Effect of dialysate bicarbonate on calciprotein particle crystallization time (T50) in hemodialysis patients-the D-Bic study.

Abstract

Background: Short calciprotein crystallization time (low T50) is directly associated with an increased risk of cardiovascular events and mortality. Here, we investigated whether increases in dialysate bicarbonate concentrations increase T50 times in dialysis patients.

Methods: In a prospective, single-center, single-arm, interventional trial in hemodialysis patients (N = 29), dialysate bicarbonate was decreased from baseline settings to 27 mmol/L (D-Bic 27) followed by an increase to 37 mmol/L (D-Bic 37), over the course of 6 weeks. The primary endpoint was the change in T50 time between the D-Bic 27 and D-Bic 37 phases. Measurements of endogenous calciprotein monomers (CPM), primary (CPP-1) and secondary (CPP-2) calciprotein particles were pre-specified secondary outcomes.

Results: Twenty-four patients completed the study per protocol. T50 time increased significantly from 246 ± 77 to 282 ± 81 min from the D-Bic 27 to the D-Bic 37 phase (P < .0001). The hydrodynamic radius (size) of secondary calciprotein particles generated in the T50 test (CPP-2_Rh) did not differ significantly between study phases (251 ± 75 vs 240 ± 78 nm, P = .27). Comparing the D-Bic 27 with the D-Bic 37 phase, CPM (16.8 × 10³ vs 16.2 × 10³ AU/µL, P = .9) and CPP-1 (4.6 × 105 vs 4.5 × 10⁵ counts/mL, P = .7) did not change significantly, but there was a significant decrease in CPP-2 levels (5.9 × 10⁴ vs 3.2 × 10⁴ counts/mL, P < .0003). Intradialytically, T50 increased, CPM and CPP-1 decreased, while CPP-2 remained stable.

Conclusions: Raising dialysate bicarbonate resulted in a significant increase in T50 time and a reduction of CPP-2 levels.