Supplemental Oxygen Causes Increased Signal Intensity in Subarachnoid Cerebrospinal Fluid on Brain FLAIR MR Images Obtained in Children during General Anesthesia

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Abstract
To prospectively test the hypothesis that high levels of the fraction of inspired oxygen (Fio(2)) during general anesthesia cause subarachnoid cerebrospinal fluid (CSF) hyperintensity during fluid-attenuated inversion-recovery (FLAIR) magnetic resonance (MR) imaging. At brain MR imaging during general anesthesia with propofol, two FLAIR sequences were performed in 20 children with American Society of Anesthesiologists physical status classification system grades of 3 or lower. The first FLAIR sequence was performed with the child breathing 100% oxygen; the second was performed with the child breathing 30% oxygen. CSF signal intensity was quantified on a three-point ordinal scale (0 = hypointense to brain parenchyma, 1 = isointense to brain parenchyma, 2 = hyperintense to brain parenchyma) by a pediatric neuroradiologist who was blinded to the Fio(2) level. The Wilcoxon signed rank test was used to determine if CSF hyperintensity was correlated with Fio(2). CSF hyperintensity was present in all 20 children (age range, 1.9-16.7 years; 12 children were boys) when the Fio(2) was 100%. The hyperintensity partially or completely disappeared in the basilar cisterns (P <.001) and cerebral sulcal subarachnoid space (P <.001) after Fio(2) was reduced from 100% to 30%. These findings are consistent with the hypothesis that increased arterial oxygen tension and consequently increased CSF Po(2) resulting from administration of high Fio(2) during general anesthesia are responsible for the increased CSF signal intensity noted on brain FLAIR MR images.