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Updated: Aug 24, 2026
Non-invasive Optical Measurement of Cerebral Metabolism and Hemodynamics in Infants
Published on: March 14, 2013
What effect does measuring children under anesthesia have on the blood oxygenation level-dependent signal? A
Valentine L Marcar1, Thomas Loenneker, Andrea E Strassle
1Department of Neuropsychology, Psychological Institute, University of Zurich, CH-8032 Zurich, Switzerland. v.marcar@psychologie.unizh.ch
Insights
Light anesthesia in children undergoing functional MRI did not significantly alter brain oxygen consumption or blood flow. This suggests that the blood oxygenation level-dependent signal remains reliable for visual stimulus studies in pediatric patients under anesthesia.
Area of Science:
- Neuroscience
- Medical Imaging
- Pediatric Anesthesiology
Background:
- Functional magnetic resonance imaging (fMRI) is crucial for pediatric neuroscience research.
- Anesthesia can potentially affect brain activity and fMRI signal.
- Understanding anesthesia's impact on cerebral blood flow and oxygen metabolism is vital for accurate pediatric neuroimaging.
Purpose of the Study:
- To investigate the effects of light sevoflurane anesthesia on brain activity during visual stimulation in children.
- To assess whether anesthesia alters cerebral metabolic rate of oxygen consumption (CMRO(2)) and cerebral blood flow (CBF) during fMRI.
- To determine the reliability of the blood oxygenation level-dependent (BOLD) signal under light anesthesia in pediatric subjects.
Main Methods:
- fMRI measurements were conducted on 10 children, with half awake and half under light sevoflurane anesthesia (0.5 MAC).
- Visual stimuli included flashed and reversing checkerboards, known to elicit different neuronal activation and CMRO(2) levels.
- Brain activation extent was quantified by counting activated pixels, and changes in CMRO(2) were assessed via deoxyhemoglobin (HbR) concentration changes using spin relaxivity.
Main Results:
- Both flashed and reversing checkerboards activated more pixels in awake children compared to anesthetized children.
- Despite fewer activated voxels under anesthesia, the relative change in HbR concentration for both stimuli was comparable between awake and anesthetized groups.
- Reversing checkerboards consistently showed higher HbR concentrations than flashed checkerboards, indicating higher CMRO(2).
Conclusions:
- Light sevoflurane anesthesia may decrease the extent of neuronal activation observed in fMRI.
- Anesthesia at the level studied does not appear to significantly impair CMRO(2) or CBF measurements.
- The BOLD signal amplitude is preserved under light anesthesia, supporting its use in pediatric fMRI studies.
Abstract:
We performed functional magnetic resonance measurements involving visual stimuli on 10 children. Half of the children were measured awake, the other half were measured under light Sevoflurane anesthesia corresponding to 0.5 mean alveolar concentration. Each child was presented with a flashed and a reversing checkerboard, which previous investigations have shown to induce identical increases in cerebral blood flow. The latter stimulus activated double the number of neurons as the former so that cerebral metabolic rate of oxygen consumption (CMRO(2)) was doubled, leading to an effective rise of the oxygen extraction fraction. We measured the extent of activation by counting the number of activated pixels and assessed the change in CMRO(2) by measuring the change in the local deoxyhemoglobin (HbR) concentration, using change in spin relaxivity. In both groups of children, the extent of activation was larger for the flashed than the reversing checkerboard, although the absolute number of activated voxels was smaller for the children who were measured under anesthesia. The HbR concentration was significantly higher during the presentation of the reversing compared with the flashed checkerboard. The relative change in the HbR concentration to the flashed and reversing checkerboard was the same in the children who were measured under anesthesia as in the children who were measured awake. We conclude that light levels of anesthesia may reduce the extent of activation but does not unduly influence either CMRO(2) or cerebral blood flow, thus preserving the blood oxygenation level-dependent signal amplitude.
