Measurements of Radioisotopes in Blood Applied to Determinations of the True Hematocrit. ∗

Abstract

Summary

Simplified methods for sample preparation for use in estimation of I¹³¹, Ca⁴⁵, and Na²² in blood and plasma are described. These methods will permit the administration of minimum amounts of I¹³¹ labeled plasma proteins in studies of blood and plasma volumes. The degree of plasma trapping in the centrifuged hematocrit was determined from measurements of I¹³¹ labeled albumin and Ca⁴⁵ concentrations in equal volumes of whole blood and plasma. With normal human and dog blood 7-9% of the packed cell column in the hematocrit tube is plasma. The amount of plasma trapped decreases with decreasing cell column height. The practical implications of the last observation are mentioned.