Protocol was not feasible - only 1 of 18 enrollees completed procedures.

Salt and water excess is an essential mechanism of hypertension. This is particularly relevant to patients with end stage kidney disease (ESKD) on dialysis. We have demonstrated that individualization of the sodium concentration in the dialysate as to match the patient's own serum sodium concentration leads to less thirst, interdialytic weight gain, and better BP control in hypertensive patients. In this study we will evaluate the mechanisms underlying this response by measuring systemic hemodynamics, body volume spaces, and biochemical marker of volume status.

Recent evidence from our group shows that individualization of the sodium concentration in the dialysate to match the patient's own serum sodium results in less thirst, less interdialytic weight gain, less HD-related symptoms, and better blood pressure control in hypertensive subjects. In this project we will evaluate the effect of dialysate sodium individualization on systemic hemodynamics, body volume compartments and biochemical markers of volume control in hypertensive hemodialysis patients. We will use a single-blind cross-over design with randomized blocks. After a 3-week baseline period where pre-HD serum sodium will be measured weekly to establish each patient's average serum sodium, subjects will be randomized to 3 weeks on standard dialysate sodium (140 mmol/L) or individualized dialysate sodium (same concentration as the average pre-HD serum sodium during the baseline period), then crossed over to the other for another 3 weeks after a 1-week washout period (dialysate Na 140 mmol/L). The remainder of the dialysis prescription, prescribed dry weight and vasoactive drugs will remain unchanged throughout the study. Clinical information, pre/intra/post-HD blood pressure and thirst scores will be measured weekly at the mid-week dialysis session. In addition, we will measure systemic hemodynamics (cardiac output and systemic vascular resistance), bioimpedance measurements of intracellular and extracellular volume, arterial stiffness (aortic augmentation index, aortic pulse wave velocity), interdialytic (44h) ambulatory BP monitoring, and plasma BNP, renin, aldosterone and norepinephrine at baseline and at the end of each block.

Inclusion Criteria:

• ESKD on hemodialysis
• Hypertension, defined as average pre-HD BP >150/85 mmHg or use of antihypertensive drugs
• Average pre-HD serum sodium <139 mmol/L

Exclusion Criteria:

• Intradialytic hypotension
• Atrial fibrillation or other chronic tachyarrhythmia (due to effects on measuring equipment)
• Uncontrolled hypertension (average pre-HD BP >200/105 mmHg)
• Uncontrolled diabetes mellitus (due to problems on interpretation of serum sodium values)
• Debilitating illness
• Inability to provide written informed consent