Is hypercalcaemia immediately life-threatening? A prospective study.

Objective: Hypercalcaemia is often considered as an emergency because of a potential risk of life-threatening arrhythmias or coma. However, there is little evidence, apart from case studies, that hypercalcaemia can be immediately life-threatening. The aim of our study was to prospectively assess whether hypercalcaemia (Ca ≥ 3 mmol/L) was associated with immediately life-threatening complications. Design and methods: We conducted a prospective observational study aiming to include the first one hundred patients aged ≥18 who had a calcium concentration ≥3 mmol/L, admitted to the emergency department (ED). The primary outcome was the number of life-threatening cardiac arrhythmias (ventricular tachycardia, ventricular fibrillation, sinus arrest and second- or third-degree atrioventricular blocks) or neurological complications defined by a Glasgow Coma Scale score <9 during the stay in the ED. The secondary outcomes were correlation between calcium concentrations and ECG (electrocardiogram) QTc intervals, Glasgow Coma Scale scores and mortality during the following 12-month follow-up period. Results: The median calcium concentration was 3.3 mmol/L (3.1-3.7). Cancer was the first cause of hypercalcaemia. No patient presented a life-threatening cardiac arrhythmia during their stay in the ED. Three patients presented a life-threatening neurological complication. There was no correlation between calcaemia and QTc intervals or Glasgow Coma Scale score. Prognosis was poor, and 43 patients died during the 12 months. Conclusions: We found no cases of immediately life-threatening cardiac arrhythmias. Three patients had indeed a life-threatening neurological complication but always had at least one other major factor that could severely alter mental status, such as profound metabolic acidosis. Significance statement: This paper aims to revisit what most physicians, whether specialists or not, consider to be scientifically proven facts concerning the immediate threat caused by hypercalcaemia. Its novelty is threefold: first, this is the only prospective study that exists to date studying the life-threatening consequences of hypercalcaemia; second, having included one hundred patients, we found no life-threatening cardiac arrhythmias, which is not what would be expected if one reads guidelines concerning hypercalcaemia; and third, life-threatening neurological complications were very rare and only occurred in patients with at least one other major cause of altered neurological status, such as severe metabolic acidosis or hypernatraemia.