A RANDOMIZED TRIAL COMPARING 1.25 MMOL L CALCIUM DIALYSATE TO 1.75 MMOL/L CALCIUM DIALYSATE IN CAPD PATIENTS/

Background. Effective control of hyperparathyroidism and renal osteody strophy in CAPD patients requires a combination of calcitriol and calc ium carbonate (CaCO3), but is frequently limited by hypercalcaemia. Re ducing dialysate calcium (Ca) concentration may overcome this problem, but had not been examined in a controlled trial. Methods. 45 stable C APD patients were randomly assigned in a prospective, double-blind tri al to either a study group (1.25 mmol/l Ca dialysate) or a control gro up (1.75 mmol/l Ca dialysate) for 12 months. Clinical, biochemical and radiological parameters of secondary hyperparathyroidism were followe d. Results. Twenty-three patients did not complete the study due to de ath (9), transplantation (7) or conversion to haemodialysis (7). Eleve n patients in each group completed the study. Mean serum Ca, phosphate , ionized Ca, aluminium, alkaline phosphatase (AP), and bone mineral d ensity (BMD) Z-scores did not differ significantly at any time within or between the two groups. Severe hypercalcaemia was more common in th e control group (11 vs. 2, P = 0.027). Mean serum intact parathyroid h ormone (PTH) and osteocalcin (OCN) initially rose in the study group r elative to controls at 3 months (40 +/- 7 vs 12 +/- 3 pmol/l, P = 0.00 4, and 33 +/- 5 vs 15 +/- 2 mu g/l, P = 0.002 respectively), but were not sustained. Median weekly dosages of calcitriol and daily dosages o f CaCO, increased significantly in the study group (0 mu g to 1 mu g P = 0.014 and 1260 mg to 2520 mg P = 0.002 respectively), but not in th e control group. Supplementary aluminium hydroxide (AI(OH)(3)) was req uired for phosphate control in both study (n = 5) and control patients (n = 4). Conclusions. Lowering dialysate calcium concentration reduce d the frequency of severe hypercalcaemia and allowed prescription of l arger quantities of calcitriol and CaCO3. However, in this study it of fered no advantage in terms of AI(OH)(3) requirement, while bone mass density did and may have initially exacerbated secondary hyperparathyr oidism not change.