THE MEASUREMENT OF BLEEDING VOLUME IN THE DOG FOR STUDIES ON BLOOD SUBSTITUTES

Abstract

Barbitalized dogs who survived a preparatory bleeding of 20 cc./kg. were used. In seeking methods for measuring total bleeding volume (the blood loss required for death) by extrapolation from a partial exsanguination, it was found that relatively constant volumes were obtained after mean arterial pressure had been lowered to 60 mm. Hg. by rigorously controlled rates of blood withdrawal. The maximum expected error in computing bleeding volume as the sum of the blood drawn in lowering pressure to this level (Hia) plus the constant residual volume demonstrated in control animals (Hie) is from 17-32%, depend-ing upon the rate of blood withdrawal used. If the blood drawn for Hia measurement was heparinized and reinjected, 2d bleeding volumes measured 4 hrs. later by bleeding the animals to death, were from 70 to 90% of the first, the % ratios being higher and less variable when the more rapid rates of bleeding were used in the measurements. When no replacement was made following the H1a withdrawal, second bleeding volumes 4 hrs. later were never larger than H1e, and were usually considerably less.