Electron paramagnetic resonance assessment of brain tissue XXXX tension in anesthetized @entity35 .

@entity1 @entity2806 @entity26 @entity3652 @entity4763 @entity36724 @entity35 @entity5161 @entity72474
The adequacy of cerebral tissue oxygenation ( @entity36724 ) is a central therapeutic end point in critically ill and anesthetized @entity1 . Clinically, @entity36724 is currently measured indirectly, based on measurements of cerebrovascular oxygenation using near infrared spectroscopy and experimentally, using positron emission tomographic scanning. Recent developments in electron paramagnetic resonance (EPR) oximetry facilitate accurate, sensitive, and repeated measurements of @entity36724 . EPR is similar to nuclear magnetic resonance but detects paramagnetic species. Because these species are not abundant in brain (or other tissues) in vivo, @entity26 -responsive paramagnetic @entity72474 crystals implanted into the cerebral cortex are used for the measurement of @entity26 . The line widths of the EPR spectra of these materials are linear functions of @entity36724 . We used EPR oximetry in anesthetized @entity35 to study the patterns of @entity36724 during exposure to various inhaled and injected general anesthetics and to varying levels of inspired @entity26 . @entity35 anesthetized with 2.0 minimum alveolar anesthetic concentration @entity5161 maintained the largest @entity36724 (38.0 +/- 4.5 mm Hg) and @entity35 anesthetized with @entity3652 / @entity4763 had the smallest @entity36724 (3.5 +/- 0.3 mm Hg) at a fraction of inspired @entity26 (FIO(2)) of 0.21, P < 0.05. The maximal @entity36724 achieved under @entity3652 / @entity4763 anesthesia with FIO(2) of 1.0 was 8.8 +/- 0.3 mm Hg, whereas @entity36724 measured during @entity5161 anesthesia with FIO(2) of 1.0 was 56.3 +/- 1.7 mm Hg (P < 0.05). These data highlight the experimental utility of EPR in measuring @entity36724 during anesthesia and serve as a foundation for further study of @entity36724 in response to physiologic perturbations and therapeutic interventions directed at preventing @entity2806 . IMPLICATIONS: Using in vivo electron paramagnetic resonance oximetry, we studied the patterns of cerebral tissue oxygenation ( @entity36724 ) during exposure to various inhaled and injected general anesthetics, and to varying levels of inspired @entity26 . These data show that inhaled anesthetics result in larger levels of @entity36724 in the brain than do several injectable anesthetics. The results highlight the experimental utility of electron paramagnetic resonance in measuring @entity36724 during anesthesia and serve as a foundation for further study of @entity36724 in response to physiologic perturbations and therapeutic interventions directed at preventing @entity2806 .
