Dialysate Sodium Prescription and Blood Pressure in Hemodialysis Patients

BACKGROUND: Diffusive sodium removal has been recommended to control hypertension in hemodialysis patients. Recent evidence on hospitalizations and mortality, however, challenged the benefit of lower dialysate sodium prescriptions and ignited a debate in the dialysis community. We therefore studied the relationship between dialysate sodium and blood pressure over the longer term. METHODS: We used multiply adjusted linear mixed models to estimate the association between dialysate sodium and predialysis systolic blood pressure (SBP) as well as change in SBP (delta SBP; postdialysis minus predialysis) in 23,962 patients from the international Dialysis Outcomes and Practice Patterns Study. RESULTS: We found that 43% of hemodialysis facilities had variable (individualized) dialysate sodium prescriptions (125-155 mEq/L), whereas 57% had uniform dialysate sodium prescriptions (135-145 mEq/L) for ≥90% patients. Between-group comparisons of these 2 facility types suggested that dialysate sodium, when variably prescribed, might have been used to modify predialysis SBP (P interaction = 0.01) and perhaps delta SBP levels (P interaction = 0.08). Within facilities not prone to indication bias, because dialysate sodium was not variable, higher uniform dialysate sodium (per 2 mEq/L) was associated with slightly higher SBP (+0.9 mm Hg, 95% confidence interval (CI) = 0.1-1.6 among all patients; +1.7 mm Hg, 95% CI = 0.1-3.2 among patients not treated with blood pressure medication) and no increase in delta SBP. CONCLUSIONS: Patients assigned to hemodialysis facilities with uniformly higher dialysate sodium do not have markedly higher predialysis SBP, providing rather limited support for lowering dialysate sodium to control hypertension, particularly in view of hospitalization and mortality risks associated with lower dialysate sodium.