Transperitoneal Calcium and Magnesium Transfer during an 8-Hour Dialysis

Abstract

The authors studied transperitoneal calcium and magnesium transfer during an eight-hour dialysis in 13 CAPD patients with both 1.5% dextrose and 4.25% dextrose solutions with a Ca concentration of 1.75 mM/L and Mg 0.75 mM/L. The mean mass transfer of calcium was 0.733 mmol with 1.5% dextrose exchanges, and - 0.151 mmol with 4.25% dextrose solutions. The mean mass transfer of magnesium was negative with both 1.5% and 4.25% dextrose solutions. Mass transfer of both calcium and magnesium correlated inversely with the initial peritoneal fluid: blood osmotic gradient and positively with the initial peritoneal fluid/blood calcium or magnesium gradients. The ionic calcium gradient was dissipated rapidly because of the disappearance of pH gradient. Peritoneal fluid ionic calcium concentrations correlated positively with peritoneal fluid pH. It is suggested that calcium traverses the peritoneal membrane in the forms of ionic and chelated calcium.

Transperitoneal transfer of calcium and magnesium during peritoneal dialysis has been the subject of a few studies (1–4), which were concerned with intermittent peritoneal dialysis (1,2) or with continuous peritoneal dialysis (CAPD) involving four 2-litre exchanges daily (3, 4). Because three exchanges per day is our usual practice (15) and because there is a paucity of data on calcium and magnesium transfer during an eight-hour peritoneal dialysis, we undertook to determine transperitoneal transfer of calcium and magnesium, and to examine in detail the various factors affecting these trans peritoneal fluxes.