Effect of low versus high dialysate sodium concentration on blood pressure and endothelial-derived vasoregulators during hemodialysis: a randomized crossover study.

BACKGROUND

Intradialytic hypertension affects ∼15% of hemodialysis patients and is associated with increased morbidity and mortality. While intradialytic hypertension is associated with increases in endothelin 1 relative to nitric oxide (NO), the cause of these imbalances is unknown. In vitro evidence suggests that altering plasma sodium levels could affect endothelial-derived vasoregulators and blood pressure (BP). Thus, we hypothesized that compared to high dialysate sodium, low dialysate sodium concentration would lower endothelin 1 levels, increase NO release, and reduce BP.

STUDY DESIGN

3-week, 2-arm, randomized, crossover study.

SETTING & PARTICIPANTS: 16 patients with intradialytic hypertension.

INTERVENTION

Low (5 mEq/L below serum sodium) versus high (5 mEq/L above serum sodium) dialysate sodium concentration.

OUTCOMES

Endothelin 1, nitrite (NO2(-)), and BP.

MEASUREMENTS

Mixed linear regression was used to compare the effect of dialysate sodium (low vs high) and randomization arm (low-then-high vs high-then-low) on intradialytic changes in endothelin 1, NO2(-), and BP values.

RESULTS

The average systolic BP throughout all hemodialysis treatments in a given week was lower with low dialysate sodium concentrations compared with treatments with high dialysate sodium concentrations (parameter estimate, -9.9 [95% CI, -13.3 to -6.4] mm Hg; P < 0.001). The average change in systolic BP during hemodialysis also was significantly lower with low vs high dialysate sodium concentrations (parameter estimate, -6.1 [95% CI, -9.0 to -3.2] mm Hg; P < 0.001). There were no significant differences in intradialytic levels of endothelin 1 or NO2(-) with low vs high dialysate sodium concentrations.

LIMITATIONS

Carryover effects limited the power to detect significant changes in endothelial-derived vasoregulators, and future studies will require parallel trial designs.

CONCLUSIONS

Low dialysate sodium concentrations significantly decreased systolic BP and ameliorated intradialytic hypertension. Longer studies are needed to determine the long-term effects of low dialysate sodium concentrations on BP and clinical outcomes.