Elevated brain oxygen extraction fraction in preterm newborns with anemia measured using noninvasive MRI

Objective To test the hypothesis that cerebral oxygen extraction fraction (OEF) is elevated and inversely related to hematocrit level in anemic former very-low-birth-weight infants near term. Study design Prospective study of non-sedated preterm infants (post-menstrual age = 36 +/- 2 weeks) over a range of hematocrits (0.23-0.49). Anatomical (T-1-W, T-2-W, and diffusion-weighted), cerebral blood flow (CBF), and OEF 3-T MRI were utilized. Statistical analysis included Spearman's rank-order correlation testing between study variables and intraclass correlation coefficients (ICC) calculated between consecutively acquired OEF scans. Results Consecutive OEF measurements showed moderate-to-good agreement (ICC = 0.71; 95% CI = 0.40-0.87). OEF increased with worsening anemia (rho = -0.58; p = 0.005), and OEF and basal ganglia CBF were positively correlated (rho = 0.49; p = 0.023). Conclusion Noninvasive OEF MRI has moderate-to-good repeatability in non-sedated former preterm infants nearing term-equivalent age. Strong correlation of elevated OEF with anemia suggests hemodynamic compensation for anemia and could establish OEF as a useful biomarker of transfusion threshold for preterm infants.