Lesson Plan – Cellulitis

This is cellulitis. A bacterial infection of the skin that is usually unilateral and localised, but often with systemic symptoms. It affects the dermis and subcutaneous tissue.

Streptococcus pyogenes (2/3) and Staphylococcus aureus (1/3) are the most common bacterial pathogens.

1, Analgesia – Cellulitis can be really painful, so don’t forget pain relief

2, Antibiotics – In this patient with co morbodities (diabetes) and systemic symptoms intravenous therapy may be appropriate. Many hospitals may offer this on an “ambulatory” basis – ie the patient does not need to be admitted, but attends daily for antibiotics. The choice of antibiotic will depend on local guidelines and sensitivities. Usually penicillin based agents are chosen, although single daily dose cephalosporins may aid with outpatient therapy.

3, Rest and elevate

4, Treat the underlying cause if there is one.

• Pseudomonas aeruginosa, usually in a puncture wound of foot or hand
• Haemophilus influenzae, in children with facial cellulitis
• Anaerobes, Eikenella, Streptococcus viridans, due to human bite
• Pasteurella multocida, due to cat or dog bite
• Vibrio vulnificus, due to saltwater exposure, eg coral injury
• Aeromonas hydrophila from fresh or saltwater exposure, eg following leech bites
• Erysipelothrix (erysipeloid), in butchers.

If these are suspected the antibiotic choice is crucial as they may not respond to the usual treatments.

This is lipodermatosclerosis and not cellulitis. It is a chromic inflammatory condition and due to subcuteneous hardening of the skin.

In some ways it can mimic cellulitis, but is often bilateral and does not cause systemic symptoms.

Exercise may help with both weight reduction (which can be a predisposing factor) and venous insufficiency (via the muscle pump).

Compression (with compression stockings) and elevation may aid with venous drainage.

Medical treatments such as Stanozolol, Pentoxifylline, Hydroxychloroquine, Intralesional steroid injection of triamcinolone and Tetracyclines may be used, but would be outside the remit of the emergency physician. Surgery may be indicated to treat underlying venous insufficiency.

If a patient presents unwell with signs of infection then this leg rash is unlikely to be the cause and another source must be sought.

If there has been extension of the rash in the preceeding few days or there is new or worsening pain over the rash this could be superimposed infection and may be the source of the sepsis.

This patient has sepsis and needs urgent treatment. They have a low blood pressure and tachycardia and should be treatment in a high dependancy area such as Resus.

You should alert a senior colleague and start urgent fluid therapy. Broad spectrum antibiotics should be given intravenously.

This is necrotising fasciitis until proven otherwise,

Infection starts in the superficial fascia, often after minor trauma. Enzymes and proteins released by the responsible organisms cause necrosis of fascial layers.

It may be several days before the infection spreads vertically onto the skin, so patients can present late.

Thrombosis occurs as a result of the toxins released by the bacteria and may cause ischaemia and subsequent necrosis of the tissues.

Radiology – Xray, CT or MRI may all confirm the presence of gas and inflammation in the soft tissues.

The LRINEC score can be used although if the clincal suspicion is high then this score should not overrule decision making. It uses CRP, WCC, Hb, Sodium, Creatinine and Glucose.

This is a potentially life threatening condition and needs prompt identification and treatment. They can become very unwell very quickly.

Many of these patients will need intensive care involvement and admission to a critical care unit.

The patient may need surgical debridement to enable source control.

Identification of the causative organism is key to targetting treatment.