Rhabdomyolysis

Question 1

what is rhabdomyolysis?

Answer 1

a condition where skeletal muscle breaks down and releases breakdown products into the blood

e.g triggered by extreme over use or underuse or a traumatic injury

Question 2

cell death of muscle cells

Answer 2

myocytes undergo apoptosis, they release;

• myoglobin (can cause myoglobinuria)
• potassium (dangerous- hyperkalaemia and cardiac arrhythmia)
• phosphate
• creatinine kinase

when these breakdown products are filtered by the kidney this can cause injury to the kidney. myoglobin is toxic to the kidney in high concentrations- AKI

Question 3

causes of rhabdomyolysis

Answer 3

1. underuse= prolonged immobility e.g frail patient has a fall and spends time on the floor before being found
2. extreme rigorous exercise - beyond the fitness level oft that individual (ultra marathon, triathlon, crossfire comp)
3. crush injuries
4. seizures

Question 4

signs and symptoms of rhabdomyolysis

Answer 4

Muscle aches and pain
Oedema
Fatigue
Confusion (particularly in elderly frail patients)
Red-brown urine (myoglobinuria)

Question 5

what are the investigations fro rhabdomyolysis?

Answer 5

bloods:

• creatinine kinase (CK) >thousands/L typically rises until 12 hours, remains elevated for 1-3 days then falls
• *key investigation**
• myoglobin (myoglobinurea) a red brown colour. urine dipstick will be positive for blood
• U+E’s for AKI and hyperkalaemia
• ECG (to assess heart response to K+)

Question 6

how do we manage rhabdomyolysis?

Answer 6

suspect in trauma, crush injury, prolonged immobilisation, excessive exercise

treatment:
IV fluids (rehydrate and encourage filtration of breakdown products)

IV sodium bicarbonate (to make the urine more alkaline which will reduce toxicity of myoglobin)

IV mannitol (to increase GFR to help flush breakdowna nd reduce oedema around muscles and nerves) correct any hypovolemia first

treat any complications e.g. K+