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Effect of hydration on some orthostatic and haematological responses to head-up tiltExperiments were undertaken to determine the effects of hydration status on: (1) orthostatic responses, and on (2) relative changes in intravascular volume and protein content, during 70 deg head-up tilt (HUT). Six men underwent 45 min of HUT, preceded by 45 min supine, first dehydrated, and again 105 min later after rehydration with water. Heart rate was consistently lower following rehydration (p less than 0.01), while supine diastolic pressure was higher (p less than 0.02). Systolic pressure fell during dehydrated HUT (p less than 0.01), but not during rehydrated HUT. Postural haemoconcentration, which was reduced after rehydration (p less than 0.001), was accompanied by a decrease in intravascular albumin content (p less than 0.05). Two subjects experienced severe presyncopal symptoms during dehydrated HUT, but not during rehydrated HUT. Thus, it appears that rehydration after fluid restriction improves orthostatic tolerance. Furthermore, extravascular hydration status may be more important than intravascular hydration status in determining orthostatic tolerance.
Document ID
19860064487
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Harrison, M. H.
(NASA Ames Research Center Moffett Field, CA, United States)
Hill, L. C.
(NASA Ames Research Center Moffett Field, CA, United States)
Spaul, W. A.
(NASA Ames Research Center Moffett Field, CA, United States)
Greenleaf, J. E.
(NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
August 12, 2013
Publication Date
January 1, 1986
Publication Information
Publication: European Journal of Applied Physiology
Volume: 55
ISSN: 0301-5548
Subject Category
Aerospace Medicine
Accession Number
86A49225
Distribution Limits
Public
Copyright
Other

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