Can Changes in Dialysate Sodium Concentration Improve Blood Pressure and Endothelial Function in Chronic HD Patients?

People with end stage kidney disease cannot regulate salt and water normally, which often leads to high blood pressure, fluid overload, and a higher risk of heart disease.

Hemodialysis is a life sustaining treatment that removes waste products, excess fluid, and electrolytes from the blood. However, the treatment itself can influence blood pressure and how the blood vessels function. Many patients experience symptoms such as thirst, headaches, fatigue, and swelling, which affect both daily well being and long term health. One possible way to reduce these problems may be as simple as adjusting the amount of sodium in the dialysis fluid.

During dialysis, substances move between the patient's blood and the dialysate, the special fluid used in the machine. Sodium is one of the most important components because it helps regulate fluid balance and blood pressure. A higher sodium concentration in the dialysate can make patients feel more thirsty, cause them to drink more, and lead to fluid retention and higher blood pressure. On the other hand, lowering sodium too much can cause dizziness, low blood pressure, cramps, and discomfort during treatment. Because of this, there is ongoing debate about what the "right" sodium level should be.

Too much sodium over time may also harm the blood vessels. The inner lining of the vessels, called the endothelium, is protected by a thin layer known as the glycocalyx. This layer helps prevent sodium from entering the vessel wall and supports the production of nitric oxide, a molecule that relaxes blood vessels and reduces inflammation. High salt exposure can damage the glycocalyx and reduce nitric oxide production, making the vessels stiffer and raising blood pressure. In dialysis patients, low nitric oxide levels are linked to worse outcomes and episodes of rising blood pressure during treatment. Some small studies suggest that lowering dialysate sodium can improve blood pressure and endothelial function, but larger studies have not shown clear effects on survival. This indicates that we still do not fully understand which patients benefit most or how sodium changes affect both physical and subjective symptoms.

This study aims to fill these knowledge gaps by examining how a lower sodium concentration in the dialysate affects blood pressure, blood vessel function, fluid overload, inflammation, and patient reported symptoms. The goal is to provide new insights that could help tailor dialysis treatment to individual patients in a simple and cost effective way.

The study will compare two sodium concentrations: a lower level (133 mmol/L) and the standard level used in many clinics (139 mmol/L). Twenty five patients receiving chronic in center hemodialysis will participate. Each patient will undergo both treatments for three weeks each, in random order, with a two week washout period in between. This crossover design allows each patient to serve as their own control, making it easier to detect meaningful differences.

The main outcome is the difference in 24 hour systolic blood pressure between the two sodium levels. Secondary outcomes include changes in nitric oxide levels in the blood, measures of fluid overload using two different techniques, markers of inflammation, arterial stiffness, and patient reported symptoms such as thirst, fatigue, and overall well being. The study will also compare two methods for assessing fluid overload: bioimpedance spectroscopy and a newer carbon monoxide rebreathing technique.

Blood pressure and arterial stiffness will be measured over 44 hours using a portable device. Blood samples will be collected to analyze nitric oxide, inflammatory markers, and sodium handling in red blood cells. Fluid status will be measured using both bioimpedance and the CO rebreathing method. Patients will complete a weekly questionnaire developed together with dialysis patients to capture their experiences and symptoms.