Peritoneal magnesium elimination and its clinical relevance in peritoneal dialysis patients

Dialysis patients are at increased risk for vascular calcification and cardiovascular disease. Emerging data suggests that magnesium might be protective for the vascular system in peritoneal dialysis (PD) patients as well. However, only limited data is available on the elimination of magnesium through PD treatment. This study aims to evaluate the peritoneal magnesium elimination characteristics in comparison to other small solutes and the influence of peritoneal transport status.

Peritoneal elimination of magnesium, blood-urea-nitrogen (BUN), and creatinine during a 4-hour peritoneal equilibration test (PET) was assessed in 30 stable PD patients. Absolute magnesium elimination was compared overall and between creatinine transport tertiles.

Median age was 61 years, 50% of patients were male, 20% were on automated PD treatment. Serum magnesium was 0.84 mmol/L, and dialysate magnesium at the end of the PET was 0.57 mmol/L in the overall cohort and did not differ significantly between tertiles. The magnesium dialysate-to-plasma ratio was significantly different between the subgroups (lower tertile: median 0.60 (minimum 0.52, maximum 0.68) vs. middle tertile: 0.64 (0.58, 0.68) vs. upper tertile: 0.69 (0.67, 0.74), p < 0.001). The elimination per liter of dialysis fluid was also significantly different (8.6 (6.6, 10.4) vs. 9.4 (8.0, 10.5) vs. 10.6 (0.2, 11.8) mg/L, p = 0.002), as was the absolute removal during the 4-hour dwell (18.6 (15.8, 21.2) vs. 19.4 (13.4, 24.6) vs. 22.7 (19.6, 31.9) mg, p = 0.007, respectively).

Peritoneal magnesium elimination is similar to small solute transport characteristics. However, the absolute differences among patients with slower and faster transport types are small. Therefore, magnesium supplementation in PD patients should be guided by serum magnesium concentrations rather than the amount of peritoneal elimination.