Association of serum total and ionized calcium with all-cause mortality incritically ill patients with acute kidney injury.

Background: There have been no epidemiological studies exploring the prognostic ability of serum total and ionized calcium (tCa and iCa) in critically ill patients with acute kidney injury (AKI). We assessed the association of admission tCa and iCa concentrations with all-cause mortality in these patients.

Methods: We extracted clinical data from the MIMIC-III V1.4 database. Only the data for the first intensive care unit (ICU) admission of each patient were used and baseline data were extracted within 24 h after ICU admission. Cox proportional hazards models and subgroup analyses were used to determine the relationship between tCa and iCa concentrations and 30, 90 and 365-day all-cause mortality in critically ill patients with AKI. A total of 10,207 eligible patients were studied. In multivariate analysis, adjusted for age, ethnicity and gender, both low-tCa (< 7.9 mg/dl) and low-iCa (<1.06 mmol/l) concentrations were significant predictors of risk of all-cause mortality. Furthermore, after adjusting for more confounding factors, low-iCa concentrations remained a significant predictor of all-cause mortality at 30 days, 90 days, 365 days (HR, 95% CI: 1.19, 1.06-1.33; 1.15, 1.05-1.27; 1.10, 1.01-1.20).

Conclusions: Low-iCa concentrations were independent predictors of all-cause mortality in critically ill patients with AKI.