New insights in dialysis membrane biocompatibility: relevance of adsorption properties and heparin binding

Abstract

In the last 10 years, the concept of biocompatibility as applied to haemodialysis membranes has gained a general clinical acceptance in light of the knowledge that the clinical expression of β₂‐microglobulin (β₂m) amyloidosis found in long‐term haemodialyzed patients was governed by the characteristics of dialysis membranes. Highly permeable and biocompatible synthetic membranes interfere with the clinical expression of the disease and postpone occurrence of carpal tunnel syndrome and juxta‐articular bone cysts [1–4]. Biocompatibility is a difficult concept to define in the absence of well‐established clinical correlates. Besides ‘anaphylactoid reactions' [5], which are related more frequently to contaminated dialysate or leachable chemicals than to the sustained activation of the contact phase of coagulation in patients treated with angiotensin converting enzyme inhibitors [6,7], the concept of biocompatibility refers to any harmful effects induced by the contact of blood with dialysis membrane [8]. We consider that a membrane is less biocompatible when the sum of adverse humoral and cellular reactions occurring during haemodialysis is higher than for a reference membrane. An extended definition of biocompatibility should also include factors related to the patient's clinical conditions, such as diabetes or systemic inflammatory disease, and to factors associated with the specific supportive technique: i.e. haemodialysis, haemofiltration, haemodiafiltration, acetate‐free dialysis, etc.