Document Detail


Cerebral arterial and venous contributions to tissue oxygenation index measured using spatially resolved spectroscopy in newborn lambs.
MedLine Citation:
PMID:  21068664     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
BACKGROUND: Bedside assessments of cerebral oxygenation are sought to monitor cerebral injury in patients undergoing intensive care. Spatially resolved spectroscopy measures tissue oxygenation index (TOI, %) which reflects mixed cerebral arterial and venous oxygenations. We aimed to evaluate arterial and venous components of TOI (cerebral arterial to venous volume ratio [A:V ratio]) in the newborn lamb brain using cerebral arterial and venous blood samples, and to investigate the impact of acute hypoxemia on the A:V ratio and TOI.
METHOD: Nine lambs were ventilated with varied inspired oxygen to generate arterial oxygen saturations between 25% and 100%. Cerebral arterial and venous oxygen saturations analyzed using cooximeter of arterial and superior sagittal sinus blood were used to estimate TOI (TOIcox), assuming cerebral A:V ratio of 25:75. TOIcox was compared with the TOI measured by spatially resolved spectroscopy (TOIsrs). Actual cerebral arterial and venous volume fractions were reestimated using TOIsrs = cerebral arterial volume fraction cerebral arterial oxygen saturation + cerebral venous volume fraction*cerebral venous oxygen saturation.
RESULTS: Median (range) TOIsrs was 48.5% (32.0-64.1%), and TOIcox was 48.4% (13.7-74.4%), and the two were significantly correlated (R = 0.77). The mean difference between TOIsrs and TOIcox was 2.4% (limits of agreement ± 18.1%). The TOIsrs - TOIcox difference varied with oxygen saturations, with TOIsrs higher than TOIcox at low saturations, and lower at high saturations. Cerebral arterial volume fraction was 22.9-27.5% in normoxia and markedly increased in hypoxemia.
CONCLUSION: TOI corresponds with cerebral oxygenation. The variable agreement of TOIsrs with TOIcox may reflect changes in cerebral A:V ratio due to arterial oxygenation-related vasoreactivity.
Authors:
Flora Y Wong; Theodora Alexiou; Thilini Samarasinghe; Vojta Brodecky; Adrian M Walker
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Anesthesiology     Volume:  113     ISSN:  1528-1175     ISO Abbreviation:  Anesthesiology     Publication Date:  2010 Dec 
Date Detail:
Created Date:  2010-11-24     Completed Date:  2010-12-22     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  1300217     Medline TA:  Anesthesiology     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1385-91     Citation Subset:  AIM; IM    
Affiliation:
The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia. flora.wong@med.monash.edu.au
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MeSH Terms
Descriptor/Qualifier:
Animals
Animals, Newborn / physiology*
Anoxia / blood
Blood Volume / physiology
Cerebral Arteries / physiology*
Cerebral Veins / physiology*
Cerebrovascular Circulation / physiology
Oximetry
Oxygen / blood
Oxygen Consumption / physiology*
Sheep
Spectroscopy, Near-Infrared / methods
Chemical
Reg. No./Substance:
7782-44-7/Oxygen

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