Discriminative impact of ultrafiltration on peritoneal protein transport

Objective:The dialysate concentration of large proteins increases, on avera ge, linearly during the whole peritoneal dialysis dwell, and this linear pa ttern seems to be independent of the rate of ultrafiltration induced by dia lysis fluid. However, we observed a high variability of protein kinetics in individual dwell studies. Therefore, we studied the details of the kinetic pattern of peritoneal transport. Design and Methods: Kinetics of beta(2)-microglobulin, albumin, and total p rotein was examined in 23 clinically stable continuous ambulatory peritonea l dialysis patients using Dianeal 3.86% (15 dwell studies) or Dianeal 1.36% (9 dwell studies) dialysis fluid. Dialysate volume was measured using radi oisotopically labeled albumin as a volume marker, with corrections for samp le volume and absorption of fluid and marker from the peritoneal cavity. Th e generalized version of the Babb-Randerson-Farrell model was applied to es timate diffusive mass transport coefficient (K-BD) and sieving coefficient (S) for proteins and small solutes (urea, creatinine, glucose, sodium, pota ssium). To quantify deviations from the linear pattern of protein dialysate concentration increase, the ratio (SR) of the slope of the linear regressi on line for the initial 3-30 minutes, divided by the slope for the next 60- 360 minutes, was evaluated for albumin. Results: In 5 dwell studies with Dianeal 3.86% fluid, SR was lower than 1 [ low albumin transport (LAT) group, median SR = 0.49, range -4.39-0.71], whi le in the other 10 dwell studies with this solution, SR was higher than 1 [ high albumin transport (HAT) group, median SR = 2.77, range 1.32-7.56]. Cle arances of albumin up to 120 minutes were higher in the HAT group than in t he LAT group. The transport of fluid, beta(2)-microglobulin, and small solu tes did not differ between the LAT and the HAT groups. K-BD values for prot eins did not differ between the groups, but S values for albumin and total protein were tower for the LAT group than for the HAT group. A similar dive rsity was found in the dwell studies with Dianeal 1.36%: In three dwell stu dies, SR for albumin was lower than 1 (median SR = 0.95, range 0.70-0.97), and in six dwells it was higher than 1 (median SR = 1.55, range 1.23-1.98). In general, the SR values observed with Dianeal 1.36% were closer to 1 tha n those for Dianeal 3.86%. Conclusions: Ultrafiltration may affect the initial kinetic patterns of lar ge protein (such as albumin) transport in two opposing ways: (1) by slowing the increase of protein concentration in dialysate (due to a low sieving c oefficient, LAT group), and (2) by speeding up the increase of protein conc entration in dialysate (due to a high sieving coefficient, HAT group). The average pattern in a nonselected group of studies is, however, close to a s teady (linear) increase.