Anatomic distribution of induced changes in blood volume, evaluated by regional weighing

¹ Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington

Anesthetized cats were supported on electronic scales placed under the head, thorax, abdomen and hindquarters, and the changes in the weights supported by these scales were recorded while blood was withdrawn and while blood and saline were infused. The recorded changes in weight indicated that the abdomen and the thorax both contributed significantly to the volume of withdrawn blood and that infused fluids were taken up by both regions. The blood volume of neither region was conserved at the expense of the other. The average weight change of the hindquarters was 5–10% of the over-all response, but in many cases the weight of the hindquarters was stable during an experiment. The average error in measurement of changes in total body weight was 6%. Interactions between the scales were evaluated by injecting mercury into pouches placed at specific anatomic locations. Interactions did occur, but were not so great as to invalidate the method.