Role of hemodilution on renal responses to water immersion in
humans.
Johansen, Lars Bo, Peter Bie, Jorgen Warberg, Niels Juel Christensen,
and Peter Norsk.
Danish Aerospace Medical Centre of Research, Rigshospitalet 7522;
Dept. of Medical Physiology, University of Copenhagen, DK-2200
Copenhagen, Denmark; and Dept. of Internal Medicine and
Endocrinology, Herlev Hospital, DK-2730 Herlev, Denmark.
APStracts 2:0174R, 1995.
The present experiments were designed to elucidate (1) the role of the
lower extremity capillary bed in decreasing plasma colloid osmotic
pressure (COP) during immersion in humans (n=8) for 6 hrs, and (2)
the extent to which the natriuresis of water immersion is triggered
by this decrease in COP. Irrespective of the depth, COPs were very
similar during the immersion procedures varying between 25.5+/-0.6
and 26.4+/-0.6 mmHg which were significantly lower than during
control (28.3+/-0.3 - 28.6+/-0.3 mmHg). During neck immersion,
central venous pressure rose instantly by about 12 mmHg
(P<0.05), and remained elevated. Only a transient, marginal
increase (1.6+/-0.7 mmHg) occurred during hip immersion. Cumulated
sodium excretion during seated control, hip immersion, and neck
immersion, respectively, differed significantly and were 30+/-5,
45+/-5, and 101+/-6 mmol. It is concluded that the decrease in COP
during immersion is primarily due to fluid shifts occurring in the
capillary bed of the legs and that this may account for up to 25% of
the immersion-induced increase in renal sodium excretion.
Received 19 January 1995; accepted in final form 13 June 1995.
APS Manuscript Number R42-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 11 July 1995.