Comparative effects of 1.25 vs. 1.5 mmol/L dialysate calcium concentrations on blood pressure variability during hemodialysis: a two-center retrospective study

Introduction Hemodialysis patients frequently experience blood pressure fluctuations, which are independently associated with adverse cardiovascular outcomes. However, the optimal dialysate calcium concentration for minimizing blood pressure variability (BPV) remains controversial. Methods This retrospective cohort study investigated the differential effects of dialysate calcium concentrations of 1.25 mmol/L (DCa 1.25) versus 1.5 mmol/L (DCa 1.5) on intradialytic BPV. We analyzed 2,061 hemodialysis sessions from 711 maintenance hemodialysis patients across two centers in China. Patients were categorized based on dialysate calcium concentration: 1.25 mmol/L ( n = 473 patients, 1,425 sessions) and 1.5 mmol/L ( n = 238 patients, 636 sessions). BPV was defined as the difference between maximum and minimum blood pressure during each session. Results Compared with DCa 1.5, group DCa 1.25 demonstrated significantly lower systolic blood pressure variability (SBPV) (25.23 ± 14.55 vs. 32.42 ± 17.71 mmHg, p < 0.001), diastolic blood pressure variability (DBPV) (9.78 ± 8.07 vs. 11.56 ± 9.67 mmHg, p < 0.001), and mean arterial pressure variability (MAPV) (15.41 ± 9.40 vs. 18.71 ± 11.10 mmHg, p < 0.001). Serum total calcium changes during dialysis were smaller in the 1.25 mmol/L group [0.04 (−0.06, 0.16) vs. 0.15 (0.04, 0.26) mmol/L, p < 0.001] and positively correlated with SBPV and MAPV. In multivariate generalized linear models adjusted for potential confounders, dialysate calcium concentration of 1.5 mmol/L was independently associated with greater BPV. Discussion These findings suggest that lower dialysate calcium concentration may improve hemodynamic stability during hemodialysis by minimizing calcium flux and associated blood pressure fluctuations.