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Is adsorption an important characteristic of dialysis membranes?

1996; Elsevier BV; Volume: 49; Issue: 2 Linguagem: Inglês

10.1038/ki.1996.47

1523-1755

Manuel Pascual, Nina Tolkoff‐Rubin, Jürg A. Schifferli,

Chronic Kidney Disease and Diabetes

Is adsorption an important characteristic of dialysis membranes?Since the 1960s, cuprophane membranes (cellulose-based) have been widely used for hemodialysis.However, it has become evident over the years that the interaction of blood with cuprophane leads to a rapid and massive complement activation with leukopenia, and to the release of cytokines which may be detrimental to uremic patients [11.This led to the concept of cuprophane as a "bio-incompatible" membrane (BICM).Since the 1980s new synthetic membranes have been developed such as polysulfone, polyaciylonitrile (PAN/AN69 and other PAN), polyamide, and polymethylmethacrylate (PMMA), which have been shown not to activate complement (or to a lesser extent than cuprophane) and are generally considered biocompatible membranes (BCM).Although the complement pathway has been studied extensively, it is worth emphasizing that other humoral pathways (coagulation, contact-phase) and cellular mechanisms can also be activated during dialysis, thus rendering the definition of "biocompatibility" more complex than previously expected [1,2].For example, the PANIAN69 membrane, usually regarded as a BCM, may also be judged as a BICM for patients on angiotensinconverting enzyme inhibitors, since hypersensitivity reactions due to bradykinin release have been reported [1,3].Nevertheless, in two recent studies the term "BCM" was used to describe the use of PAN/AN69 and PMMA membranes, and importantly their use was shown to be beneficial for the patients [4, 51.Hakim recently defined the "BCM" as "one that elicits the least amount of inflammatory response in patients exposed to it" [1].In the future, it may be that an important factor-if not the most important-in defining "biocompatibility" will be the impact that dialysis membranes have on patient's morbidity and mortality [2].BCM would be those membranes proven to be beneficial for the patients, and BICM those leading to deleterious consequences or outcomes.In the past the concept of hemodialysis has focused on the processes of diffusion and mass transfer across a semipermeable membrane.In recent years, several reports have pointed out that adsorption (that is, binding to the membrane) of some lowmolecular weight proteins or peptides (LMWP) on certain types of dialysis membranes represents an additional and important mechanism of clearance during hemodialysis.Here we review examples of LMWP adsorption by dialysis membranes that may be important in terms of biocompatibility, and which may influence the morbidity and mortality of patients requiring dialysis.Other important characteristics such as the larger pore size and higher ultrafiltration coefficients of some new synthetic membranes will not be discussed.