Association Between Admission Ionized Calcium Level and Neurological Outcome of Patients with Isolated Severe Traumatic Brain Injury: A Retrospective Cohort Study

BackgroundTraumatic brain injury (TBI) is a leading cause of death and disability worldwide. Pathophysiological processes following initial insult are complex and not fully understood. Ionized calcium (Ca++) is an essential cofactor in the coagulation cascade and platelet aggregation, and hypocalcemia may contribute to the progression of intracranial bleeding. On the other hand, Ca++ is an important mediator of cell damage after TBI and cellular hypocalcemia may have a neuroprotective effect after brain injury. We hypothesized that early hypocalcemia might have an adverse effect on the neurological outcome of patients suffering from isolated severe TBI. In this study, we aimed to evaluate the relationship between admission Ca++ level and the neurological outcome of these patients.MethodsThis was a retrospective, single-center, cohort study of all patients admitted between January 2014 and December 2020 due to isolated severe TBI, which was defined as head abbreviated injury score >= 4 and an absence of severe (abbreviated injury score > 2) extracranial injuries. The primary outcome was a favorable neurological status at discharge, defined by a modified Rankin Scale of 0-2. Multivariable logistic regression was performed to determine whether admission hypocalcemia (Ca++ < 1.16 mmol L-1) is an independent predictor of neurological status at discharge.ResultsThe final analysis included 201 patients. Hypocalcemia was common among patients with isolated severe TBI (73.1%). Most of the patients had mild hypocalcemia (1 < Ca++ < 1.16 mmol L-1), and only 13 (6.5%) patients had Ca++ <= 1.00 mmol L-1. In the entire cohort, hypocalcemia was independently associated with higher rates of good neurological status at discharge (adjusted odds ratio of 3.03, 95% confidence interval 1.11-8.33, p = 0.03). In the subgroup of 81 patients with an admission Glasgow Coma Scale > 8, 52 (64.2%) had hypocalcemia. Good neurological status at discharge was recorded in 28 (53.8%) of hypocalcemic patients compared with 14 (17.2%) of those with normal Ca++ (p = 0.002). In multivariate analyses, hypocalcemia was independently associated with good neurological status at discharge (adjusted odds ratio of 6.67, 95% confidence interval 1.39-33.33, p = 0.02).ConclusionsOur study demonstrates that among patients with isolated severe TBI, mild admission hypocalcemia is associated with better neurological status at hospital discharge. The prognostic value of Ca++ may be greater among patients with admission Glasgow Coma Scale > 8. Trials are needed to investigate the role of hypocalcemia in brain injury.