**6. Dialysate calcium concentration**

A near-neutral calcium flux could be expected in patients with a dialysate calcium concentration of 1.25 mmol/L (2.5 mEq/L), although there is considerable interindividual variability among patients (Hou et al., 1991; Argiles et al., 1993). Based on calcium kinetic modelling even lower dialysate calcium concentrations of 1.0 mmol/L (2.0 mEq/L) might be needed to avoid net positive calcium balance (Gotch et al., 2010). The risks of hemodynamic instability and cardiac rhythm disturbances with a very low dialysate calcium concentration must be kept in mind (Drueke & Touam, 2009). Overall calcium balance is influenced by dietary calcium intake, vitamin D level, calcium-containing phosphate binders, use of VDRA and calcimimetics and dialysate calcium concentration. Therefore, selecting an individual dialysate calcium concentration is based on various parameters and must always be a compromise between the need to guarantee cardiovascular stability during the hemodialysis session and the goal to maintain normal bone turnover and mineralization in order to avoid bone pain and fractures but avoid extraskeletal calcification.
