Effect of calcium and citrate dialysate concentrations on the calcification propensity in hemodialysis; a prospective randomized controlled cross-over trial.

In chronic hemodialysis (HD) patients managed with thrice weekly HD, the
mortality due to cardiovascular events remains high despite of all the
technological improvements of this therapy in the last years. It has been shown
that an increased vascular calcification is directly correlated to an increased
cardiovascular mortality. In dialysis patients abnormalities in mass transport
of calcium and phosphate, which are involved in formation of calciprotein
particles (CPPs) could play a pathogenic role. The calcification propensity of
serum, measured by a novel T50 test, measures the transformation time from
primary to secondary CPPs and is highly predictive of all-cause mortality in HD
patients. In a recent study it was shown that phosphate removal during
dialysis strongly improved the T50. However, less is known on the influences of
dialysate calcium on the formation of CPP or on the role of calcium-citrate
dialysate, in which citrate is a calcium chelator.

The first objective of this study is to evaluate the effect of standard HD with
different dialysate calcium concentrations as well as HD combined with
citrate-acid dialysate on the clearance of CPPs and second the effect of these
different solutions on cardiovascular parameters.

Twenty-two prevalent conventional high-flux HD (CHD) patients will undergo, in
a random prospective design, 1 week standard high-flux HD with DCa1.50
(treatment A) followed by either citrate acid-dialysate HD (treatment B) or
high-flux HD with DCa1.25 (treatment C) for 1 week, followed by a wash-out
period of 1 week on standard high-flux HD with DCa1.50 (treatment A), followed
by either citrate acid-dialysate HD (treatment B) or high-flux HD with DCa1.25
(treatment C) for 1 week.

In the study 22 HD patients will be treated in a randomized order with either a
dialysate calcium (DCa) of 1.25 mmol/l (DCa 1.25), a DCa of 1.50 mmol/l (DCa
1.50), or citrate-acid dialysate (containing 1.5 mmol/l calcium) for 3
treatments (1 week) each.

In this study, only non-invasive techniques which pose a minimal burden to the
patient will be used. Blood sampling, HRV-, and the PWV-measurements will be
combined with regular blood takings when patients are present in their dialysis
unit. The different dialysate calcium concentrations as well as citric-acid
dialysate are registered products and used in routine practice.