Dialysate sodium concentration: The forgotten salt shaker

The effect of different dialysate sodium concentrations on ambulatory blood pressure in hemodialysis patients: a prospective interventional study

Background

Hypertension is associated with increased morbidity and mortality in hemodialysis patients. Existing recommendations suggest reduction of sodium load, but the effect of dialysate sodium on blood pressure (BP) is not fully elucidated. The aim of the present study is to investigate the effect of different dialysate sodium concentrations on 72-h ambulatory BP in hemodialysis patients.

Methods

This prospective study included patients on standard thrice-weekly hemodialysis. All patients initially underwent six sessions with dialysate sodium concentration of 137 meq/L, followed consecutively by another six sessions with dialysate sodium of 139 meq/L and, finally, six sessions with dialysate sodium of 141 meq/L. At the start of the sixth hemodialysis session on each sodium concentration, 72-h ABPM was performed over the long interdialytic interval to evaluate ambulatory systolic and diastolic BP (SBP and DBP) during the overall 72-h, different 24-h, daytime and night-time periods.

Results

Twenty-five patients were included in the final analysis. A significant increase in the mean 72-h SBP was observed with higher dialysate sodium concentrations (124.8 ± 16.6 mmHg with 137 meq/L vs 126.3 ± 17.5 mmHg with 139 meq/L vs 132.3 ± 19.31 mmHg with 141 meq/L, P = 0.002). Similar differences were noted for DBP; 72-h DBP was significantly higher with increasing dialysate sodium concentrations (75.1 ± 11.3 mmHg with 137 meq/L vs 76.3 ± 13.7 mmHg with 139 meq/L vs 79.5 ± 13.9 mmHg with 141 meq/L dialysate sodium, P = 0.01). Ambulatory BP during the different 24-h intervals, daytime and night-time periods was also progressively increasing with increasing dialysate sodium concentration.

Conclusion

This pilot study showed a progressive increase in ambulatory BP with higher dialysate sodium concentrations. These findings support that lower dialysate sodium concentration may help towards better BP control in hemodialysis patients.

Personalizing electrolytes in the dialysis prescription: what, why and how?

Maintenance hemodialysis patients suffer from multiple comorbidities and treatment-related complications. A personalized approach to hemodialysis prescription could reduce some of these burdens by preventing complications such as excessive changes in blood pressure, arrhythmias, post-dialysis fatigue and decreased quality of life. A patient-centered approach to dialysate electrolyte concentrations represents one such opportunity. In addition to modifications in dialysate electrolyte concentrations, consideration of individual factors such as patients' serum concentrations, medication profiles, nutritional status and comorbidities is critical to tailoring hemodialysis prescriptions to optimize patient outcomes. The development of personalized dialysis treatment depends on the collection of comprehensive patient data, advances in technology, resource allocation and patient involvement in decision-making. This review discusses how the treatment of maintenance hemodialysis patients could benefit from individualized changes in certain dialysis fluid components.

Calculation of the Gibbs-Donnan factors for multi-ion solutions with non-permeating charge on both sides of a permselective membrane

Separation of two ionic solutions with a permselective membrane that is impermeable to some of the ions leads to an uneven distribution of permeating ions on the two sides of the membrane described by the Gibbs–Donnan (G–D) equilibrium with the G–D factors relating ion concentrations in the two solutions. Here, we present a method of calculating the G–D factors for ideal electroneutral multi-ion solutions with different total charge of non-permeating species on each side of a permselective membrane separating two compartments. We discuss some special cases of G–D equilibrium for which an analytical solution may be found, and we prove the transitivity of G–D factors for multi-ion solutions in several compartments interconnected by permselective membranes. We show a few examples of calculation of the G–D factors for both simple and complex solutions, including the case of human blood plasma and interstitial fluid separated by capillary walls. The article is accompanied by an online tool that enables the calculation of the G–D factors and the equilibrium concentrations for multi-ion solutions with various composition in terms of permeating ions and non-permeating charge, according to the presented method.

Impact of dialysate sodium concentration on vascular refilling

BACKGROUND

Although relationship between dialysate sodium concentration and hemodynamic stability has been well studied over the years, outcomes of absolute blood volume (ABV) maintenance and vascular refilling volume (V_ref ) modifications were not included, as its analysis has not been easily accessible to direct investigation. However, recent studies report a simple and feasible methodology to assess ABV and V_ref during hemodialysis (HD) treatments. It is the aim of this study to analyze whether sodium concentration in dialysate modifies ABV drop and V_ref .

METHODS

The study was performed in 19 patients under HD. During three different sessions, sodium concentration in dialysate was randomized to three different profiles: low sodium concentration (LNa, 138 mEq/L), neutral sodium concentration (NNa, 140 mEq/L), and high sodium concentration (HNa, 143 mEq/L). ABV and V_ref were calculated using Kron et al methodology.

RESULTS

Predialysis values of the measured parameters showed similar results for the three profiles. Sodium concentration showed an effect on ABV drop, V_ref, and vascular refilling fraction (F_ref ). Pair-wise comparison revealed mean ABV decreased 0.21 L less when using HNa profile versus LNa profile (p = 0.027), a mean V_ref increase of 0.39 L (p = 0.038), and a mean F_ref increase of 9.94% (p = 0.048).

CONCLUSIONS

This study shows that the use of HNa profiles increases V_ref and F_ref and reduces ABV drop during dialysis treatments when compared to LNa profiles.

Dextrose solution for priming and rinsing the extracorporeal circuit in hemodialysis patients: A prospective pilot study

INTRODUCTION

Excess sodium intake and consequent volume overload are major clinical problems in hemodialysis (HD) contributing to adverse outcomes. Saline used for priming and rinsing of the extracorporeal circuit is a potentially underappreciated source of intradialytic sodium gain. We aimed to examine the feasibility and clinical effects of replacing saline as the priming and rinsing fluid by a 5% dextrose solution.

MATERIALS AND METHODS

We enrolled non-diabetic and anuric stable HD patients. First, the extracorporeal circuit was primed and rinsed with approximately 200-250 mL of isotonic saline during 4 weeks (Phase 1), subsequently a similar volume of a 5% dextrose solution replaced the saline for another 4 weeks (Phase 2), followed by another 4 weeks of saline (Phase 3). We collected data on interdialytic weight gain (IDWG), pre- and post-dialysis blood pressure, intradialytic symptoms, and thirst.

RESULTS

Seventeen chronic HD patients (11 males, age 54.1 ± 18.7 years) completed the study. The average priming and rinsing volumes were 236.7 ± 77.5 and 245.0 ± 91.8 mL respectively. The mean IDWG did not significantly change (2.52 ± 0.88 kg in Phase 1; 2.28 ± 0.70 kg in Phase 2; and 2.51 ± 1.2 kg in Phase 3). No differences in blood pressures, intradialytic symptoms or thirst were observed.

CONCLUSIONS

Replacing saline by 5% dextrose for priming and rinsing is feasible in stable HD patients and may reduce intradialytic sodium loading. A non-significant trend toward a lower IDWG was observed when 5% dextrose was used. Prospective studies with a larger sample size and longer follow-up are needed to gain further insight into the possible effects of using alternate priming and rinsing solutions lowering intradialytic sodium loading.

TRIAL REGISTRATION

Identifier NCT01168947 (ClinicalTrials.gov).

Automated individualization of dialysate sodium concentration reduces intradialytic plasma sodium changes in hemodialysis

In standard care, hemodialysis patients are often treated with a center‐specific fixed dialysate sodium concentration, potentially resulting in diffusive sodium changes for patients with plasma sodium concentrations below or above this level. While diffusive sodium load may be associated with thirst and higher interdialytic weight gain, excessive diffusive sodium removal may cause intradialytic symptoms. In contrast, the new hemodialysis machine option “Na control” provides automated individualization of dialysate sodium during treatment with the aim to reduce such intradialytic sodium changes without the need to determine the plasma sodium concentration. This proof‐of‐principle study on sodium control was designed as a monocentric randomized controlled crossover trial: 32 patients with residual diuresis of ≤1000 mL/day were enrolled to be treated by high‐volume post‐dilution hemodiafiltration (HDF) for 2 weeks each with “Na control” (individually and automatically adjusted dialysate sodium concentration) versus “standard fixed Na” (fixed dialysate sodium 138 mmol/L), in randomized order. Pre‐ and post‐dialytic plasma sodium concentrations were determined at bedside by direct potentiometry. The study hypothesis consisted of 2 components: the mean plasma sodium change between the start and end of the treatment being within ±1.0 mmol/L for sodium‐controlled treatments, and a lower variability of the plasma sodium changes for “Na control” than for “standard fixed Na” treatments. Three hundred seventy‐two treatments of 31 adult chronic hemodialysis patients (intention‐to‐treat population) were analyzed. The estimate for the mean plasma sodium change was −0.53 mmol/L (95% confidence interval: [−1.04; −0.02] mmol/L) for “Na control” treatments and −0.95 mmol/L (95% CI: [−1.76; −0.15] mmol/L) for “standard fixed Na” treatments. The standard deviation of the plasma sodium changes was 1.39 mmol/L for “Na control” versus 2.19 mmol/L for “standard fixed Na” treatments (P = 0.0004). Whereas the 95% CI for the estimate for the mean plasma sodium change during “Na control” treatments marginally overlapped the lower border of the predefined margin ±1.0 mmol/L, the variability of intradialytic plasma sodium changes was lower during “Na control” versus “standard fixed Na” treatments. Thus, automated dialysate sodium individualization by “Na control” approaches isonatremic dialysis in the clinical setting.