Intradialytic and interdialytic effects of treatment with 1.25 and 1.75 mmol/L of calcium dialysate on arterial compliance in patients on hemodialysis

Arterial compliance (AC) is an important determinant of vascular structure, and abnormalities of BC can greatly affect the cardiovascular system. Give n the vasoconstrictive properties of increased levels of serum ionized calc ium (iCa), we investigated the way that dialysate calcium level can influen ce AC in the hemodialysis (HD) population. In a crossover randomized design , 19 dialysis patients undergoing regular bicarbonate HD (three times weekl y) underwent two cycles of four successive HD sessions each with a low (LdC a; 1.25 mmol/L) and high dialysate calcium concentration (HdCa; 1.75 mmol/L ), At the fourth session of each cycle, iCa level and hemodynamic parameter s (systolic blood pressure [SBP], diastolic blood pressure, mean arterial p ressure [MAP], pulse pressure [PP], heart rate, and AC) were measured pre-H D and post-HD. AC was measured noninvasively at the brachial artery by arte rial pulse waveform analysis. The dialysate calcium level was a significant determinant of both pre-ND (r = 0.335; P < 0.05) and post-HD iCa level (r = 0.767; P < 0.001), Pre-HD AC increased significantly (P < 0.05) by 0.01 /- 0.02 mL/mm Hg (7% +/- 19%) on switching from HdCa to LdCa treatment. Mul tiple regression analysis showed that both pre-HD PP and iCa level were maj or inverse determinants of pre-HD AC in both the LdCa (R-2 = 0.65; P < 0.00 1) and HdCa (R-2 = 0.51; P < 0.01) treatment groups. AC increased by 32% (P < 0.01) and 37% (P < 0.05) during LdCa and HdCa dialysis, respectively. In tradialytic changes in AC were inversely correlated with changes in SEP and PP. In the HdCa group, changes in iCa level related significantly to MAP ( r = 0.464; P < 0.05), The results show that changes in AC during HD are mai nly mediated through concurrent changes of systemic hemodynamics, which are largely affected by dialysate calcium level through parallel changes in iC a level. Interdialytically, a significant, blood pressure-independent, inve rse relationship between AC and iCa level exists. Therefore, HD with LdCa, by reducing the incidence of HD-induced hypercalcemia, may have a beneficia l role in preventing the ongoing reduction of AC in HD patients and thus im proving cardiovascular prognosis. (C) 2000 by the National Kidney Foundatio n, Inc.