Access the full text.
Sign up today, get DeepDyve free for 14 days.
References for this paper are not available at this time. We will be adding them shortly, thank you for your patience.
Abstract Fritsch-Yelle, Janice M., Peggy A. Whitson, Roberta L. Bondar, and Troy E. Brown. Subnormal norepinephrine release relates to presyncope in astronauts after spaceflight. J. Appl. Physiol. 81(5): 2134–2141, 1996.—Postflight orthostatic intolerance is experienced by virtually all astronauts but differs greatly in degree of severity. We studied cardiovascular responses to upright posture in 40 astronauts before and after spaceflights lasting up to 16 days. We separated individuals according to their ability to remain standing without assistance for 10 min on landing day. Astronauts who could not remain standing on landing day had significantly smaller increases in plasma norepinephrine levels with standing than did those who could remain standing (105 ± 41 vs. 340 ± 62 pg/ml; P = 0.05). In addition, they had significantly lower standing peripheral vascular resistance (23 ± 3 vs. 34 ± 3 mmHg ⋅ l −1 ⋅ min; P = 0.02) and greater decreases in systolic (−28 ± 4 vs. −11 ± 3 mmHg; P = 0.002) and diastolic (−14 ± 7 vs. 3 ± 2 mmHg; P = 0.0003) pressures. The presyncopal group also had significantly lower supine (16 ± 1 vs. 21 ± 2 mmHg ⋅ l −1 ⋅ min; P = 0.04) and standing (23 ± 2 vs. 32 ± 2 mmHg ⋅ l −1 ⋅ min; P = 0.038) vascular resistance, supine (66 ± 2 vs. 73 ± 2 mmHg; P = 0.008) and standing (69 ± 4 vs. 77 ± 2 mmHg; P = 0.007) diastolic pressure, and supine (109 ± 3 vs. 114 ± 2 mmHg; P = 0.05) and standing (99 ± 4 vs. 108 ± 3 mmHg; P = 0.006) systolic pressures before flight. This is the first study to clearly document these differences among presyncopal and nonpresyncopal astronauts after spaceflight and also offer the possibility of preflight prediction of postflight susceptibility. These results clearly point to hypoadrenergic responsiveness, possibly centrally mediated, as a contributing factor in postflight orthostatic intolerance. They may provide insights into autonomic dysfunction in Earthbound patients. orthostatic hypotension adrenergic Footnotes Address for reprint requests: J. M. Fritsch-Yelle, Cardiovascular Laboratory, SD3/, Johnson Space Center, Houston, TX 77058. This research was supported by National Aeronautics and Space Administration Contract NAS9-18942 and Natural Sciences and Engineering Research Council, Medical Research Council, Canadian Space Agency Industry University Partnership Grant 669-008/93. Copyright © 1996 the American Physiological Society
Journal of Applied Physiology – The American Physiological Society
Published: Nov 1, 1996
Read and print from thousands of top scholarly journals.
Already have an account? Log in
Bookmark this article. You can see your Bookmarks on your DeepDyve Library.
To save an article, log in first, or sign up for a DeepDyve account if you don’t already have one.
Copy and paste the desired citation format or use the link below to download a file formatted for EndNote
Access the full text.
Sign up today, get DeepDyve free for 14 days.
All DeepDyve websites use cookies to improve your online experience. They were placed on your computer when you launched this website. You can change your cookie settings through your browser.