CAPD with low calcium dialysate and calcium carbonate: results of a 24-week study

Twelve patients (median age 44.5 years) on CAPD, who had previously used a dialysate calcium concentration of 1.75 mmol/l (for a median time of 11.5 months) were started on a low calcium dialysate (LCD) with a calcium concentration of 1.25 mmol/l and followed up for 24 weeks. During the first eight weeks, no changes in the doses of oral phosphate binders were made and serum ionized calcium decreased from 1.30 +/- 0.02 (mean +/- SE) mmol/l to 1.17 +/- 0.02 (p < 0.0001) and serum PTH (1-84) rose from 68 (median, range 16-397) ng/l to 147 (70-449, p = 0.005). After week 8, increasing doses of calcium carbonate were used to achieve target calcium levels of 1.20-1.30 mmol/l. No aluminum-containing binders were used. Calcium carbonate doses were increased from 2.3 (median, range 0.75-12) g/d to 6.8 (3.8-15.0, p = 0.0004) and serum phosphorus concentrations decreased from 2.00 mmol/l (median, range 1.25-2.67) at 8 weeks to 1.61 (1.18-2.39) at 24 weeks (p = 0.023). Serum intact PTH(1-84) values remained elevated despite the gradually increasing serum calcium concentrations. Hypercalcemia was recorded in 20/36 (56%) of blood samples during a period of four weeks before the start of LCD, and such episodes were observed in 15/89 (17%) of samples (p < 0.001) on LCD during the period when calcium carbonate doses were increased. It is concluded that on LCD 1) the number of episodes of hypercalcemia was markedly reduced, 2) higher calcium carbonate doses could be used, and thus 3) the control of serum phosphorus improved.(ABSTRACT TRUNCATED AT 250 WORDS)