Association of Serum Magnesium, Total and Ionized Calcium Levels with ICU Mortality: A 208-Hospital Retrospective Analysis

Serum Magnesium and Calcium Levels Linked to ICU Mortality

  • Boyang Cai School of Public Health, Department of Preventive Medicine, Guangdong Pharmaceutical University
  • Yaoshen Liang School of Public Health, Department of Preventive Medicine, Guangdong Pharmaceutical University
  • Wenli Zheng Department of Critical Care Medicine, Guangdong Sanjiu Brain Hospital
  • Qiong Zeng Department of Critical Care Medicine, Guangdong Sanjiu Brain Hospital
  • Linfeng Ye Department of Critical Care Medicine, Guangdong Sanjiu Brain Hospital
  • Chunmei He Department of Critical Care Medicine, Guangdong Sanjiu Brain Hospital
DOI: https://doi.org/10.5937/jomb0-59611
Keywords: Ionized Calcium, ICU Mortality, Electrolyte Imbalance, Critical Care, Electrolyte Management

Abstract


Background: To investigate the associations of serum magnesium, total calcium, and ionized calcium levels with ICU mortality, addressing conflicting evidence on electrolyte imbalances in critically ill patients.
Methods: This retrospective cross-sectional study analyzed 16,249 adult ICU patients from 208 U.S. hospitals (2014-2015) using the eICU Collaborative Database. Serum magnesium, total calcium, and ionized calcium levels were measured within 24 hours of ICU admission. ICU mortality was the primary outcome. Multivariate logistic regression, adjusted for 15 confounders (e.g., age, sex, APACHE scores, comorbidities), and restricted cubic spline (RCS) models assessed linear and non-linear associations, with subgroup analyses by disease severity.
Results: In fully adjusted models, ionized calcium showed a significant non-linear association with ICU mortality (OR: 0.90 per 1 mmol/L increase, 95% CI: 0.83-0.97, P=0.009). Piecewise regression identified a threshold at 1.2 mmol/L: below this, each 1 mmol/L increase reduced mortality risk by 14% (OR: 0.86, 95% CI: 0.79-0.94, P=0.001); above it, risk increased by 97% (OR: 1.97, 95% CI: 1.12-3.49, P=0.019). This protective effect was stronger in patients with lower APACHE II scores (P-interaction=0.021). Magnesium (OR: 0.95, 95% CI: 0.79-1.14, P=0.594) and total calcium (OR: 1.02, 95% CI: 0.93-1.11, P=0.689) showed no significant associations.
Conclusion: Ionized calcium exhibits a U-shaped relationship with ICU mortality, with an optimal range near 1.2 mmol/L, particularly in less severe cases. These findings suggest prioritizing ionized calcium monitoring in ICU settings and warrant prospective validation.

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Published
2025/07/30
Issue
Ahead of print
Section
Original paper

Copyright (c) 2025 Boyang Cai, Yaoshen Liang, Wenli Zheng, Qiong Zeng, Linfeng Ye, Chunmei He

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