Low dialysate calcium in continuous ambulatory peritoneal dialysis: A randomized controlled multicenter trial

Abstract

Hypercalcemia is a common complication in continuous ambulatory peritoneal dialysis (CAPD) patients treated with calcium-containing phosphate binders and using the standard dialysate calcium concentration of 3.5 mEg/L (SCa). Lowering the dialysate calcium was proposed to overcome this problem. The current randomized controlled multicenter study was designed to investigate efficiency and safety of a low calcium dialysate (2.00 mEq/L; LCa) compared with SCa (3.5 mEq/L) in CAPD patients. After an 8-week run-in period, 103 stable CAPD patients, 68 men, 35 women, aged 54.5 years (range, 20 to 77)) were randomly allotted to treatment with either LCa or SCa. All patients received calcium carbonate as oral phosphate binder to achieve serum phosphate levels < 6.2 mg/dL. If persistent hypercalcemia arose, CaCO 3 was replaced by AI(OH) 3 until normocalcemia was achieved. All patients received 0.25 μg calcitriol/d. Parameters monitored included total and ionized serum calcium, serum phosphate, phosphate binder intake, incidence of hypercalcemia, serum aluminium, intact parathyroid hormone (1,84PTH), osteocalcin, alkaline phosphatase, bone mineral density and hand skeletal x-ray. Primary end points were (a) number of hypercalcemic episodes, (b) tolerated doses of calcium-containing phosphate binders, and (c) 1,84PTH. After 6 months of therapy, total and ionized calcium were lower in LCa patients (total Ca:9.6 v 10.08 mEq/L, P = 0.005; iCa: 4.76 v 5.15 mg/dL; P = 0.013). In the LCa group, siginificantly fewer episodes of hypercalcemia were recorded (total S-calcium > 10.8 mg/dL: LCa 24 v SCa 86 episodes; P < 0.005). Use of LCa permitted the administration of more CaCO 3 (mean daily tablet number: LCa, 5.9 v SCa, 4.2; P < 0.05). More AI(OH) 3 was required in the SCa group (2.0 v 0.7 tablets/d per patient; P < 0.01). Control of serum phosphate was comparable, and initial and final serum levels did not differ between the groups. 1,84 PTH levels were within the desired range in the LCa group (medians: start of run-in, 15 pmol/L; start of therapy, 15.5 pmol/L; wk 24, 14 pmol/L), whereas in the SCa group, 1,84 PTH declined to the normal range (start of run-in, 15 pmol/L; start of therapy, 9.2; wk 24, 7.05 pmol/L; normal, 1 to 6 pmol/L). No radiologic signs of renal osteodystrophy or demineralization of the bones were observed with LCa. Adverse events were rare, with the exception of peritonitis. The frequency of peritonitis episodes and exit-site infections was similar, however, in LCa and SCa patients. In conclusion, this randomized controlled multicenter study in a large number of CAPD patients documents significantly better tolerance of calcium-containing phosphate binders with no adverse effects on PTH levels or other end points after 6 months of treatment when dialysate calcium concentration is lowered to 2.0 mEq/L.