Rhabdomyolysis is associated with which electrolyte disturbance?

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Rhabdomyolysis causes massive release of intracellular contents from damaged muscle into the bloodstream. Potassium is mainly inside cells, so when muscle tissue breaks down, a large amount of potassium spills into the extracellular space, producing hyperkalemia. This is the most clinically important electrolyte change because it can cause dangerous cardiac arrhythmias, so monitoring potassium and ECG changes is a priority and treatment focuses on stabilizing the heart and moving potassium back into cells (eg, calcium for membrane stabilization if needed, insulin with glucose, bicarbonate, or other measures).

Early in rhabdomyolysis, calcium may be low because calcium is deposited in damaged muscle and phosphate is released; calcium often normalizes or may become high during recovery, but the immediate, hallmark electrolyte disturbance is hyperkalemia. Hypernatremia or hyponatremia are not typical defining features of rhabdomyolysis.