Changes in sympathoadrenal response to standing in humans after
space flight.
Whitson, Peggy A., John B. Charles, W. Jon Williams, and Nitza M.
Cintron.
Medical Sciences Division, NASA Johnson Space Center, Houston, TX
77058 USA
APStracts 2:0093A, 1995.
Plasma catecholamines levels and cardiovascular responses to standing
were determined in astronauts before and after several Space Shuttle
missions. Blood pressure, heart rate, and cardiac output were
measured and blood samples for catecholamine analyses were drawn at
the end of the supine and standing periods. Supine plasma
norepinephrine and epinephrine concentrations increased 34% and 65%,
respectively, on landing day compared to before flight. Standing on
landing day resulted in a 65% and 91% increase in plasma
norepinephrine and epinephrine, respectively. Supine and standing
norepinephrine levels remained elevated 3 days after landing while
epinephrine levels returned to preflight levels. On landing day,
supine heart rate and systolic blood pressure increased 18% and 8.9%,
respectively, and standing heart rate and diastolic blood pressure
were elevated by 38% and 19%, respectively. On standing, stroke
volume was decreased by 26% on landing day compared to before flight.
Collectively these data indicate that the decreased orthostatic
function after space flight results largely from the decreased stroke
volume. Possible mechanisms contributing to this condition are
discussed.
Received 8 September 1994; accepted in final form 2 March 1995.
APS Manuscript Number A948-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 21 March 1995.