Are Dialysate Sodium Levels Too High?

Abstract

Universal lower dialysate [Na+] is often advocated as a means of improving the dire cardiovascular plight of our dialysis patients. However, there is evidence associating lower dialysate [Na+] and increased morbidity and mortality especially in frailer patients, probably as a result of more frequent intra-dialytic hypotension. In this editorial, we summarize arguments for and against lower dialysate [Na+], and provide recommendations around selecting the most appropriate dialysate [Na+] for specific clinical subsets that may benefit from manipulation of salt and water balance. The lack of overall clarity on relative benefits and risks of lower dialysate [Na+] does not support the case for empirical "across the board" change, and experimental testing in clinical trials is required to determine safe and effective use.

Effect of Dialysate Sodium Concentration on Sodium Gradient and Hemodialysis Parameters

“…Furthermore, IDH occurred at a SG of zero, regardless of SGna, SGcna, or SGcnag. This result was surprising because, in most patients, a DNa between 138 and 142mEq/L is considered to be the standard in current clinical practice 20) .…”

“…Some specialists have recommended the use of a fixed DNa of ~137 mEq/L 21) , whereas others have suggested it is reasonable to prescribe a DNa between 138 and 142mEq/L in most patients 20) . However, they also recommended that it is important to consider whether a given patient is within a specific clinical subset, in which there is clear evidence that a positive Na balance may benefit from the manipulation of DNa 20) . Another group even recommended reducing the DNa to 134-138mEq/L 22) .…”

Rationale and design of the Sodium Lowering In Dialysate (SoLID) trial: a randomised controlled trial of low versus standard dialysate sodium concentration during hemodialysis for regression of left ventricular mass

“…A more accessible alternative may be available in reducing sodium exposure through lower dialysate [Na+]. Sodium loading by either excessive dietary intake or excessive diffusion via dialysate has been shown to increase both BP and intra-dialytic weight gain (IDWG) [41]. Moreover, elevation in plasma [Na+] can induce hypertension independently of EC fluid volume, through mechanisms that probably include stiffening of vascular endothelium [42-46].…”

“…Overall, there is clinical equipoise around lower dialysate [Na+] due to the multiple physiological consequences of reducing salt exposure in this population, and the uncertain net effect on CV outcomes as a result of these often competing and often conflicting physiological responses (Figure 2) [41]. The SOdium Lowering In Dialysate (SoLID) trial has been designed to answer the following clinical question: Does lower dialysate [Na+] improve CV mortality risk compared to conventional dialysate [Na+], in prevalent home HD patients who are exposed over a duration of a year?…”

“… Causal diagram relating low salt exposure during hemodialysis to cardiovascular mortality risk (reproduced with permission from Marshall and Dunlop [41] ). …”