Carboxyhemoglobin as a biomarker of oxidative stress and neonatal brain injury

Introduction: Oxidative stress is one of the most important factors in the pathogenesis of neonatal brain injury in preterm infants. High level of carboxyhemoglobin (COHb) has been found to be associated with an increased risk for oxidative stress-related prematurity complications. Our aim was to assess the possible association between COHb fraction and brain growth and injury in very preterm infants (VPI). Methods: We retrospectively studied infants with gestational age <30 weeks, 34 with no white matter injury (WMI) and 19 with WMI. COHb fractions measured on the 1st and 7th days of life were collected. Brain growth and injury were evaluated with MRI images performed at term equivalent age (TEA). The infants’ neurodevelopment was evaluated at 24 ± 2 months corrected age. Multivariate regression analyses were performed to assess the correlation between COHb and brain growth and injury. Results: COHb fraction on day 1 was positively associated with interhemispheric distance (IHD). COHb fraction on day 7 was positively associated with WMI. ROC curve analysis showed that COHb fraction on day 7 significantly predicted WMI (AUC 0.674, 95% C.l. 0.491–0.848) with a sensitivity of 63% and a specificity of 74% at a cutoff point of 1.5%. No associations were found between COHb and neurodevelopment. Discussion: COHb fraction measured in the first week of life can predict brain growth and injury in VPI at TEA. These results suggest the role of COHb as a promising early biomarker of neurological impairments, also thanks to the ease of its measurement.