| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
School of Kinesiology, University of Western Ontario, London, Ontario, Canada N6A 3K7
Humans exposed to real or simulated
microgravity experience decrements in blood pressure regulation during
orthostatic stress that may be related to autonomic dysregulation
and/or hypovolemia. We examined the hypothesis that hypovolemia,
without the deconditioning effects of bed rest or spaceflight, would
augment the sympathoneural and vasomotor response to graded orthostatic
stress. Radial artery blood pressure (tonometry), stroke volume (SV),
brachial blood flow (Doppler ultrasound), heart rate
(electrocardiogram), peroneal muscle sympathetic nerve activity (MSNA;
microneurography), and estimated central venous pressure (CVP) were
recorded during five levels (
5, 10, 15, 20 and 40 mmHg)
of randomly assigned lower body negative pressure (LBNP)
(n = 8). Forearm (FVR) and total peripheral vascular
resistance (TPR) were calculated. The test was repeated under randomly
assigned placebo (normovolemia) or diuretic (spironolactone: 100 mg/day, 3 days) (hypovolemia) conditions. The diuretic produced an
~16% reduction in plasma volume. Compared with normovolemia, SV and
cardiac output were reduced by ~12% and ~10% at baseline and
during LBNP after the diuretic. During hypovolemia, there was an upward
shift in the %
MSNA/CVP, FVR/CVP, and TPR/CVP
relationships during 0 to 20 mmHg LBNP. In contrast to normovolemia,
blood pressure increased at 40 mmHg LBNP during hypovolemia due to
larger gains in the %MSNA/CVP and TPR/CVP relationships.
It was concluded that acute hypovolemia augmented the neurovascular
component of blood pressure control during moderate orthostasis,
effectively compensating for decrements in SV and cardiac output.
baroreflex; muscle sympathetic nerve activity; Doppler ultrasound; lower body negative pressure; vascular resistance; spironolactone
This article has been cited by other articles:
|
|
 |
|
  D. A. Salzer, P. J. Medeiros, R. Craen, and J. K. Shoemaker Neurogenic-nitric oxide interactions affecting brachial artery mechanics in humans: roles of vessel distensibility vs. diameter Am J Physiol Regulatory Integrative Comp Physiol, October 1, 2008; 295(4): R1181 - R1187. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 I. Krabbendam, B. J. Janssen, A. P. J. Van Dijk, H. W. Jongsma, W. J. G. Oyen, F. K. Lotgering, and M. E. A. Spaanderman The Relation Between Venous Reserve Capacity and Low Plasma Volume Reproductive Sciences, July 1, 2008; 15(6): 604 - 612. [Abstract] [PDF]
|
|
|
|
 |
|
 M. M. Wenner, W. C. Rose, E. P. Delaney, M. E. Stillabower, and W. B. Farquhar Influence of plasma osmolality on baroreflex control of sympathetic activity Am J Physiol Heart Circ Physiol, October 1, 2007; 293(4): H2313 - H2319. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. S. Kimmerly, S. W. Wong, D. Salzer, R. Menon, and J. K. Shoemaker Forebrain regions associated with postexercise differences in autonomic and cardiovascular function during baroreceptor unloading Am J Physiol Heart Circ Physiol, July 1, 2007; 293(1): H299 - H306. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. D. O'Leary, R. L. Hughson, J. K. Shoemaker, D. K. Greaves, D. E. Watenpaugh, B. R. Macias, and A. R. Hargens Heterogeneity of responses to orthostatic stress in homozygous twins J Appl Physiol, January 1, 2007; 102(1): 249 - 254. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. S. Dyson, J. K. Shoemaker, and R. L. Hughson Effect of acute sympathetic nervous system activation on flow-mediated dilation of brachial artery Am J Physiol Heart Circ Physiol, April 1, 2006; 290(4): H1446 - H1453. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. J. Behnke, D. J. Padilla, L. F. Ferreira, M. D. Delp, T. I. Musch, and D. C. Poole Effects of arterial hypotension on microvascular oxygen exchange in contracting skeletal muscle J Appl Physiol, March 1, 2006; 100(3): 1019 - 1026. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Charkoudian, J. H. Eisenach, M. J. Joyner, S. K. Roberts, and D. E. Wick Interactions of plasma osmolality with arterial and central venous pressures in control of sympathetic activity and heart rate in humans Am J Physiol Heart Circ Physiol, December 1, 2005; 289(6): H2456 - H2460. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. S. Kimmerly, D. D. O'Leary, R. S. Menon, J. S. Gati, and J. K. Shoemaker Cortical regions associated with autonomic cardiovascular regulation during lower body negative pressure in humans J. Physiol., November 15, 2005; 569(1): 331 - 345. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W. W. Waters, S. H. Platts, B. M. Mitchell, P. A. Whitson, and J. V. Meck Plasma volume restoration with salt tablets and water after bed rest prevents orthostatic hypotension and changes in supine hemodynamic and endocrine variables Am J Physiol Heart Circ Physiol, February 1, 2005; 288(2): H839 - H847. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. M. McCurley, S. U. Hanlon, S.-k. Wei, E. F. Wedam, M. Michalski, and M. C. Haigney Furosemide and the progression of left ventricular dysfunction in experimental heart failure J. Am. Coll. Cardiol., September 15, 2004; 44(6): 1301 - 1307. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Kamiya, D. Michikami, Q. Fu, S. Iwase, J. Hayano, T. Kawada, T. Mano, and K. Sunagawa Pathophysiology of orthostatic hypotension after bed rest: paradoxical sympathetic withdrawal Am J Physiol Heart Circ Physiol, August 7, 2003; 285(3): H1158 - H1167. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. J. Mueller and E. M. Hasser Enhanced sympathoinhibitory response to volume expansion in conscious hindlimb-unloaded rats J Appl Physiol, May 1, 2003; 94(5): 1806 - 1812. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. S. Kimmerly and J. K. Shoemaker Hypovolemia and MSNA discharge patterns: assessing and interpreting sympathetic responses Am J Physiol Heart Circ Physiol, April 1, 2003; 284(4): H1198 - H1204. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
