Serum Sodium Levels Predict Mortality in Elderly Acute Kidney Injury Patients: A Retrospective Observational Study.

Purpose We examined the relationship between different levels of serum sodium and mortality among elderly patients with acute kidney injury (AKI). Methods We retrospectively enrolled elderly patients from Chinese PLA General Hospital from 2007, to 2018. All-cause mortality was examined according to eight predefined sodium levels: <130.0 mmol/L, 130.0-134.9 mmol/L, 135.0-137.9 mmol/L, 138.0-141.9 mmol/L, 142.0-144.9 mmol/L, 145.0-147.9 mmol/L, 148.0-151.9 mmol/L, and ≥152.0 mmol/L. We estimated the risk of all-cause mortality using a multivariable adjusted Cox analysis, with a normal sodium level of 135.0-137.9 mmol/L as a reference. Results In total, 744 patients were suitable for the final evaluation. After 90 days, the mortality rates in the eight strata were 36.1, 27.8, 19.6, 24.4, 30.7, 48.6, 52.8, and 57.7%, respectively. In the multivariable adjusted analysis, patients with sodium levels <130.0 mmol/L (HR: 2.247; 95% CI: 1.117-4.521), from 142.0 to 144.9 mmol/L (HR: 1.964; 95% CI: 1.100-3.508), from 145.0 to 147.9 mmol/L (HR: 2.942; 95% CI: 1.693-5.114), from 148.0 to 151.9 mmol/L (HR: 3.455; 95% CI: 2.009-5.944), and ≥152.0 mmol/L (HR: 3.587; 95% CI: 2.151-5.983) had an increased risk of all-cause mortality. After 1 year, the mortality rates in the eight strata were 58.3, 47.8, 33.7, 38.9, 45.5, 64.3, 69.4, and 78.4%, respectively. Patients with sodium levels <130.0 mmol/L (HR: 1.944; 95% CI: 1.125-3.360), from 142.0 to 144.9 mmol/L (HR: 1.681; 95% CI: 1.062-2.660), from 145.0 to 147.9 mmol/L (HR: 2.631; 95% CI: 1.683-4.112), from 148.0 to 151.9 mmol/L (HR: 2.411; 95% CI: 1.552-3.744), and ≥152.0 mmol/L (HR: 3.037; 95% CI: 2.021-4.563) had an increased risk of all-cause mortality. Conclusion Sodium levels outside the interval of 130.0-141.9 mmol/L were associated with increased risks of 90-day mortality and 1-year mortality in elderly AKI patients.