Biocompatibility in hemapheresis: new materials.

: The development of new technologies implying the use of semidialytic synthetic membranes in therapeutic apheresis, lays stress also on the problem of biocompatibility. The first alterations of plasma proteins and of the immune system are observable 15 minutes after the beginning of the apheretic session. This may suggest that the acute clinical reactions observed during apheresis are related to biocompatibility. However, the first chronic side effects, comparable to those observed in hemodialysis, do not occur before 10-20 sessions. It is known, in fact, that even when inactive materials, such as the last generation membrane, are used, plasma exchange affects the immune system and may determine plasma protein alterations (protein film, erythrocytic damage, ADP release, beginning of the coagulation process, complement consumption). The whole system or the type of membrane, the involucre, the potting glue and the lines affect the interactions. The contact of blood with a foreign surface initiates a number of local reaction, with subsequent reactivity of the organism. The activation of the complement system, coagulative system, fibrinolytic system and callicrein-kinin system is therefore responsible for the cell functional modifications. It is necessary to underline the role of the membrane surface used, in that the activation of the complement system, of the gathering of platelets and of the cell activity modification all increase with the increase in surface. Biocompatibility may be affected not only by the membranes, but also by the substitution fluids and by the anticoagulant used.