Cryobiology overview of red cell preservation: achievements and prospective.

Preserved red cells are transfused to improve the delivery of oxygen to tissue. The preserved red cells must circulate to increase the red cell volume and improve the oxygen carrying capacity. The correlation between oxygen transport function and the red cell 2,3 DPG level has been known since 1967. but it was only recently that the importance of the oxygen delivering capacity of transfused red cells during the immediate posttransfusion period became apparent. Red cells with low 2,3 DPG levels and increased affinity for oxygen will increase cardiac output and/or decrease venous pO2 for at least 4 hours after transfusion. Oxygen transport function is maintained longer in red cells stored in CPD than in ACD-stored red cells. Supplementation of CPD red cells with inosine, ascorbate; dihydroxyacetone and other substances helps to maintain the oxygen transport function during storage at 4 C. Liquid-stored red clls can be biochemically modified before freeze-preservation to increase the 2,3 DPG levels to to 1-1/2 to 2 times normal; these red cells have decreased oxygen affinity. The red cells have acceptable posttransfusion survival and improved oxygen releasing capacity for at least 72 hours after transfusion. The well-being of certain patients may be placed in jeopardy of they are given preserved red cells with increased affinity for oxygen. The patient may not be able to meet the accompanying demand for increased blood flow, and the venous-capillary oxygen tension may fall to a critical level. Clearly, patients in hemorrhagic and septic shock, those subjected to extracorporeal circulation during cardiac surgery, and anemic patients with myocardial or cerebrovascular insufficiency are best treated with red cells that have 150% normal 2,3 DPG levels.