Different cascade filtration operating modalities in clinical use.

Cascade filtration (CF) can be performed in either the single-pass or dead-end configuration. The distinction, as predicted by experimental models, is that solute removal is lower but constant in the former, and higher but variable with the quantity of filtrate in the latter. Moreover, unpredictable plugging reduces permeability during operation. It is therefore unclear which configuration is preferable in clinical use. In four cryo- and three macroglobulinemic patients, the data of 10 dead-end CF (QP) and 11 modified single-pass CF with high flow rate recycling plasma (QD) were compared. Both groups had similar starting values. Centrifugal primary plasma separation was performed. No exogenous reinfusions were used. Either 0.8 and 1.2 sq.m. surface secondary filters were employed. The ratio of plasma processed to patients' plasma volume was 1.1 +/- 0.3 in QP, and 0.94 +/- 0.09 in QD. The mean percentage removals of albumin, IgG and IgM respectively were 25.8 +/- 9, 32 +/- 17 and 47.5 +/- 26% in QP, 30.5 +/- 12, 40.5 +/- 19 and 48 +/- 17.5% in QD: albumin vs IgM p less than 0.025 in QP and p less than 0.02 in QD. A/G ratio increased from 1.6 +/- 0.5 to 2.06 +/- 0.6 in QP, and from 1.5 +/- 0.3 to 1.7 +/- 0.3 in QD. Plugging occurred in both groups, requiring 2.3 +/- 1.8 washouts/run in QP vs 1.5 +/- 1.2 in QD. IgM removal was comparable. Removal of albumin and IgG was slightly higher in QD. Similar performances can be obtained with either technique in clinical use, provided an adequate fractionation surface is available.