Dialysate calcium individualisation: a pending issue.

Abstract

Calcium is one of the key elements to consider in patients on dialysis due to its relationship with cardiovascular risk. The introduction of non-calcium-based phosphate binders and calcimimetics has changed the setting for pre-dialysis serum calcium in recent years from 9.5-10.5mg/dl to 8.5-9.5mg/dl. To assess more accurately the changes in calcium (Ca) during haemodialysis sessions and to individualise prescriptions, the aim of this study was to assess the intradialytic changes of two different dialysate Ca concentrations before and after hemodialysis and their implications in controlling calcium-phosphate metabolism. We analysed 98 patients with a mean age of 59.3 ± 15 years, 68 of which were men and 30 women. Each patient received two HD sessions with two different dialysate Ca concentrations: 2.5 mEq/l (Ca25 group) or 3.0 mEq/l (Ca30 group). Pre- and post-dialysis Ca, phosphorus (P) and PTH were determined, and associated medications were recorded. For a more individualised analysis, patients were divided into four subgroups of Ca<8.5mg/dl, 8.5-9.0mg/dl, 9.0-9.5mg/dl, and >9.5mg/dl, according to pre-dialysis serum calcium levels. There were no differences in pre-dialysis values of Ca: 8.81 ± 0.65 (CA25) and 8.88 ± 0.61 (CA30), P: 4.01 ± 1.3 (CA25) and 4.19 ± 1.2 (CA30), or PTH: 352 ± 288 (CA25) and 369 ± 310 (CA30). Post-dialysis Ca and PTH did not change significantly with CA25 dialysate, although there was a significant post-dialysis Ca increase to 10.2 ± 0.6 (P<.001) accompanied by a decrease in post-dialysis PTH (181 ± 227, P<.001) with CA30. However, with CA25 dialysate, when different subgroups of pre-dialysis Ca were analysed: <8.5mg/dl (30.6%), 8.5-9.0mg/dl (31.6%), 9.1-9.5mg/dl (23.5%) and >9.5mg/dl (14.3%) we observed a Ca increase during the session in the <8.5 (P<.001) and 8.5-9.0 (P<.01) subgroups. Ca was unchanged in the 9.1-9.5 group and Ca decreased when the initial Ca values were >9.5mg/dL (P<.01). A Ca increase (P<.001) and a decrease in PTH (P<.01) were observed in all subgroups with CA30 dialysate. A total of 42% of patients were taking calcimimetics, 47% paricalcitol, and 32% calcium-based phosphate binders, although these drugs were not linked with pre- or post-dialysis Ca levels in or dialysate treatment. We concluded that the prescription of Ca dialysate needs to be individualised based on pre- and post-dialysis Ca values and the need for an increase, decrease, or no changes in post-dialysis calcium in relation to the clinical condition of the patient's phosphorous-calcium metabolism.