Effects of tracer, volume, osmolarity and infection on fluid kinetics during CAPD

A review is given on various aspects of using the disappearance rate of intraperitoneally administered macromolecules for the determination of fluid kinetics in CAPD patients. The rationale and mathematics for the calculation of transcapillary ultrafiltration and of indirect measurement of lymphatic absorption are described. A comparison is made between autologous haemoglobin, human albumin and dextran 70. Dextran 70 appeared most useful; one brand of human albumin increased solute transport. Lymphatic absorption was higher after the installation of a 3-litre dialysate volume than after a 2-litre one, and also higher during peritonitis than after recovery from infection. A gradual increase in intraperitoneal volume, as obtained with glucose 3.86% dialysate, had no apparent effect on the disappearance rate of dextran 70. It is concluded that intraperitoneally administered dextran 70 is a clinically useful marker for the description of fluid kinetics in CAPD patients under various conditions.