Heretofore, studies of the effects of hemorrhage on animals have been inextricably associated with studies of shock. A few workers have reported experiments in which the independent variable was the loss of varying volumes of blood,1,2 but their goal was either to produce or to elucidate some mechanism of shock. Walcott1 determined the blood volume of dogs by means of Evans blue (T-1824) and the centrifuged hematocrit. These dogs were bled from their femoral artery 41% to 58% of their measured blood volume. He found that all animals died when bled 53% or more of their blood volume. Roughly 50% of the animals bled a smaller per cent of blood volume survived. In a later paper, however, Walcott3 states that bleeding an animal according to a fixed percentage of blood volume is an unreliable means of producing shock. Thereafter, Walcott used a modification of Mann's4
SWAN H, BLAVIER J, MARCHIORO T, JENKINS D, MONTGOMERY V. Experimental Hemorrhage: Prediction of Mortality Following Acute Measured Hemorrhage in the Dog. AMA Arch Surg. 1959;79(2):176–184. doi:10.1001/archsurg.1959.04320080012002
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