Changes in blood plasma during progressive dehydration

Progressive dehydration of resting male subjects was accomplished by exposure to 43.3 C dry bulb, 29 C wet bulb for 12 hr. For control experiments, evaporative weight loss was replaced with 0.1% saline. For dehydrating subjects, the following relationships with evaporative weight losses were obtained: %Delta osmotic pressure = 1.14 (% evap wt loss) — 0.43; %Delta Na+ = 1.37 (% evap wt loss) — 0.45; %Delta K+ — 2.19 (% evap wt loss) — 1.29; %Delta hematocrit = 1.4 (%Delta evap wt loss) — 2.65. Comparison of dehydration with rehydration results indicated augmentation of plasma volume with fluids containing high concentrations of potassium. An average decrease in plasma volume of 13.6% (T-1824) from 2.5 to 11 hr after initial heat exposure in dehydrating subjects was accompanied by a 15.7% increase in total protein. Albumin increased 11.6% while globulin increase averaged 22.5%. Plasma protein fractions are not static during dehydration, probably due to augmentation of each protein fraction, particularly globulin. Measurement of plasma volume by T-1824 more likely indicates changes in protein concentration rather than plasma volume changes. A relationship between hematocrit changes and plasma albumin concentrations is suggested. plasma sodium; plasma potassium; plasma osmolarity; hematocrits; plasma albumin; plasma globulins Submitted on February 23, 1965