Calcium and magnesium mass transfer in peritoneal dialysis patients using 1.25 mmol/L calcium, 0.25 mmol/L magnesium dialysis fluid

Objective: To examine the effect of a reduced calcium/magnesium dialysis fluid (1.25/0.25 mmol/L, respectively) on calcium and magnesium mass transfer in both 1.36% and 3.86% glucose solutions. Design: Each patient underwent four test exchanges, two with a standard dialysis fluid containing 1.36% and 3.86% glucose, and two with a reduced calcium/magnesium fluid containing 1.36% and 3.86% glucose. Calcium and magnesium were measured in dialysate and serum at 0 and 240 minutes. Setting: Single renal unit of a university teaching hospital. Patients: Sixteen patients established on CAPD, and peritonitis-free, for at least 3 months. Results: A lower dialysate calcium results in negative mass transfer when serum-ionized calcium exceeds dialysate calcium (mean -0.21 ± 0.15 mmol/exchange), and positive mass transfer when serum-ionized calcium is less than dialysate calcium in 1.36% glucose solutions (mean 0.57 ± 0.18 mmol/exchange). A negative correlation was found between serum-ionized calcium level and calcium mass transfer. With a 3.86% reduced calcium/magnesium solution, calcium mass transfer is always negative (-0.88 ± 0.18 mmol/exchange) due to ultrafiltration and solute drag. Fifteen patients were found to be hypermagnesemic at the time of the study. Magnesium mass transfer was neutral with the standard 1.36% glucose fluid (mean -0.01 mmol/exchange), but negative with the reduced calcium/magnesium 1.36% glucose fluid (mean -0.58 ± 0.13 mmol/exchange). With the 3.86% glucose solution, both fluids produced negative magnesium mass transfer (mean -0.32 ± 0.11 and -1.07 ± 0.11 mmol/exchange for standard and reduced calcium/magnesium fluids, respectively). Conclusions: We conclude that this fluid formulation should reduce hypercalcemia and hypermagnesemia in CAPD patients.