Transitional Hemodynamics in Preterm Neonates: Clinical Relevance

Cardiac Development and Related Clinical Considerations

The anatomy, physiology, and hemodynamics of the premature heart vary along the range of gestational ages cared for in neonatal intensive care units, from 22 weeks to term gestation. Clinical management of the preterm neonate should account for this heterogenous development. This requires an understanding of the impact of ex utero stressors on immature and disorganized cardiac tissue, the different state of hemodynamics across intracardiac shunts impacting the natural transition from fetal to neonatal life, and the effects of intensive pharmacologic and non-pharmacologic interventions that have systemic consequences influencing cardiac function. This article provides a review of the increasing but still limited body of literature on the anatomy, hemodynamics, and electrophysiology of the preterm heart with relevant clinical considerations.

Comparative efficacy of volume expansion, inotropes and vasopressors in preterm neonates with probable transitional circulatory instability in the first week of life: a systematic review and network meta-analysis

BACKGROUND

There exists limited agreement on the recommendations for the treatment of transitional circulatory instability (TCI) in preterm neonates OBJECTIVE: To compare the efficacy of various interventions used to treat TCI METHODS: Medline and Embase were searched from inception to 21st July 2023. Two authors extracted the data independently. A Bayesian random effects network meta-analysis was used. Recommendations were formulated using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) framework.

INTERVENTIONS

Dopamine, dobutamine, epinephrine, hydrocortisone, vasopressin, milrinone, volume and placebo.

MAIN OUTCOME MEASURES

Mortality, major brain injury (MBI) (intraventricular haemorrhage > grade 2 or cystic periventricular leukomalacia), necrotising enterocolitis (NEC) ≥stage 2 and treatment response (as defined by the author).

RESULTS

15 Randomized Controlled Trials (RCTs) were included from the 1365 titles and abstracts screened. Clinical benefit or harm could not be ruled out for the critical outcome of mortality. For the outcome of MBI, epinephrine possibly decreased the risk when compared to dobutamine and milrinone (very low certainty). Epinephrine was possibly associated with a lesser risk of NEC when compared with dopamine, dobutamine, hydrocortisone and milrinone (very low certainty). Dopamine was possibly associated with a lesser risk of NEC when compared with dobutamine (very low certainty). Vasopressin possibly decreased the risk of NEC compared with dopamine, dobutamine, hydrocortisone and milrinone (very low certainty). Clinical benefit or harm could not be ruled out for the outcome response to treatment.

CONCLUSIONS

Epinephrine may be used as the first-line drug in preterm neonates with TCI, the evidence certainty being very low. We suggest future trials evaluating the management of TCI with an emphasis on objective criteria to define it.

Engineered tissue geometry and Plakophilin-2 regulate electrophysiology of human iPSC-derived cardiomyocytes

Engineered heart tissues have been created to study cardiac biology and disease in a setting that more closely mimics in vivo heart muscle than 2D monolayer culture. Previously published studies suggest that geometrically anisotropic micro-environments are crucial for inducing "in vivo like" physiology from immature cardiomyocytes. We hypothesized that the degree of cardiomyocyte alignment and prestress within engineered tissues is regulated by tissue geometry and, subsequently, drives electrophysiological development. Thus, we studied the effects of tissue geometry on electrophysiology of micro-heart muscle arrays (μHM) engineered from human induced pluripotent stem cells (iPSCs). Elongated tissue geometries elicited cardiomyocyte shape and electrophysiology changes led to adaptations that yielded increased calcium intake during each contraction cycle. Strikingly, pharmacologic studies revealed that a threshold of prestress and/or cellular alignment is required for sodium channel function, whereas L-type calcium and rapidly rectifying potassium channels were largely insensitive to these changes. Concurrently, tissue elongation upregulated sodium channel (NaV1.5) and gap junction (Connexin 43, Cx43) protein expression. Based on these observations, we leveraged elongated μHM to study the impact of loss-of-function mutation in Plakophilin 2 (PKP2), a desmosome protein implicated in arrhythmogenic disease. Within μHM, PKP2 knockout cardiomyocytes had cellular morphology similar to what was observed in isogenic controls. However, PKP2-/- tissues exhibited lower conduction velocity and no functional sodium current. PKP2 knockout μHM exhibited geometrically linked upregulation of sodium channel but not Cx43, suggesting that post-translational mechanisms, including a lack of ion channel-gap junction communication, may underlie the lower conduction velocity observed in tissues harboring this genetic defect. Altogether, these observations demonstrate that simple, scalable micro-tissue systems can provide the physiologic stresses necessary to induce electrical remodeling of iPS-CM to enable studies on the electrophysiologic consequences of disease-associated genomic variants.

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.

Severity of preterm birth and the risk of pulmonary hypertension in childhood: A population-based cohort study in Sweden

BACKGROUND

Preterm birth (<37 completed gestational weeks) has been linked to pulmonary hypertension (PH), but the relationship to severity of preterm birth has not been studied.

OBJECTIVES

We investigated associations between extremely (<28 weeks), very (28-31 weeks), moderately (32-36 weeks) preterm birth, early-term birth (37-38 weeks) and later PH. Additionally, we explored associations between birthweight for gestational age and PH.

METHODS

This registry-based cohort study followed 3.1 million individuals born in Sweden (1987-2016) from 1 up to a maximum of 30 years of age. The outcome was diagnosis or death from PH in national health registers. Adjusted hazard ratios (HR) were estimated using Cox regression analysis. Unadjusted and confounder-adjusted incidence rate differences were also calculated.

RESULTS

Of 3,142,812 individuals, there were 543 cases of PH (1.2 per 100,000 person-years), 153 of which in individuals without malformations. Compared with individuals born at 39 weeks, adjusted HRs with 95% confidence interval (CI) for PH for extremely, moderately, and very preterm birth were 68.78 (95% CI 49.49, 95.57), 13.86 (95% CI 9.27, 20.72) and 3.42 (95% CI 2.46, 4.74), respectively, and for early-term birth 1.74 (1.31, 2.32). HRs were higher in subjects without malformations. There were 90 additional cases of PH per 100,000 person-years in the extremely preterm group (50 after excluding malformations). Very small for gestational age (below 2 SD from estimated birthweight for gestational age and sex) was also associated with increased risk of PH (adjusted HR 2.02, 95% CI 1.14, 3.57).

CONCLUSIONS

We found an inverse association between gestational age and later PH, but the incidence and absolute risks are low. The severity of preterm birth adds clinically relevant information to the assessment of cardiovascular risks in childhood.

Does Perinatal Intermittent Hypoxia Affect Cerebrovascular Network Development?

Perinatal hypoxia is an inadequate delivery of oxygen to the fetus in the period immediately before, during, or after the birth process. The most frequent form of hypoxia occurring in human development is chronic intermittent hypoxia (CIH) due to sleep-disordered breathing (apnea) or bradycardia events. CIH incidence is particularly high with premature infants. During CIH, repetitive cycles of hypoxia and reoxygenation initiate oxidative stress and inflammatory cascades in the brain. A dense microvascular network of arterioles, capillaries, and venules is required to support the constant metabolic demands of the adult brain. The development and refinement of this microvasculature is orchestrated throughout gestation and in the initial weeks after birth, at a critical juncture when CIH can occur. There is little knowledge on how CIH affects the development of the cerebrovasculature. However, since CIH (and its treatments) can cause profound abnormalities in tissue oxygen content and neural activity, there is reason to believe that it can induce lasting abnormalities in vascular structure and function at the microvascular level contributing to neurodevelopmental disorders. This mini-review discusses the hypothesis that CIH induces a positive feedback loop to perpetuate metabolic insufficiency through derailment of normal cerebrovascular development, leading to long-term deficiencies in cerebrovascular function.

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.

Cerebral oxygenation and body position in the preterm infant: A systematic review and meta-analysis

AIM

After preterm birth, supine head midline position is supported for stable cerebral blood flow (CBF) and prevention of intraventricular haemorrhage (IVH), while prone position supports respiratory function and enables skin-to-skin care. The prone compared to supine position could lead to a change in near-infrared derived cerebral tissue oxygen saturation (rScO2), which is a surrogate for cerebral blood flow (CBF). By monitoring rScO2 neonatologists aim to stabilise CBF during intensive care and prevent brain injury. In this systematic review and meta-analysis, we investigate the effect of the body position on rScO2.

METHODS

A comprehensive literature search was performed to identify all trials that included preterm infants in the first 2 weeks after birth and compared rScO2 in the prone versus supine head in midline position of the infant. A meta-analysis, including two subgroup analyses based on postnatal age (PNA) and gestational age (GA), was performed.

RESULTS

Six observational cohort studies were included. In the second, but not the first week after birth, a significant higher rScO2 in the prone position was found with a mean difference of 1.97% (95% CI 0.87-3.07). No rScO2 difference was observed between positions in the extremely preterm nor the preterm group.

CONCLUSION

No consistent evidence was found that body position influences rScO2 in the first 2 weeks after preterm birth. Subgroup analysis suggests that in the second week after birth, the prone position might result in higher cerebral rScO2 than the supine position with head in midline. Multiple factors determine the best body position in preterms.

Differing Impact of Preterm Birth on the Right and Left Atria in Adulthood

Background Preterm birth affects 10% of live births and is associated with an altered left ventricular and right ventricular phenotype and increased cardiovascular disease risk in young adulthood. Because left atrial (LA) and right atrial (RA) volume and function are known independent predictors of cardiovascular outcomes, we investigated whether these were altered in preterm-born young adults. Methods and Results Preterm-born (n=200) and term-born (n=266) adults aged 18 to 39 years underwent cardiovascular magnetic resonance imaging. LA and RA maximal and minimal volumes (absolute, indexed to body surface area, and as a ratio to ventricular volumes) were obtained to study atrial morphology, while LA and RA stroke volume, strain, and strain rate were used to assess atrial function. Secondary analyses consisted of between-group comparisons based on degree of prematurity. Absolute RA volumes and RA volumes indexed to right ventricular volumes were significantly smaller in preterm-born compared with term-born adults. In addition, RA reservoir and booster strain were higher in preterm-born adults, possibly indicating functional compensation for the smaller RA volumes. LA volumes indexed to left ventricular volumes were significantly greater in preterm-born adults as compared with term-born adults, although absolute LA volumes were similar between groups. LA and RA changes were observed across gestational ages in the preterm group but were greatest in those born very-to-extremely preterm. Conclusions Preterm-born adults show changes in LA and RA structure and function, which may indicate subclinical cardiovascular disease. Further research into underlying mechanisms, opportunities for interventions, and their prognostic value is warranted.

Clinical determinants of cerebrovascular reactivity in very preterm infants during the transitional period

BACKGROUND

Preterm infants are at enhanced risk of brain injury due to altered cerebral haemodynamics during postnatal transition. This observational study aimed to assess the clinical determinants of transitional cerebrovascular reactivity and its association with intraventricular haemorrhage (IVH).

METHODS

Preterm infants <32 weeks underwent continuous monitoring of cerebral oxygenation and heart rate over the first 72 h after birth. Serial cranial and cardiac ultrasound assessments were performed to evaluate the ductal status and to diagnose IVH onset. The moving correlation coefficient between cerebral oxygenation and heart rate (TOHRx) was calculated. Linear mixed-effect models were used to analyse the impact of relevant clinical variables on TOHRx. The association between TOHRx and IVH development was also assessed.

RESULTS

Seventy-seven infants were included. A haemodynamically significant patent ductus arteriosus (hsPDA) (β = 0.044, 95% CI: 0.007-0.081) and ongoing dopamine treatment (β = 0.096, 95% CI: 0.032-0.159) were associated with increasing TOHRx, indicating impaired cerebrovascular reactivity. A significant association between TOHRx, mean arterial blood pressure (β = -0.004, 95% CI: -0.007, -0.001) and CRIB-II score (β = 0.007, 95% CI: 0.001-0.015) was also observed. TOHRx was significantly higher in infants developing high-grade IVH compared to those without IVH.

CONCLUSIONS

Dopamine treatment, low blood pressure, hsPDA and high CRIB-II are associated with impaired cerebrovascular reactivity during postnatal transition, with potential implications on IVH development.

IMPACT

The correlation coefficient between cerebral oxygenation and heart rate (TOHRx) provides a non-invasive estimation of cerebrovascular reactivity, whose failure has a potential pathogenic role in the development of IVH in preterm infants. This study shows that cerebrovascular reactivity during the transitional period improves over time and is affected by specific clinical and therapeutic factors, whose knowledge could support the development of individualized neuroprotective strategies in at-risk preterm infants. The evidence of increased TOHRx in infants developing high-grade compared to low-grade or no IVH during the transitional period further supports the role of impaired cerebrovascular reactivity in IVH pathophysiology.

Prematurity and Congenital Heart Disease: A Contemporary Review

Congenital heart disease (CHD) is the most commonly reported birth defect in newborns. Neonates with CHD are more likely to be born prematurely, and a higher proportion of preterm neonates have CHD than their term counterparts. The implications of preterm birth on the cardiac and noncardiac organ systems are vast and require special management considerations. The feasibility of surgical interventions in preterm neonates is frequently limited by patient size and delicacy of immature cardiac tissues. Thus, special care must be taken when considering the appropriate timing and type of cardiac intervention. Despite improvements in neonatal cardiac surgical outcomes, preterm and early term gestational ages and low birthweight remain important risk factors for in-hospital mortality. Understanding the risks of early delivery of neonates with prenatally diagnosed CHD may help guide perioperative management in neonates who are born preterm. In this review, we will describe the risks and benefits of early delivery, postnatal cardiac and noncardiac evaluation and management, surgical considerations, overall outcomes, and future directions regarding optimization of perinatal evaluation and management of fetuses and preterm and early term neonates with CHD.

Understanding the Preterm Human Heart: What do We Know So Far?

Globally, preterm birth affects more than one in every 10 live births. Although the short‐term cardiopulmonary complications of prematurity are well known, long‐term health effects are only now becoming apparent. Indeed, preterm birth has been associated with elevated cardiovascular morbidity and mortality in adulthood. Experimental animal models and observational human studies point toward changes in heart morphology and function from birth to adulthood in people born preterm that may contribute to known long‐term risks. Moreover, recent data support the notion of a heterogeneous cardiac phenotype of prematurity, which is likely driven by various maternal, early, and late life factors. This review aims to describe the early fetal‐to‐neonatal transition in preterm birth, the different structural and functional changes of the preterm human heart across developmental stages, as well as potential factors contributing to the cardiac phenotype of prematurity.

Value of bedside echocardiography in predicting persistent patency of the ductus arteriosus during the early postnatal period in very low birth weight infants

OBJECTIVES

To study the value of bedside echocardiography in predicting persistent patency of the ductus arteriosus during the early postnatal period in very low birth weight (VLBW) infants.

METHODS

A retrospective analysis was performed for 51 VLBW infants who were admitted from March 2020 to June 2021, with an age of ≤3 days and a length of hospital stay of ≥14 days. According to the diameter of patent ductus arteriosus (PDA) on days 14 and 28 after birth, the infants were divided into three groups: large PDA group (PDA diameter ≥2 mm), small PDA group (PDA diameter <2 mm), and PDA closure group (PDA diameter =0 mm). The echocardiographic parameters measured at 72 hours after birth were compared among the three groups. The receiver operating characteristic (ROC) curve was used to evaluate the value of the echocardiographic parameters in predicting persistent patency of the ductus arteriosus (PDA≥2 mm) at the ages of 14 and 28 days.

RESULTS

On day 14 after birth, there were 17 infants in the large PDA group, 11 in the small PDA group, and 23 in the PDA closure group. On day 28 after birth, there were 14 infants in the large PDA group, 9 in the small PDA group, and 26 in the PDA closure group. There were significant differences in gestational age, birth weight, rate of pulmonary surfactant use, and incidence rate of hypotension among the three groups (P<0.05). PDA diameter, end-diastolic velocity of the left pulmonary artery, left ventricular output, and left ventricular output/superior vena cava flow ratio measured at 72 hours after birth were associated with persistent patency of the ductus arteriosus at the ages of 14 and 28 days (P<0.05), and the ratio of the left atrium to aorta diameter was associated with persistent patency of the ductus arteriosus at the age of 28 days (P<0.05). The ROC curve analysis showed that the area under the curve that the PDA diameter measured at 72 hours after birth predicting the persistent patency of the ductus arteriosus at the ages of 14 and 28 days was the largest (0.841 and 0.927 respectively), followed by end-diastolic velocity of the left pulmonary artery, with the area under the curve of 0.793 and 0.833 respectively.

CONCLUSIONS

The indicators obtained by beside echocardiography at 72 hours after birth, especially PDA diameter and end-diastolic velocity of the left pulmonary artery, can predict persistent patency of the ductus arteriosus at the ages of 14 and 28 days in VLBW infants, which provides a basis for the implementation of early targeted treatment strategy for PDA.

Intraventricular hemorrhage prediction in premature neonates in the era of hemodynamics monitoring: a prospective cohort study

Unstable hemodynamics and prematurity are the main players in intraventricular hemorrhage (IVH) development. Our objective was to study 8 the use of superior vena cava flow (SVCF), left ventricular output (LVO), and right ventricular output (RVO), and anterior cerebral artery (ACA) Doppler measures in prediction of IVH in the first week of life in preterm infant ≤ 32 weeks and birth weight ≤ 1500 g. This prospective cohort study was conducted in 55NICU of Alexandria University maternity hospital. Of 147 enrolled patients, 132 infants born ≤ 32 weeks GA and birth weight ≤ 1500 g were eligible for- the study. One hundred twenty-seven infants completed the study. Infants were scanned for ACA-RI using transfontanellar ultrasound, and SVCF, LVO, and RVO using functional echocardiography in the first 24 h after birth. Patients had another two scans on DOL3 and 7 to detect IVH development. Low SVCF and high ACA-RI significantly increased the risk of IVH using logistic regression models with OR, 3.16; 95%CI, 1.19-8.39; P = 0.02 and OR, 1.64; 95%Cl, 1.10-2.44; P = 0.02, respectively. Low SVCF and high ACA-RI significantly increased risk of catastrophic IVH P = 0.025 and 0.023, respectively. Combined use of low SVCF < 55 ml/kg/min and ACA-RI > 0.75 is predictor of IVH with sensitivity 40.8% and 82.1% specificity.

CONCLUSIONS

There are strong relations between both low SVCF and high ACA-RI, and IVH development in premature neonates ≤ 32 weeks and birth weight ≤ 1500 g, with more significance towards catastrophic IVH. Admission RSS and LVO are the strongest factors affecting SVCF. Maternal anemia, patent ductus arteriosus size (mm/kg), and capillary refill time were significantly associated with high ACA-RI. These findings help in more understanding of pathophysiological factors affecting central perfusion that might affect the longer term neurodeveopmental outcome.

TRIAL REGISTRATION

This work was registered in clinical trial.gv no NCT05050032.

WHAT IS KNOWN

•Whether SVCF and RI-ACA can predict IVH in preterm neonates is still debatable.

WHAT IS NEW

•Low SVC flow and high ACA-RI significantly increased risk of IVH, confirming the role of hypoperfusion-reperfusion cycle in IVH development. The most striking result that combined metrics using the cut-off value of < 41 ml/kg/min for SVCF and > 0.85 for ACA-RI "in the first day of life" can correctly reject the presence of IVH in 98% of patients "during the first week of life."

The effect of placental transfusion on hemodynamics in premature newborns: a randomized controlled trial

Despite of growing evidence of the beneficial effects of placental transfusion techniques, there is no available sufficient data about their effects on vulnerable hemodynamics and myocardium of premature infants. The purpose of this work is to study ventricular functions and hemodynamics after applying different placental transfusion techniques, delayed cord clamping (DCC), cut cord milking (C-UCM), and intact cord milking (I-UCM). Sixty-four infants delivered whether by C-section or vaginal delivery were randomly assigned to undergo C-UCM (20-30 cm), I-UCM (3-4 strippings), and DCC (30-60 s). Functional echocardiography was done on day 1 and day 3 of life for 57 infants. Primary outcome variable was superior vena cava flow measurement in infants having placental transfusion in the first 24 h of life and between 64 and 72 h. Secondary outcomes were other echocardiographic and clinical hemodynamic parameters, and biventricular functions in those infants. Of a total 196 preterm infants ≤ 32 weeks delivered in the study period, from January 2021 to August 2021, 57 infants were eligible and survived till the second examination. They were randomly assigned to the three groups. Neonates randomly assigned to DCC had significantly higher superior vena cava flow and lower right ventricular systolic function in the first 24 h of life. This finding vanished at day 3. Neonates undergone different methods of placental transfusions had similar hemoglobin, admission temperature, and mean blood pressure in the first 24 h of life.

CONCLUSION

Despite their potential benefits, placental transfusions have shown to alter the hemodynamics and adversely affect myocardial function of premature neonates.

TRIAL REGISTRATION

This trial was registered in the clinical trial gov NCT04811872.

WHAT IS KNOWN

• Placental transfusion techniques might have benefits regarding prematurity- related morbidities and mortality.

WHAT IS NEW

• Placental transfusion might adversely affect the myocardium and alter hemodynamics in premature infants.

Sudden Onset of Severe Pulmonary Hypertension in a Preterm Infant: A Case Report on the Role of Maternal Use of Serotonin Re-Uptake Inhibitors During Pregnancy and Concurrent Risk Factors

Persistent pulmonary hypertension of the newborn (PPHN) is a severe condition caused by failed circulatory adaptation at birth. Pulmonary hypertension is most common in full-term infants and rare in preterms, although it is increasingly diagnosed also in extremely preterm infants. Previous studies demonstrated the association between maternal use of selective serotonin re-uptake inhibitors during gestation and pulmonary hypertension. This brief report describes the complex physiopathological correlations that were identified in a case of severe pulmonary hypertension in a fetal growth restricted (FGR) preterm infant, with a history of maternal use of antidepressants during pregnancy. Perinatal factors, triggers and aggravating mechanisms caused a dramatic clinical course. Maternal history of escitalopram therapy throughout pregnancy was noted. Uteroplacental insufficiency, fetal hypoxia, FGR, preeclampsia, preterm delivery, antenatal steroids, and cesarean section were documented as concurrent risk factors. Myocardial immaturity and dysfunction, secondary to FGR and prematurity aggravated the hemodynamic compromise. The short time gap between pharmacological ductal closure and the onset of PPHN may suggest a cause-effect relationship, as observed in previous reports. Placental histopathologic findings are reported.

Vasoactive medications in extremely low gestational age neonates during the first postnatal week

OBJECTIVE

The management of early hypotension in extremely low gestational age neonates (ELGANs) varies greatly between centers. The objective of this study was to provide updated data on the use of vasoactive medications in ELGANs during the first postnatal week.

STUDY DESIGN

We identified ELGANs (22-27 weeks gestational age) cared for at Pediatrix neonatal intensive care units from 2009 to 2018. We evaluated the frequency of exposure to vasoactive medications by gestational age, and compared use of vasoactive medications between two epochs (2009-2013 and 2014-2018).

RESULTS

A total of 10,070/34,234 (29%) ELGANs received ≥1 vasoactive medication. Dopamine was the most frequently used vasoactive medication. The majority (83%) of treated ELGANs initiated therapy on postnatal days 0-1. Overall use of vasoactive medications was slightly lower in 2014-2018 than 2009-2013 (28 vs 31%, p < 0.001).

CONCLUSION

A substantial proportion of ELGANs were exposed to vasoactive medications during the first postnatal week.

Recognition and management of neonatal hemodynamic compromise

Hemodynamic compromise of the neonate can occur in various clinical situations, including but not limited to maladaptation during the early transitional period, sepsis, congenital heart anomalies, hemodynamically significant patent ductus arteriosus, persistent pulmonary hypertension of the newborn, systemic inflammatory diseases such as necrotizing enterocolitis, and dehydration. Despite the handful of advances in neonatal care through ground-breaking clinical trials, the management of neonatal shock is often dependent on the bedside clinician's experience and training without the aid of high-level evidence. However, the recognition for the importance of comprehensive and serial hemodynamic assessment is growing. There is now a wealth of literature investigating the use of functional echocardiography, near-infrared spectroscopy, and noninvasive impedance-based cardiometry to complement common bedside hemodynamic measures such as blood pressure and heart rate measurement. In this review article, the pathophysiology of neonatal hemodynamic compromise is outlined, and concomitant best-evidence management for hemodynamic compromise in the neonate is proposed.

The Controversy Persists: Is There a Qualification Criterion to Utilize Inhaled Nitric Oxide in Pre-term Newborns?

Inhaled nitric oxide (iNO) use in premature newborns remains controversial among clinicians. In 2014, the American Academy of Pediatrics, Committee on Fetus and Newborn released a statement that the available data do not support routine iNO use in pre-term newborns. Despite the absence of significant benefits, 2016 California data showed that clinicians continue to utilize iNO in pre-term infants. With studies as recent as January 2017, the Cochrane review confirmed no major advantages of iNO in pre-term newborns. Still, it recognized that a subset of pre-term infants with pulmonary hypertension (PHTN) had not been separately investigated. Furthermore, recent non-randomized controlled trials have suggested that iNO may benefit specific subgroups of pre-term newborns, especially those with PHTN, prolonged rupture of membranes, and antenatal steroid exposure. Those pre-term infants who showed a clinical response to iNO had increased survival without disability. These findings underscore the need for future studies in pre-term newborns with hypoxemic respiratory failure and PHTN. This review will discuss the rationale for using iNO, controversies regarding the diagnosis of PHTN, and additional novel approaches of iNO treatment in perinatal asphyxia and neonatal resuscitation in the pre-term population < 34 weeks gestation.

Cardiovascular Pharmacological Support Among Preterm Infants in Chinese Referral Center Neonatal Intensive Care Units

Objective: To describe cardiovascular pharmacological support in infants born at <34 weeks' gestation within the first postnatal week in Chinese neonatal intensive care units (NICUs). Design: A secondary analysis of data from a multicenter randomized controlled study (REIN-EPIQ). A questionnaire regarding cardiovascular support practices was also completed by all participating NICUs. Setting: Twenty-five tertiary hospitals from 19 provinces in China. Patients: All infants born at <34 weeks' gestation and admitted to participating NICUs within the first postnatal week from May 2015 to April 2018 were included. Infants who were discharged against medical advice were excluded. Measures and Main Results: Among the 26,212 preterm infants <34 weeks, 16.1% received cardiovascular pharmacological support. The use rates increased with decreasing gestational age and birth weight, with 32.5% among infants <28 weeks and 35.9% among infants <1,000 g. Cardiovascular pharmacological support was independently associated with higher risks of death (aOR 2.8; 95% CI 2.4-3.3), severe intraventricular hemorrhage (IVH) (aOR 2.1; 95% CI 1.8-2.5) and bronchopulmonary dysplasia (BPD) (aOR 2.2; 95% CI 2.0-2.5). Overall 63.1% courses of cardiovascular pharmacological support were >3 days. Prolonged cardiovascular pharmacological support (>3 days) was independently associated with lower rates of survival without morbidity in very-low-birth-weight infants, compared with infants with shorter durations. Dopamine was the most commonly used cardiovascular agent. The cardiovascular pharmacological support rates varied from 1.9 to 65.8% among the participating NICUs. Conclusions: The rate of cardiovascular pharmacological support within the first postnatal week was high with prolonged durations in Chinese NICUs. Marked variation in cardiovascular support existed among participating NICUs. Cardiovascular pharmacological support during the early postnatal period, especially prolonged, may be associated with adverse neonatal outcomes. Clinical Trial Registration: The original trial was registered as "Reduction of Infection in Neonatal Intensive Care Units using the Evidence-based Practice for Improving Quality" (ID: NCT02600195) on clinicaltrials.gov. https://clinicaltrials.gov/ct2/show/NCT02600195?term=NCT02600195&draw=2&rank=1.

Assessment of BOLD response in the fetal lung

OBJECTIVE

Assessment of lung development and maturity is of utmost importance in prenatal counseling. Blood oxygen level-dependent (BOLD) effect MRI was developed for functional evaluations of organs. To date, no data are available in fetal lungs and nothing is known about the existence of a BOLD effect in the lungs. The aim of our study was to evaluate if a BOLD response could be detected in fetal lungs.

MATERIALS AND METHODS

From January 2014 to December 2016, 38 healthy pregnant women were prospectively enrolled. After a routine scan on a 1.5-T MRI device (normoxic period), maternal hyperoxia was induced for 5 min before the BOLD sequence (hyperoxic period). R2* was evaluated by fitting average intensity of the signal, both for normoxic (norm) and hyperoxic (hyper) periods.

RESULTS

A significant BOLD response was observed after maternal hyperoxia in the lungs with a mean R2* decrease of 12.1 ± 2.5% (p < 0.001), in line with the placenta response with a mean R2* decrease of 19.2 ± 5.9% (p < 0.0001), confirming appropriate oxygen uptake. Conversely, no significant BOLD effect was observed for the brain nor the liver with a mean ∆R2* of 3.6 ± 3.1% (p = 0.64) and 2.8 ± 3.7% (p = 0.23).

CONCLUSION

This study shows for the first time in human that a BOLD response can be observed in the normal fetal lung despite its prenatal "non-functional status." If confirmed in congenital lung and chest malformations, this property could be used in addition to the lung volume for a better prediction of postnatal respiratory status.

KEY POINTS

• Blood oxygen level-dependent (BOLD) effect MRI was developed for functional evaluations of organs and could have interesting implications for the fetal organs. • Assessment of lung development is of utmost importance in prenatal counseling, but to date no data are available in fetal lungs. • BOLD response can be observed in the normal fetal lung opening the way to studies on fetus with pathological lungs.

Less invasive surfactant administration reduces incidence of severe intraventricular haemorrage in preterms with respiratory distress syndrome: a cohort study

OBJECTIVE

Less invasive surfactant administration (LISA) has proved to safely improve morbidity in extreme preterms with respiratory distress syndrome (RDS). Its effect regarding intraventricular hemorrhage (IVH) remains controversial between most recent systematic reviews. We aimed to evaluate its effect over incidence of severe IVH in this population.

STUDY DESIGN

We compared the incidence of IVH in a prospective cohort of consecutively born preterm infants <34 weeks' gestation receiving LISA (n = 108) with a historical cohort receiving surfactant delivery via tracheal tube and managed with mechanical ventilation (n = 100).

RESULTS

No significant differences regarding perinatal characteristics were observed between both groups. There was a significant reduction in the incidence of severe IVH in LISA group as compared with the historical group [OR = 0.054 (95% CI 0.01-0.2) p = 0.000. NNT 5]. In addition, a significant trend towards decreased mortality was also observed in the study group [OR = 0.2 (95% CI 0.04-0.9) p = 0.027, NNT 9]. Intervention group infants also showed lower oxygenation requirements during the first 72 h post surfactant administration and a reduced incidence of pneumothorax. They were less frequently intubated [31 infants (28.4%) vs. 100 [100%]; P < 0.001] and required fewer days of mechanical ventilation. However, no significant difference in bronchopulmonary dysplasia incidence was observed between both groups.

CONCLUSIONS

LISA approach effectively reduces severe IVH in very low and low birth weight (BW) preterms with RDS. In addition we observe a significant trend towards reduction in both need and duration of MV support, air leak, and overall mortality in the intervention group.

Intraventricular Hemorrhage in Very Preterm Infants: A Comprehensive Review

Germinal matrix-intraventricular-intraparenchymal hemorrhage (GMH-IVH-IPH) is a major complication of very preterm births before 32 weeks of gestation (WG). Despite progress in clinical management, its incidence remains high before 27 WG. In addition, severe complications may occur such as post-hemorrhagic hydrocephalus and/or periventricular intraparenchymal hemorrhage. IVH is strongly associated with subsequent neurodevelopmental disabilities. For this review, an automated literature search and a clustering approach were applied to allow efficient filtering as well as topic clusters identification. We used a programmatic literature search for research articles related to intraventricular hemorrhage in preterms that were published between January 1990 and February 2020. Two queries ((Intraventricular hemorrhage) AND (preterm)) were used in PubMed. This search resulted in 1093 articles. The data manual curation left 368 documents that formed 12 clusters. The presentation and discussion of the clusters provide a comprehensive overview of existing data on the pathogenesis, complications, neuroprotection and biomarkers of GMH-IVH-IPH in very preterm infants. Clinicians should consider that the GMH-IVH-IPH pathogenesis is mainly due to developmental immaturity of the germinal matrix and cerebral autoregulation impairment. New multiomics investigations of intraventricular hemorrhage could foster the development of predictive biomarkers for the benefit of very preterm newborns.

Cardiovascular and cerebrovascular responses to cardio-respiratory events in preterm infants during the transitional period

KEY POINTS

Non-invasive simultaneous multiparametric monitoring allows the in vivo evaluation of cerebral and cardiovascular haemodynamic responses to different types of recurrent episodes of intermittent hypoxia and/or bradycardia, also defined as cardio-respiratory events (CRE), in preterm neonates during postnatal transition. By decreasing left cardiac output, bradycardia further contributes to cerebral hypoxia during CRE. The presence of a haemodynamically significant patent ductus arteriosus results in a deeper impairment of cerebral oxygen status in response to CRE, whereas the brain-sparing remodelling of the fetal circulation resulting from placental insufficiency is associated with more favourable haemodynamic responses to intermittent hypoxia. During transition, the haemodynamic impact of CRE is influenced not only by the event type, but also by specific clinical features; this highlights the importance of developing individualized approaches to reduce the hypoxic burden in this delicate phase.

ABSTRACT

The present observational prospective study aimed to investigate cerebral and cardiovascular haemodynamic responses to different types of cardio-respiratory events (CRE) in preterm infants during postnatal transition, as well as evaluate the impact of relevant clinical characteristics. Infants with gestational age (GA) <32 weeks and/or birth weight <1500 g were enrolled after birth. Cerebral oxygenation index (cTOI), fractional oxygen extraction (cFTOE), cardiac output (CO), cardiac contractility (iCON) and systemic vascular resistances (sVR) were simultaneously monitored over the first 72 h by near-infrared spectroscopy and electrical velocimetry. CRE were clustered into isolated bradycardia (IB), isolated desaturation (ID) and combined desaturation/bradycardia (DB). For each parameter, percentage changes from baseline (%Δ) were calculated. The impact of different CRE types and clinical variables on %Δ was evaluated with generalized estimating equations. In total, 1426 events were analysed. %ΔcTOI significantly differed among ID, IB and DB (P < 0.001), with the latter showing the greatest drop. %ΔcFTOE decreased significantly during DB (P < 0.001) and ID (P < 0.001) compared to IB. DB and IB were associated with more negative %ΔCO (P < 0.001) and more positive %ΔsVR (P < 0.001) compared to ID. A slight iCON reduction was observed during DB compared to ID (P = 0.043). Antenatal umbilical Doppler impairment, GA and the presence of a haemodynamically significant patent ductus arteriosus had a significant independent impact on %ΔcTOI, %ΔcFTOE and %ΔCO. During the transitional period, the haemodynamic responses to CRE are influenced by the event type and by specific neonatal characteristics, suggesting the importance of targeted individualized approaches for minimizing the risk of cerebral injury in the preterm population.

Sex-dependent effect of perinatal hypoxia on cardiac tolerance to oxygen deprivation in adults

Epidemiological studies have demonstrated a relationship between the adverse influence of perinatal development and increased risk of ischemic heart disease in adults. From negative factors to which the fetus is subjected, the most important is hypoxia. The fetus may experience hypoxic stress under different conditions, including pregnancy at high altitude, pregnancy with anemia, placental insufficiency, and heart, lung, and kidney disease. One of the most common insults during the early stages of postnatal development is hypoxemia due to congenital cyanotic heart defects. Experimental studies have demonstrated a link between early hypoxia and increased risk of ischemia/reperfusion injury (I/R) in adults. Furthermore, it has been observed that late myocardial effects of chronic hypoxia, experienced in early life, may be sex-dependent. Unlike in males, perinatal hypoxia significantly increased cardiac tolerance to acute I/R injury in adult females, expressed as decreased infarct size and lower incidence of ischemic arrhythmias. It was suggested that early hypoxia may result in sex-dependent programming of specific genes in the offspring with the consequence of increased cardiac susceptibility to I/R injury in adult males. These results would have important clinical implications, since cardiac sensitivity to oxygen deprivation in adult patients may be significantly influenced by perinatal hypoxia in a sex-dependent manner.

Medications and in-hospital outcomes in infants born at 22-24 weeks of gestation

OBJECTIVE

To evaluate the most commonly used medications and in-hospital morbidities and mortality in infants born 22-24 weeks of gestation.

STUDY DESIGN

Multicenter retrospective cohort study of infants born 22-24 weeks of gestation (2006-2016), without major congenital anomalies and with available medication data obtained from neonatal intensive care units managed by the Pediatrix Medical Group.

RESULTS

This study included 7578 infants from 195 sites. Median (25th, 75th percentile): birthweight was 610 g (540, 680); the number of distinct medications used was 13 (8, 18); and different antimicrobial exposure was 4 (2, 5). The most common morbidities were BPD (41%) and grade III or IV IVH (20%), and overall survival varied from 46% (2006) to 57% (2016).

CONCLUSIONS

A large number of medications were used in periviable infants. There was a high prevalence of in-hospital morbidities, and survival of this population increased over the study period.

Agreement of Cardiac Output Measurements between Bioreactance and Transthoracic Echocardiography in Preterm Infants during the Transitional Phase: A Single-Centre, Prospective Study

INTRODUCTION

Bioreactance cardiac output (CO) monitors are able to non-invasively and continuously monitor CO. However, as a novel tool to measure CO, it must be proven to be accurate and precise.

OBJECTIVE

To determine the agreement between CO measured with a bioreactance monitor and transthoracic echocardiography-derived left ventricular output parameters in preterm infants.

METHODS

This is a prospective observational study in 63 preterm neonates with non-invasive respiratory support, not requiring inotrope support. The infants underwent continuous bioreactance monitoring of CO and stroke volume (SV) and simultaneous transthoracic echocardiography every 6 h until 72 h of life.

RESULTS

The agreement between bioreactance and transthoracic echocardiography, for both SV and CO, was poor. The percentage error was 67.5% for SV and 71.6% for CO. The mean error was 60.4% for SV and 69.8% for CO. Bias was affected by numerous variables. After correcting for time, CO and SV bias were significantly affected by the presence of an open patent ductus arteriosus and the level of CO.

CONCLUSION

Bioreactance cannot be considered interchangeable with transthoracic echocardiography to measure CO in preterm infants during the transition phase. Agreement between bioreactance and other CO metrics should be assessed before concluding its accuracy or inaccuracy in neonates.

Respiratory distress syndrome: influence of management on the hemodynamic status of ≤ 32-week preterm infants in the first 24 hours of life

Objective

To investigate the influence of respiratory distress syndrome management on clinical and echocardiographic parameters used for hemodynamic evaluation in ≤ 32- week newborns.

Methods

Thirty-three ≤ 32-week newborns were prospectively evaluated and subjected to invasive mechanical ventilation. The need for exogenous surfactant and clinical and echocardiographic parameters in the first 24 hours of life was detailed in this group of patients.

Results

The mean airway pressure was significantly higher in newborn infants who required inotropes [10.8 (8.8 - 23) cmH₂O versus 9 (6.2 - 12) cmH₂O; p = 0.04]. A negative correlation was found between the mean airway pressure and velocity-time integral of the pulmonary artery (r = -0.39; p = 0.026), right ventricular output (r = -0.43; p = 0.017) and measurements of the tricuspid annular plane excursion (r = -0.37; p = 0.036). A negative correlation was found between the number of doses of exogenous surfactant and the right ventricular output (r = -0.39; p = 0.028) and pulmonary artery velocity-time integral (r = -0.35; p = 0.043).

Conclusion

In ≤ 32-week newborns under invasive mechanical ventilation, increases in the mean airway pressure and number of surfactant doses are correlated with the worsening of early cardiac function. Therefore, more aggressive management of respiratory distress syndrome may contribute to the hemodynamic instability of these patients.

Reactive oxygen species as mediators of oxygen signaling during fetal-to-neonatal circulatory transition

Reactive oxygen species (ROS) are frequently seen as pathological agents of oxidative stress. However, ROS are not always deleterious and can also act as cell signaling molecules. Vascular oxygen sensing and signaling during fetal-to-neonatal circulatory transition is a remarkable example of the physiological regulatory actions of ROS. The fetal relative hypoxic environment induces hypoxic pulmonary vasoconstriction (HPV) and ductus arteriosus (DA) relaxation favoring the presence of high pulmonary vascular resistance and right-to-left ductal shunt. At birth, the increase in oxygen tension causes relaxation of pulmonary arteries (PAs) and normoxic DA vasoconstriction (NDAV), thus diverting blood flow to the lungs. Although the response to changes in oxygen tension is diametrically opposite, the mechanisms responsible for HPV and NDAV appear to be the result of a similar interaction between triggering and modulating factors that lead to an increase in cytosolic Ca²⁺ concentration and Ca²⁺ sensitization of the contractile apparatus. Growing evidence points to an increase in ROS (mitochondria- and/or NADPH-derived superoxide and/or H₂O₂), leading to inhibition of voltage-gated K⁺ channels, membrane depolarization, and activation of voltage-gated L-type Ca²⁺ channels as critical events in the signaling pathway of both HPV and NDAV. Several groups of investigators have completed this pathway adding other elements such as neutral sphingomyelinase-derived ceramide, the sarcoplasmic/endoplasmic reticulum (through ryanodine and inositol 1,4,5-trisphosphate receptors), Rho kinase-mediated Ca²⁺ sensitization, or transient receptor potential channels. The present review focus on the role of ROS as mediators of the homeostatic oxygen sensing system during fetal and neonatal life not only in the PAs and DA but also in systemic arteries.

The Transitional Heart: From Early Embryonic and Fetal Development to Neonatal Life

Formation of the human heart involves complex biological signals, interactions, specification of myocardial progenitor cells, and heart tube looping. To facilitate survival in the hypoxemic intrauterine environment, the fetus possesses structural, physiological, and functional cardiovascular adaptations that are fundamentally different from the neonate. At birth, upon separation from the placental circulation, the neonatal cardiovascular system takes over responsibility of vital processes for survival. The transition from the fetal to neonatal circulation is considered to be a period of intricate physiological, anatomical, and biochemical changes in the cardiovascular system. With a successful cardiopulmonary transition to the extrauterine environment, the fetal shunts are functionally modified or eliminated, enabling independent life. Investigations using medical imaging tools such as ultrasound and magnetic resonance imaging have helped to define normal and abnormal patterns of cardiac remodeling both in utero and ex utero. This has not only allowed for a better understanding of how congenital cardiac malformations alter the hemodynamic transition to the extrauterine environment but also how other more common complications during pregnancy including intrauterine growth restriction, preeclampsia, and preterm delivery adversely affect offspring cardiac remodeling during this early transitional period. This review article describes key cardiac progenitors involved in embryonic heart development; the cellular, physiological, and anatomical changes during the transition from fetal to neonatal circulation; as well as the unique impact that different pregnancy complications have on cardiac remodeling.

NT-proBNP as an Early Marker of Diastolic Ventricular Dysfunction in Very-Low-Birth-Weight Infants

The objective is to examine the correlation between plasma levels of N-terminal pro-brain natriuretic peptide (NT-proBNP) and tissue Doppler imaging (TDI) echocardiographic parameters in the first 28 days of life in very-low-birth-weight infants (VLBWI). VLBWI admitted to the Neonatal Intensive Care Unit (NICU) at Hospital Puerta del Mar, Spain, from January 2015 to January 2017 were prospectively enrolled. Weekly determination of plasma NT-proBNP (pg/mL), and echocardiograms were done during the first 28 days of life. 101 preterm infants with a mean GA of 28.85 weeks (± 1.85 SD) and mean birth weight of 1152 g (± 247.4 SD) were included. A total of 483 echocardiograms and 139 NT-proBNP determinations were performed. We found a negative correlation between plasma NT-proBNP levels and diastolic velocities: mitral A' (ρ = - 0.15, p = 0.04), mitral E' (ρ = - 0.17, p = 0.02), tricuspid A' (ρ = - 0.20, p = 0.006), tricuspid E' (ρ = - 0.24, p = 0.0009). In the first 24 h of life, NT-proBNP levels were strongly correlated with mitral A' and E' velocities in patients with no patent ductus arteriosus (PDA) (ρ = - 0.75, p = 0.04). In preterm patients, elevated NT-proBNP levels are related to worse diastolic myocardial function. In the first 24 h, this correlation is much stronger in the absence of PDA.

The Relationship between blood pressure parameters and left ventricular output in neonates

OBJECTIVE

To evaluate the relationship between systolic (SBP), diastolic (DBP), mean (MBP) blood pressures and pulse pressure (PP), and left ventricular output (LVO), a surrogate of systemic blood flow.

STUDY DESIGN

This retrospective study included neonates who underwent targeted neonatal echocardiography (TNE) in 3-tertiary NICUs over 2 years. Associations between LVO and BP components were investigated. Analysis was adjusted for relevant covariates.

RESULT

1060 studies from 485 neonates were included, with a mean GA of 28.4 ± 4.6 weeks and birth weight of 1234 ± 840 grams. LVO was associated positively with SBP and PP, and negatively with GA. PP demonstrated the highest predictive value for identifying infants with LVO < 150 ml/kg/min (area under the curve 0.75 [95% CI 0.68, 0.82]). MBP and DBP demonstrated no correlation with LVO.

CONCLUSION

BP parameters correlate poorly with LVO, irrespective of GA and underlying etiology. Narrow PP may be more reflective of low LVO than low SBP.

Optimal oxygen saturation in extremely premature neonates

So far, great efforts have been made to understand the demands of extremely premature neonates (EPNs´; born before the 28(th) week of gestation) on postnatal care, including optimal oxygen saturation, that will allow them to survive without disability. A major yet unresolved problem is to find an "optimal range" of their oxygen saturation and to maintain it without drops or increases, i.e., without hypoxia or hyperoxia. The individual sections of this paper deal with the changes of SpO(2) (an estimate of SaO(2) measured by pulse oximetry) that occur before, during, and after premature labor, postnatal factors affecting SpO(2), and especially how to find an acceptable compromise in choosing the most effective and minimally harmful range of SpO(2) for EPNs' with the careful FiO(2) adjustment and continually monitored SpO(2). At present, the two SpO(2) ranges, narrow (90-94%) vs. wider (88-94%), are most discussed. However, the question of how much oxygen is too much or little remains unanswered. There is even a view that there is no uniform optimal SpO(2) range for EPNs, and that each newborn has its own, individually specific range that changes due to its intrinsic and/or extrinsic factors.

Merits and perils of targeted neonatal echocardiography-based hemodynamic research: a position statement

In the neonatal setting, point-of-care ultrasound is increasingly being used to help clinicians with the evaluation of heart function. Practices in neonatology, particularly with regard to acute and chronic hemodynamic managements, were traditionally more driven on dogma and predefined thresholds and not always supported by demonstrable physiology. For the first time, targeted neonatal echocardiography (TNE) provided neonatal intensivists with a bedside tool that made real-time assessment of neonatal hemodynamics status feasible in even the tiniest of babies. This opened the door towards more targeted physiological driven practices, allowing us to test historical approaches to clinical problems in a more precise way. Despite the standardization of TNE training and the creation of a formalized curriculum, little attention has been paid to the establishment of an empirical framework to adjudicate scientific investigation. In this position statement, we reflect on the evolution of TNE in Canadian neonatal intensive care units, appraise its strengths and limitations, and suggest guiding principles for clinicians and researchers to consider as they take this field forward.

Four-Dimensional Ultrasound for Evaluating Newborn Cardiac Output: A Pilot Study of Healthy Infants

BACKGROUND

There is currently no reliable non-invasive method of measuring cardiac output in neonatal intensive care. Spatiotemporal image correlation (STIC) is a novel four-dimensional (4D) ultrasound technique that was developed to assess the foetal heart, and it may be a useful way to assess neonatal haemodynamics.

OBJECTIVE

This study aimed to evaluate the feasibility and reproducibility of determining neonatal cardiac output using STIC ultrasound in newborn infants.

DESIGN

Infants were recruited opportunistically from a neonatal intensive care unit and then examined by 2 independent observers. STIC was used to obtain images of the heart. End-diastolic and end-systolic ventricular volumes were measured using virtual organ computer-aided analysis (VOCAL) and used to calculate cardiac output. Reproducibility was assessed with intraclass correlation coefficients (ICC) and agreement with Bland-Altman analysis.

RESULTS

Twenty-four clinically stable infants of 34-43 weeks corrected gestational age were assessed. Both observers successfully acquired 4D STIC volumes in all infants. Left ventricular output showed good reproducibility, with an intra-observer ICC of 0.86 (0.69-0.94) and inter-observer ICC of 0.87 (0.70-0.95). Right ventricular output also showed good reproducibility, with an intra-observer ICC of 0.88 (0.70-95) and inter-observer ICC of 0.84 (0.63-0.93).

CONCLUSIONS

Determining cardiac output using 4D STIC ultrasound is feasible and reproducible in well newborn infants. With further evaluation, this technique may provide valuable information about haemodynamic status in newborn infants requiring intensive care.

Modeling Cerebral Blood Flow Dependence on Carbon Dioxide and Mean Arterial Blood Pressure in the Immature Brain With Accounting for the Germinal Matrix

Intraventricular hemorrhage (IVH) is one of the most critical complications in the development of preterm infants. The likelihood of IVH is strongly associated with disturbances in cerebral blood flow (CBF) and with microvascular fragility in the germinal matrix (GM). The CBF value and its reactivity to changes in arterial carbon dioxide pressure (pCO₂) and mean arterial blood pressure (MABP) are relevant indicators in the clinical assessment of preterm infants. The objective of the present study is mathematical modeling of the influence of pCO₂ and MABP on CBF in immature brain, based on clinical data collected from 265 preterm infants with 23–30 gestational weeks. The model was adapted to the peculiarities of immature brain by taking into account the morphological characteristics of the GM capillary network and vascular reactivity, according to gestational and postnatal age. An analysis of model based values of CBF and its reactivity to changes in MABP and pCO₂ was performed separately for each gestational week and for the first two days of life both for preterm infants with and without IVH. The developed model for the estimation of CBF was validated against equivalent experimental measurements taken from the literature. A good agreement between the estimated values of CBF, as well as its reaction on changes in MABP and pCO₂ and the equivalent values obtained in experimental studies was shown.

Clinical aspects of incorporating cord clamping into stabilisation of preterm infants

Fetal to neonatal transition is characterised by major pulmonary and haemodynamic changes occurring in a short period of time. In the international neonatal resuscitation guidelines, comprehensive recommendations are available on supporting pulmonary transition and delaying clamping of the cord in preterm infants. Recent experimental studies demonstrated that the pulmonary and haemodynamic transition are intimately linked, could influence each other and that the timing of umbilical cord clamping should be incorporated into the respiratory stabilisation. We reviewed the current knowledge on how to incorporate cord clamping into stabilisation of preterm infants and the physiological-based cord clamping (PBCC) approach, with the infant's transitional status as key determinant of timing of cord clamping. This approach could result in optimal timing of cord clamping and has the potential to reduce major morbidities and mortality in preterm infants.

Association between plasma cortisol and death or vasopressor refractory hypotension in preterm neonates: a prospective, cohort study

OBJECTIVES

Temporal relation between adrenal insufficiency and hypotension is poorly understood. We examined the association between basal and post-stimulation cortisol and death or vasopressor refractory hypotension in preterm neonates.

STUDY DESIGN

Prospective cohort study in ≤30 weeks' and/or <1,250 g weight. Primary outcome-composite of death or vasopressor refractory hypotension by day 14 of life. Plasma cortisol levels were measured at 24-36 h (T1), 72-84 h (T2) and 10 days (T3), and post-stimulation cortisol at T1 and later at T2 and T3 if the adrenal response was inadequate earlier.

RESULTS

Basal cortisol (µg/dl) at 24-36 h was significantly higher in the outcome group (37.2 ± 21.1 vs. 22.04 ± 14.6; mean difference (MD) (95% confidence interval (CI)): -15.1 (-23.6, -6.6); p = 0.005). High basal cortisol at 24-36 h (odds ratio (OR) (95% CI): 1.044 (1.009, 1.079); p = 0.01) and need for ventilation (OR (95% CI): 9.7 (1.2, 81.2); p = 0.04) independently increased the risk of death or vasopressor refractory hypotension.

CONCLUSION

Preterm neonates who died or developed vasopressor refractory hypotension by day 14 had significantly elevated basal cortisol at 24-36 h of life.

Utility of prenatal Doppler ultrasound to predict neonatal impaired cerebral autoregulation

OBJECTIVE

Determine if abnormal prenatal Doppler ultrasound indices are predictive of postnatal impaired cerebral autoregulation.

STUDY DESIGN

Prospective cohort study of 46 subjects, 24⁰-29⁶ weeks' gestation. Utilizing near-infrared spectroscopy and receiver-operating characteristic analysis, impaired cerebral autoregulation was defined as >16.5% time spent in a dysregulated state within 96 h of life. Normal and abnormal Doppler indices were compared for perinatal outcomes.

RESULTS

Subjects with abnormal cerebroplacental ratio (n = 12) and abnormal umbilical artery pulsatility index (n = 13) were likely to develop postnatal impaired cerebral autoregulation (p ≤ 0.02). Abnormal cerebroplacental ratio was associated with impaired cerebral autoregulation between 24 and 48 h of life (p = 0.016). These subjects have increased risk for fetal growth restriction, lower birth weight, lower Apgar scores, acidosis, and severe intraventricular hemorrhage and/or death (p < 0.05).

CONCLUSION

Abnormal cerebroplacental ratio and umbilical artery pulsatility index are associated with postnatal impairment in cerebral autoregulation and adverse outcome.

Early modifications of cardiac function in preterm neonates using speckle tracking echocardiography

BACKGROUND AND AIMS

Preterm newborns undergo hemodynamic challenges in the postnatal period. The aim of this study was to investigate myocardial mechanics changes in the postnatal period in preterm infants using speckle tracking echocardiography (STE).

MATERIAL AND METHODS

Thirty-nine preterm infants ≤34 weeks' gestation underwent cardiac ultrasound evaluation during the first 96 hours of life. A repeated echocardiogram at 3 weeks of age was performed. Echocardiographic assessment involved left ventricular ejection fraction, mitral E/A ratio, S' and E' velocities, E/E' ratio, tricuspid annular plane systolic excursion (TAPSE), left atrium-to-aorta ratio, ductal diameter and ductal shunt pattern. Left ventricular longitudinal, circumferential and radial strain, apex-basal rotation and twist were measured from the apical 4-chamber and short-axis views using STE.

RESULTS

The mean gestational age was 30 ± 2.7 weeks with a mean birth weight of 1318 ± 485 g. Apical segments demonstrated higher longitudinal strain than basal and mid-ones. In all gestational ages, endocardial longitudinal strain was higher than the epicardial. Epicardial longitudinal strain significantly increased during the first 3 weeks, resulting in the change in basal rotation from counterclockwise to clockwise and thus in the acquisition of twist. Deformation parameters were higher in infants with a hemodynamic significant patents ductus arteriosus.

CONCLUSIONS

Echocardiographic assessment of myocardial deformation parameters is feasible in preterm infants. Our data suggest that the maturational process of the myocardium is due to the development of the epicardial layer after birth, which allows the acquisition of the twist.

Hemodynamic Effects on Systemic Blood Flow and Ductal Shunting Flow after Loading Dose of Intravenous Caffeine in Preterm Infants according to the Patency of Ductus Arteriosus

BACKGROUND

In preterm infants, caffeine citrate is used to stimulate breathing before they are weaned from mechanical ventilation and to reduce the frequency of apnea. In recent studies, effects of caffeine on the cardiovascular system have been emphasized in preterm infants with patent ductus arteriosus (PDA).

METHODS

This study aimed to assess the short-term hemodynamic effects on systemic blood flow and ductal shunting flow after loading standard doses of intravenous caffeine in preterm infants. Echocardiographic studies were performed by a single investigator, before and at 1 hour and 4 hours after an intravenous infusion of a loading dose as 20 mg/kg caffeine citrate for 30 minutes.

RESULTS

In 25 preterm infants with PDA, left ventricular output decreased progressively during 4 hours after caffeine loading. Superior vena cava (SVC) flow decreased and ductal shunting flow increased at 1 hour and then recovered at 4-hour to baseline values. A diameter of PDA significantly decreased only at 4-hour after caffeine loading. There were no significant changes of these hemodynamic parameters in 29 preterm infants without PDA.

CONCLUSION

In preterm infants with PDA, a standard intravenous loading dose of 20 mg/kg caffeine citrate was associated with increasing ductal shunting flow and decreasing SVC flow (as a surrogate for systemic blood flow) 1 hour after caffeine loading, however, these hemodynamic parameters recovered at 4 hours according to partial constriction of the ductus arteriosus. Close monitoring of hemodynamic changes would be needed to observe the risk for pulmonary over-circulation or systemic hypo-perfusion due to transient increasing ductal shunting flow during caffeine loading in preterm infants with PDA.

Effects of Prophylactic Indomethacin on Vasopressor-Dependent Hypotension in Extremely Preterm Infants

OBJECTIVE

To determine whether a moderate-to-large patent ductus arteriosus (PDA) is responsible for vasopressor-dependent hypotension, occurring at the end of the first postnatal week.

STUDY DESIGN

We performed a retrospective, double cohort controlled study of infants delivered at ≤27+6 weeks' gestation (n = 313). From January 2004 through April 2011, all infants were treated with prophylactic indomethacin ([PINDO] epoch). From May 2011 through December 2015, no infant was treated with indomethacin until at least 8 postnatal days (conservative epoch). Echocardiograms were performed on postnatal days 6 or 7. Hypotension was managed by a predefined protocol. The primary outcome was the incidence of dopamine-dependent hypotension, defined as having received at least 6 µg/kg/min dopamine for at least 24 hours during postnatal days 4-7.

RESULTS

As expected, the incidence of moderate-to-large PDA at the end of the first week differed significantly between epochs (PINDO = 8%; conservative = 64%). In multivariate analyses, infants in the PINDO epoch had a significantly lower incidence of vasopressor-dependent hypotension (11%) than infants in the conservative epoch (21%; OR = 0.40, 95% CI 0.20-0.82). Infants in the PINDO epoch also required less mean airway pressure, had a lower respiratory severity score, and lower mode of ventilation score than infants in the conservative epoch during postnatal days 4-7. The effects of PINDO on both the incidence of vasopressor-dependent hypotension and the need for respiratory support were no longer significant when analyses were adjusted for "presence or absence of a moderate-to-large PDA."

CONCLUSION

PINDO decreases vasopressor-dependent hypotension and the need for respiratory support at the end of the first postnatal week. These effects are mediated by closure of the PDA.

Low Plasma Protein Levels at Birth Are Associated with Poor Cardiovascular Adaptation and Serious Adverse Outcome in Infants with Gestational Age <32 Weeks: The ProHémie Study

BACKGROUND

Retrospective studies suggest that early hypoproteinemia has prognostic value for adverse outcome in preemies, but the underlying pathophysiology is unknown. We hypothesized that the prognostic relevance of hypoproteinemia could be related to its association with impaired cardiovascular function and organ perfusion during transition.

OBJECTIVES

To describe the plasma protein status and the measures of cardiovascular function according to the outcome in infants <32 weeks' gestation.

METHODS

One hundred and twenty-eight infants were prospectively included from birth to discharge. During the first 24 h of life, we assessed the cardiovascular function and systemic and organ blood flow by Doppler ultrasound, and monitored cerebral and renal regional oxygen saturation (cRSO2, rRSO2) using near-infrared spectroscopy. These measures were analyzed in relationship to hypoproteinemia (total plasma protein level <40 g/L at 12 h of life) and severe adverse outcome (death or survival with severe neurological injury).

RESULTS

Hypoproteinemia was associated with a higher risk of a severe adverse outcome after adjustment of confounding variables (adjusted OR = 6.8; 95% CI 1.3-34). Compared to normoproteinemic infants and after adjustment for gestational age, hypoproteinemic ones had more significantly: hypotension (7 vs. 13%, p = 0.03), abnormal capillary refilling time (20 vs. 36%, p < 0.001), abnormal renal blood flow (resistive index 0.78 ± 0.11 vs. 0.85 ± 0.09, p = 0.04), lower rRSO2 (82.9 ± 9.2 vs. 73.6 ± 10.5%, p = 0.04), and lower systemic vascular resistance (0.155 ± 0.058 vs. 0.108 ± 0.037 mm Hg/L/kg; p = 0.04). The cRSO2 patterns were significantly decreased in infants with severe adverse outcome and independent from protein status.

CONCLUSION

Hypoproteinemia is associated with impaired cardiovascular function. Further studies are required to elucidate the interplay between changes in protein levels, postnatal hemodynamics and clinical outcome.