RELATIONSHIP BETWEEN BODY-SIZE, FILL VOLUME, AND MASS-TRANSFER AREA COEFFICIENT IN PERITONEAL-DIALYSIS

A peritoneal dialysate fill volume of 2 L has become the standard of c linical practice, but the relationships between body size, fill volume , and mass transfer area coefficient (KoA) have not been well establis hed. These relationships were studied in 10 stable peritoneal dialysis patients who underwent six peritoneal equilibration studies (2 h each ) at fill volumes of 0.5, 1, 1.5, 2, 2.5, and 3 L. The concentration-t ime profiles for urea, creatinine, and glucose were measured at each f ill volume, and residual volumes were calculated from the preceding dw ell period. A modified Henderson equation was used to calculate the Ko A for the three solutes as a function of fill volume. By normalizing t he KoA for each solute to the value at 2 L, the data for all three sol utes collapsed onto the same trend line when plotting the normalized K oA versus dialysate volume. Between 0.5- and 2-L fill volumes, the ave rage normalized KoA increases in an almost linear fashion, its value a lmost doubling over this range. Between 2- and 3-L fill volumes, there is less than a 10% change in the normalized KoA. However, fill volume s for peak urea KoA were found to increase with increasing body surfac e area (R = 0.76), being around 2.5 L for an average-sized patient and increasing to between 3 and 3.5 L for body surface areas > 2 m(2). To maximize solute transport, these relationships between body size, vol ume, and KoA should be considered when choosing fill volumes for conti nuous ambulatory peritoneal dialysis and automated peritoneal dialysis and when deciding reserve and tidal volumes for tidal peritoneal dial ysis.