Blamick CA, Tatro DL, Convertino VA.
Aviat Space Environ Med. 1989 May; 60: 486.
The Bionetics Corporation, Kennedy Space Center, FL 32899.
INTRODUCTION. Dehydration and orthostatic hypotension are common in astronauts after spaceflight. Acute redistribution of blood volume has been associated with alterations in the sensitivity of the carotid-cardiac baroreflex. In contrast, we recently demonstrated that plasma volume reduction during bedrest was poorly correlated with reduced sensitivity of the carotid baroreflex and orthostatic hypotension. To further clarify this issue, we tested carotid-cardiac baroreflex responses under various hydration states. METHODS. Four men (34-44 yr) underwent measurements for baroreflex response under 3 hydration states; dehydrated (DE), euhydrated (EU), and hyperhydrated (HY). A carotid-cardiac response curve was generated using a neck cuff device that delivered pressure changes between +40 and -65 mmHg in continuous steps of 15 mmHg. RESULTS. The slopes of the reflex response relation were not different among hydration states (4.8 +/- .9, 4.5 +/- .7, 4.8 +/- .3 msec/mmHg for DE, EU, HY, respectively). However, the capacity of the baroreflex to buffer hypotension by increasing heart rate was greater (P < .05) in HY compared to EU. CONCLUSIONS. Acute changes in hydration state do not alter carotid-cardiac baroreflex sensitivity. Reduced hydration and decreased baroreflex sensitivity which can contribute to orthostatic hypotension following spaceflight appear to operate independently.
Publication Types:
Keywords:
- Baroreflex
- Bed Rest
- Blood Volume
- Heart
- Heart Rate
- Humans
- Hypotension, Orthostatic
- Male
- Plasma Volume
- Reflex
- Space Flight
- NASA Center KSC
- NASA Discipline Cardiopulmonary
- NASA Discipline Number 14-10
- NASA Program Biomedical Research
Other ID:
UI: 102212904
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