Low-calcium dialysate improves mineral metabolism in hemodialysis patients

Background: The Kidney Disease Outcomes Quality Initiative (K/DOQI) Guidelines for Bone Metabolism and Disease in Chronic Kidney Disease recommend 1.25 mmol/l Ca dialysate for both hemodialysis and peritoneal dialysis, while 1.5 mmol/l Ca dialysate has been used in our dialysis center. Methods: Therefore, we switched the dialysate calcium concentration from 1.5 - 1.25 mmol/l and observed the effects on serum calcium (S-Ca), phosphorus (S-P), 1-84 parathyroid hormone (whole PTH, w-PTH), bone-specific alkaline phosphatase (BAP), and tartrate-resistant acid phosphatase isoform 5b (TRACP-5b) for 6 months in 58 hemodialysis patients. Prescription of active vitamin D (VD) metabolites and Ca carbonate was increased in response to the changes in laboratory data. Results: Decrease of S-Ca was evident at 2 weeks and S-Ca remained low for 6 months. Transient elevation of S-P, which might be caused by stimulated bone resorption, was observed after the switch. In patients with low PTH (w-PTH less than 90 pg/ml before the switch), continuous increase of w-PTH, BAP, and TRACP-5b was observed. This appeared to be a favorable response because the risk of adynamic bone disease was high in this group of patients. On the other hand, acute elevation of the 3 parameters was well-controlled in patients with moderate and high PTH (w-PTH from 90 - 180 pg/ml, w-PTH more than 180 pg/ml, respectively) by increased dosage of active VD. Conclusion: These results demonstrate that 1.25 mmol/l Ca dialysate improved mineral metabolism by lowering S-Ca and releasing oversuppression of PTH. Our data also suggest that appropriate use of active VD could prevent acute rise of PTH.