Effects of acute variation of dialysate calcium concentrations on arterial stiffness and aortic pressure waveform

Abstract

Background. Abnormal mineral metabolism in chronic kidney disease plays a critical role in vascular calcification and arterial stiffness. The impact of presently used dialysis calcium concentration (DCa) on arterial stiffness and aortic pressure waveform has never been studied. The aim of the present study is to evaluate, in haemodialysis (HD) patients, the impact of acute modification of DCa on arterial stiffness and central pulse wave profile (cPWP).Method. A randomized Latin square cross-over study was used to evaluate the three different concentrations of DCa (1.00, 1.25 and 1.50 mmol/L) during the second HD of the week for 3 consecutive weeks. Subjects returned to their baseline DCa for the following two treatments, allowing for a 7-day washout period between each experimental HD. cPWP, carotido-radial (c-r) and carotido-femoral (c-f) pulse wave velocities (PWV), plasma level of ionized calcium (iCa) and intact parathyroid hormone (PTH) were measured prior to and immediately after each experimental HD session. Data were analysed by the general linear model for repeated measures and by the general linear mixed model.Results. Eighteen patients with a mean age of 48.9 ± 18 years and a median duration of HD of 8.7 months (range 1–87 months) completed the study. In post-HD, iCa decreased with DCa of 1.00 mmol/L (−0.14 ± 0.04 mmol/L, P < 0.001), increased with a DCa of 1.50 mmol/L (0.10 ± 0.06 mmol/L, P < 0.001) but did not change with a DCa of 1.25 mmol/L. Tests of within-subject contrast showed a linear relationship between higher DCa and a higher post-HD Δc-f PWV, Δc-r PWV and Δmean BP (P < 0.001, P = 0.008 and P = 0.002, respectively). Heart rate-adjusted central augmentation index (AIx) decreased significantly after HD, but was not related to DCa. The timing of wave refection (Tr) occurred earlier after dialysis resulting in a linear relationship between higher DCa and post-HD earlier Tr (P < 0.044). In a multivariate linear-mixed model for repeated measures, the percentage increase in c-f PWV and c-r PWV was significantly associated with the increasing level of iCa, whereas the increasing level of ΔMBP was not significant. In contrast, the percentage decrease in Tr (earlier wave reflection) was determined by higher ΔMBP and higher ultrafiltration, whereas the relative change in AIx was inversely determined by the variation in the heart rate and directly by ΔMBP.Conclusion. We conclude that Dca and acute changes in the serum iCa concentration, even within physiological range, are associated with detectable changes of arterial stiffness and cPWP. Long-term studies are necessary to evaluate the long-term effects of DCa modulation on arterial stiffness.

Intradialysis Hypertension in End-Stage Renal Disease Patients

“…37 Other studies have reported that increased calcium in dialysate acutely worsens arterial compliance and minimizes intradialytic BP reduction. 38 At least in theory, high calcium dialysate may worsen the hemodynamic response to ultrafiltration dialysis in patients with intradialytic hypertension.…”

Adverse Effects of Conventional Thrice-Weekly Hemodialysis: Is It Time to Avoid 3-Day Interdialytic Intervals?

“…Since impaired mineral metabolism is a strong and independent predictor of mortality in hemodialysis [27] , the intermittently higher calcium phosphate product during the long interdialytic interval may worsen the outcomes in these patients. Furthermore, recent studies have shown that high dialysate calcium concentrations acutely raise BP and worsen arterial compliance during dialysis [28] . Prospective studies support that session-to-session variability in serum calcium and phosphate levels is a predictor of mortality in hemodialysis [29,30] .…”

Nephrology literature watch

“…Some epidemiologic and cohort studies have implicated calcium loads from either the dialysate or from oral phosphate binders in the development of vascular calcifi cations, but this association has not been observed in all observational settings. 8,[10][11][12][13] In the general population, calcium supplementation is associated with reduced blood pressure and has been advocated by some as potentially reducing cardiovascular risk through a favorable effect on blood pressure. The results of two large studies, one of which is reviewed here (Pentti and colleagues), challenge conventional wisdom and provide evidence for potential harm with calcium supplementation in a healthy elderly population.…”