Volume distribution of Evans blue dye and iodinated albumin in the dog

¹ Departments of Physiology, Baylor University College of Medicine, and The University of Texas Dental Branch, Houston, Texas

Three hundred seventy-two morphine-pentobarbitalized dogs were divided into groups according to the sampling time after injections of T-1824, I¹³¹, or both simultaneously. The data were programmed for digital computer analysis. In dogs receiving the tags separately the mean plasma volume was 50.0 ± 0.63 and 49.8 ± 0.72 ml/kg for dye and I¹³¹, respectively. Three simultaneous T-1824 and I¹³¹-tagged albumin injections were made with samples taken at 5, 10, 15, 20, 30, 45, and 60 min after each injection. Mixing was complete at approximately 5 min. Mean plasma volumes were 52.5 ± 2.24 ml/kg for the dye and 49.3 ± 1.69 ml/kg for the I¹³¹. The difference was not significant. In this group there was a good agreement between plasma volumes when calculated from the seven point curve or from three points only, indicating that all points were part of the same straight line. Therefore, a shorter time period with fewer samples is advantageous. Furthermore, when maximum accuracy is not required, the 5-min sample gives a reasonable estimate of plasma volume.