Large unit red cell cryopreservation with hydroxyethyl starch.

Red blood cells can be preserved by freezing using either intraor extracellular agents. The most common intracellular agent, glycerol, is currently employed in general use and provides clinically acceptable red cells following post-thaw washing (13). Extracellular agents do not enter the cell during freezing. Therefore, red cells preserved with these agents may be administered without post-thaw processing depending on the agent used and the cell preservation obtained. For example, polyvinylpyrvolidone (PVP) and dextran received considerable attention as extracellular agents but are currently considered unacceptable. PVP yields good cell preservation but the molecular weight which affords the best cryopreservation is retained for long periods in the reticuloendothelial system ( 12 ). Dextran is unacceptable because it does not yield adequate cell preservation. Hydroxyethyl starch (HES) possesses many of the characteristics required of an acceptable extracellular cryoprotective agent since it yields high cell recoveries and is nonantigenic (7) and nontoxic (3, 10). A high molecular weight HES is currently in use as a plasma expander. Red cell cryopreservation utilizing HES and other extracellular agents requires