Renal System >
Rhabdomyolysis

Clinical condition of acute kidney injury (AKI) and electrolyte abnormalities due to skeletal muscle breakdown and release of cellular contents

Risk Factors
  • Trauma
    • Crush injuries and burns, ischaemia, infection, diabetic ketoacidosis, alcoholism (DKA), falls, long lies, compartment syndrome, seizures, dehydration, medication (statins, cyclosporine, erythromycin, colchicine), recreational drugs (cocaine, amphetamines, ecstasy, LSD)
  • Exertional rhabdomyolysis
    • Exertional activity e.g. marathons, heatstroke, cold exposure, dehydration
  • Genetic and metabolic conditions
    • Genetic conditions that affect fat/lipid, carbohydrate or purine metabolism, hypothyroidism, electrolyte imbalances, carnitine deficiency, McArdle’s disease, lactate dehydrogenase deficiency, Duchenne muscular dystrophy
Aetiology
  • Muscle necrosis or myoglobinuria due to trauma or damage caused by above risk factors
Pathophysiology
  • Disruption of myocyte cellular metabolism → disruption of homeostasis + cellular necrosis → release of substances extracellularly e.g. myoglobin and electrolytes → AKI and myoglobinuria (myoglobin toxicity) + electrolyte imbalances
Clinical Presentation
  • Renal
    • Myoglobinuria (reddish-brown urine)
    • Low urine output
    • Haematuria
  • Neuromuscular
    • Muscle swelling & pain
    • Limb paraesthesia
  • General
    • Fever
    • Fatigue
    • Nausea & Vomitting
    • Confusion/Agitation
Investigations
  • Bloods:
    • Urea and Electrolytes – ↑ ­creatine kinase (5x baseline), ↑ ­creatinine, ↑ K+, ↓ Ca2+, ↑ ­PO43-
  • Imaging: n/a
  • Special:
    • Urinalysis – Any myoglobinuria or haematuria?
Management
  • Conservative: n/a
  • Medical:
    • If due to a crush injury – free trapped limb and decompress
    • Aggressive fluid therapy to replace fluid sequestered in necrotic tissue: saline 1.5L/hr and urine output maintained at 300mL/hr until myoglobinuria is resolved and normal CK → 0.45% saline with sodium bicarbonate and mannitol
    • HCO3- given to alkalinise urine to pH 6.5 → decreases myoglobin toxicity
    • Correct electrolyte abnormalities, particularly if hyperkalaemia or hypocalcaemia are life-threatening → haemodialyses may be needed
  • Surgical: n/a
Complications
  • Short-term
    • Hyperkalaemia
    • Hypocalcaemia
    • Hepatic inflammation
    • Cardiac arrhythmia
    • Cardiac arrest
    • Compartment syndrome.
  • Long-term
    • Acute renal failure
    • DIC
    • Compartment syndrome.

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