Journal of Applied Physiology, Vol 39, Issue 1 66-70, Copyright © 1975 by American Physiological Society
Comparison of water immersion and saline infusion as a means of inducing volume expansion in man
M. Epstein, D. S. Pins, R. Arrington, A. G. Denunzio and R. Engstrom
Although previous studies have demonstrated that water immersion to the
neck (NI) results in both central hypervolemia and a significant
natriuresis, it is unclear whether the magnitude of the "volume stimulus"
of NI is comparable to that induced by the extracellular fluid volume
expansion (ECVE) induced by acute saline administration. The present study
was undertaken therefore to compare the natriuresis induced by these two
different stimuli. All subjects were studied on four occasions while in
balance on a diet containing 150 meq of sodium and 80 meq of potassium
daily: seated control; seated immersion; and saline administration in both
the seated and recumbent posture. The increment in UNaV during NI was
indistinguishable from that of seated saline. Similarly, the kaliuretic
response during NI was similar to that induced by seated saline infusion.
In contrast, supine saline infusion resulted in a greater increment in UNaV
than either NI or seated saline. The present data indicate that the "volume
stimulus" of immersion is identical with that of standard saline-induced
ECVE in normal seated subjects. Furthermore, the ability of NI to induce a
natriuresis without a concomitant increase in total blood volume and with a
decrease in body weight, rather than the increase which attends saline
infusion, suggests that NI may be a preferred investigative tool for
assessing the effects of ECVE in man.
