Fluid Replacement and Heat Stress, 1993
Pp. 127-142. Washington, D.C.
National Academy Press
Hiroshi Nose1, Gary W. Mack, Xiangrong Shi, and Ethan R. Nadel
Maintenance of blood volume is important for optimal regulation of both arterial blood pressure and body temperature during exercise and thermal stress (Fortney et al., 1981a,b; Fortney et al., 1983; Nadel, 1984). A reduction of the central circulating blood volume, due either to hypovolemia accompanying dehydration or dilation of the peripheral vasculature, results in a fall in cardiac filling pressure and stroke volume and, if uncompensated, also in cardiac output (Fortney et al., 1983; Miki et al., 1983a). Among the possible compensations is the body's ability to mobilize water from the extravascular to the intravascular space (Miki et al., 1983b; Mohsenin and Gonzalez, 1984; Morimoto et al., 1981; Nose et al., 1983).
Senay (1979) recently reviewed the dehydration literature and reported that water appeared to be lost from the plasma at a rate one to five times that of other fluid compartments during dehydration. Costill (1977) ascribed the relatively greater plasma water loss to movement accompanying the major ions lost in sweat and urine, which are those of the extracellular
Hiroshi Nose, Foundation Laboratory and Departments of Epidemiology and Public Health and Physiology, Yale University School of Medicine, New Haven, CT 06519