The body hematocrit/venous hematocrit ratio and the "splenic reservoir".

D URING measurements of total body red cell volume by the Cr51-technic in this laboratory, normal or elevated values were observed in several patients with moderate “anemia”, as judged by the hematocrit of peripheral venous blood. #{176} In each instance, marked to massive splenomegaly was present and increased localization of red cell radioactivity in the spleen was noted by body surface scanning technics. In three of these subjects, there were no indications of increased hemolysis. Since the relative red cell concentration (i.e., hematocrit) of splenic blood exceeds that of the blood in the peripheral veins, #{176} pooling of blood of high hematocrit in a large spleen might conceivably be responsible for the discrepancy between the finding of a normal or elevated tctal body red cell volume and a comparatively low venous hematocrit. This could occur only with a “splenic reservoir” large enough to create a marked disparity between the total body hematocritf (computed by direct measurement of total body red cell and total body plasma volume) and the relative red cell volume (hematocrit) of peripheral venous blood. Chaplin et al.7 have demonstrated a remarkably constant ratio (0.910 ± 0.026) between body hematocrit and venous hematocrit and have found no significant deviation of values in twelve subjects with splenomegaly. Somewhat contrary results have been noted by others.5’9 In view of these discrepancies and of the personal observations cited above, a study of the relationships between body hematocrit, venous hematocrit and spleen size was conducted in 37 patients, many of whom had various degrees of splenomegaly. The effect of extravascular fluid retention on the BH/VH ratio was also studied.t