Characterization of mechanical in vitro hemolysis and subhemolysis

Blood damaging effects of artificial perfusion devices such as assist devic es, heart valve prostheses, for example, must be evaluated in vitro before being used in the clinical setting. For this purpose, mainly animal blood h as been used, and a number of associated problems are currently being discu ssed. Differences in the use of the term hemolysis - meaning breakdown of e rythrocytes or increased plasma hemoglobin, result in incompatibility among different authors. In addition, subhemolytic damage and its quantification has not been investigated to any extent. Another problem are the differenc es in the mechanical fragility of erythrocytes from different animal specie s, and the question of transferability to the in vivo situation. Furthermor e, the variability of mechanical stability within a given species is often greater than the differences between one species and another. International efforts are now being made to standardize haemolytic test conditions and t he present study is meant as a contribution to this. In the first part we describe an extension of our LYSE number model. Charac teristically, the model uses dimensionless similarity numbers, LY and MY, t hus making the results obtained under different test conditions comparable with one another. The LY number reflects the breakdown of cells (decreasing hematocrit), the MY number an increase in plasma hemoglobin. Differences b etween LY and MY are an indication of subhemolytic events.