Supplementary Material for: Fetal Hemoglobin and Cerebral Tissue Oxygenation during Immediate Postnatal Transition

<b><i>Introduction:</i></b> Concentration of fetal hemoglobin (HbFc) in human neonates determines oxygen-carrying capacity of blood and the position of oxyhemoglobin dissociation curve. Near-infrared spectroscopy enables the measurement of regional cerebral tissue oxygen saturation (rScO₂) and in combination with measurements of pulsatile arterial oxygen saturation (SpO₂), the calculation of cerebral fractional tissue oxygen extraction (cFTOE). <b><i>Methods:</i></b> We aimed to investigate the impact of HbFc on rScO₂, cFTOE, and SpO₂ in preterm and term neonates during the first 15 min after birth. Blood analyses provided total blood hemoglobin (Hb) and HbFc measurements. Correlations between HbFc, Hb and rScO₂, cFTOE, and SpO₂ in each minute were analyzed. <b><i>Results:</i></b> Ninety term and 19 preterm neonates without medical support were included. HbFc was significantly higher in preterm neonates, whereas there were no significant differences in Hb between the groups. In preterm neonates, we found positive correlations of both HbFc and Hb with rScO₂ and negative correlations of HbFc and Hb with cFTOE in the first minutes after birth. In contrast, there were no significant correlations between the same parameters in term neonates. Correlations between HbFc or Hb and SpO₂ were either insignificant, negligible, or very low in both groups. <b><i>Discussion/Conclusion:</i></b> In preterm neonates, higher HbFc was associated with higher rScO₂ and lower cFTOE in the first minutes after birth. This phenomenon could not be confirmed in term neonates and might reflect immature autoregulation of oxygen delivery to the brain or lower oxygen consumption in preterm neonates in the first minutes of immediate postnatal transition.