d. Dilute each dose of amoxicillin/clavulanic acid in 5 ml/kg of 0.9% sodium chloride in children less than 20 kg and in a bag of 100 ml of 0.9% sodium chloride in children 20 kg and over and in adults. Do not dilute in glucose.
Children less than 3 months: 50 mg/kg every 12 hours 
Children ≥ 3 months and < 40 kg: 50 mg/kg every 8 hours (max. 6 g daily)
Children ≥ 40 kg and adults: 2 g every 8 hours

• Other treatments:
  • Deep vein thrombosis prophylaxis;
  • Appropriate management of pain (see Pain, Chapter 1);
  • Early nutritional support.