Placental, fetal, and transitional circulation revisited

Surfactant and neonatal hemodynamics during the postnatal transition

Surfactant replacement therapy (SRT) has revolutionized the management of respiratory distress syndrome (RDS) in premature infants, leading to improved survival rates and decreased morbidity. SRT may, however, be associated with hemodynamic changes, which can have both positive and negative effects on the immature cardiovascular system, during the transitional adaptation from fetal to extrauterine environment. However, there is a relative paucity of evidence in this domain, with most of them derived from small heterogeneous observational studies providing conflicting results. In this review, we will discuss the hemodynamic changes that occur with surfactant administration during this vulnerable period, focusing on available evidence regarding changes in pulmonary and systemic blood flow, cerebral circulation and their clinical implications.

Transitional circulation and hemodynamic monitoring in newborn infants

Transitional circulation is normally transient after birth but can vary markedly between infants. It is actually in a state of transition between fetal (in utero) and neonatal (postnatal) circulation. In the absence of definitive clinical trials, information from applied physiological studies can be used to facilitate clinical decision making in the presence of hemodynamic compromise. This review summarizes the peculiar physiological features of the circulation as it transitions from one phenotype into another in term and preterm infants. The common causes of hemodynamic compromise during transition, intact umbilical cord resuscitation, and advanced hemodynamic monitoring are discussed. IMPACT: Transitional circulation can vary markedly between infants. There are alterations in preload, contractility, and afterload during the transition of circulation after birth in term and preterm infants. Hemodynamic monitoring tools and technology during neonatal transition and utilization of bedside echocardiography during the neonatal transition are increasingly recognized. Understanding the cardiovascular physiology of transition can help clinicians in making better decisions while managing infants with hemodynamic compromise. The objective assessment of cardio-respiratory transition and understanding of physiology in normal and disease states have the potential of improving short- and long-term health outcomes.

A review on development of placental transfusion in term and preterm infants

In recent years, it has been verified that placental transfusion can replenish blood volume of neonates, improve organ perfusion in the early postnatal stage, and facilitate the transition from fetal circulation to adult circulation. Meanwhile, placental transfusion can reduce the need for blood transfusion and the onset of intraventricular hemorrhage, necrotizing enterocolitis, bronchopulmonary dysplasia, and other complications. Furthermore, it can improve the iron store and the long-term prognosis of central nervous system, and reduce infant mortality. Different methods have been used, including delayed cord clamping, intact umbilical cord milking, and cut umbilical cord milking. The World Health Organization (WHO) and other academic organizations recommend the routine use of delayed cord clamping at birth for the most vigorous term and preterm neonates. However, details of placental transfusion should be clarified, and the short/long-term impacts of this technology on some infants with special conditions still require further study.

Cardiovascular and respiratory physiology in children

Children are at increased risk of perioperative respiratory and cardiovascular complications because of their unique respiratory and cardiovascular physiology compared to adults. Anaesthesia can exaggerate respiratory deterioration in young children because of their inability to control respiration and inherent susceptibility to rapid desaturation, airway obstruction, early respiratory fatigue and lung atelectasis. Premature infants (less than 60 weeks of postconceptional age) can be exposed to the danger of prolonged apnoea and consequent worsening of respiratory function. The transitional phase of circulation is vulnerable to revert to persistent foetal circulation in neonates. Myocardium and autonomic control of the heart is immature and different in neonates and infants compared to older children and adults and are predisposed to inadvertent life-threatening haemodynamic changes during the perioperative period. In this review article, we discuss respiratory and cardiovascular physiology in neonates, infants and younger children and their differences with older children and adults. We mainly focus on transitional physiology of both respiratory and cardiovascular system in newborns and infants and the deleterious changes that may occur during anaesthesia or perioperatively.

Chronological Echocardiographic Changes in Healthy Term Neonates within Postnatal 72 Hours Using Doppler Studies

BACKGROUND

This study evaluated echocardiographic changes in full-term healthy neonates during early transitional period from postnatal 0-72 hours at 12-hour intervals by echocardiography.

METHODS

This was a prospective, observational, and longitudinal single-center cohort study. Morphometric, functional, systolic, diastolic, and tissue Doppler imaging (TDI) parameters (patent ductus arteriosus [PDA], aorta, superior vena cava [SVC], stroke volume [SV], cardiac output [CO], cardiac index [CI], early diastolic flow velocity [E], late diastolic flow velocity [A], early filling in TDI [E'], peak systolic annular velocity in TDI [S'], late velocity peak in TDI [A'], and myocardial performance index [MPI]) were evaluated in left ventricle (LV) and right ventricle (RV) with 56 newborns.

RESULTS

Sizes and peak velocities of PDA before postnatal 24 hours were significantly changed than those after postnatal 24 hours. Aortic velocity time integral (VTI), systolic blood pressure (BP), LV SV/kg, LV CO/kg, LV CI, and SVC flow/LV CO before 24 hours showed significantly changes than those after 24 hours. Also, LV and RV MPI before 24 hours were significantly higher than those after 24 hours. LV E/E' was significantly higher than RV E/E'.

CONCLUSION

Postnatal 24 hours is critical time for hemodynamic closure of PDA because aortic VTI, systolic BP, LV SV, LV CO, LV CI, and SVC flow/LV CO showed simultaneously significant changes after 24 hours at the same time as 24 hours of physiological closure of PDA. Chronological and dramatic changes of systolic, diastolic, and TDI parameters during early postnatal period can be used to compile normal baseline data of healthy full-term neonates.

Tissue Doppler, strain, and strain rate measurements assessed by two-dimensional speckle-tracking echocardiography in healthy newborns and infants

OBJECTIVES

To evaluate cardiac maturational and haemodynamic alteration in healthy newborns and infants and determine reference values in this period using tissue Doppler, strain, and strain rate echocardiography.

MATERIAL AND METHODS

The study included 149 healthy subjects. Babies from 1 day to 3 months were selected from the well-baby nursery department, and infants were selected from paediatric clinics during routine visits for health maintenance. Subjects were allocated to four groups: preterm (36-37 weeks, n = 32), term (≥ 38 weeks, n = 32), 1 month of age (n = 47), and 3 months of age (n = 38). Standard echocardiographic evaluations, pulsed wave Doppler, tissue Doppler echocardiography, strain, and strain rate studies were applied by the same person using a MyLab50 echo machine. Longitudinal and circumferential systolic strain and strain rate measurements were assessed by two-dimensional speckle-tracking echocardiography in all subjects.

RESULTS

The longitudinal systolic velocity, strain, and strain rate values derived from left ventricle apical four-, three-, and two-chamber images, and circumferential systolic velocity, strain, and strain rate values derived from left ventricle short-axis images decreased from the base to the apex in all subjects (p < 0.001).

CONCLUSION

Significant cardiac haemodynamic alterations occurred during the newborn and early infancy periods and were detected by tissue Doppler, strain, and strain rate echocardiography. Although two-dimensional speckle-tracking echocardiography is useful and can produce improved, reliable results in clinical practice, it has some limitations. Therefore, more studies on this issue are required.

The perinatal transition of the circulating metabolome in a nonhuman primate

INTRODUCTION

The fetal-to-neonatal transition is one of the most complex processes in biological existence; much is unknown about this transition on the molecular and biochemical level. Based on growing metabolomics literature, we hypothesize that metabolomic analysis will reveal the key biochemical intermediates that change during the birth transition.

RESULTS

Using two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC × GC-TOFMS), we identified 100 metabolites that changed during this transition. Of these 100 metabolites, 23 demonstrated significant change during the first 72 h. Of note, four intermediates of the tricarboxylic acid (TCA) cycle were identified (α-ketoglutaric acid, fumaric acid, malic acid, and succinyl-CoA), demonstrating a consistent rate of rise during the study. This may signify the transition of the neonate from a hypoxic in utero environment to an oxygen-rich environment. Important signaling molecules were also identified, including myo-inositol and glutamic acid.

DISCUSSION

GC × GC-TOFMS was able to identify important metabolites associated with metabolism and signaling. These data can be used as a baseline for normal birth transition, which may aid in future perinatal research investigations.

METHODS

Late-preterm Macaca nemestrina were delivered by hysterotomy, with plasma drawn from the cord blood and after birth at eight additional time points to 72 h of age.

PPHN: is sildenafil the new nitric? A review of the literature

Persistent pulmonary hypertension of the newborn (PPHN) is a life-threatening neonatal pathology resulting from poor hemodynamic and respiratory transition to extrauterine life. Inhaled nitric oxide (iNO) is a current, commonly used treatment of PPHN. However, some infants with PPHN do not respond to iNO therapy. Because of the significant morbidity and mortality associated with PPHN, it is useful to look at other possible therapies. This article explores the use of sildenafil in the treatment of PPHN, either as a supplement to iNO or as an alternative to iNO. Current research, including a case study, is reviewed. An emphasis is placed on the administration and efficacy of sildenafil in synergy with, and in lieu of, current iNO therapy in the treatment of PPHN.

Fetal-to-neonatal transition--what is normal and what is not?

These articles review the physiologic adaptations occurring during the transition from fetal to neonatal life and examine common red flags which may alert care providers to an infant experiencing delayed transition or an underlying disease process, congenital abnormality, or birth injury.

In vitro hemodynamic investigation of the embryonic aortic arch at late gestation

This study focuses on the dynamic flow through the fetal aortic arch driven by the concurrent action of right and left ventricles. We created a parametric pulsatile computational fluid dynamics (CFD) model of the fetal aortic junction with physiologic vessel geometries. To gain a better biophysical understanding, an in vitro experimental fetal flow loop for flow visualization was constructed for identical CFD conditions. CFD and in vitro experimental results were comparable. Swirling flow during the acceleration phase of the cardiac cycle and unidirectional flow following mid-deceleration phase were observed in pulmonary arteries (PA), head-neck vessels, and descending aorta. Right-to-left (oxygenated) blood flowed through the ductus arteriosus (DA) posterior relative to the antegrade left ventricular outflow tract (LVOT) stream and resembled jet flow. LVOT and right ventricular outflow tract flow mixing had not completed until approximately 3.5 descending aorta diameters downstream of the DA insertion into the aortic arch. Normal arch model flow patterns were then compared to flow patterns of four common congenital heart malformations that include aortic arch anomalies. Weak oscillatory reversing flow through the DA junction was observed only for the Tetralogy of Fallot configuration. PA and hypoplastic left heart syndrome configurations demonstrated complex, abnormal flow patterns in the PAs and head-neck vessels. Aortic coarctation resulted in large-scale recirculating flow in the aortic arch proximal to the DA. Intravascular flow patterns spatially correlated with abnormal vascular structures consistent with the paradigm that abnormal intravascular flow patterns associated with congenital heart disease influence vascular growth and function.