Transitional Changes in Cardiac and Cerebral Hemodynamics in Term Neonates at Birth

ObjectiveTo describe cardiac function, cerebral regional oxygen saturation (rSO2), and cerebral blood flow (CBF) that correspond to changes in arterial oxygen saturation (SaO2) in normal term neonates immediately after birth and after the transition.Study designIn this prospective observational study, cardiac function and cerebral hemodynamics were assessed by echocardiography and Doppler ultrasonography 3 times during the first 20 minutes after vaginal delivery, then again at 24-48 hours after delivery. Cerebral rSO2 (by near-infrared spectroscopy) and preductal SaO2 (by pulse oximetry) were assessed continuously.ResultsIn 20 neonates, SaO2 increased progressively from 65% at 1 minute after birth to 97% at 17 minutes after birth. Cerebral rSO2 increased from 47% at 1 minute to 83% at 8 minutes, then decreased progressively to 73% at 20 minutes. Middle cerebral artery mean velocity decreased from 34 cm/s at 7 minutes to 25 cm/s at 14 minutes. The patent ductus arteriosus (PDA) shunt was balanced at 5 minutes but became increasingly left to right. Left ventricular stroke volume was increased. Middle cerebral artery mean velocity demonstrated an inverse relationship with the PDA shunt. Further hemodynamic changes were noted on the posttransitional assessment.ConclusionAfter birth, ductal shunting rapidly changes from balanced to left to right, with a responsive increase in left ventricular stroke volume. Cerebral rSO2 increases as SaO2 rises during the first 8 minutes, subsequently, it decreases due to a drop in CBF and despite a further increase in SaO2. The reduction in CBF is likely due to an increase in arterial O2 content, PDA shunting, or both.