Introduction

Rhabdomyolysis is the result of breakdown of muscle tissue, with the subsequent release of muscle products into the bloodstream.

Aetiology

Causes
  • Trauma – most common
  • Prolonged immobilisation
  • Drug reactions – e.g. statins, fibrates, alcohol, ecstacy, heroin, carbon monoxide, neuroleptic malignant syndrome
  • Infection – coxackie, EBV, influenza
  • Metabolic disorders
  • Genetic muscular disorders – e.g. McArdle’s disease, Duchenne’s muscular dystrophy
 

Pathology

The breakdown of muscle tissue release several products into the blood, including:
 

Signs & Symptoms

  • Often associated with the cause
  • Muscle aches
  • Oedema
  • Red-brown urine
 

Complications

Investigations

  • Bloods
    • ↑CK > 1000iU/L
    • U+E’s – hyperkalaemia
  • Urine Dipstick
    • +ve for haemoglobin, but absence of red cells on microscopy – due to myoglobin

Treatment

  • URGENT – treat hyperkalaemia (if >6.5mmol/L, or ECG changes)
    • Untreated, it can cause VENTRICULAR FIBRILLATION
      • Other ECG changes include; ‘tented T waves’, flat p waves, increased PR interval, wide QRS – which can get wider and wider, resulting in VT and VF
    • Treatment
      • IV calcium gluconate – this provides cardioprotection but does not alter serum potassium concentration
      • Insulin + glucose – e.g. 20U insulin + 50g glucose 50% IV. Insulin is taken up into cells in conjunction with potassium, thus, serum K is lowered
      • Nebulised salbutamol – also moves K into cells
      • Polysytrene sulfonate resin – 15g/8h in water, or can be given as an enema if vomiting present (can cause vomiting)
      • Dialysisrarely needed
  • IV fluids
    • Reduce the risk of ARF
    • Keep urine output at >300ml/hour until myoglobinurea is resolved
    • 1.5L/hour may be required
  • IV sodium bicarbonate
    • Can be useful to increase the urine pH >6.5, which makes myoglobin less toxic
  • With treatment, most patients make a full recovery (as the cause is usually identifiable and resolvable), without any long-term effects

 

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