Method for determining plasma volume, determination of blood volume thereby, and apparatus therefore

A method for determining in a subject the volume of plasma in the subject's circulation which comprises:

• (a) introducing into the subject's circulation a predetermined amount of a pharmaceutically-acceptable solution comprising a predetermined quantity of biodegradable, nontoxic macromolecules, which macromolecules are sufficiently larger than endothelial junctions in the subject's capillaries so that they are incapable of permeating the subject's capillaries, and each of which macromolecules is labeled with a detectable marker;
• (b) allowing the solution to circulate for a period of time sufficient to distribute the macromolecules throughout the subject's circulatory system;
• (c) obtaining a sample of plasma from the subject;
• (d) determining the concentration of macromolecules in the sample by quantitatively measuring the detectable marker in the sample;
• and
• (e) calculating the volume of liquid which would dilute the sample to the concentration determined in step (d) from the predetermined amount of solution introduced into the subject's circulation and the predetermined quantity of macromolecules contained therein, thereby determining the volume of plasma in the subject's circulation.