Size distribution measurements of microaggregates in stored blood

Microaggregates in various blood preparations were studied, before and after filtration, using an optical scattering (laser) technique which measures number density and size of aggregates in flowing blood. These measurements were comparable to screen filtration pressures. In all blood units, storage increased aggregates in the 20 to 170-microns range. Whole blood and red blood cells were comparable, while removal of leukocytes and platelets by an inverted spin technique essentially prevented formation of aggregates in all size ranges. Platelet-depleted units of whole blood also reduced aggregates. Removal of cryoprecipitate did not significantly affect aggregate size distribution; however, blood modified by both platelet and cryoprecipitate removal reduced aggregates. Commercially available microfilters reduced aggregates initially, but some increase ("shedding") occurred with continued use. The optical scattering technique did not require the dilution or red blood cell lysis needed in other techniques. Therefore, this method has potential for aggregate detection in in vivo flowing blood.