Comparative evaluation of new fine-screen filters: effects on blood flow rate and microaggregate removal

Fine-screen filters were studied in a simulated clinical situation wherein ten units of outdated concentrated erythrocytes were rapidly transfused per filter to determine flow rates and effectivenesses of debris removal. Preliminary studies to evaluate flow rates with outdated whole blood indicated that the Bentley PFF-100, Fenwal 4C9003, and Biotest MF-10 fine-screen filters allowed flow rates sufficient to justify further detailed testing. For comparative purposes, the filter the authors have used clinically, the Pall Ultipor 40-micrometers filter, was studied again. As many as ten units of outdated, concentrated erythrocytes (hematocrits 75--85 per cent) were infused through each of the fine-screen filters at 300 torr pressure. All filters (except one of five Pall filters) accepted all ten units. The Bentley PFF-100 filter allowed the highest flow rates, such that the tenth unit of erythrocytes required 5 +/- 3 min (1 SD) to pass the filter. The Biotest MF-10, Bentley PFF-100 and Fenwal 4C9003 filters retained more debris/g erythrocytes, decreased screen filtration pressure, and eliminated more particulate matter (as determined by Coulter counter testing) than did the Pall Ultipor filter. When three or more units of blood are transfused, any of the four filters tested is cost-effective when compared with the current 170-micrometer standard transfusion filter.