Automated suspension of washed erythrocytes in fresh-frozen plasma for exchange transfusion. Obtaining a desired hematocrit.

Stored red blood cells may be automatically saline washed and resuspended in fresh-frozen plasma to yield a final product with any hematocrit that is desired. The technique provides for rapid processing and issue of blood and minimal risk of contamination of the unit. Red blood cells are more readily available than whole blood, and their use, with fresh-frozen plasma, in exchange transfusion, provides similar advantages, including low potassium content and normal content of procoagulants and bilirubin binding capacity. The method of reconstruction is based on calculations that use empirically determined estimates of average hematocrit and specific gravity of red blood cells and the volumetric flow characteristics of a programmable IBM 2991 Blood Processor. Only the weight of the stored red blood cell unit is required as a measurement at the time of preparing the resuspended cells. Quality-control studies of the final hematocrit indicates a 2.4 per cent standard deviation from a target value of 55 per cent.