Hypocalcemia is associated with increased risk of in-hospital mortality in patients undergoing continuous renal replacement therapy with regional citrate anticoagulation: a retrospective cohort study

Regional citrate anticoagulation (RCA) is widely used in continuous renal replacement therapy (CRRT), and hypocalcemia represents one of its most serious complications. However, the association between hypocalcemia and clinical outcomes remains unclear. A retrospective cohort study was conducted utilizing a prospectively established database comprising patients who underwent CRRT with RCA at a single center from April 2018 to February 2021. The association between hypocalcemia, defined as a minimum serum ionized calcium level (iCa) < 1.0 mmol/L, and in-hospital mortality was evaluated using generalized estimating equations (GEE) models. A total of 113 patients (427 CRRT sessions) were included. Hypocalcemia occurred in 108 sessions (25.3%), with a median onset time of 2.00 h (IQR 1.00–3.00) after CRRT initiation. In the multivariable GEE analysis adjusted for presence of sepsis upon ICU admission, SOFA score on the day of CRRT initiation, minimum pH during each session, and number of CRRT sessions, hypocalcemia remained significantly associated with an increased risk of in-hospital mortality (OR 4.11, 95% CI 1.44–11.69, p < 0.05). Each 0.1 mmol/L increase in minimum iCa was associated with a 36% reduction in the risk of in-hospital mortality (OR 0.64, 95% CI 0.45–0.91, p < 0.05). Hypocalcemia was associated with an increased risk of in-hospital mortality among patients receiving CRRT with RCA, highlighting the importance of strict monitoring and timely correction of hypocalcemia in clinical practice, particularly during the early phase of RCA-CRRT. However, the observational study design precludes causal inference.