Which electrolyte abnormality in rhabdomyolysis can lead to cardiac arrest?

• A. Hyperkalemia
• B. Hypokalemia
• C. Hypercalcemia
• D. Hyponatremia

Answer: (A)

Rhabdomyolysis releases intracellular potassium into the bloodstream, causing hyperkalemia, which is the electrolyte abnormality most likely to trigger cardiac arrest. Potassium levels outside the normal range disrupt cardiac electrical activity: elevated extracellular potassium depolarizes the resting membrane potential and inactivates sodium channels, slowing conduction and predisposing to dangerous rhythms. As potassium rises, ECG changes progress from tall, peaked T waves and widened QRS to a sine-wave pattern and ultimately pulseless arrest. Other electrolyte disturbances seen with rhabdomyolysis, such as low potassium, high calcium, or low sodium, do not carry the same immediate risk of arrest in this context.