TKA^SFUSION OF BLOOD 825 



blood have their uses but they cannot take the place of blood if increased 

 oxygen carrying power is needed. 



2. The Effect upon the Blood Volume. In most conditions for 

 which transfusion is indicated, a diminished volume of circulating blood 

 usually exists, either by reason of a mechanical reduction in the whole 

 blood, as after acute hemorrhage, or on account of a diminished content 

 of red corpuscles which is associated with most types of anemia, Keduc- 

 tion of the plasma volume, may occur following blood loss, and in other 

 anemias when the hemoglobin is below 30 per cent. Transfusion of blood 

 after a severe hemorrhage may help to restore the plasma volume to about 

 its normal figure but the total blood volume may not be regained except 

 through regeneration of corpuscles unless it is made up by repeated trans- 

 fusions. Hypertransfusion should be avoided because of the possibility of 

 bone marrow depression, as demonstrated experimentally by Kobertson(c). 



In chronic anemia, in contrast to acute anemia due to blood loss the 

 volume of the plasma is usually not abnormal if the patient has a normal 

 fluid intake. When transfusion is undertaken for such a condition, the 

 only gain in total blood volume is due to the addition of corpuscles. 

 Under such a circumstance the plasma of the transfused blood rapidly 

 leaves the circulation for the tissues. This consideration is an important 

 one, since it shows that alterations in the blood volume in anemia are 

 almost wholly dependent upon variations in the total mass of corpuscles, 

 as discussed by Bock. There is no method of increasing the total blood 

 volume in chronic anemia except by the addition of corpuscles. 



3. The Effect upon the Factors of Coagulation. In the various 

 forms of purpura hemorrhagica there occurs a deficiency in the number 

 of blood platelets which is associated with the pathologic hemorrhage 

 frequently encountered in these cases. In hemophilia, as Minot and 

 Lee (a) have shown, there occurs a qualitative deficiency of the blood plate- 

 lets. In other conditions in which pathologic hemorrhage occurs, there are 

 often unknown alterations in the physical chemistry of the blood which in- 

 terfere with normal clot formation. This may be due to an upsetting of the 

 balance of prothrombin and antithrombin as, for example, by a decrease 

 of the former or increase of the latter substance, or there may be a de- 

 ficiency of fibrinogen or some other not well recognized alteration. The 

 only truly efficient way of remedying a defect in one or more of the 

 factors that promote clotting, is by transfusion of normal blood which 

 contains all of the factors. It is to be recognized that serious bleeding 

 associated with a deficiency in the numbers of platelets, does not occur 

 until these elements have been reduced from their normal number of about 

 300,000 to 60,000 per c.mm. or below. If a liter of normal blood is trans- 

 fused the platelets will be increased in the recipient's blood by about 

 70,000 per c.mm. Thus, when transfusion is necessary to stop bleeding 

 due to a deficiency of platelets, a large amount of blood should be given 



