Low serum calcium promotes traumatic intracerebral hematoma expansion by the response of immune cell: A multicenter retrospective cohort study.

To explore the potential role of serum calcium levels at admission in the expansion of acute traumatic intracerebral hematoma (tICH) and to construct a novel nomogram to predict tICH expansion. In this multicenter retrospective study, 640 and 237 patients were included in the training and validation datasets, respectively. Risk factors for acute tICH expansion were selected by logistic regression analysis. Causal mediation and interaction analysis were used to explore the relationship between serum calcium promotion of tICH expansion and inflammatory response. Receiver operating characteristic, calibration and clinical decision curves were applied to estimate the performance of multivariate models. Low serum calcium level was strongly associated with acute tICH expansion in patients with brain contusion. There was no significant interaction of hypocalcemia across multiple subgroups including sex, age, and coagulation dysfunction. 24.5% of the mechanisms by which hypocalcemia promotes acute tICH expansion can be explained by an inflammatory response. The addition of serum calcium made the modified model (serum calcium plus basic model) more accurate than basic model with subdural hematoma, multihematoma fuzzy sign, time to baseline CT, level on Glasgow Coma Scale score, platelet count, baseline tICH volume ≥ 5 mL, and monocyte-to-lymphocyte ratio. Low serum calcium level is a novel risk factor for acute tICH expansion, the mechanism of which may be mediated in part through the response of immune cell. The online dynamic nomogram provides a user-friendly tool for the prediction of acute tICH expansion.