Rhabdomyolysis

Question 1

How does Rhabdomyolysis present?

Answer 1

Mostly asymptomatic

If electrolyte imbalance and AKI → Life threatening

Question 2

Name some common causes of Rhabdomyolysis

Answer 2

Traumatic - Crush injury, struggling against restraints, Tibial/Femoral fracture → Compartment syndrome

Non-traumatic exertional - Marathon runners, Hypokalaemia (K⁺ needed for muscle perfusion)

Non-traumatic, non-exertional - alcohol/opiates → immobilisation, infection: HIV/HSV/EB

Question 3

What is the aetiology of Rhabdomyolysis?

Answer 3

Muscle breakdown, release of contents

Obstruction with haem pigment casts

Proximal tubular injury by haem iron

Volume depletion - 10-12L of flluid accumulate in damaged muscles within 24-48h of injury

Question 4

What are the signs of Rhabdomyolysis?

Answer 4

Red to brown urine - pigmented granular casts

Elevated serum enzyme level: CK, LDH

Electrolyte abnormalities: Hypocalcaemia (calcium deposit in damaged muscles) → when recover, calcium released → Hypercalcaemia

Also: Hyperkalaemia, hyperphosphataemia, hyperuricaemia

Question 5

How do you prevent Rhabdomyolyis?

Answer 5

Fluid repletion (isotonic saline) - improve renal perfusion, washout obstructing casts by increasing urine output. Monitor for fluid overload → oedema

Forced alkaline diuresis:

• Sodium bicarbonate - alkalinise urine → forced diuresis; reduces myoglobin precipitation with Tam-Horsfall protein; reduces free radical release from myoglobin
• Mannitol - forced diuresis; free radical scavenger. Do not use if kidney failure already present (increased plasma osmolality, volume expansion, can → pulmonary oedema)

Question 6

What is the treatment for Rhabdomyolysis?

Answer 6

Dialysis

Monitor for compartment syndrome

Manage electrolyte imbalance