The filtration limitations of ultrapore filters.

The filtration effectiveness of four commercially available microaggregate filters was determined using 14-day-old stored human blood in a constant infusion system. All filters significantly reduced the volumes of microaggregates contained in 500 ml. of blood. Three of the filters tested either occluded or failed to effectively remove microdebris from larger volumes of blood. These filters should be employed only for single blood transfusions. A fourth filter--of grid design--was effective in removing microdebris from 2,000 ml. of blood, the limits of the study. When employing microaggregate filters in massive transfusion situations for the prevention of pulmonary dysfunction, filtration characteristics and efficiencies of the filters employed must be known so that inadvertent administration of microdebris to the patient might be prevented.