AN ACCURATE METHOD OF PLASMA-VOLUME MEASUREMENT BY DIRECT ANALYSIS OFEVANS BLUE SPECTRA IN PLASMA WITHOUT DYE EXTRACTION - ORIGINS OF ALBUMIN-SPACE VARIATIONS DURING MAXIMAL EXERCISE

The Evens blue dye (EBD) dilution method, including a dye extraction s tep, is a standard way of measuring plasma volume. This report describ es a new direct spectrophotometric method, which is simple and specifi c and avoids the dye extraction step. To begin with, all the contamina nts which may appear during a plasma volume study were added to plasma samples, prior to the absorbance measurements. In this way we calcula ted correction factors for the haemolysis and the turbidity of the pla sma samples, without dye. The study of the visible spectra showed that the correction factors could be obtained by measuring absorbances at only four visible wavelengths: 780, 720, 619 and 578 nm. The addition of various amounts of contaminants to dye-containing plasma samples al lowed us to obtain precise values for the absorbance errors. The previ ously defined correction factors were then applied, and the residual a bsorbance errors were found to become nil. This spectrophotometric met hod can be used to check the efficiency of a dye-extraction procedure, as well as to study other biological fluids containing EBD. When used to analyse a chronological series of blood samples this method appear ed to provide an effective way of simultaneously studying the processe s of plasma volume concentration and albumin extravasation induced by maximal exercise.