Filtration of the Microaggregates in Stored Blood

Previous work suggests that pulmonary insufficiency after massive transfusion may be due to embolization of the microaggregates of platelets, leukocytes and amorphous material in stored blood. A Model T Coulter Counter® was used to measure the number and size of particles in stored blood from 10 to 164 μ Filtration of the stored blood through a standard infusion filter (170 μ pore) did not lower the particle counts. A 40 μ pore filter removed large ( P < 0.001) but not medium or small particles. A Dacron wool filter significantly lowered particles in all size ranges. Simultaneous screen filtration pressure data showed that only Dacron wool effectively filtered the blood. When blood was centrifuged before being filtered, the weight of material removed by the 170 μ filter was more than doubled ( P < 0.05) but that removed by Dacron wool was unchanged. The present studies stress the inefficiency of currently used blood filters and suggests that Dacron wool effectively filters stored blood.