Peritoneal Fluid Kinetics During CAPD Measured with Intraperitoneal Dextran 70

Simultaneous measurement of transcapillary ultrafiltration (TCUF), lymphatic absorption rate (LAR), and intraperitoneal volume (IPV) was performed by means of intraperitoneally-administered polydisperse dextran 70 in nine CAPD patients during a 4 hr dialysis dwell (glucose 1.36%). The recovery of dextran was 88 +/- 1%. LAR, calculated as the amount of dextran lost, divided by the dialysate dextran concentration, was 1.30 +/- 0.12 ml/min. The time course of TCUF could be described as a hyperbola. Therefore, the application of the Lineweaver-Burke plot made it possible to calculate TCUFmax (median 641 mL) and its half-time (t50: median 211 min). delta IPV4h, calculated as the difference between the Lineweaver-Burke adjusted TCUF4h and LA4h, was correlated with measured delta IPV4h after drainage (r = 0.89, p less than 0.001). The latter was dependent upon LAR (r = -0.71) and effective peritoneal surface area, as represented by mass transfer area coefficients (MTC) of low molecular weight solutes (creatinine r = -0.76, glucose r = -0.81). High MTC values of these solutes were exponentially related to a short t50 (creatinine r = -0.76). LAR was correlated with the MTC of intraperitoneally administered inulin (r = 0.83). Dextran 70 had no measurable effect on solute transport. It is concluded that dextran 70 is a useful marker for the measurement of peritoneal fluid kinetics, even during CAPD with a low glucose concentration in the dialysate.