Dialysate, Plasma Sodium, Mortality in Hemodialysis Patients

Cardiovascular disease is a major contributor to mortality in patients receiving hemodialysis, due in part to abnormal fluid status and plasma sodium concentrations. Removal of fluid and sodium is facilitated with ultrafiltration, and diffusive exchange of sodium is pivotal in sodium removal and tonicity adjustment. Lower dialysate sodium may increase sodium removal at the expense of tonicity, reduced blood volume refilling, and intradialytic hypotension risk. Higher dialysate sodium preserves blood volume and hemodynamic stability but reduces sodium removal. 

Julie Pinter and colleagues conducted a study involving a multinational cohort of 68,196 patients to determine whether a dialysate sodium of ≤138 mmol/L would have an effect on survival outcomes compared with dialysate sodium >138 mmol/L, after adjusting for plasma sodium concentration. 

The cohort included incidence hemodialysis patients from 875 Fresenius Medical Care Nephrocare clinics in 25 countries between 2010 and 2019. The association between time-varying dialysate and plasma sodium exposure and all-cause mortality was modeled using a multivariable Cox regression model stratified by country and adjusted for demographic and treatment variables, including bioimpedance measures of fluid status. 

On average, the 68,196 patients underwent three hemodialysis sessions per week. Dialysate sodium of 138 mmol/L was prescribed in 63.2%, 139 mmol/L in 15.8%, 140 mml/L in 20.7%, and other concentrations in 0.4% of the cohort. The majority (78.6%) of the centers used a standardized concentration. 

Follow-up continued for a mean of 40 months. During that period, 21,644 patients (one-third) died. Following adjustment for plasma sodium concentrations and other confounding variables, there was an association between dialysate sodium ≤138 mmol/L and higher mortality (multivariate HR for the total population, 1.57; 95% CI, 1.25-1.98).  

Results of subgroup analyses did not show evidence of effect modification by plasma sodium concentrations or other patient-specific variables. 

“These observational findings stress the need for randomized evidence to reliably define optimal standard dialysate sodium prescribing practices,” the authors said. 

Source: Journal of the American Society of Nephrology