Rhabdomyolysis

Question 1

How does rhabdomyolysis occur?

Answer 1

Normally, ion channels on the plasma membrane of muscles maintain low intracellular Na+ and Ca2+ concentrations, and high K+ concentrations. Muscle depolarisation results in an influx of calcium causing the muscle to contract (ATP-dependent).

When a muscle injury or ATP depletion occurs:
1. Excessive intracellular influx of Na+ (increases water flow into cell) and Ca2+ (sustained contraction which further depletes ATP).
2. The elevation of calcium also activates calcium-dependent proteases and phospholipases, promoting lysis of the cellular membrane and causing further damage to ion channels.
3. This can result in an inflammatory cascade which causes necrosis of the muscle fibres and releases the muscle contents into the extracellular space and the blood stream.

Question 1

What is rhabdomyolysis?

Answer 1

TGhe breakdown of skeletal muscle fibres and release of muscle cell (myocyte) contents, myoglobin, electrolytes, and proteins into the blood.

Question 2

What are some causes of rhabdomyolysis?

Answer 2

Statin use
Trauma
Exercise
Heat stroke
Neuroleptic malignant syndrome (NMS)
Malignant hyperthermia

Question 3

What are symptoms of rhabdomyolysis?

Answer 3

Muscle pains and aches
Dark coloured urine (due to presence of myoglobin)
Fatigue and weakness
Electrolyte imbalances
Hypovolemia - decreased volume of fluid in the vascular system

Question 4

What are some complications of rhabdomyolysis?

Answer 4

Electrolyte imbalances can lead to heart issues (hyperkalaemia, hypocalcemia)

AKI due to myoglobin causing renal tubule obstruction

Hypovolemia can lead to hypovolemic shock - medical emergency, organ failure

Question 5

How is rhabdomyolysis diagnosed?

Answer 5

Using a blood test to measure creatine kinase levels (5x upper limit). Creatine kinase converts creatine to creatine phosphate in the muscle which is required for muscle contraction. It is a marker of muscle breakdown.

Question 6

How is rhabdomyolysis managed?

Answer 6

Continuous assessment of airways, breathing, and circulation.
IV fluid hydration to prevent AKI and renal impairment. Maintains urine production to flush out muscle proteins and electrolytes.
Monitor with ECG for abnormal heart rhythms.
Monitor electrolytes.
Monitor eGFR and creatinine