Feasibility of Assessing Sodium-Associated Body Fluid Composition in End-Stage Renal Disease

Background: Cardiovascular disease accounts for more than half of all deaths in the hemodialysis (HD) population. Although much of this mortality is associated with fluid overload (FO), FO is difficult to measure, and many HD patients have significant pulmonary congestion despite the absence of clinical presentation. Cohort studies have observed that FO, as measured by bioimpedance spectroscopy (BIS), correlates with mortality. Other studies have observed that lower sodium intake is associated with less fluid-related weight gain, improved hypertension, and survival. Whether sodium intake influences FO in HD patients as measured by BIS is not known. Objective: The aims of the study were to determine the feasibility of assessing the impact of sodium restriction on body fluid composition as measured by BIS among patients with three levels of sodium intake and to determine if there are statistical and/or clinical differences in BIS measures across sodium intake groups. Methods: We used a double-blinded randomized controlled trial design with three levels of sodium restriction, 2,400 mg per day, 1,500 mg per day, and unrestricted (control group), to test our aims. Forty-two HD patients from a tertiary acute care academic institution associated with three urban DaVita dialysis centers were enrolled. Participants remained in the inpatient center for 5 days and 4 nights and were randomly assigned to sodium intake groups. Body fluid composition was measured with BIS. Results: Recruitment, enrollment, and retention statistics supported the feasibility of the study design. Regression analyses showed that there were no statistically significant differences among sodium intake groups on any of the outcomes. Discussion: Our data suggest the need for additional research into the effects of sodium restriction on body fluid composition.