Hemodynamic Changes in the Transition Period in the Preterm and Term Infant: Basic Concepts

Abstract

The transition of the cardiovascular system from fetal life to extrauterine life occurs through different physiological mechanisms. The development of the lungs are parallel to the development of the cardiovascular system. Cardiac and vascular tone are affected by genetic and environmental factors, including hormonal influences and autonomic reflexes. During the transition period, significant changes occur in preload, myocardial contractility, and afterload. The timing of cord clamping has a profound effect on these changes. Cerebral autoregulation is severely impaired in preterm infants, and cerebral blood flow is almost completely pressure-passive, especially in extremely preterm infants. Disrupted autoregulation is also more frequent in sick infants. Knowledge of transitional factors in different periods is essential for proper management of newborn infants.