Simultaneous Determination of the Volume of Red Cells and Plasma for Survival Studies of Stored Blood

A method is described for the determination of the in vivo survival of stored human red cells. Cr51 labeled red cells and I125 labeled human serum albumin are infused simultaneously to esti‐mate the whole blood volume and establish the 100 per cent retention value for subsequent red cell survival determination. The whole body hematocrit correction factor, necessary for the determination of 100 per cent retention value, has been established by the simul‐ taneous measurement of the red cell and plasma volumes in a group of 71 patients. Cr51 and I125 gamma emissions are separated for plasma and red cell volume determinations by measuring their values on a scaler equipped with a pulse height analyzer. This method has proven to be a safe and suitable means for the accurate establishment of in vivo survival of stored red cells, red cell mass, and plasma volume.