THE EFFECT OF HEMORRHAGE AND REPLACEMENT ON THE APPARENT VOLUME OF PLASMA AND CELLS

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Abstract
No evidence was obtained for an increase in the rate of disappearance of the dye T-1824 during almost complete exsanguination or in the 4-hr, period following reinjn. of blood, in expts. in barbitalized dogs. Indirect measurement of circulating plasma vol. during exsanguination therefore seems legitimate. Such measurements indicated that fluid was added to plasma at the mean rate of 0.154 [plus or minus] 0.0114 cc./kg./min. when blood was drawn at the rate of 2 ml./kg./2 min. until mean arterial pressure fell below 20 mm. Hg. When the animals were kept alive by reinjn. of blood, and were bled to death at the same rate 4 hrs. later, the rate of plasma replenishment during the 2d bleeding was only 0.088 [plus or minus] 0.0119 ml./kg./min. The rate of addition of fluid to plasma was usually increased at the time when arterial pressure began to decline steeply during the bleeding. Evidence was obtained that the circulating cell vol. is over-estimated by an avg. of about 29% if it is calculated from the plasma vol. and the hematocrit in drawn blood. When measured by this method, the gain in circulating cells following injn. was about 29% greater than the vol. injd.; and the loss during bleeding was about 29% greater than the vol. withdrawn. The % error seems to remain fairly constant throughout all stages of exsanguination. The error appears in most cases to be completely masked during the 1st bleeding in the expts., presumably by expulsion of cells from the cell reservoirs.