Clinical Usefulness of Low Calcium Dialysate in CAPD Patients with High Risk of Low-turnover Bone Disease

Cho, Young Jun; Choi, Hyuk Jun; Cho, Ji Hyung; Jang, Min Hwa; Sin, Yong Bong; Park, Sun Hee; Lee, Duk Hyun; Cho, Seong; Kim, Yong Lim; Cho, Dong Kyu

Abstract

Hypercalcemia is a common complication in CAPD patients treated with calcium-containing phosphate binders and using the standard dialysate(Ca++ : 3.5 mEq/L). Furthermore, the high calcium concentration in standard dialysate may have a suppressive effect on parathyroid hormone(iPTH) level, contributing to the high prevalence of low-urnover bone disease. We studied the effect of low calcium dialysate(Ca++ : 2.5 mEq/L) for those patients with high risk of low- turnover bone disease. Among 386 patients(1996. 1.- 1999. 12.) who had been stable on CAPD for at least 3 months, 46 patients were included in this study. The patients were divided into 3 groups on the basis of the iPTH levels(<150 pg/mL) and/or corrected serum calcium levels(>10 mg/dL) before the conversion to low calcium dialysate. Group 1(n=29), iPTH <150 pg/mL and Ca++>10 mg/dL; Group 2 (n=14), iPTH <150 pg/mL and Ca++<10 mg/dL; Group 3(n=3), iPTH >150 pg/mL and Ca++ >10 mg/ dL. During a 2-month run-in period, those patients were treated with standard dialysate. After that, a 12-month therapy with low calcium dialysate was followed. Biochemical data including calcium, phosphorus, iPTH and alkaline phosphatase were measured regularly and daily phosphate binder and calcitriol intake(pill counting) were assessed during the run-in and therapy period. We obtained the following result: the prevalence of hypercalcemia(Ca++>10.5 mg/dL) was 5.7%(22/ 386 patients). Serum calcium levels decreased during the therapy period(12 months)(10.5+/-1.4 vs 9.4+/-1.3 mg/dL, p<0.05). Serum phosphorus levels remained unchanged. Mean serum alkaline phosphatase level increased(203.0+/-92.9 vs 257.2+/-103.4 U/L, p<0.05). Serum iPTH levels increased (92.7+/-128.8 vs 225.3+/-237.3 pg/mL,p<0.05). The mean intake of oral phosphate binders was not significantly different between run-in period and therapy period. But calcitriol doses increased 0.038+/-0.087 at run-in period to 0.158+/-0.288 tablets/person/day at therapy period(p<0.05). In the six patients, low calcium dialysate was converted to standard dialysate due to high iPTH level (n=3), symptomatic hypo calcemia(n=2), and uncontrolled edema(n=1). In conclusion, in the study of 46 patients over 12 month period, the usage of 2.5 mEq/L calcium dialysate resulted in a significant decrement in calcium levels and increased iPTH levels. Therefore, we propose that dialysis with a low calcium dialysate is an acceptable form of therapy for the patients with high risk of low-turnover bone disease showing hypercalcemia and low iPTH level. However, further study will be needed for evaluating the effect of low calcium dialysate in low-turnover bone disease.