Document Detail

CO2 reactivity testing without blood pressure monitoring?
MedLine Citation:
PMID:  9933278     Owner:  NLM     Status:  MEDLINE    
BACKGROUND AND PURPOSE: Responsiveness to CO2 is an established test of cerebrovascular reserve capacity. Arterial partial pressure of CO2 (PCO2) and arterial blood pressure (BP) are key parameters for cerebral blood flow. To investigate the interaction between PCO2 and BP, we performed a study with simultaneous measurement of CO2 and BP during CO2 reactivity testing with transcranial Doppler sonography. METHODS: Eighty-one healthy volunteers, aged 19 to 74 years, underwent examination defined by a protocol with multimodality monitoring of BP, heart rate (HR), PCO2, and Doppler frequencies (DFs) of the left middle cerebral artery (MCA). Reproducibility was tested in a subgroup of 14 volunteers >/=65 years of age by CO2 reactivity testing on different days. RESULTS: Increase of PCO2 was accompanied by a parallel increase of mean+/-SD time values of DF (3. 6+/-1.6%/mm Hg CO2). BP levels were significantly elevated after 60-second hypercapnia (mean values, 0.5+/-0.55 mm Hg/mm Hg CO2). A significant decrease over time was seen only for pulsatility in DF but not in BP. Analysis of variance and covariance with repeated measures revealed a highly significant effect of CO2 on MCA Doppler shift. A less-pronounced effect on DF was seen for BP. Correlation analysis showed no significance for CO2 reactivity, but a significant correlation between test and retest was seen in BP-related CO2 reactivity. CONCLUSIONS: The CO2 response curve showed the known linear increase of DF. The parallel significant increase in BP most likely results from activation of the central sympathetic nervous system. The poor reproducibility for Doppler CO2 reactivity is to some extent explainable by variability of BP. CO2-induced increases in BP can have relevant influence on MCA Doppler shift and lead to misinterpretation of Doppler CO2 test results.
A Hetzel; S Braune; B Guschlbauer; K Dohms
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Publication Detail:
Type:  Case Reports; Comparative Study; Journal Article    
Journal Detail:
Title:  Stroke; a journal of cerebral circulation     Volume:  30     ISSN:  0039-2499     ISO Abbreviation:  Stroke     Publication Date:  1999 Feb 
Date Detail:
Created Date:  1999-03-01     Completed Date:  1999-03-01     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0235266     Medline TA:  Stroke     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  398-401     Citation Subset:  IM    
Department of Neurology, University of Freiburg, Freiburg, Germany. HETZEL@NZ11.UKL.Uni-Freiburg.DE
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MeSH Terms
Blood Flow Velocity
Blood Pressure / drug effects,  physiology*
Brain / blood supply*
Carbon Dioxide / blood,  diagnostic use*
Carotid Stenosis / blood,  physiopathology
Cerebral Arteries / physiology,  ultrasonography
Cerebrovascular Circulation*
Hypercapnia / blood,  chemically induced,  physiopathology
Middle Aged
Reproducibility of Results
Ultrasonography, Doppler, Transcranial
Vasodilation / drug effects
Reg. No./Substance:
124-38-9/Carbon Dioxide

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

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