Serum sodium levels and patient outcomes in an ambulatory clinic-based chronic kidney disease cohort.

Background: Chronic kidney disease (CKD) patients are prone to both hypo- and hypernatremia. Little has been published on the epidemiology of hypo- and hypernatremia in ambulatory patients with non-dialysis CKD. Methods: Data collected in two contemporaneous CKD cohort studies, the Renal Research Institute (RRI)-CKD study (n = 834) and the Study of Treatment of Renal Insufficiency: Data and Evaluation (STRIDE) (n = 1,348) were combined and analyzed to study the association between serum sodium (Na+) and clinical outcomes. Results: Baseline estimated glomerular filtration rate (eGFR) and Na+ were 26 +/- 11 ml/min/1.73 m(2) and 140.2 +/- 3.4 mEq/l, respectively. The prevalence of Na+ <= 135 mEq/l and >= 144 mEq/l was 6 and 16%, respectively. Higher baseline Na+ was significantly associated with male sex, older age, systolic blood pressure, BMI, serum albumin, presence of heart failure, and lower eGFR. The risk of end-stage renal disease (ESRD) was marginally significantly higher among patients with Na+ <= 135 mEq/l, compared with 140< Na+ <144 mEq/l (referent), in time-dependent models (adjusted hazard ratio, HR = 1.52, p = 0.06). Mortality risk was significantly greater at 135< Na+ <= 140 mEq/l (adjusted HR = 1.68, p = 0.02) and Na+ >= 144 mEq/l (adjusted HR = 2.01, p = 0.01). Conclusion: CKD patients with Na+ <= 135 mEq/l were at a higher risk for progression to ESRD, whereas both lower and higher Na+ levels were associated with a higher risk of mortality. While caring for CKD patients, greater attention to serum sodium levels by clinicians is warranted and could potentially help improve patient outcomes. (C) 2015 S. Karger AG, Basel