Pulmonary microembolism associated with massive transfusion: II. The basic pathophysiology of its pulmonary effects.

In animals pulmonary hypertension, a decrease in total body O2 consumption and metabolic acidosis occur after transfusion of blood with an elevated screen filtration pressure (SFP) through standard blood transfusion filters. The purpose of this study was to define in detail the pulmonary abnormalities that develop following transfusion of blood with an elevated SFP through standard blood transfusion filters. Exchange transfusions of approximately twice blood volume were administered through standard commercially available blood transfusion filters (measured pore size--200 microns) to 6 animals. SFP measurements verified the presence of large numbers of aggregates in the transfusions. Although filters reduced SFP of the stored blood somewhat, numerous microaggregates passed the filters, and post-filtration SFP remained high. After transfusion average O2 consumption decreased to 77% of normal and metabolic acidosis developed. Pulmonary arterial hypertension was associated with an increase in pulmonary shunting of blood and a decrease in pulmonary diffusing capacity. The presence of extensive numbers of microemboli in the pulmonary arteriolar and capillary bed was confirmed by microscopic examination of lung tissue.