Résumé
Background: hyponatremia, defined as a natremia <135 mEq/L, is the most common hydrolytic disorder in the traumatic brain injury population. Two main mechanisms are SIADH and Cerebral Salt Wasting Syndrome (CSW). The aim of this study was to assess for each mechanism prevalence, risks factors, especially in terms of free water or sodium intakes, evolution and outcomes.Methods: a retrospective cohort study included 353 severe trauma patients with traumatic brain injury in a level 1 trauma center over 3 years. Using precise diagnostic criteria based on free water clearance (urine/plasma osmolarity, diuresis) and natriuresis, patients were classified in 3 subgroups: SIADH, CSW, and Undetermined.Results: 58 (16%) developed hyponatremia within the first 30 days of management, mostly within the first 10 days. 31 (53%) were SIADHs, 13 (22%) were CSWs, 14 (24%) were Undetermined forms. SIADH subgroup was composed of less severe patients (lower IGS2 and ISS). In contrast, the CSW subgroup was made up of more severe patients who had more episodes of diabetes insipidus. No difference was found in terms of total, free water and salt intakes between SIADH, CSW and no-hyponatraemic patients. Some hyponatremia occurred in Undetermined subgroup, probably related to excessive free water intakes.Conclusion: hyponatremia is a frequent metabolic dysregulation in traumatic brain injury patients. SIADH and CSW represent the majority of these hyponatremias, with different risk factors and prognoses. Total, free water, and salt intakes did not favor the development of SIADH or CSW episodes. Excessive free water intakes could however induce more hyponatremia related to altered urine dilution ability in critical care conditions.