pH-Corrected Ionised Calcium Predicts Coagulopathy After Major Trauma: A Retrospective Cohort Study

To evaluate the prognostic utility of pH-corrected ionised calcium (ciCa²⁺) as calculated by blood gas analysers in major trauma patients.

We conducted a retrospective cohort study of trauma patients aged ≥ 16 years with an Injury Severity Score (ISS) ≥ 13 presenting to a New Zealand tertiary trauma centre from January 2021 to June 2022. Patients were excluded if they did not meet New Zealand Trauma Registry criteria, received blood products before ionised calcium (iCa²⁺) measurement, or had missing key laboratory data. Outcomes were in-hospital mortality, coagulopathy and transfusion. We compared prognostic performance of ciCa²⁺ versus iCa²⁺ using logistic regression and pairwise comparison of receiver operating characteristic curves.

Among 232 patients, 110 (47.4%) had an initial ciCa²⁺ ≤ 1.1 mmol/L. In unadjusted analysis, ciCa²⁺ ≤ 1.1 mmol/L was not associated with mortality (OR 2.18, 95% CI 0.99-4.79; p = 0.08). After adjusting for age and ISS, lower ciCa²⁺ was independently associated with mortality (aOR per 0.1 mmol/L increase 0.58, 95% CI 0.35-0.97; p = 0.04), but this was attenuated after adjusting for lactate (aOR 1.30, 95% CI 0.74-2.28; p = 0.37). ciCa²⁺ was strongly associated with coagulopathy (OR 23.0, 95% CI 1.32-395; p < 0.01) and transfusion (OR 2.54, 95% CI 1.41-4.58; p < 0.01), with superior discrimination over iCa²⁺ for both (AUROC 0.95 vs. 0.56 and 0.69 vs. 0.54, respectively; p < 0.01).

ciCa^{2 +} outperformed uncorrected iCa²⁺. As a routine blood gas parameter incorporating key elements of trauma pathophysiology-hypocalcaemia and acidaemia-it may offer a practical tool for early risk stratification in trauma.