Supplemental oxygen causes increased signal intensity in subarachnoid cerebrospinal fluid on brain FLAIR MR images obtained in children during general anesthesia

PURPOSE: To prospectively test the hypothesis that high levels of, the fraction of inspired oxygen (F-IO2) during general anesthesia cause subarachnoid cerebrospinal, fluid (CSF) hyperintensity during fluid-attenuated inversion-recovery (FLAIR) magnetic resonance (MR) imaging. MATERIALS AND METHODS: 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 F-IO2 level. The Wilcoxon signed rank test was used to determine if CSF hyperintensity was correlated with F-IO2. RESULTS: CSF hyperintensity was present in all 20 children (age range, 1.9-16.7 years; 12 children were boys) when the F-IO2 was 100%. The hyperintensity partially or completely disappeared in the basilar cisterns. (P<.001) and cerebral sulcal subarachnoid space (P<.001),after F-IO2 was reduced from 100% to 30%. CONCLUSION: These findings are consistent with the hypothesis that increased arterial oxygen tension and consequently increased CSF P-O2 resulting from administration of high F-IO2 during general anesthesia are responsible for the increased CSF signal intensity noted on brain FLAIR MR images. (C) RSNA, 2004.