Association between serum sodium trajectories and all-cause mortality in critically ill patients with ischemic stroke: a retrospective analysis of the MIMIC-IV database.

BACKGROUND: The relationship between serum sodium levels and stroke prognosis has been investigated, but the effect of serum sodium fluctuations on severe stroke patients remains uncertain. We aimed to evaluate the association between serum sodium trajectories within 72 h of admission and all-cause mortality in intensive care unit (ICU) patients with ischemic stroke. METHODS: This retrospective study utilized data from the Medical Information Mart for Intensive Care (MIMIC) database, including patients diagnosed with ischemic stroke from 2008 to 2022. Serum sodium trajectories within 72 h of admission were classified using a latent class trajectory model. Kaplan-Meier survival curves and Cox proportional hazards models were employed to assess the relationship between trajectories and all-cause mortality. Subgroup analyses were conducted to assess the consistency of this association across various populations. RESULTS: Among 881 enrolled patients, two distinct serum sodium trajectory groups were identified: class 1 (n = 778, 88.3%) exhibited stable sodium levels within the normal range, while class 2 (n = 103, 11.7%) showed rapid fluctuations. Kaplan-Meier analyses revealed that patients in class 2 had higher all-cause mortality at 30-day, 90-day, 180-day, and 1-year follow-ups (all P < 0.001). Multivariate COX regression analyses consistently showed elevated mortality risk in class 2 versus class 1 across all timepoints: ICU (HR: 2.17; 95% CI 1.27-3.68; P = 0.004), in-hospital (HR: 2.51; 95% CI 1.64-3.85; P < 0.001), 30-day (HR: 2.41; 95% CI 1.67-3.49; P < 0.001), 90-day (HR: 2.17; 95% CI 1.56-3.03; P < 0.001), 180-day (HR: 2.13; 95% CI 1.55-2.92; P < 0.001) and 1 year (HR: 1.99; 95% CI 1.46-2.71; P < 0.001). Subgroup analyses confirmed the robustness of these findings. CONCLUSIONS: In critically ill patients with ischemic stroke, rapidly fluctuating serum sodium levels are independently associated with increased short-term and long-term all-cause mortality. Further investigations are needed to elucidate the role of sodium dynamics in stroke outcomes.