Rhabdomyolysis

Question 1

What is rhabdomyolysis?

Answer 1

Muscle necrosis and release of intracellular constituents into the circulation

Question 2

Describe the presentation of rhabdomyolysis

Answer 2

Asymptomatic

Life threatening electrolyte imbalanc & AKI

Question 3

List the four main causes of rhabdomyolysis

Answer 3

Traumatic

Non-traumatic - Exertional vs. Non-exertional

Electrolyte imbalance

Endocrine

Question 4

What traumatic causes can cause rhabdomyolysis?

Answer 4

Exertional
- marathon runners, hot weather, hypokalaemia, prolonged convulsions, metabolic myopathy, malignant hyperthermia, hypothermia

Non-exertional

• alcohol, opiates = immobilisation
• statins, colchchine, cyclosporin
• infections - HIV, HSV, EBV

Question 5

What electrolyte imbalances can cause rhabdomyolysis?

Answer 5

Hypokalaemia

Hypophosphataemia

Question 6

What endocrine conditions can cause rhabdomyolysis?

Answer 6

DKA, HONK

Hypothyroidism

Question 7

Why does rhabdomyolysis cause AKI?

Answer 7

Obstruction with haem pigment casts

Proximal tubular injury by haem iron

Volume depletion
- 10-12L of fluid may accumulate in damaged muscles within 24-48 hrs post-injury

Question 8

How should rhabdomyolysis be diagnosed?

Answer 8

Red to brown urine - pigmented granular casts, red to brown supernatant

Elevated serum enzyme level - CK, LDH

Electrolyte abnormalities

• increased = K, PO4, Uric acid, Ca (in recovery)
• decreased = Ca (deposition in damaged muscles)

Question 9

How to prevent AKI following rhabdomyolysis?

Answer 9

Fluid repletion - saline 1-2 L/hr; Urine output=200-300mL/hr is desirable

Forced alkaline diuresis - sodium bicarbonate

Mannitol forced diuresis

Complications of alkalinisation - worsening hypocalcaemia

Complications of mannitol

Question 10

How to treat established AKI?

Answer 10

Dialysis

Monitor for compartment syndrome

Manage electrolyte imbalance