The Relation between Storage Time of Erythrocytes and Their Percentage Viability after Transfusion

During storage of blood the percentage of viable erythrocytes decreases at such a rate that when these percentages are plotted against time of storage, they fall on an S-shaped curve. This curve can be explained on the assumption that the resistance of red cells to in vitro aging is normally distributed, i.e., follows the normal probability curve. By a mathematical transformation used in other cases of biological standardization, the curve can be changed to a straight line, the slope of which, if accurately determined with a sufficient number of recipients, is the most accurate method of estimating the rate of in vitro aging. To illustrate the method, the rate of in vitro aging has been determined for the following storage procedures: (a) addition of ACD solution; (b) addition of two different solutions containing EDTA as anticoagulant; (c) prevention of coagulation by removal of calcium with an ion-exchange resin and subsequent addition of glucose-lactate or glucose acetate solution. Of these, the last had the fastest rate of in vitro aging and the first the slowest. Possible reasons for this are discussed. In addition, blood was stored in plastic bags rejected by the manufacturer because of toxic substances in the plastic; here a fraction of the cells was rapidly rendered nonviable while the remainder aged normally.