Profound hyperkalemia without electrocardiographic manifestations.

Although the electrocardiogram (ECG) is not considered a reliable indicator of mild to moderate hyperkalemia, profound elevations of serum potassium concentration generally produce classic ECG manifestations. We report two cases of severe hyperkalemia (greater than 9.0 mEq/L) in which the ECGs did not reveal the expected manifestations of hyperkalemia. Thus, even with profound serum potassium elevations, the ECG cannot reliably be used to exclude the presence of hyperkalemia or to monitor therapy designed to lower the serum potassium concentration.