Document Detail


Cerebral autoregulation in subjects adapted and not adapted to high altitude.
MedLine Citation:
PMID:  11022056     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
BACKGROUND AND PURPOSE: Impaired cerebral autoregulation (CA) from high-altitude hypoxia may cause high-altitude cerebral edema in newcomers to a higher altitude. Furthermore, it is assumed that high-altitude natives have preserved CA. However, cerebral autoregulation has not been studied at altitude. METHODS: We studied CA in 10 subjects at sea level and in 9 Sherpas and 10 newcomers at an altitude of 4243 m by evaluating the effect of an increase of mean arterial blood pressure (MABP) with phenylephrine infusion on the blood flow velocity in the middle cerebral artery (Vmca), using transcranial Doppler. Theoretically, no change of Vmca in response to an increase in MABP would imply perfect autoregulation. Complete loss of autoregulation is present if Vmca changes proportionally with changes of MABP. RESULTS: In the sea-level group, at a relative MABP increase of 23+/-4% during phenylephrine infusion, relative Vmca did not change essentially from baseline Vmca (2+/-7%, P=0.36), which indicated intact autoregulation. In the Sherpa group, at a relative MABP increase of 29+/-7%, there was a uniform and significant increase of Vmca of 24+/-9% (P<0.0001) from baseline Vmca, which indicated loss of autoregulation. The newcomers showed large variations of Vmca in response to a relative MABP increase of 21+/-6%. Five subjects showed increases of Vmca of 22% to 35%, and 2 subjects showed decreases of Vmca of 21% and 23%. CONCLUSIONS: All Sherpas and the majority of the newcomers showed impaired CA. It indicates that an intact autoregulatory response to changes in blood pressure is probably not a hallmark of the normal human cerebral vasculature at altitude and that impaired CA does not play a major role in the occurrence of cerebral edema in newcomers to the altitude.
Authors:
G F Jansen; A Krins; B Basnyat; A Bosch; J A Odoom
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Publication Detail:
Type:  Clinical Trial; Controlled Clinical Trial; Journal Article    
Journal Detail:
Title:  Stroke; a journal of cerebral circulation     Volume:  31     ISSN:  1524-4628     ISO Abbreviation:  Stroke     Publication Date:  2000 Oct 
Date Detail:
Created Date:  2000-10-13     Completed Date:  2000-10-26     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  0235266     Medline TA:  Stroke     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  2314-8     Citation Subset:  IM    
Affiliation:
Department of Anesthesiology, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands.
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MeSH Terms
Descriptor/Qualifier:
Adaptation, Physiological / drug effects,  physiology*
Adult
Altitude*
Blood Flow Velocity / drug effects,  physiology
Blood Pressure / drug effects,  physiology*
Cerebrovascular Circulation / drug effects,  physiology
Female
Homeostasis / drug effects,  physiology
Humans
Infusions, Intravenous
Male
Middle Cerebral Artery / physiology*,  ultrasonography
Phenylephrine / administration & dosage
Rest / physiology
Ultrasonography, Doppler, Transcranial
Chemical
Reg. No./Substance:
59-42-7/Phenylephrine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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