Effect of combining different calcium concentration dialysate on calcium balance in peritoneal dialysis patients

Background  Calcium and phosphorus metabolic disturbance are common in dialysis patients and associated with increased morbidity and mortality. Therefore, maintaining the balance of calcium and phosphate metabolism and suitable intact parathyroid hormone (iPTH) level has become the focus of attention. We investigated the effects of different peritoneal dialysate calcium concentrations on calcium phosphate metabolism and iPTH in continuous ambulatory peritoneal dialysis (CAPD) patients.

Methods  Forty stable CAPD patients with normal serum calcium were followed for six months of treatment with 1.25 mmol/L calcium dialysate (DCa1.25, PD4, 22 patients) or a combination of 1.75 mmol/L calcium dialysate (DCa1.75, PD2) and PD4 (18 patients) twice a day respectively. Total serum calcium (after albumin correction), serum phosphorus, iPTH, alkaline phosphatase (ALP) and blood pressure were recorded before and 1, 3 and 6 months after treatment commenced.

Results  No significant difference was found in baseline serum calcium, phosphorus between the two patient groups, but the levels of iPTH were significantly different. No significant changes were found in the dosage of calcium carbonate and active vitamin D during 6 months. In the PD4 group, serum calcium level at the 1st, 3rd, 6th months were significantly lower than the baseline (P <0.05). There was no significant difference in serum phosphorus after 6 months treatment. iPTH was significantly higher (P <0.001) at the 1st, 3rd, and 6th months compared with the baseline. No differences were seen in ALP and blood pressure. In the PD4+PD2 group, no significant changes in serum calcium, phosphorus, iPTH, ALP and BP during the 6-month follow-up period.

Conclusions  Treatment with 1.25 mmol/L calcium dialysate for six months can decrease serum calcium, increase iPTH, without change in serum phosphorus, ALP, and BP. The combining of PD4 and PD2 can stabilize the serum calcium and avoid fluctuations in iPTH levels.