Orthostatic intolerance after spaceflight.
Buckey, Jay C., Jr, Lynda D. Lane, Benjamin D. Levine, Donald E.
Watenpaugh, Sheryl J. Wright, Willie E. Moore, F. Andrew Gaffney, and
C. Gunnar Blomqvist.
Departments of Internal Medicine and Physiology, Division of
Cardiology, University of Texas Southwestern Medical Center, Dallas,
Texas 75235-9034,
APStracts 2:0288A, 1995.
Orthostatic intolerance occurs commonly after spaceflight and
important aspects of the underlying mechanisms remain unclear. We
studied fourteen individuals supine and standing before and after the
three Space Shuttle missions of nine to fourteen days. After
spaceflight, nine of the fourteen (64%) crew members could not
complete a 10 minute stand test that all completed preflight. Pre-
and postflight supine hemodynamics were similar in both except for
slightly higher systolic and mean arterial pressures preflight in the
finishers (+15+/-3.7 mmHg and +8+/-1.2 mmHg, p<0.05, mean
data+/-SEM). Postflight, finishers and non finishers had equally
large postural reductions in stroke volume (-47+/-3.7 and -48+/-3.3
ml.) and increases in heart rate (+35+/-6.6 and +51+/-5.2 bpm).
Cardiac output during standing was also similar, 3.6+/-0.4 and 4.1+/
-0.3 l/min. However, the finishers had a greater postflight
vasoconstrictor response with higher total peripheral resistance
(TPR) during standing (22.3+/-1.2 units pre- and 29.4+/-2.3
postflight) than non finishers (TPR 20.1+/-1.1 units pre- and 19.9+/
-1.4 postflight) . We conclude that (a) the primary systemic
hemodynamic event, i.e. the postural decrease in stroke volume, was
similar in finishers and non-finishers, (b) the heart rate response
and cardiac output during standing were not significantly different,
but (c) the postural vasoconstrictor response was significantly
greater (p<0.01) among the finishers.
Received 23 December 1995; accepted in final form 7 June 1995.
APS Manuscript Number A1308-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 11 July 1995.