Kinetics and dynamics of ionized calcium in a porcine major trauma model

BACKGROUND: Disturbances in ionized calcium (iCa²⁺) are common after major trauma and correlate parabolically with coagulopathy, transfusion, and mortality. However, the mechanisms underlying iCa²⁺ changes during trauma and resuscitation remain poorly understood. This exploratory study aimed to develop an experimental animal model to characterize the dynamics and kinetics of iCa²⁺ during trauma and resuscitation. METHODS: A controlled porcine polytrauma model (PT, n=6)-including thoracic, abdominal, musculoskeletal trauma, controlled hemorrhage, and ischemia-reperfusion-was compared with nontrauma controls (C, n=4). Continuous hemodynamic monitoring and serial blood sampling during trauma, hemorrhage, ischemia-reperfusion, damage control resuscitation (DCR), transfusion, and observation enabled analysis of iCa²⁺ in relation to hemodynamic and acid-base status, ion interactions, and endocrine parameters. RESULTS: Two animals in the polytrauma group died during the experiment and were excluded from analysis. Baseline iCa²⁺ levels were comparable between groups (C: 1.38 [95% CI: 1.36-1.41] vs. PT: 1.42 [95% CI: 1.35-1.49] mmol/L, p =0.211) and remained stable in controls. In the polytrauma group, iCa²⁺ initially increased with early respiratory acidosis following thoracic trauma, then progressively decreased during hemorrhagic shock and ischemia-reperfusion. A further rapid decrease followed transfusion of citrated autologous whole blood ( p <0.001). Phosphate, lactate, and magnesium increased during shock, while bicarbonate and albumin decreased. Parathyroid hormone peaked, whereas calcitonin and 25-hydroxy-Vit D reached their lowest levels at the nadir of hypocalcemia. iCa²⁺ recovered during DCR, returning to baseline by the end of observation ( t =240 min, 1.39 [1.30-1.47] mmol/L, p =0.593). CONCLUSIONS: iCa²⁺ changes dynamically during trauma and resuscitation, in parallel with alterations in acid-base status, circulating ions, transfusion, and endocrine responses. iCa²⁺ can spontaneously recover to baseline with adequate resuscitation without calcium supplementation. This exploratory study can contribute to the development of a robust experimental model for future translational research. ( J Trauma Acute Care Surg . 2026;00:00-00. Copyright © 2026 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Association for the Surgery of Trauma.).