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.
Keywords: serum sodium, acute kidney injury, elderly, mortality