Simultaneous determination of extracellular volume and blood volume with the Volemetron

A new instrument, the “Volemetron”***, constructed to measure blood volume with radioactive isotopes, was adapted to determine 82Br distribution volume. Details of the technique arc given. Mean values of both RISA and 82Br distribution volume in normal men and women were determined. They were in accordance with those given by other authors, and showed a better correlation with body surface than with body weight. Both determinations can be completed together within 21/2 h. The usefulness of a relatively simple combined determination is illustrated, and the desirability of a rapid and repeatable technique is stressed. Many investigations have been conducted in the past years to evaluate the blood volume and extracellular volume in man. Despite the obvious value of quantitative information about the body fluid compartments in pathological conditions, the techniques elaborated, though reasonably accurate, have found as yet little application in clinical practice. Methods applying the principle of dilution of radio-isotopes have greatly simplified these problems, but still require some time for counting and calculation. The introduction of a semi-automatic counting and computing device, the “Volemetron”, based on the “classic” dilution principles made it possible to determine blood volume within 15 min using 131I-tagged serum albumin (RISA). We considered the need for a rapid and rapidly repeatable method for determination of ECV of equal importance. We have found it possible to use the same apparatus with some modification for the determination of the distribution volume of 81Br