Electrolyte disorders are a significant cause of morbidity and mortality for adults in the intensive care unit and hospital. Hypocalcemia occurs in 15% to 88% of hospital admissions. The incidence of ionized hypocalcemia has been reported at 15% to 50% in patients in the intensive care unit.1  Another 15% of hospitalized adults demonstrate hypercalcemia.2  The purpose of this column is to explain the actions of calcium on cardiac depolarization and repolarization and explore the manifestations of serum calcium derangements in a 12-lead electrocardiograph (ECG) tracing. We report the diagnosis and management of 2 composite scenarios that illustrate hypocalcemia and hypercalcemia with illustrative ECGs.

M.K., a 50-year-old white woman, presented to the preadmission testing area prior to a scheduled surgery for an elective tonsillectomy for airway obstruction. During the review of systems, she reported feeling “weak and tired,” with new muscle cramps and circumoral paresthesia. Her surgeon was not...

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