Erythrocyte volume, plasma volume, and acid-base changes in exercise and heat dehydration

Abstract

Variations in erythrocyte volume [mean corpuscular volume (MCV)] were evaluated during exercise and heat stress to determine the influence on calculated plasma volume and content changes. The results of this study on 17 men indicate that the human red blood cell can increase, decrease, or remain constant in volume during physical stress depending on the combined interactions of plasma osmolality and blood pH. Shrinking of MCV can occur when the increase in plasma osmolality is larger than 5 mosmol/kg H2O and the blood pH remains within 0.1 pH units of its resting value. Erythrocyte swelling is usually noticed with maximal exercise when the blood pH is less than 7.10, in spite of 20 mosmol/kg H20 increments in plasma osmolality. The regression equations indicate that during 30 min of exercise in a cool environment the plasma shifts calculated by either the hematocrit or the hematocrit + hemoglobin method fall within 1% of each other, but during resting heat exposure the hematocrit technique under-estimates the fluid shift by 2.5-3.0%. Application of these considerations to the calculation of plasma content changes during stress made it clear that the pattern of plasma potassium content is quite different with maximal as compared with submaximal exercise.

Effects of Short-term Exercise in the Heat on Thermoregulation, Blood Parameters, Sweat Secretion and Sweat Composition of Tropic-dwelling Subjects

“…These findings are consistent with previous reports on hyperosmotic plasma during exercise (Costill et al, 1974;Greenleaf et al, 1979;Van Beaumont et al, 1981;Kolka et al, 1982;Miles et al, 1983).…”

“…Hemaglobin (Hb) concentration was determined using a the cyanmethemoglobin method and Hematocrit (Hct) was determined in triplicate after microcentrifugation. Hct was used to calculate the percentage change in plasma volume using the formula by Van Beaumont et al (1981). Another 2 mL of blood was transferred to a tube containing Sodium Flouride (NaF) and the remaining 5 mL of blood was transferred into a plain tube.…”

Fetal Rehydration Via Intraamniotic Fluid: Contribution of Fetal Swallowing

“…The 9 mosmol/kg as a result of the fetal absorption of water from the amniotic increase in maternal plasma osmolality is well within the range cavity. These findings differ from the results of Gilbert and Brace seen after exercise, thermal dehydration, or mild water depriva-(12), who observed decreased fetal blood volume after an intion in normal human adults (8,9). Fetal plasma osmolality and traamniotic infusion of distilled water to euhydrated sheep.…”

Muscle Trauma and Immune Activation after a Downhill Marathon (Tyrolean Speed Marathon)

“…Serum neopterin was analyzed by ELISA (BRAHMS Diagnostica, Hennigsdorf/Berlin, Germany). All parameters given in concentrations per volume blood were corrected for exercise-induced changes in plasma volume according to the formula of van Beaumont (18).…”