Background Several large dialysis organizations have lowered the dialysate sodium concentration (DNa) in an effort to ameliorate hypervolemia. The implications of lower DNa on intra-dialytic hypotension (IDH) during hospitalizations of hemodialysis (HD) patients is unclear. Methods In this double-blind single center randomized controlled trial, hospitalized maintenance HD patients were randomized to receive higher (142 mmol/L) or lower (138 mmol/L) DNa for up to six sessions. Blood pressure (BP) was measured in a standardized fashion pre-HD, post-HD and every 15 minutes during HD. The endpoints were: 1) the average decline in systolic BP (pre-HD minus lowest intra-HD; primary endpoint); and 2) the proportion of total sessions complicated by IDH (drop of ≥20 mmHg from the pre-HD systolic BP; secondary endpoint). Results A total of 139 patients completed the trial, contributing 311 study visits. There were no significant differences in the average SBP decline between the higher and lower DNa groups (23 ±16 vs. 26 ±16 mmHg; P = 0.57). The proportion of total sessions complicated by IDH was similar in the higher DNa group, compared with the lower DNa group (54% vs. 59%; OR 0.72; 95%CI 0.36 to 1.44; P = 0.35). In post-hoc analyses adjusting for imbalances in baseline characteristics, higher DNa was associated with 8 mmHg (95%CI 2 to 13 mmHg) less decline in SBP, compared with lower DNa. Patient symptoms and adverse events were similar between groups. Conclusions In this RCT for hospitalized maintenance HD patients, we found no difference in the absolute SBP decline between those who received higher versus lower DNa in intention-to-treat analyses. Post-hoc adjusted analyses suggested a lower risk of IDH with higher DNa – thus, larger multi-center studies to confirm these findings are warranted.

Introduction: Intradialytic hypotension (IDH) is a common complication of hemodialysis (HD) and is associated with excess morbidity and mortality. Higher serum phosphate is associated with adverse cardiovascular outcomes in maintenance HD patients; however, its association with IDH has not previously been assessed. Methods: This is an analysis of a prospective cohort of 969 HD patients (80,968 HD sessions) receiving HD at a large dialysis organization (LDO) and a post-hoc analysis of 1838 HD patients (10,594 HD sessions) in the Hemodialysis study (HEMO), a multicenter randomized controlled trial that examined standard or high-dose HD and low-flux or high-flux membranes. Unadjusted and adjusted mixed effects regression models were fit to determine the association of pre-HD serum phosphate with IDH, defined as a nadir intra-HD systolic blood pressure (SBP) <90 mmHg.Findings: In the LDO cohort, baseline mean pre-HD serum phosphate was 5.2 AE 1.7 mg/dl. IDH occurred in 15.6% of HD sessions. In the adjusted model, higher pre-HD serum phosphate (per 1 mg/dl) was associated with a 12% increased risk of IDH (aOR 1.12, 95% CI 1.10-1.13, p <0.001). In exploratory models where pre-HD laboratory values were available, the effect estimate was attenuated but remained statistically significant (aOR 1.05; 95% CI 1.02-1.08; p <0.01). Participants in the highest (compared with the lowest) quartile of pre-HD serum phosphate had a 56% greater risk of IDH in the adjusted model (aOR Q4:Q1 1.56; 95% CI 1.44-1.68, p <0.001). The association of higher phosphate with IDH was consistent in the HEMO data.Discussion: Higher pre-HD serum phosphate is independently associated with an increased risk of IDH. As HD may cause an acute decline in serum phosphate, future studies to investigate the mechanisms of this association are warranted.

See related article, "Proportion of Hemodialysis Treatments with High Ultrafiltration Rate and the Association with Mortality," on pages 1359-1366.