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 (T1-W, T2-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 (ρ = -0.58; p = 0.005), and OEF and basal ganglia CBF were positively correlated (ρ = 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.