Originally published in Circulation Research 1, 102 (1953). 



59. APPLICATION OF 'THORIUM B" LABELLED RED 

 CORPUSCLES IN BLOOD VOLUME STUDIES 



George Hevesy, and Gustav Nylin 



From the Cardiological Clinics, Sodersjukhuset, Stockholm 

 A method for determining blood volume utilizing thorium B, which has 

 advantages over the use of ^sp, is described in detail. The problems of protecting 

 the patient and operator from radiation activity are discussed in an appendix. 



The successful application of radioactive indicators in physiology 

 caused the early introduction of a radioactive component into the erythro- 

 cytes and their use in blood volume determinations. Radio-iron labelled 

 eryhrocytes found extended apphcation in animal experiments^^^ These 

 are not suitable for determination of the blood volume of humans, since 

 iron-labelled red corpuscles can only be obtained in vivo, and thus the 

 application of this method depends on the availability of iron-labelled 

 donors. 



On the other hand the use of in vitro with P^s labelled red corpuscles^^^ 

 has found a very extended application in clinical blood volume cleter- 

 minations^^' *). This method necessitates incubation of the blood sample 

 with radioactive phosphate for an appreciable time. It also requires 

 centrifuging of blood samples and washing of red corpuscles, which 

 consume some time. 



An ideal radioactive method of clinical blood volume determination 

 should fulfill the following conditions: 



(a) The radioactive source should be available at a moment's notice, 

 and should not need replacement for some years. 

 _ (b) The rays emitted by the radioactive indicator should be easily 

 measurable. 



(c) No significant loss of the radioactive indicator by the red corpuscles 

 should take place in the circulation in the course of the experiment. 



(d) The half-life of the radioactive indicator should be sufficiently 

 long, amounting to at least several minutes, to enable a trained nurse 

 to carry out the radioactive measurements without difficulty. The half- 

 life should, however, be shorter, and preferably appreciably shorter 

 than one day, since it may be necessary to repeat the blood volume 

 determination after some time. 



(e) Centrifugation of the injected or secured blood samples should 

 not be necessary. It should suffice to compare the radioactivity of a 

 known aliquot of the injected labelled blood, poured into a glass 



