Standardized units of RBCs: Is it time for implementation?

BACKGROUND: Current practice for the preparation of RBCs from whole blood f or transfusion results in poorly standardized contents of RBC Hb. The princ iple of apheresis, metering the anticoagulant into the collected blood, whi ch is pumped into an empty container, allows variation in the collected vol ume according to properties of the donor. STUDY DESIGN AND METHODS: The total Hb mass of each person in a representat ive group of Swedish blood donors was evaluated by using Hb concentration a nd blood volume (BV), with the latter calculated from each donor's weight a nd height. The number of blood units that could be collected without exceed ing 13 percent of the BV was estimated at a standardized content of RBC Hb set at 40, 45, and 50 g. RESULTS: With Hb standards of 45 and 50 g per unit of RBCs, it would be pos sible to collect I unit, but not more, from 93 female donors in the study; with 40 g of Hb as the standard, 2 units could be collected from 6 percent of the donors. Using a standard of 40 g of Hb, it would be possible to coll ect 2 units or more from 95 percent of 121 male donors. The corresponding f igures at Hb standards of 45 and 50 g were 81 and 50 percent, respectively, of the male donors. The largest number of units that could be collected wo uld thus be obtained at a 40-g Hb standard. However, the greatest total mas s of RBC Hb would have been obtained at 45 g. Even the yield of plasma woul d reach a maximum at this RBC Hb standard. CONCLUSION: Depending on the donor's Hb and BV, it is possible to collect e ither 1 or 2 units of RBCs without exceeding 13 percent of any donor's BV, provided the collected volume of blood in each unit is less than the curren t standard. Such practice would allow better use of the donor population. T wo-unit blood collections may reduce donor exposure in transfusions. Applyi ng a standard at 45 g of RBC Hb per unit was found to permit the collection of maximum RBC Hb and plasma in the evaluated population of Scandinavian d onors. Perhaps it is time to discuss a change in current rules for the prep aration of RBCs for transfusion.