Predictability of the Changes in Hematocrit which Follow Repeated Withdrawal of Blood.

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Abstract
With the assumption that total blood volume remains constant through replacement of lost cells and plasma by extravascular fluid, it can be shown that the hematocrit of any particular blood sample (Hctn) in a consecutive series of samples of constant size, is given by the exponential equation: [image] Where; Hct. = hematocrit of the initial sample in a series s = sample size (constant over the series) BV = total blood volume n = number of blood samples taken The formula predicted, with an error of 2% or less, decreasing hemato-crits which followed a removal of 7-11 successive blood samples of 2.5-3.5 ml each, within a period of 6 hours or less in the adult male chicken. The formula failed to predict the Hcts observed in an 8-day test on fasting chickens in which 1.5 ml blood samples were obtained at 12-24 hour intervals. In the course of this study, the blood volume of the 2.5 kg White Leghorn male was determined to be 6.6 [plus or minus]0.25 ml/100 g body weight.