Bradykinin production during donor plasmapheresis procedures

Background and Objectives Extracorporeal circuits made of artificial substa nces may induce blood cells and humoral activation. Negatively charged surf aces may activate Factor XII and the prekallikrein-kinin cascade, resulting in bradykinin (BK) production. BK has been considered to be involved in se vere hypotensive reactions occurring during therapeutic apheresis in patien ts taking angiotensin-converting enzyme (ACE) inhibitors or in those receiv ing platelet transfusion. In this study we investigated BK production durin g donor plasmapheresis procedures. Patients and Methods Eighteen volunteer donors entered the study protocol. Nine of them were taking ACE inhibitors. Their blood pressure (BP) was moni tored both pre- and post-apheresis, and BK determination was carried out us ing a competitive enzyme immunoassay (EIA), in plasma samples collected bot h during and at completion of the procedure. In addition, a limited number of thawed plasma units were checked for BK. Results No side-effects were observed during the procedures. However, donor s taking ACE inhibitors showed a higher variation of their systolic BP comp ared to those who were not taking ACE inhibitors, while diastolic BP percen tage variations did not differ significantly between the two groups. The BK concentration was considerably higher in donors taking ACE inhibitors: 183 +/- 26 versus 82 +/- 6 ng/ml [P < 0.0001) after the first collection cycle and 142 +/- 20 versus 65 +/- 11 ng/ml (P < 0.0001) in the final samples. B K was also detected, at a lower concentration (15 ng/ml), in one out of fou r thawed plasma units obtained from donors taking ACE inhibitors and at 1 n g/ml in one out of two thawed plasma units from the control group. Conclusion Donors taking ACE inhibitors and undergoing plasmapheresis showe d higher levels of BK compared to the control group. Furthermore, the detec tion of BK in plasma units after a freeze-thaw procedure might explain the sudden hypotensive reaction occurring during therapeutic plasma exchange wh en plasmapheresis units are adopted as substitution fluids. Further investi gations are needed to assess the real clinical importance of the presence o f BK in plasma units.