Biochemical effects of high dialysate calcium in hemodialysis patients with hyperparathyroidism: a 10 month study

In the past 15 years, there has been a trend to decrease dialysate calcium concentrations to prevent hypercalcemia. However, low dialysate calcium can provoke hyperparathyroidism. The time course of the effect of increasing dialysate calcium is not well characterized, and the effect on calcium-phosphate product is unclear. Therefore, we studied the effect of increasing dialysate calcium from 1.5 to 1.75 mM in 21 stable patients on hemodialysis who had serum phosphate of less than 2 mM and serum calcium of less than 2.4 mM. Over 10 months, parathyroid hormone levels fell from 39.6 to 16.6 pM (p < 0.0001), whereas serum calcium increased from 2.27 to 2.41 mM. There were no significant changes in serum phosphate or the calcium-phosphate product. Three patients became hypercalcemic when their parathyroid hormone levels were suppressed to less than 10 pM. We conclude that in carefully selected patients, increasing dialysate calcium can safely treat hyperparathyroidism with minimal risk of complications. This treatment has the advantage over the use of vitamin D therapy of being less expensive, independent of patient compliance, and less likely to cause increases in serum phosphate or calcium-phosphate product.