The BicMag study is a prospective, randomized, controlled cross-over study that aims to examine the potential additive effect of a dialysate enriched with both bicarbonate and magnesium on mineral buffering capacity in the blood of chronic hemodialysis patients.

We hypothesize that simultaneously increasing bicarbonate and magnesium concentrations in the dialysate will enhance mineral buffering capacity more effectively than either intervention alone. Ninty-one chronic hemodialysis patients will be enrolled in this randomized, controlled, cross-over study. Using a balanced Latin square design, participants will undergo four sequential 3-week treatment phases with the following dialysates:

• D-Standard: 32 mmol/L bicarbonate, 0.5 mmol/L magnesium
• D-Bic: 37 mmol/L bicarbonate, 0.5 mmol/L magnesium
• D-Mag: 32 mmol/L bicarbonate, 1 mmol/L magnesium
• D-BicMag: 37 mmol/L bicarbonate, 1 mmol/L magnesium. The primary endpoint is calciprotein crystallization time (T50); the secondary endpoint is serum levels of endogenous calciprotein particles.

Inclusion Criteria:

• Age ≥ 18 years
• Prevalent patients (≥ 3 months) treated with thrice weekly hemodialysis or hemodiafiltration
• Dialysate calcium of 1.25 mmol/l

Exclusion Criteria:

• Inability to provide informed consent
• Currently participating in another investigational device or drug study or non-interventional study
• Dialysate calcium other than 1.25 mmol/l
• Parathyroidectomy planned during the study
• Elective living-donor kidney transplant scheduled during the study period
• Therapy with bisphosphonates within the past 12 months or denosumab within the past 6 months
• Pregnant or nursing (lactating) women