Document Detail

Phenylephrine decreases frontal lobe oxygenation at rest but not during moderately intense exercise.
MedLine Citation:
PMID:  20223999     Owner:  NLM     Status:  MEDLINE    
Whether sympathetic activity influences cerebral blood flow (CBF) and oxygenation remains controversial. The influence of sympathetic activity on CBF and oxygenation was evaluated by the effect of phenylephrine on middle cerebral artery (MCA) mean flow velocity (Vmean) and the near-infrared spectroscopy-derived frontal lobe oxygenation (ScO2) at rest and during exercise. At rest, nine healthy male subjects received bolus injections of phenylephrine (0.1, 0.25, and 0.4 mg), and changes in mean arterial pressure (MAP), MCA Vmean, internal jugular venous O2 saturation (SjvO2), ScO2), and arterial PCO2 (PaCO2) were measured and the cerebral metabolic rate for O2 (CMRO2) was calculated. In randomized order, a bolus of saline or 0.3 mg of phenylephrine was then injected during semisupine cycling, eliciting a low (approximately 110 beats/min) or a high (approximately 150 beats/min) heart rate. At rest, MAP and MCA Vmean increased approximately 20% (P<0.001) and approximately 10% (P<0.001 for 0.25 mg of phenylephrine and P<0.05 for 0.4 mg of phenylephrine), respectively. ScO2 then decreased approximately 7% (P<0.001). Phenylephrine had no effect on SjvO2, PaCO2, or CMRO2. MAP increased after the administration of phenylephrine during low-intensity exercise (approximately 15%), but this was attenuated (approximately 10%) during high-intensity exercise (P<0.001). The reduction in ScO2 after administration of phenylephrine was attenuated during low-intensity exercise (-5%, P<0.001) and abolished during high-intensity exercise (-3%, P=not significant), where PaCO2 decreased 7% (P<0.05) and CMRO2 increased 17% (P<0.05). These results suggest that the administration of phenylephrine reduced ScO2 but that the increased cerebral metabolism needed for moderately intense exercise eliminated that effect.
Patrice Brassard; Thomas Seifert; Mads Wissenberg; Peter M Jensen; Christian K Hansen; Niels H Secher
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2010-03-11
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  108     ISSN:  1522-1601     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2010 Jun 
Date Detail:
Created Date:  2010-06-03     Completed Date:  2010-10-08     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1472-8     Citation Subset:  IM    
Department of Anesthesia, The Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
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MeSH Terms
Blood Flow Velocity / drug effects,  physiology
Cerebrovascular Circulation / drug effects,  physiology*
Frontal Lobe / drug effects,  physiology*
Oxygen / metabolism*
Oxygen Consumption / drug effects,  physiology*
Phenylephrine / administration & dosage*
Physical Exertion / drug effects,  physiology*
Vasoconstrictor Agents / administration & dosage
Young Adult
Reg. No./Substance:
0/Vasoconstrictor Agents; 59-42-7/Phenylephrine; 7782-44-7/Oxygen
Comment In:
J Appl Physiol (1985). 2010 Jun;108(6):1447-9   [PMID:  20299620 ]

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

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