Can Low-Calcium Peritoneal Dialysis Solution Safely Replace the Standard Calcium Solution in the Majority of Chronic Peritoneal Dialysis Patients?

OBJECTIVE: To evaluate the use of low-calcium solution as the standard solution in chronic peritoneal dialysis patients. DESIGN: Prospective long-term follow-up study over a one-year period. SETTING: University hospital. INTERVENTIONS: The change of the calcium concentration of the dialysate from 1.75 mmol/L to 1.25 mmol/L. MAIN OUTCOME MEASURES: Serum calcium and phosphorus concentration and intact parathyroid hormone (iPTH). PATIENTS: Fifty normo- and hypercalcemic patients using the standard 1.75 mmol/L calcium solution. RESULTS: Serum ionized calcium (iCa) decreased significantly during the first six months, resulting in a significant increment of iPTH (baseline value: 0.9-79, median 9.4 pmol/L; at six months: 1.1-111, median 20.6 pmol/L; p < 0.05). In 28 patients completing the study, iPTH remained significantly elevated, despite high normal iCa. At similar changes of iCa, patients with baseline iPTH > 20 pmol/L showed a significantly higher increase in iPTH than patients with low iPTH (24.0 vs 5.0; p < 0.01), despite a more than doubled dose of alfacalcidol and calcium carbonate (mean dose of 1580 increased to 3277 mg/day). During the follow-up, 21 episodes of hypercalcemia were observed. Phosphorus control was adequate. CONCLUSIONS: Low-calcium solution cannot be used as a standard solution, especially in patients with iPTH levels indicating mild or severe hyperparathyroidism, because in these patients iPTH may rise further.