Rhabdomyolysis

Question 1

What products are released during myocyte death?

Answer 1

Myoglobin (causing myoglobinuria)

Potassium

Phosphate

Creatine kinase

Question 2

What is rhabdo?

Answer 2

Rhabdomyolysis is a condition where skeletal muscle tissue breaks down and releases breakdown products into the blood.

This is usually triggered by an event that causes the muscle to break down, such as extreme underuse or overuse or a traumatic injury.

Question 3

Complications of rhabdomyolysis:

Answer 3

1. Hyperkalaemia - can cause arrhythmias and potentially cardiac arrest
2. AKI - from toxic breakdown products such as myoglobin
   • AKI causes toxic breakdown products to further accumulate in the blood

Question 4

Causes of rhabdomyolysis

Answer 4

Anything that causes significant damage to muscle cells can cause rhabdomyolysis:

• Prolonged immobility, particularly frail patients that fall and spend time on the floor before being found
• Extremely rigorous exercise beyond the person’s fitness level (e.g. ultramaraton, triathalon, crossfit competition)
• Crush injuries
• Seizures

Question 5

Signs and symptoms of rhabdomyolysis

Answer 5

Muscle aches and pains

Oedema

Fatigue

Confusion (particularly in elderly patients)

Red-brown urine

Question 6

Investigations and findings in rhabdomyolysis:

Answer 6

Creatine kinase (CK):
 - key investigation in establishing the diagnosis. It will be in the thousands to hundreds of thousands of Units/L. CK typically rises until 12 hours, then remains elevated for 1-3 days, then falls gradually. A higher CK increases the risk of kidney injury.

Myoglobinurea - myoglobin in urine, gives it red/brown colour
- urine dipstick will be positive for blood

U&Es:
- Signs of AKI and hyperkalaemia

ECG - important in assessing hearts response to hyperkalaemia

Question 7

management of rhabdomyolysis:

Answer 7

IV fluids are the mainstay of treatment.
The aim is to rehydrate the patient and encourage filtration of the breakdown products.

Consider IV sodium bicarbonate.
This aims to make the urine more alkaline (pH ≥ 6.5), reducing the toxicity of the myoglobin on the kidneys. The evidence on this is not clear and there is some debate about whether to use it.

Consider IV mannitol.
This aims to increase the glomerular filtration rate to help flush the breakdown products and to reduce oedema surrounding muscles and nerves. Hypovolaemia should be corrected before giving mannitol. The evidence on this is not clear and there is some debate about whether to use it.

Treat complications, particularly hyperkalaemia.
Hyperkalaemia can be immediately life threatening as it can cause arrhythmias (particularly ventricular fibrillation).