Arterial stiffness alterations during hemodialysis: the role of dialysate calcium

Background/aims: We investigated the way dialysate calcium (dCa) level can influence arterial stiffness (AS), measured by stiffness index (SI), a surrogate of pulse wave velocity, and reflection index (RI), a measure of the amount of pulse wave reflection, derived by digital volume pulse (DVP).

Methods: Fourteen hemodialysis (HD) patients underwent two consecutive midweek 4-hour HD treatments in randomized order with a low dCa concentration of 1.25 mmol/l (LdCa) and a high dCa concentration of 1.75 mmol/l (HdCa), respectively. Before HD and at 1-hour intervals during the subsequent 4-hour HD sessions, SI and RI measurements were obtained from DVP contour analysis. Blood pressure (BP) and heart rate (HR) were measured after each measurement of AS. Ionized serum calcium (iCa) was measured before HD and at 120 and 240 min into the HD session.

Results: iCa increased and decreased by 15.3 and 5.4% in the HdCa and LdCa groups, respectively, at the end of HD. SI and RI increased by 5.7 and 6% in the HdCa group, respectively, whereas they remained unchanged in the LdCa group. The treatment effect and the time x treatment effect were significant for both indices (ANOVA). BP and HR changes did not differ between treatments.

Conclusion: Contrary to LdCa, HdCa treatment induced a BP-independent, significant increase in measured AS parameters. In the long run, HD with LdCa, by reducing the incidence of HD-induced hypercalcemia, may have a beneficial role in minimizing the cardiovascular risk related to the intermittent, intradialytic increase in AS, inherent in the chronic use of HdCa.