Adverse effects of dialyzers manifesting during the dialysis session.

The intradialytic symptoms that can be linked to components of the extracorporeal circuit of greatest clinical importance are the Type A (anaphylactoid) reactions. Most of these are IgE-mediated reactions due to ethylene oxide and are preventable by adequate degassing of the dialyzer by the manufacturer and by adequate rinsing of the dialyzer just prior to use. AN69-associated reactions are a second group, and are probably mediated by membrane-induced bradykinin generation coupled with ACE-inhibitor induced prolongation of bradykinin half-life. Type A reactions occur in a reuse setting, alos, and these may be related to some as yet poorly understood interaction between bleach, reuse sterilants, and certain dialyzer membranes, again, with ACE inhibitors playing an amplifier role. There is no compelling evidence linking membrane-induced complement activation to type A dialyzer reactions. However, there is a large body of evidence in animal models that exposure to complement fragment-releasing membranes can increase the pulmonary artery pressure and increase thromboxane formation. Thus, at least in principle, a case can be made for using unsubstituted cellulose membranes with caution in patients with a history of atopy or eosinophilia, particularly if acetate dialysate is to be used. Such a caution, however, must be viewed as conjectural in the absence of definitive evidence. Type B dialyzer reactions (mild back and chest pain 20-60 min into the dialysis session) is a phenomenon that is in the process of vanishing. The reason why is unclear. These reactions may have been due to some sort of dialyzer contaminant, or they may have been due to complement fragment release and required the use of acetate dialysate as a cofactor. In any event, recent well designed studies fail to find any differences in symptoms between unsubstituted cellulose and synthetic membranes. Membrane-induced complement fragment release also may play a minor role in dialysis hypoxemia, but evidence is conflicting in this area. Again, the use of acetate dialysate appears to be an important cofactor. Post-dialysis events which may be conceivably linked to the delayed effects of complement fragment releasing membranes need to be evaluated in controlled studies. Studies suggesting increased post-dialysis catabolism with use of unsubstituted cellulose membranes need to be confirmed in dialysis patients, and symptomatic correlates should be sought and evaluated.