Impact of Carbon Dioxide on Cerebral Oxygenation and Vital Parameters in Stable Preterm and Term Infants Immediately after Birth
<b><i>Introduction:</i></b> Carbon dioxide (pCO<sub>2</sub>) induces changes in the tone of cerebral vessels. The aim of the present study was to evaluate the impact of pCO<sub>2</sub> on cerebral regional tissue oxygen saturation (crSO<sub>2</sub>), cerebral fractional tissue oxygen extraction (cFTOE), and cerebral tissue oxygen extraction (cTOE), measured with near-infrared spectroscopy (NIRS), in preterm and term infants 15 min after birth. <b><i>Methods:</i></b> Post hoc analyses of secondary outcome parameters of prospective observational studies were performed. Stable preterm and term infants with cerebral NIRS monitoring (INVOS 5100C) until minute 15 after birth and a blood gas analysis, performed between minutes 14–18 after birth, were included. Heart rate (HR) and arterial oxygen saturation (SpO<sub>2</sub>) were recorded. pCO<sub>2</sub> was correlated with crSO<sub>2</sub>, cFTOE, cTOE, SpO<sub>2</sub>, HR, and partial pressure of oxygen (pO<sub>2</sub>). <b><i>Results:</i></b> Eleven preterm infants with a median (IQR) gestational age of 34.8 (32.7–36.1) weeks were analyzed. Mean ± SD pCO<sub>2</sub> was 53.5 ± 4.2 mm Hg. At minute 15 after birth, crSO<sub>2</sub> was 82.6 (74.3–91.3)%, cFTOE 0.15 ± 0.09, cTOE 14.6 ± 8.4%, SpO<sub>2</sub> 97.4 ± 2.1%, and HR 152 (136–167) bpm. pCO<sub>2</sub> correlated negatively with crSO<sub>2</sub> (<i>p</i> = 0.012) and positively with cFTOE (<i>p</i> = 0.035) and cTOE (<i>p</i> = 0.037). Eighty-four term infants with a gestational age of 39.0 (38.5–38.9) weeks were analyzed. pCO<sub>2</sub> was 53.5 ± 6.3 mm Hg. At minute 15 after birth, crSO<sub>2</sub> was 84.4 (80.8–85.1)%, cFTOE 0.14 ± 0.08, cTOE 13.6 ± 7.9%, SpO<sub>2</sub> 96.5 ± 2.6%, and HR 155 (153–163) bpm. pCO<sub>2</sub> did only negatively correlate with pO<sub>2</sub> (<i>p</i> = 0.034) in term infants. <b><i>Conclusion:</i></b> In preterm infants, higher pCO<sub>2</sub> was associated with lower crSO<sub>2</sub> and higher cFTOE/cTOE. In term infants, no associations were observed. The present findings suggest that the vasodilatative effect of pCO<sub>2</sub> is less pronounced in preterm infants during immediate postnatal transition.