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Changes in sympathoadrenal response to standing in humans after spaceflight
P A Whitson1, J B Charles, W J Williams
1Medical Sciences Division, National Aeronautics and Space Administration Johnson Space Center, Houston, Texas 77058, USA.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|August 1, 1995
Summary
Spaceflight alters astronauts' cardiovascular function, leading to decreased stroke volume and impaired orthostatic tolerance upon return. This study investigated changes in plasma catecholamines and cardiovascular responses after space missions.
Area of Science:
- Cardiovascular Physiology
- Space Medicine
- Neuroendocrinology
Background:
- Spaceflight is known to induce significant physiological deconditioning.
- Orthostatic intolerance is a common issue astronauts experience upon returning to Earth's gravity.
Purpose of the Study:
- To investigate the effects of spaceflight on plasma catecholamine levels.
- To assess cardiovascular responses to standing (orthostatic function) before and after space missions.
Main Methods:
- Measured plasma norepinephrine and epinephrine concentrations in astronauts.
- Recorded blood pressure, heart rate, and cardiac output during supine and standing periods.
- Collected blood samples pre-flight and post-flight, including 3 days after landing.
Main Results:
- Plasma catecholamine levels (norepinephrine and epinephrine) significantly increased post-flight, both in supine and standing positions.
- Astronauts exhibited elevated heart rate and blood pressure upon landing.
- Stroke volume decreased by 26% upon standing after spaceflight, correlating with reduced orthostatic function.
Conclusions:
- Decreased stroke volume is the primary factor contributing to impaired orthostatic function after spaceflight.
- Elevated plasma catecholamines post-flight suggest an altered sympathoadrenal response.
- Further research is needed to elucidate the mechanisms behind these spaceflight-induced cardiovascular changes.