Calculation of percentage changes in volumes of blood, plasma, and red cells in dehydration.

DILL, D. B., AND I>. L. &STILL. Calculation of pcrccntage changes in volumes of blood, plasma, and red cells in dehydration. J. Appl. Physiol. 37(2): 247-248. 1974.-Observations on hematocrit (Hct) and hemoglobin (Hb) were Inade in six men before and after running long enough to cause a 4y0 decrease in body weight. Subscripts B and A were used to denote before dehydration and after dehydration, respectively. Relations were derived between BVn, BVA, Hbn, HbA, Hctg, and HctA with which one can calculate the percentage decreases in BV, CV, and PV, as well as the concentration of hemoglobin in red cells, g. 100 ml-l (MCHC). When subjects reach the same level of dehydration the water loss from the various body compartments may vary reflecting difference in salt losses in sweat. Changes in PV calculated from the increase in plasma protein concentration averaged 7.5(z compared with 12.2 y0 calculated from changes in Hb and Hct. The difference could be accounted for by a loss of 6v10 plasma protein from the circulation.