Influence of lowering dialysate calcium concentration on chronic kidney disease-mineral and bone disorder in maintenance hemodialysis patients

Objective To explore the influence of lowering dialysate calcium concentration on the parameters of chronic kidney disease (CKD)-mineral bone disorder (MBD) and drug dosage of maintenance hemodialysis patients, and find out the target group of the dialysate calcium concentration 1.25.Methods The clinical data of maintenance hemodialysis patients in our hospital were analyzed retrospectively. The observation period was set as consecutive 12 months after the Ca concentration decreased from 1.5 to 1.25 mmol/L. The serum levels of calcium, phosphate, PTH and alkaline phosphatase before and after Ca conversion were compared. The effect of lowering Ca on the prescription of calcium carbonate and calcitriol was also determined. Patients were further divided into three groups according to their baseline PTH level to evaluate the impact of Ca 1.25 on secondary hyperparathyroidism.Results 281 patients were finally enrolled in this study. During the first year after Ca conversion, mean serum calcium and phosphate levels did not change significantly (P>0.05), while alkaline phosphatase and PTH concentrations increased (P<0.05). The rate of achievement of target serum calcium and phosphate one year after lowering Ca was not different from that at baseline (P>0.05). However, the rate of achievement of target PTH dropped from 56.1% to 49.8% and this difference was considered statistically significant (P<0.05). The dose of calcium carbonate did not change after the Ca conversion (P>0.05), while average calcitriol dose increased from (1.87±1.09) to (2.62±1.26) μg/week obviously (P<0.05). Serum PTH level increased over time independent of baseline PTH. But the group with highest baseline PTH (>300 ng/L) tended to exceed the upper limit of PTH target range after the Ca conversion (59.5%).Conclusions Compared to Ca 1.5, Ca 1.25 hardly causes change on serum calcium and phosphate level. However, it can increase PTH level, consequently leading to secondary hyperparathyroidism and high turnover renal osteodystrophy may be exacerbated. Patients with lower baseline serum PTH level are likely to benefit from Ca 1.25.