Water permeability of high-flux dialyzer membranes after Renalin reprocessing

Dialysis with high-flux membranes is widely used, in part, because they are thought to increase the removal of middle molecules when compared with low-flux membranes. Dialyzer reprocessing; however, is thought to alter middle molecule clearance. Renalin, a mixture of germicidal agents, has widespread use in dialyzer reprocessing. We determined the effect of Renalin reprocessing on the water permeability of three different dialyzers of Fresenius (F80A and 200A) and Gambro (17R) manufacture using the dead-end filtration method. Two hundred and seventeen, predominantly used but some new, dialyzers were evaluated. Water permeability of the used, but not the new, dialyzers fell abruptly and dramatically with reprocessing. The permeability fell almost 70% in the F80A dialyzer after three reprocessing procedures with similar, but somewhat slower declines, seen in the other two dialyzers. We conclude that there is a decline in water permeability seen in Renalin reprocessed dialyzers. This factor and the associated change in solute clearance and ultrafiltration characteristics should be considered in assessing the effectiveness of dialyzer reprocessing.

Effect of Peracetic Acid Reprocessing on the Transport Characteristics of Polysulfone Hemodialyzers

Peracetic acid is used extensively for reprocessing hemodialyzers, despite several indications that reprocessing alters the dialyzer transport characteristics. The objective of this study was to obtain quantitative data for the effects of peracetic acid reprocessing on the clearance and sieving coefficients of urea, vitamin B12, and polydisperse dextrans using Fresenius F80A polysulfone dialyzers. Reprocessing restored the urea and vitamin B12 clearance to close to their original values. However, the reprocessed dialyzers had substantially lower clearance of the larger molecular weight dextrans, which was attributed to reductions in the effective pore size caused by residual plasma proteins within the membrane. Storage in peracetic acid provided some additional removal of residual proteins, although the clearance and sieving coefficients of the larger dextrans remained well below their original values. Peracetic acid caused no degradation of the membrane polymer, in sharp contrast to results obtained with bleach reprocessing.

Effect of Bleach Reprocessing Upon the Clearance Characteristics and Surface Charge of Polysulfone Hemodialyzers

The effects of reprocessing upon hemodialysis have been debated since the introduction of this practice. The objective of this study was to develop a quantitative understanding of the effects of bleach reprocessing upon Fresenius polysulfone dialyzers. Data were obtained for the clearance of urea, vitamin B12, and polydisperse dextrans before and after reprocessing, both with and without exposure to plasma in a simulated dialysis session. Bleach reprocessing of the native dialyzer caused a significant increase in solute clearance because of the removal of polyvinylpyrrolidone from the membrane copolymer. This was confirmed by zeta potential measurements that showed a substantial increase in the negative charge on the membrane surface. Exposure to plasma proteins during hemodialysis effectively protected the dialyzer from chemical degradation by the bleach, with only small changes in solute clearance after the optimal reprocessing cycle. However, inadequate exposure to bleach was unable to restore the original solute clearance while over cleaning with bleach caused an increase in clearance. Considerable care must be taken in the proper design of reprocessing cycles for hemodialysis membranes.

Low-Molecular Weight Proteins in End-Stage Renal Disease: Potential Toxicity and Dialytic Removal Mechanisms

ABSTRACT. Low-molecular-weight proteins (LMWP) are now recognized as a distinct class of uremic toxins, and numerous compounds in this category have been identified. Dr. Henderson has spent much of his career investigating ways to enhance the removal of intermediate- and large-sized uremic retention molecules. As LMWP clearly fall under this category, it is fitting to provide a review of several aspects of this molecular class. Normal renal metabolism of LMWP is discussed along with the changes that occur during chronic renal insufficiency. The effect of end-stage renal disease on plasma LMWP concentrations is assessed. As examples of the potential uremic toxicity of this molecular class, leptin, adrenomedullin, and the compounds associated with increased susceptibility to infection are highlighted. Finally, an overview of LMWP removal mechanisms for both hemodialysis and the convective therapies is provided.