Transitional changes in cardiac and cerebral hemodynamics in term neonates at birth

Objective: To describe cardiac function, cerebral regional oxygen saturation (rSO(2)), and cerebral blood flow (CBF) that correspond to changes in arterial oxygen saturation (SaO(2)) in normal term neonates immediately after birth and after the transition.

Study design: In 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 rSO(2) (by near-infrared spectroscopy) and preductal SaO(2) (by pulse oximetry) were assessed continuously.

Results: In 20 neonates, SaO(2) increased progressively from 65% at 1 minute after birth to 97% at 17 minutes after birth. Cerebral rSO(2) 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.

Conclusion: After birth, ductal shunting rapidly changes from balanced to left to right, with a responsive increase in left ventricular stroke volume. Cerebral rSO(2) increases as SaO(2) rises during the first 8 minutes, subsequently, it decreases due to a drop in CBF and despite a further increase in SaO(2). The reduction in CBF is likely due to an increase in arterial O(2) content, PDA shunting, or both.