Mortality and reproducibility of calcium measurements in patients with hypercalcemia reporting to the emergency department of a tertiary German hospital

Severe hypercalcemia often results in the referral of patients to the emergency department (ED), as life-threatening consequences are feared. However, the available literature concerning the causes of hypercalcemia, mortality and therapeutic responses in these patients is scarce. We retrospectively analyzed a cohort of 1310 patients with a total serum calcium concentration ≥ 2.65 mmol/l, who reported to the ED of the University Hospital Cologne, Germany, between January 1st, 2010, and March 31st, 2021, for any reason, investigating hypercalcemia-associated diagnoses, ECG changes, symptoms of hypercalcemia, the course of calcium values over the first 5 days and hospital mortality. The most common causes of hypercalcemia were malignancies, primary hyperparathyroidism and dehydration. Patients with sarcoidosis and vitamin D intoxication had the highest mean calcium levels at presentation. In patients with mild hypercalcemia, elevated total calcium values were often not reproducible in consecutive samples. Hypercalcemia due to dehydration, sepsis and subsequent to cardiopulmonary resuscitation (CPR) resulted in lower mean calcium levels, which quickly normalized in the following days. Hypercalcemia was well controlled with the applied therapies, even in the majority of patients who died during their hospital stay. We found no major abnormalities in the ECG analysis, and no death due to cardiac arrhythmias was documented in the patient charts. The mortality rate of patients varied greatly depending on the cause of hypercalcemia. Patients with malignancies had high mortality irrespective of total calcium levels at admission, whereas patients with sarcoidosis and hyperparathyroidism had low mortality despite high calcium levels. We found no evidence for acute death due to hypercalcemia. The degree of hypercalcemia might not be the main factor influencing mortality in these patients. Given that mild hypercalcemia is often not reproducible in consecutive blood samples, persistent hypercalcemia should be confirmed before further work-up is initiated.