Fraction of Inspired Oxygen in Relation to Cerebrospinal Fluid Hyperintensity on FLAIR MR Imaging of the Brain in Children and Young Adults Undergoing Anesthesia

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Abstract
OBJECTIVE. Cerebrospinal fluid (CSF) hyperintensity has been described on fluid-attenuated inversion recovery (FLAIR) imaging in anesthetized patients who underwent MR imaging without apparent subarachnoid abnormality. The purpose of our study was to delineate likely causes for this hyperintensity. Specifically, we sought to determine whether a high inspired oxygen fraction given as part of the anesthetic was responsible for the CSF hyperintensity seen on FLAIR imaging. MATERIALS AND METHODS. A retrospective study was conducted using anesthetic records and brain MR images of 70 children and young adults who had a FLAIR sequence while undergoing general anesthesia. Information about inspired oxygen fraction, oxygen saturation, and type of anesthetic agents preceding the FLAIR sequence was obtained from the anesthetic record. A pediatric neuroradiologist who was unaware of the inspired oxygen fraction and anesthetic agent ascertained the presence of CSF hyperintensity in the basilar cisterns and cerebral sulcal subarachnoid space. RESULTS. Twenty-one patients received an inspired oxygen fraction less than or equal to 0.60, and 49 received an inspired oxygen fraction greater than 0.60. Inspired oxygen fraction greater than 0.60 was significantly associated with the presence of CSF hyperintensity in the basilar cisterns (p < 0.001) and in the cerebral sulcal subarachnoid space (p = 0.03). The type of anesthetic agent, patient's sex, or status (based on the American Society of Anesthesiology physical status and classification system), and presence of cardiopulmonary disease or seizure disorder were not associated with CSF hyperintensity. CONCLUSION. High inspired oxygen fraction during anesthesia is associated with CSF hyperintensity in the basilar cisterns and the cerebral sulcal subarachnoid space on FLAIR imaging in children and young adults. Physicians should be aware of this finding to avoid misinterpreting this artifact as an abnormality.