Dynamic Variability of Sodium and Potassium Predicts Mortality in Critically Ill Patients With Ischemic Stroke: Evidence From Two Critical Care Cohorts.

BACKGROUND: Ischemic stroke (IS) is one of the leading causes of death and long-term disability worldwide. Electrolyte fluctuations, particularly in sodium and potassium, may play a critical role in the mortality of IS. METHODS: This retrospective cohort study utilized the MIMIC-IV database and NWICU to examine the association between sodium and potassium variability (coefficient of variation [CV]) and mortality in IS patients. A total of 3266 IS patients were included. The study focused on 30-, 90-, and 360-day all-cause mortality. Patients were stratified into quartiles based on CV values for sodium and potassium variability. Multivariable Cox proportional-hazards models were used to assess associations. Cumulative incidence was estimated using Kaplan-Meier methods. Restricted cubic spline (RCS) analyses were conducted to examine the associations of sodium and potassium CVs with the primary outcomes. Sensitivity analyses further examined the impact of electrolyte levels and variability on mortality. RESULTS: In this study, 2593 patients from MIMIC-IV and 673 patients from NWICU were analyzed by sodium and potassium fluctuation quartiles. Sodium and potassium variability were significantly associated with mortality at 30-day, 90-day, and 360-day intervals, with continuous sodium variability showing HRs of 1.22 (30-day), 1.18 (90-day), and 1.17 (360-day), and Q4 significantly increasing risk (HR = 1.78, 1.51, 1.49, respectively). In NWICU, Q4 sodium variability was an independent risk factor for 30-day mortality (HR = 4.04, p < 0.001). Sensitivity analyses confirmed that both high and low sodium and potassium levels were associated with increased mortality risks. CONCLUSIONS: Fluctuations in sodium and potassium levels were strongly linked to increased short-term and long-term mortality risk in intensive care unit (ICU) patients. Patients with high variability in both electrolytes had the worst prognosis.