| 1. |
- Passant, Ulla, et al.
(författare)
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Cortical blood flow during head-up postural change in subjects with orthostatic hypotension
- 1993
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Ingår i: Clinical autonomic research : official journal of the Clinical Autonomic Research Society. ; 3:5, s. 311-8
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Tidskriftsartikel (refereegranskat)abstract
- Regional cerebral blood flow was measured with the 133-Xenon inhalation method in seven healthy subjects with orthostatic hypotension not due to autonomic failure (i.e. non-neurogenic clinical disorder). Measurements were performed during supine rest and during head-up tilt (70 degrees). All subjects had a consistent drop in systolic blood pressure and the typical symptomatology of orthostatic hypotension. The results showed lower mean hemispheric blood flow during head-up tilt than during supine rest. In addition, a consistent and significant redistribution of the regional flow values was seen, with a reduction in frontal and an increase in postcentral areas. The frontal flow decrease during tilt was more marked than in subjects without orthostatic hypotension and was not related to variations in the level of PCO2 or to respiration. In contrast to the clinical symptoms of orthostatic hypotension (dizziness, nausea, visual disturbances, and in some cases syncope), the cortical blood flow reduction was, however, relatively moderate.
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| 2. |
- Warkentin, Siegbert, et al.
(författare)
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Redistribution of blood flow in the cerebral cortex of normal subjects during head-up postural change
- 1992
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Ingår i: Clinical autonomic research : official journal of the Clinical Autonomic Research Society. ; 2:2, s. 119-24
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Tidskriftsartikel (refereegranskat)abstract
- Regional cerebral blood flow was measured in 21 normotensive subjects during supine rest and during head-up tilt to 70 degrees. The results showed significant and consistent regional cerebral blood flow changes in the frontal areas with lower relative flow distribution values (percentage of mean flow) during head-up tilt than during supine rest. The lower frontal flow distribution values during tilt were not related to habituation, to repeated measurements, or to the estimated level of arterial CO2 which was derived from expired end-tidal CO2 levels. None of the subjects had orthostatic hypotension and there was no significant difference in mean hemispheric blood flow between lying down and standing up. There was no significant gender difference in regional cerebral blood flow, although female subjects tended to have higher mean hemispheric flow than males in both postures. It remains to be established whether the flow decreases in the frontal cortex are caused by cerebral functional factors or by haemodynamic mechanisms.
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