834 GEOKGE K. MINOT AND AELIE V. BOCK 



as Dona'von, have reported the same result. Two cases of nitrobenzene 

 poisoning that we have personally observed had their oxyhemoglobin re- 

 duced to 30 per cent and 35 per cent, respectively. Both recovered with 

 transfusion. 



V. The Amount of Blood to be Transfused 



It is generally agreed that a donor may give blood up to one quarter 

 of his blood volume without serious discomfort. A man weighing TO 

 kilograms has a blood volume of about 5,500 c.c., hence blood may be taken 

 from him for purposes of transfusion up to about 1,300 c.c. It is seldom 

 necessary to use such a mass of blood for transfusion, but it may be helpful 

 to have in mind the limit of safety for the donor. This limit varies 

 directly with the body weight. 



What constitutes a proper amount of blood to be given for the different 

 conditions in which transfusion is indicated has been suggested by various 

 authors as a result of clinical experience. It has not been possible to 

 make definite quantitative measurements of the various factors involved, 

 and therefore only a general statement can be made with reference to this 

 important subject. In every instance the weight of the patient to be 

 transfused should be considered in order to avoid hypertransfusion. A 

 normal individual has a volume of blood equal to 80 to 85 c.c. per kilo- 

 gram of weight. A patient weighing TO kilograms, with severe anemia, 

 may have his blood volume reduced to 50 c.c. per kilogram, representing a 

 reduction in blood volume of approximately 40 per cent. It would be 

 futile to attempt to restore the normal blood volume by means of trans- 

 fusion in such a case and fortunately this is never necessary. On the 

 other hand, if repeated transfusions are done at intervals of a few days tc 

 control hemorrhage, as in hemophilia, hypertransfusion causing polycy- 

 themia should be avoided. 



In the routine use of transfusion, owing to the great elasticity of 

 the vascular bed, hypertransfusion seldom occurs. It is manifested chiefly 

 by cough, by pain in the back, and, in rare instances, pulmonary edema 

 may develop, as linger has recently described. These symptoms may 

 occur regardless of the rate at which blood is transfused. It is probable 

 that the same symptoms might be produced by a relative hypertransfusioi 

 that is, by the introduction of a large amount of blood into the circulation 

 of a patient having a greatly reduced blood volume, such symptoms being 

 due to temporary embarrassment of the circulation. 



When transfusion is indicated for loss of hemoglobin after hemorrhage, 

 a large transfusion, 1,000 c.c., may be necessary. In chronic anemic con- 

 ditions smaller amounts of blood, 300 to T50 c.c., may serve as well as 

 larger amounts. In chronic anemia there is some evidence to show that a 

 small quantity of blood, repeated within a few days, may be more bene- 



