Hemodilution, central blood volume, and renal responses following
an isotonic saline infusion in humans.
Johansen, Lars Bo, Peter Bie, J_rgen Warberg, Niels Juel Christensen,
Mette Hammerum, Regitze Videbaek, and Peter Norsk.
Danish Aerospace Medical Centre of Research, Rigshospitalet 7805;
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 3:0301R, 1996.
To test the hypothesis that hemodilution is a mediator of the renal
responses to an isotonic saline infusion in the supine position, 8
males underwent: 1) i. v. infusion of 1.5 l of saline over 21 min
(SALINE), 2) infusion of 1.5 l of saline in combination with lower
body negative pressure for 3 hrs (LBNP+SALINE) to maintain central
blood volume unchanged, and 3) a control study without infusion or
LBNP. During the SALINE series, central venous pressure (CVP) and
left atrial diameter (LAD) increased by 4.4+/-0.6 mmHg and 2.6+/-0.4
mm (P<0.05), respectively, whereafter they declined towards pre
-infusion levels. During LBNP+SALINE, CVP and LAD were unchanged.
Plasma colloid osmotic pressure remained unchanged during control and
showed identical decreases by 5 mmHg (P<0.05) in the SALINE and
LBNP+SALINE series. During the 3rd h of LBNP, renal sodium excretion
(UNaV) peaked with 296+/-55 [mu]mol/min vs. a higher value of 383+/
-54 [mu]mol/min (P<0.05) during SALINE. The increase in UNaV
above that of control during the 3rd h of LBNP+SALINE constituted 48
% of that during SALINE. Plasma renin activity and plasma aldosterone
concentration showed similar patterns of decrease following saline
infusion irrespective of LBNP while plasma norepinephrine was
elevated late in the LBNP period compared to during SALINE and
control (P<0.05). It is concluded that the maintenance of a
constant CVP and LAD reduces the natriuresis of acute saline loading
by about half. Thus, hemodilution in conjunction with suppression of
renin and aldosterone release (independent of change in CVP and LAD)
might account for the remaining natriuresis of infusion.
Received 29 February 1996; accepted in final form 30 July 1996.
APS Manuscript Number R120-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996