A MODEL-BASED ISOTOPIC ANALYSIS OF O-2 TRANSPORT DURING ANEMIA AND TRANSFUSION

We studied the relative role of blood flow to limit oxygen (Oz) transp ort in patients suffering from chronic anemia and with respect to the transfusion of packed red cells. The stable isotopic oxygen molecules O-16(2) and (OO)-O-16-O-18 were used. O-16(2) diffuses 3 % faster and in addition passes the respiratory chain 1.3 % more rapidly thar. (OO) -O-16-O-18, but within convective pathways it is transported as rapidl y as (OO)-O-16-O-18. Thus, with increasing limitation by blood flow, t he isotopic composition of oxygen changes less. By using a series resi stance model we calculated the oxygen partial pressure difference betw een arterial and venous blood (PavO(2)) on the basis of the change in (OO)-O-16-O-18/O-16(2) ratios. Nine patients suffering from chronic an emia as well as 14 normal volunteers were studied. In five patients tr ansfusions had to be performed periodically. By means of respiratory m ass spectrometry, (OO)-O-16-O-18)/O-16(2) ratios were determined in ex piratory gas mixtures. PavO(2) dropped more distinctly through transfu sion (-13 mmHg < PavO(2) < -6 mmHg) than due to chronic anemia (-5 mmH g < PavO(2) < -2 mmHg). We concluded that the amelioration of the hemo globin concentration of blood did more than compensate for the impedim ent of O-2 release which is induced by the decrease in the mean 2,3-di phosphoglycerat content of packed red cells End the increase in viscos ity due to transfusion.