Short- and Long-term Effects of Dialysate Calcium Concentrations on Mineral and Bone Metabolism in Hemodialysis Patients: The K4 Study

Rationale & Objective: The short- and long-term impact of conversion of dialysate calcium concentration from either 2.5 or 3.0 mEq/L to 2.75 mEq/L on mineral and bone metabolism remains unknown in hemodialysis patients. Study Design: Nonrandomized intervention study. Setting & Population: 12 hemodialysis patients treated at baseline with a 2.5-mEq/L dialysate calcium concentration and another 12 hemodialysis patients treated with a 3.0-mEq/L dialysate calcium concentration. Intervention: Use of 2.75-mEq/L dialysate calcium concentration. Outcomes: Changes in intradialytic calcium and phosphate clearance and changes in predialysis and intradialytic serum and ionized mineral and biochemical parameters over the 24 weeks following dialysate calcium conversion. Results: Conversion of dialysate calcium concentration from 2.5 to 2.75 mEq/L increased intradialytic calcium loading and serum total and ionized calcium levels, whereas conversion of dialysate calcium from 3.0 to 2.75 mEq/L decreased intradialytic calcium loading and serum total and ionized calcium levels. Dialysate calcium concentration conversion did not affect intradialytic serum parathyroid hormone level, intradialytic phosphate elimination, or predialysis serum calcium, phosphate, parathyroid hormone, and fibroblast growth factor 23 levels. Intradialytic calcium influx was determined by dialysate calcium concentration and predialysis serum calcium levels, whereas intradialytic phosphate elimination was determined by predialysis serum phosphate levels. Limitations: Small sample size and no control groups treated with 2.5- and 3.0-mEq/L dialysate calcium concentrations during the 24 weeks of the observation period. Conclusions: Conversion of dialysate calcium concentration from either 3.0 or 2.5 to 2.75 mEq/L results in expected changes in calcium loading based on predialysis calcium concentration. The dialysate calcium concentration should be personalized based on clinical factors.