Blood exchange in replacement transfusions; theoretic considerations.

E XCHANGE transfusions have been accepted as the therapy of choice in severe cases of erythroblastosis fetalis. Bessis and Bernard’ and others25 have reported the value of replacement transfusions in patients with acute leukemia, anemia, toxemias, anuria, etc. The technics employed in these transfusions in children and adults have been adequately described 5; the advantages of any one particular procedure over the others are relatively unimportant. The indications for exchange transfusions are fairly evident: (I) in infants with erythroblastosis fetalis, the removal of as many Rh positive cells as possible and their replacement with Rh negative cells; (i) increasing the total circulating red cell mass to a normal level in anemic individuals without increasing the total blood volume; ( ) removal by replacement transfusion of large amounts of toxic products retained in the plasma of patients with anuria due to various causes; ( ) inducing remissions in acute leukemia. Our results in io cases of acute leukemia treated with replacement transfusions have been poor; the value of this method of treatment is still to be established. In planning an exchange transfusion in erythroblastosis fetalis it is desirable to obtain the maximum exchange of red cells using the minimum amount of blood and, if anemia is present, to correct it. Where noxious agents circulating in the plasma are to be removed, a maximum exchange of plasma is desirable with the red cell volume kept at an optimum level. The replacement should be done in the least traumatic way, which implies that the original blood volume should be disturbed as little as possible during the course of the procedure, unless the initial blood volume is pathologically high or low. In these cases, adequate measures should be taken at the beginning or end of the exchange transfusion to correct the abnormality. Two distinct methods of exchange transfusions are possible: i. Discrete, intermittent or discontinuous exchange in which equal volumes of blood are administered and withdrawn alternately (or vice versa). Numerous variations of this technic are possible: the volumes administered may be smaller or larger than those withdrawn; the initial volume withdrawn or administered may be larger than successive increments, thus reducing or increasing the circulating blood volume for the duration of the exchange transfusion; at the end of the transfusion the total circulating blood volume may or may not be brought back to the initial level.