Low calcium peritoneal dialysis solution. Effects on calcium metabolism and bone disease in CAPD patients

Calcium carbonate (CaCO3) is an effective phosphate (PO4) binder in uremics, and its use reduces aluminum (AI) intake. By maintaining high serum Ca2+ levels, it decreases serum parathyroid hormone (PTH) levels. Hypercalcemia, however, often limits the dosage. To evaluate the effects of a low Ca2+ peritoneal dialysis solution (PDS; 1.25 mmol/L) on calcium metabolism, the following were studied in continuous ambulatory peritoneal dialysis (CAPD) patients with hypercalcemia (six with high PTH levels, and high turnover bone disease [Group 1], and six with low PTH levels, and low turnover bone disease [Group 2] documented by bone biopsies): 1) serum Ca2+ and PO4 levels; 2) serum PTH levels; 3) serum AI levels; and 4) bone morphology. The follow-up was 12 months. In both groups, within the third month, there was a decrease in serum Ca2+. In Group 2, serum PTH increased, reaching the norm, and in Group 1 it further increased, exceeding the norm. Because in both groups serum Ca2+ was normal, it was possible to give oral CaCO3 (10.5 +/- 2.5 g/day) to control PO4 levels while stopping AI gels. This did not induce any increase in serum Ca2+, whereas serum AI fell significantly. In Group 1, to avoid a further rise of serum PTH, the low Ca2+ PDS was supplemented with calcitriol (mean 3.5 +/- 0.5 microgram/day); this was followed by a reduction in serum PTH with no increase in serum Ca2+ or PO4.(ABSTRACT TRUNCATED AT 250 WORDS)