Critical Care Hypercalcemia — a Hyperparathyroid State

Summary

Hypocalcemia is a well known finding in critically ill patients. Subsequent occurrence of mild hypercalcemia has also been reported.

In order to investigate the incidence and nature of critical care hypercalcemia serum calcium was measured in 83 critically ill ICU patients (TISS score ≥ 40) and related to the occurrence of acute renal failure (ARF) and severity of illness, evaluated by the APACHE-II and the multiple organ failure scoring systems.

Thirty-two percent of the patients developed hypercalcemia (serum calcium ≥2.60 mmol/1) during their ICU stay. These hypercalcemic episodes (mean maximal value 2.71 ± 0.12 mmol/1) were more common and occurred earlier in patients with co-existing ARF. However, multiple regression analysis showed the number of failing organ systems in the first days to be the best predictors for later occurrence of hypercalcemia (p < 0.0001).

When serum parathyroid hormone (PTH) was measured in 6 of the patients without ARF during their hypercalcemic episodes, PTH was not suppressed but slightly elevated, to a similar extent as in patients with mild primary hyperparathyroidism.

In conclusion, a high incidence of hypercalcemia was found in critically ill ICU patients. The hypercalcemia was mild and was more frequently found in patients with co-existing renal failure. The most powerful predictor to later occurrence of hypercalcemia was however the severity of the illness in itself. The raised levels of PTH found during the hypercalcemic episodes suggest ICU hypercalcemia to be caused by parathyroid overactivity.

Key words

Critical care - Calcium - Hypercalcemia - Parathyroid hormone - Hyperparathyroidism