Necrotising infections of the skin and soft tissues


– These infections are characterized by the invasion of the soft tissues: skin, subcutaneous tissue, superficial or deep fascia, muscles. They include necrotizing cellulitis, necrotizing fasciitis, myonecrosis, gas gangrene, etc.

– The 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 spp.

– The delay in treatment of a minor wound and certain types of wounds such as gunshot wounds or stabbings, open fractures or non-sterile intramuscular injections/circumcisions, favour the development of a necrotizing infection. The risk factors for a necrotizing infection are immunosuppression, diabetes, malnutrition and advanced age in adults and malnutrition, varicella and omphalitis in children.

– A necrotizing infection is a surgical emergency and has a poor prognosis.

Clinical features

– Early in the infection, it may be difficult to differentiate necrotizing infections from nonnecrotizing infections. Initial signs and symptoms of erythema, swelling and pain can resemble cellulitis. Location depends on the portal of entry.

– Lesions progress rapidly despite antibiotic therapy, with the development of the typical signs of a necrotizing infection: pain disproportionate to appearance and tense oedema outside the area of erythema, followed by haemorrhagic blisters and necrosis (cold bluish or blackish hypoaesthetic macules).

– Signs of late infection: crepitus on palpation and fetid odour (gas gangrene).

– Necrotizing infections are associated with signs of a severe systemic infection: altered mental status, hypotension and shock.

Laboratory

– If available, the following tests can help identify an early necrotizing 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).

– Obtain specimens for bacterial culture in the operating room and blood cultures if possible.

Treatment

Prompt surgical management accompanied by IV antibiotic therapy may at times reduce the high mortality. In case of septic shock, stabilize the patient prior to surgical transfer.

– 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.

– Triple antibiotic therapy for at least 10 to 14 days or more depending on clinical response:
amoxicillin/clavulanic acid (co-amoxiclav) slow IV injection (3 minutes) or IV infusion (30 minutes)1
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
or
ceftriaxone 
slow IV (3 minutes) or IV infusion (30 minutes)2
Children 1 month and over: 100 mg/kg once daily
Adults: 2 g once daily
+
clindamycin IV infusion (30 minutes)3
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
+
gentamicin slow IV injection (3 minutes) or IV infusion (30 minutes)3
Neonates 0 to 7 days (< 2 kg): 3 mg/kg once daily
Neonates 0 to 7 days (≥ 2 kg): 5 mg/kg once daily
Neonates 8 days to < 1 month: 5 mg/kg once daily
Children 1 month and over and adults: 6 mg/kg once daily

Stop gentamicin after 48 hours if on surgical second look there is no evidence of progression of necrosis or if cultures do not grow Pseudomonas aeruginosa.

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



Footnotes
Ref Notes
1 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 over 20 kg and in adults. Do not dilute in glucose.
2

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 over 20 kg and in adults.

3 Dilute each dose of clindamycin or gentamicin 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 over 20 kg and in adults. [ a b ]