Calcium metabolism markers and their effects on mortality in COVID-19 patients admitted to intensive care unit

INTRODUCTION: To evaluate the status of serum calcium, parathyroid hormone (PTH), and 25 (OH) vitamin D and their effects on mortality in patients with COVID-19 who were admitted to the intensive care unit (ICU).
METHODS: This was a retrospective chart review. Laboratory data at ICU admission included serum creatinine, corrected calcium, phosphorus, albumin, magnesium, among others. Same laboratory measurements were repeated two more times during hospitalization. The length of ICU stay, mortality, and need for mechanical ventilation were also recorded. Hypocalcemia, hypomagnesemia, and hypovitaminosis D rates were examined along with independent predictors of in-hospital mortality.
RESULTS: A total of 100 patients were included. The median length of ICU stay was 11.0 days. Mortality rate was 52%. Rates of vitamin D insufficiency and deficiency were 29% and 52%, respectively. Thirty percent of patients had serum calcium levels less than normal. On admission, 11% of the patients had hypomagnesemia. Patients with hypomagnesemia had lower serum calcium levels compared to normomagnesemic patients (8.7±0.6 vs. 9.2±0.7 mg/dL, p=0.031). Serum PTH levels were significantly different between hypomagnesemic and normomagnesemic patients. In contrast, 25(OH)vitamin D levels were comparable in both hypomagnesemic and normomagnesemic patients. In multivariate analysis, only the need for mechanical ventilation remained as a significant predictor of in-hospital mortality.
DISCUSSION AND CONCLUSION: Hypocalcemia was less common compared to the literature, whereas Vitamin D deficiency was widespread. Serum magnesium level appeared as an important modifier of serum calcium levels in these patients. Hypocalcemia was not associated with COVID-19 disease severity or mortality.