Cerebral arterial and venous contributions to tissue oxygenation index measured using spatially resolved spectroscopy in newborn lambs
| Autor: | Flora Y. Wong, Thilini Samarasinghe, Vojta Brodecky, Theodora Alexiou, Adrian M. Walker |
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| Rok vydání: | 2010 |
| Předmět: |
Hypoxemia
Oxygen Consumption Cerebral oxygenation Intensive care medicine Animals In patient Oximetry Hypoxia Cerebral injury Blood Volume Sheep Spectroscopy Near-Infrared business.industry Spatially resolved Oxygenation Cerebral Arteries Cerebral Veins Oxygen Anesthesiology and Pain Medicine Animals Newborn Tissue oxygenation index Anesthesia Cerebrovascular Circulation medicine.symptom business |
| Zdroj: | Anesthesiology. 113(6) |
| ISSN: | 1528-1175 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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