Pathophysiology, management, and outcome of persistent pulmonary hypertension of the newborn: a clinical review

Meconium aspiration syndrome: a comprehensive review

Meconium aspiration syndrome (MAS) is a complex respiratory disease that continues to be associated with significant morbidities and mortality. The pathophysiological mechanisms of MAS include airway obstruction, local and systemic inflammation, surfactant inactivation and persistent pulmonary hypertension of the newborn (PPHN). Supplemental oxygen and non-invasive respiratory support are the main therapies for many patients. The management of the patients requiring invasive mechanical ventilation could be challenging because of the combination of atelectasis and air trapping. While studies have explored various ventilatory modalities, evidence to date does not clearly support any singular modality as superior. Patient's pathophysiology, symptom severity, and clinician/unit expertise should guide the respiratory management. Early identification and concomitant management of PPHN is critically important as it contributes significantly to mortality and morbidities.

Intravenous sildenafil for treatment of early pulmonary hypertension in preterm infants

Data is lacking on the effect of continuous intravenous sildenafil treatment in preterm infants with early pulmonary hypertension (PH), especially in very low birth weight (VLBW) infants. Preterm infants (< 37 weeks of gestational age) with intravenous sildenafil treatment and diagnosis of PH between 01/12 and 12/21 were retrospectively screened for analysis. The primary clinical endpoint was defined as response to sildenafil according to the improvement of the oxygenation index (OI), the saturation oxygenation pressure index (SOPI) and PaO₂/FiO₂-ratio. Early-PH was defined as diagnosis < 28 day of life (DOL). 58 infants were finally included, with 47% classified as very low birth weight (VLBW) infants. The primary endpoint was reached in 57%. The likelihood to die during in-hospital treatment was more than three times higher (72 vs 21%, p < 0.001) in infants without response to sildenafil. The echocardiographic severity of PH and right-ventricular dysfunction (RVD) decreased significantly from baseline to 24 h (p = 0.045, and p = 0.008, respectively). Sildenafil treatment leads to significant improvement of the oxygenation impairment in 57% of the preterm infants, with similar response rates in VLBW infants. Intravenous sildenafil treatment is associated with a significant decrease of the PH-severity and RVD.

Genome-wide association study identifies WWC2 as a possible locus associated with persistent pulmonary hypertension of the newborn in the Thai population

BACKGROUND

There is known to be significant genetic involvement in persistent pulmonary hypertension of the newborn (PPHN), but to date there is not a clear understanding of this situation, and clarifying that involvement would be of considerable assistance in devising effective treatments for the disease. This case-control study was undertaken to search for genetic variants associated with PPHN in the Thai population using a genome-wide association study (GWAS).

METHODS

A 659,184 single nucleotide polymorphisms from 387 participants (54 PPHN cases and 333 healthy participants) were genotyped across the human genome using an Illumina Asian Screening Array-24 v1.0 BeadChip Array. After quality control, we obtained 443,063 autosomal SNPs for the GWAS analysis. The FaST-LMM and R packages were used for all statistical analyses.

RESULTS

For the case-control analysis, the genomic inflation factor (λ) was 1.016, rs149768622 T>C in the first intron of WWC2 gene showed the strongest association with a P value of 3.76E-08 and odds ratio (OR) of 13.24 (95% CI: 3.91-44.78). The variants at the LOC102723906/LOC105377599, CADM4, GPM6A, CIT, RIMBP2, LOC105374510, LOC105375193, PTPRN2, CDK14, and LCORL loci showed suggestive evidence of associations with PPHN (P<1E-05).

CONCLUSIONS

This GWAS found that rs149768622 T>C in the WWC2 gene was possibly associated with PPHN. However, replication and functional studies are needed to validate this association and further explore the role(s) of the WWC2 gene in PPHN.

The role of bedside functional echocardiography in the assessment and management of pulmonary hypertension

Pulmonary hypertension is an emergency in neonatal intensive care units with high morbidity and mortality. Its timely assessment and management is crucial for intact survival. Over the last couple of decades, there have been significant advances in management and techniques, which have resulted in improved survival. The use of neonatologist-performed echocardiography (NPE) is now increasingly utilized on neonatal intensive care units to understand the pathophysiology of the disease and to direct the treatment to the underlying cause. Its use is now established not only in cases of congenital diaphragmatic hernia and in the newborn with refractory hypoxemia, but also in other conditions such as bronchopulmonary dysplasia and the premature infant with difficulty in oxygenation. The use of NPE, however, requires the availability of trained personnel, equipment, and a close working relationship with pediatric cardiology.

The Efficacy and Safety of Pulmonary Vasodilators in Pediatric Pulmonary Hypertension (PH): A Systematic Review and Meta-analysis

Background: We performed a meta-analysis to evaluate the efficacy and safety of pulmonary vasodilators in pediatric pulmonary hypertension (PH) patients. Methods: We searched electronic databases including PubMed, EMBASE, and the Cochrane Library up to May 2020, and conducted a subgroup analysis for pulmonary vasodilators or underlying disease. Results: Fifteen studies with 719 pediatric PH patients were included in the meta-analysis. Adverse events did not differ (p = 0.11, I ² = 15%) between the pulmonary vasodilators group and the control group, neither in the subgroups. In total, compared with the control group treatment, pulmonary vasodilators significantly decreased the mortality (p = 0.002), mean pulmonary artery pressure (mPAP, p = 0.02), and mechanical ventilation duration (p = 0.03), also improved the oxygenation index (OI, p = 0.01). In the persistent pulmonary hypertension of the newborn (PPHN) subgroup, phosphodiesterase type 5 inhibitors (PDE5i) significantly reduced mortality (p = 0.03), OI (p = 0.007) and mechanical ventilation duration (p = 0.004). Administration of endothelin receptor antagonists (ERAs) improved OI (p = 0.04) and mechanical ventilation duration (p < 0.00001) in PPHN. We also found that in the pediatric pulmonary arterial hypertension (PPAH) subgroup, mPAP was pronouncedly declined with ERAs (p = 0.006). Systolic pulmonary artery pressure (sPAP, p < 0.0001) and pulmonary arterial/aortic pressure (PA/AO, p < 0.00001) were significantly relieved with PDE5i, partial pressure of arterial oxygen (PaO₂) was improved with prostacyclin in postoperative PH (POPH) subgroup (p = 0.001). Compared with the control group, pulmonary vasodilators could significantly decrease PA/AO pressure (p < 0.00001) and OI (p < 0.00001) in the short-term (duration <7 days) follow-up subgroup, improve mPAP (p = 0.03) and PaO₂ (p = 0.01) in the mid-term (7-30 days) follow-up subgroup, also decrease mortality, mPAP (p = 0.0001), PA/AO pressure (p = 0.0007), duration of mechanical ventilation (p = 0.004), and ICU stay (p < 0.00001) in the long-term follow subgroup (>30 days). Conclusion: Pulmonary vasodilators decrease the mortality in pediatric PH patients, improve the respiratory and hemodynamic parameters, reduce the mechanical ventilation duration.

Pulmonary hypertension and mitral regurgitation in an infant with an anatomically normal mitral valve

A full-term, female presented on her date of birth with severe pulmonary hypertension (PH) and mitral regurgitation (MR), requiring veno-arterial extracorporeal membrane oxygenation. After the treatment, her PH and MR were resolved with no anatomic abnormality present. We propose a positive feedback loop of PH causing right ventricular dilation and interventricular septal shifts, worsening MR, and elevated left atrial, and potentially pulmonary, pressures.

Getting an Early Start in Understanding Perinatal Asphyxia Impact on the Cardiovascular System

Perinatal asphyxia (PA) is a burdening pathology with high short-term mortality and severe long-term consequences. Its incidence, reaching as high as 10 cases per 1000 live births in the less developed countries, prompts the need for better awareness and prevention of cases at risk, together with management by easily applicable protocols. PA acts first and foremost on the nervous tissue, but also on the heart, by hypoxia and subsequent ischemia-reperfusion injury. Myocardial development at birth is still incomplete and cannot adequately respond to this aggression. Cardiac dysfunction, including low ventricular output, bradycardia, and pulmonary hypertension, complicates the already compromised circulatory status of the newborn with PA. Multiorgan and especially cardiovascular failure seem to play a crucial role in the secondary phase of hypoxic-ischemic encephalopathy (HIE) and its high mortality rate. Hypothermia is an acceptable solution for HIE, but there is a fragile equilibrium between therapeutic gain and cardiovascular instability. A profound understanding of the underlying mechanisms of the nervous and cardiovascular systems and a close collaboration between the bench and bedside specialists in these domains is compulsory. More resources need to be directed toward the prevention of PA and the consecutive decrease of cardiovascular dysfunction. Not much can be done in case of an unexpected acute event that produces PA, where recognition and prompt delivery are the key factors for a positive clinical result. However, the situation is different for high-risk pregnancies or circumstances that make the fetus more vulnerable to asphyxia. Improving the outcome in these cases is possible through careful monitoring, identifying the high-risk pregnancies, and the implementation of novel prenatal strategies. Also, apart from adequately supporting the heart through the acute episode, there is a need for protocols for long-term cardiovascular follow-up. This will increase our recognition of any lasting myocardial damage and will enhance our perspective on the real impact of PA. The goal of this article is to review data on the cardiovascular consequences of PA, in the context of an immature cardiovascular system, discuss the potential contribution of cardiovascular impairment on short and long-term outcomes, and propose further directions of research in this field.

Maternal Diabetes Mellitus and Persistent Pulmonary Hypertension of the Newborn: Accumulated Evidence From Observational Studies

OBJECTIVES

Maternal diabetes mellitus (including pre-existing and gestational diabetes mellitus) is linked with adverse infant outcomes. However, the question of whether maternal diabetes increases the risk of persistent pulmonary hypertension of the newborn (PPHN) is unclear. Herein, we conducted a systematic review and meta-analysis to summarize clinical evidence to determine the association between maternal diabetes mellitus and PPHN.

METHODS

In this systematic review and meta-analysis, we systematically searched PubMed, Embase, Cochrane Library, Web of Science and Google Scholar to identify relevant studies according to predefined criteria. Data from selected studies were extracted, and meta-analysis was performed using fixed effects modelling.

RESULTS

In all, we included 7 unique studies with aggregated data on 2 million individuals and >5,000 cases of PPHN. Maternal diabetes was significantly associated with a higher risk of PPHN (risk ratio [RR], 1.37; 95% confidence interval [CI], 1.23 to 1.51). Both case-control and cohort studies exhibited that the presence of maternal diabetes increased the risk of PPHN (case-control: RR, 1.91; 95% CI, 1.02 to 2.79; cohort: RR, 1.36; 95% CI, 1.22 to 1.50). By omitting 1 study at a time, sensitivity analysis made sure that no individual study was entirely responsible for the combined results.

CONCLUSIONS

Maternal diabetes was associated with increased risk of PPHN. For babies with refractory hypoxemia, with mothers with diabetes, PPHN should be taken into consideration in clinical practice.

The Off-Label Use of Inhaled Nitric Oxide as a Rescue Therapy in Neonates with Refractory Hypoxemic Respiratory Failure: Therapeutic Response and Risk Factors for Mortality

OBJECTIVES

The indication of inhaled nitric oxide (iNO) used in preterm infants has not been well defined. Neonates with refractory hypoxemia may benefit from the pulmonary vasodilatory effects of iNO. The aim of this study was to investigate the off-label use of iNO as a rescue therapy.

METHODS

Between January 2010 and December 2017, all neonates who received iNO as a rescue therapy from a tertiary-level medical center were enrolled, and those who were not diagnosed with persistent pulmonary hypertension of newborn (PPHN) were defined as having received off-label use of iNO. The controls were 636 neonates with severe respiratory failure requiring high-frequency oscillatory ventilation but no iNO.

RESULTS

A total of 206 neonates who received iNO as a rescue therapy were identified, and 84 (40.8%) had off-label use. The median (interquartile) gestational age was 30.5 (26.3-37.0) weeks. Neonates receiving iNO had significantly more severe respiratory failure and a higher oxygenation index than the controls (p < 0.001). Respiratory distress syndrome and secondary pulmonary hypertension after severe bronchopulmonary dysplasia (BPD) were the most common causes of the off-label iNO prescription. Of the 84 neonates with off-label use of iNO, 53 (63.1%) had initial improvement in oxygenation, but 44 (52.4%) eventually died. The overall mortality rate was 41.7% (86/206). After multivariate logistic regression, extremely preterm (odds ratio [OR] 5.51; p < 0.001), presence of pulmonary hemorrhage (OR 2.51; p = 0.036) and severe hypotension (OR 2.78; p = 0.008) were the independent risk factors for final mortality.

CONCLUSIONS

iNO is applicable to be an off-label rescue therapy for premature neonates with refractory hypoxemia due to severe pulmonary hypertension and bronchopulmonary dysplasia.

Selective Serotonin Reuptake Inhibitors and Persistent Pulmonary Hypertension of the Newborn: An Update Meta-Analysis

BACKGROUND

Persistent pulmonary hypertension of the newborn (PPHN) is a serious condition associated with substantial mortality and morbidity. Previous studies have suggested a possible link between maternal selective serotonin reuptake inhibitor (SSRI) use and the risk of PPHN. This study aimed to provide an up-to-date review and meta-analysis of the topic.

METHODS

Using the search terms [SSRI OR SSRIs OR selective serotonin reuptake inhibitors OR antidepressant OR Prozac OR fluoxetine OR Lexapro OR escitalopram] AND [pregnancy OR maternal OR newborn OR persistent pulmonary hypertension OR PPHN OR neonat* OR fet*], a preliminary search on the PubMed, Medline, EMBASE, Web of Science, and Google Scholar database yielded 7327 articles published in English between January 1, 1960 and October 1, 2017.

RESULTS

A total of 9 cohort and case-control studies, with a total of 7,540,265 subjects were systematically reviewed. Random-effects meta-analysis of eight studies revealed a significantly increased risk of PPHN with maternal SSRI use during pregnancy, with a pooled OR of 1.516 (95% confidence interval: 1.035-1.997, p < 0.001). Overall, the absolute increase in risk of PPHN with SSRI use appears small, with an absolute risk difference of 0.619 per 1000 livebirths and a number needed to harm of 1615 women.

CONCLUSIONS

Current evidence suggests that there were significantly greater odds of PPHN with SSRI use during pregnancy. However, the clinical significance of this association remains modest and likely outweighed by the potential benefits of treatment of perinatal depression. The risk of PPHN associated with SSRI therapy might not warrant the recommendation to withdraw antidepressant therapy, as evidence from other studies show that untreated perinatal depression presents additional adverse maternal and fetal outcomes. Given the increasing prevalence of maternal depression and consequent use of antidepressant medications, further research with robust longitudinal or randomized, controlled studies and mechanistic investigations are needed.

Comprehensive Evaluation of Right Heart Performance and Pulmonary Hemodynamics in Neonatal Pulmonary Hypertension : Evaluation of cardiopulmonary performance in neonatal pulmonary hypertension

PURPOSE OF REVIEW

Pulmonary hypertension is characterized by an elevation of pulmonary artery pressures and prolonged exposure of the right ventricle to high afterload that collectively contribute to morbidity and mortality in both the term and preterm infants. This review summarizes the pathogenesis, etiologies, and hemodynamic profiles of the conditions that result in pulmonary hypertension in neonates. We explore the application of echocardiographic techniques for the assessment of right ventricular performance and pulmonary hemodynamics that enhance and guide the diagnosis and management strategies in neonates.

RECENT FINDINGS

Clinical assessments based on the determinants of mean pulmonary artery pressures (pulmonary vascular resistance, pulmonary blood flow, and pulmonary capillary wedge pressure) provide a physiologic approach in determining the acute and chronic etiologies of pulmonary hypertension in neonates. In addition, advances in neonatal echocardiography now afford the capability to obtain quantitative information that often precedes the qualitative information acquired by conventional methods and also provide sensitive markers of right ventricle performance for prognostic information based on the determinants of mean pulmonary artery pressures. Neonatal pulmonary hypertension represents a physiologic spectrum that accounts for the variance in clinical presentation and response to therapies. Physiology-based approaches to etiological identification, coupled with the emerging echocardiographic methods for the assessment of pulmonary hypertension in neonates will likely help to identify cardiovascular compromise earlier, guide therapeutic intervention, monitor therapeutic effectiveness, and improve overall outcome.

Prenatal exposure to selective serotonin reuptake inhibitors and serotonin norepinephrine reuptake inhibitors and risk for persistent pulmonary hypertension of the newborn: a systematic review, meta-analysis, and network meta-analysis

BACKGROUND

There is a marked increase in the use of selective serotonin reuptake inhibitors and serotonin norepinephrine reuptake inhibitors in the last decade. Many newborns are likely to be exposed during pregnancy and labor.

OBJECTIVE

We aimed to evaluate the association between exposure to selective serotonin reuptake inhibitors and serotonin norepinephrine reuptake inhibitors during pregnancy and the risk for persistent pulmonary hypertension of the newborn. We sought to compare the risk for persistent pulmonary hypertension of the newborn between specific selective serotonin reuptake inhibitor agents.

STUDY DESIGN

MEDLINE, Embase, and Cochrane were searched up to July 2017. No language restrictions were applied. Search key words included: "SSRI," "SNRI," "pregnancy," "risk," "new-born," and "pulmonary hypertension." Retrospective cohort studies and case-control studies reporting the risk for persistent pulmonary hypertension of the newborn in the offspring of women exposed to selective serotonin reuptake inhibitors or serotonin norepinephrine reuptake inhibitors during pregnancy, were extracted. Two independent researchers identified relevant data. Random effects meta-analysis was used to pool results. Odds ratios were calculated with subsequent 95% confidence intervals. Network meta-analysis was conducted, incorporating direct and indirect comparisons among different selective serotonin reuptake inhibitors. The primary outcome was risk for persistent pulmonary hypertension of the newborn after exposure to selective serotonin reuptake inhibitors or serotonin norepinephrine reuptake inhibitors during pregnancy.

RESULTS

A total of 11 studies were identified. A total of 156,978 women and their offspring were exposed to selective serotonin reuptake inhibitors or serotonin norepinephrine reuptake inhibitors during pregnancy. Persistent pulmonary hypertension of the newborn was detected among 452 exposed offspring, representing an incidence rate of 2.9 cases per 1000 live births and a number needed to harm of 1000. The risk for persistent pulmonary hypertension of the newborn was significantly increased in the analysis of exposure to selective serotonin reuptake inhibitor/serotonin norepinephrine reuptake inhibitor in any trimester (odds ratio, 1.82; 95% confidence interval, 1.31-2.54; I² = 72%), as well as in analysis restricted to exposure week >20 (odds ratio, 2.08; 95% confidence interval, 1.44-3.01; I² = 76%). In network meta-analysis, sertraline was ranked most likely to have the lowest risk for persistent pulmonary hypertension of the newborn among the different selective serotonin reuptake inhibitors (P = .83).

CONCLUSION

Exposure to selective serotonin reuptake inhibitors or serotonin norepinephrine reuptake inhibitors during pregnancy is associated with an increased risk for persistent pulmonary hypertension of the newborn. According to our findings, sertraline ranked as most likely to have the lowest risk for persistent pulmonary hypertension of the newborn compared to other selective serotonin reuptake inhibitors, suggesting it may have the best safety profile for use in pregnancy in this regard. Further studies are needed to fully establish these results.

Efficacy and safety of a novel nitric oxide generator for the treatment of neonatal pulmonary hypertension: Experimental and clinical studies

Persistent pulmonary hypertension of the newborn (PPHN) is a complex pathology resulting from a failure of the post-natal reduction in pulmonary vascular resistance leading to hypoxemia. The standard therapy is inhaled Nitric Oxide (NO) improving oxygenation but its availability is limited, especially in hospitals with restricted financial resources. We evaluated the efficacy and safety of a new device generating NO (TAS + PLUS), in three experimental piglet models of pulmonary hypertension (PH), and we later tested its application in a pilot study of newborn patients suffering from PPHN. Piglets with experimentally induced PH showed a decrease in pulmonary arterial pressure (PAP) after breathing NO. Both acute and chronic exposure of piglets and rats did not cause any adverse effect in blood gas levels and biological parameters. A pilot study including 32 patients suffering from PPHN showed an increase in oxygen saturation (SatO₂) and partial pressure of oxygen in arterial blood (PaO₂) leading to a decrease of Oxygenation Index (OI) after compassionate treatment with NO from TAS + PLUS device. The device showed effectiveness and safety both in experimental PH and in the clinical setting. Therefore, it represents an excellent alternative for PPHN management in conditions where commercial NO is unavailable.

Umbilical cord blood metabolomics reveal distinct signatures of dyslipidemia prior to bronchopulmonary dysplasia and pulmonary hypertension

Pulmonary hypertension (PH) is a common consequence of bronchopulmonary dysplasia (BPD) and remains a primary contributor to increased morbidity and mortality among preterm infants. Unfortunately, at the present time, there are no reliable early predictive markers for BPD-associated PH. Considering its health consequences, understanding in utero perturbations that lead to the development of BPD and BPD-associated PH and identifying early predictive markers is of utmost importance. As part of the discovery phase, we applied a multiplatform metabolomics approach consisting of untargeted and targeted methodologies to screen for metabolic perturbations in umbilical cord blood (UCB) plasma from preterm infants that did ( n = 21; cases) or did not ( n = 21; controls) develop subsequent PH. A total of 1,656 features were detected, of which 407 were annotated by metabolite structures. PH-associated metabolic perturbations were characterized by reductions in major choline-containing phospholipids, such as phosphatidylcholines and sphingomyelins, indicating altered lipid metabolism. The reduction in UCB abundances of major choline-containing phospholipids was confirmed in an independent validation cohort consisting of UCB plasmas from 10 cases and 10 controls matched for gestational age and BPD status. Subanalyses in the discovery cohort indicated that elevations in the oxylipins PGE1, PGE2, PGF2a, 9- and 13-HOTE, 9- and 13-HODE, and 9- and 13-KODE were positively associated with BPD presence and severity. This expansive evaluation of cord blood plasma identifies compounds reflecting dyslipidemia and suggests altered metabolite provision associated with metabolic immaturity that differentiate subjects, both by BPD severity and PH development.

Phosphodiesterase inhibitors: Potential role in the respiratory distress of neonates

Phosphodiesterases (PDEs) are a superfamily of enzymes that catalyze the hydrolysis of phosphodiester bonds of 3',5' cyclic adenosine and guanosine monophosphate (cAMP and cGMP). PDEs control hydrolysis of cyclic nucleotides in many cells and tissues. Inhibition of PDEs by selective or nonselective PDE inhibitors represents an effective targeted strategy for the treatment of various diseases including respiratory disorders. Recent data have demonstrated that PDE inhibitors can also be of benefit in respiratory distress in neonates. This article outlines the pharmacological properties of nonselective and selective PDE inhibitors and provides up-to-date information regarding their use in experimental models of neonatal respiratory distress as well as in clinical studies.

Application of Neonatologist Performed Echocardiography in the assessment and management of persistent pulmonary hypertension of the newborn

Pulmonary hypertension contributes to morbidity and mortality in both the term newborn infant, referred to as persistent pulmonary hypertension of the newborn (PPHN), and the premature infant, in the setting of abnormal pulmonary vasculature development and arrested growth. In the term infant, PPHN is characterized by the failure of the physiological postnatal decrease in pulmonary vascular resistance that results in impaired oxygenation, right ventricular failure, and pulmonary-to-systemic shunting. The pulmonary vasculature is either maladapted, maldeveloped, or underdeveloped. In the premature infant, the mechanisms are similar in that the early onset pulmonary hypertension (PH) is due to pulmonary vascular immaturity and its underdevelopment, while late onset PH is due to the maladaptation of the pulmonary circulation that is seen with severe bronchopulmonary dysplasia. This may lead to cor-pulmonale if left undiagnosed and untreated. Neonatologist performed echocardiography (NPE) should be considered in any preterm or term neonate that presents with risk factors suggesting PPHN. In this review, we discuss the risk factors for PPHN in term and preterm infants, the etiologies, and the pathophysiological mechanisms as they relate to growth and development of the pulmonary vasculature. We explore the applications of NPE techniques that aid in the correct diagnostic and pathophysiological assessment of the most common neonatal etiologies of PPHN and provide guidelines for using these techniques to optimize the management of the neonate with PPHN.

Therapeutic hypothermia in infants with hypoxic-ischemic encephalopathy and reversible persistent pulmonary hypertension: short-term hospital outcomes

AIM

Neonatal hypoxic ischemic encephalopathy (HIE) patients are at times accompanied by persistent pulmonary hypertension (PPHN), which is by itself another risk factor of adverse outcomes. We aimed to assess the outcome of therapeutic hypothermia (TH) in these patients whom we managed to reverse the shunt flow, as they are expected to be at much higher risk of adverse neurodevelopmental outcome.

METHODS

We reviewed the medical records of 116 HIE infants (13 with PPHN and 103 without PPHN) who underwent TH between 2012 and 2016. We analyzed the short-term hospital outcomes and brain study results (electroencephalogram and magnetic resonance imaging) of TH in these patients.

RESULTS

While infants with PPHN were significantly more likely to be outborn or have meconium aspiration syndrome, and required a longer duration of inotrope and intensive care support, electroencephalographic and brain magnetic resonance findings did not significantly differ according to PPHN status.

CONCLUSION

Based on our study, the hospital outcomes of infants with HIE accompanied by reversible PPHN who underwent TH were in general not significantly graver than those not accompanied by PPHN. Our results suggest that undergoing TH may be more beneficial in HIE infants with PPHN and the risks for possible adverse effects may not be as so high.

Mitochondrial Complex IV Subunit 4 Isoform 2 Is Essential for Acute Pulmonary Oxygen Sensing

RATIONALE

Acute pulmonary oxygen sensing is essential to avoid life-threatening hypoxemia via hypoxic pulmonary vasoconstriction (HPV) which matches perfusion to ventilation. Hypoxia-induced mitochondrial superoxide release has been suggested as a critical step in the signaling pathway underlying HPV. However, the identity of the primary oxygen sensor and the mechanism of superoxide release in acute hypoxia, as well as its relevance for chronic pulmonary oxygen sensing, remain unresolved.

OBJECTIVES

To investigate the role of the pulmonary-specific isoform 2 of subunit 4 of the mitochondrial complex IV (Cox4i2) and the subsequent mediators superoxide and hydrogen peroxide for pulmonary oxygen sensing and signaling.

METHODS AND RESULTS

Isolated ventilated and perfused lungs from Cox4i2^-/- mice lacked acute HPV. In parallel, pulmonary arterial smooth muscle cells (PASMCs) from Cox4i2^-/- mice showed no hypoxia-induced increase of intracellular calcium. Hypoxia-induced superoxide release which was detected by electron spin resonance spectroscopy in wild-type PASMCs was absent in Cox4i2^-/- PASMCs and was dependent on cysteine residues of Cox4i2. HPV could be inhibited by mitochondrial superoxide inhibitors proving the functional relevance of superoxide release for HPV. Mitochondrial hyperpolarization, which can promote mitochondrial superoxide release, was detected during acute hypoxia in wild-type but not Cox4i2^-/- PASMCs. Downstream signaling determined by patch-clamp measurements showed decreased hypoxia-induced cellular membrane depolarization in Cox4i2^-/- PASMCs compared with wild-type PASMCs, which could be normalized by the application of hydrogen peroxide. In contrast, chronic hypoxia-induced pulmonary hypertension and pulmonary vascular remodeling were not or only slightly affected by Cox4i2 deficiency, respectively.

CONCLUSIONS

Cox4i2 is essential for acute but not chronic pulmonary oxygen sensing by triggering mitochondrial hyperpolarization and release of mitochondrial superoxide which, after conversion to hydrogen peroxide, contributes to cellular membrane depolarization and HPV. These findings provide a new model for oxygen-sensing processes in the lung and possibly also in other organs.

Treprostinil for persistent pulmonary hypertension of the newborn, with early onset sepsis in preterm infant: 2 Case reports

RATIONALE

Persistent pulmonary hypertension of the newborn (PPHN) is a syndrome of failed circulatory adaptation at birth with persisting increased pulmonary vascular resistance that is associated with high mortality rates especially in preterm infants.

PATIENT CONCERNS

We reported 2 cases of PPHN in preterm infants with respiratory distress syndrome and early onset sepsis refractory to therapy with vasopressors, inotropes, and inhaled nitric oxide (iNO), in whom treatment with treprostinil was successful.

DIAGNOSES

Infants showed a difference of more than 10% between pre- and postductal saturation of peripheral oxygen by pulse oximetry. Echocardiogram showed flattened ventricular septum, right to left shunting through the patent ductus arteriosus, and tricuspid regurgitation velocity above 2.9 m/s.

INTERVENTIONS

The patients received treprostinil through central venous line because iNO therapy was not effective.

OUTCOMES

Within 6 to 12 hours after treatment with treprostinil, the patients showed dramatic clinical improvement, and no systemic side effects were observed, including intraventricular hemorrhage (≥grade II).

LESSONS

IV treprostinil might be given to preterm infants with severe PPHN, who did not respond to conservative therapies, including iNO.

Nogo-B Receptor Modulates Pulmonary Artery Smooth Muscle Cell Function in Developing Lungs

Nogo-B and its receptor (NgBR) are involved in blood vessel growth in developing lungs, but their role in pulmonary artery smooth muscle cell (PASMC) growth is unknown. We hypothesized that NgBR regulates growth of PASMCs by modulating the function of endoplasmic reticulum (ER) and formation of reactive oxygen species (ROS). In utero constriction of the ductus arteriosus created pulmonary hypertension in fetal lambs (hypertensive fetal lamb [HTFL]). PASMCs isolated 8 days after surgery were assessed for the alteration of protein levels by immunoblots and ROS formation by dihydroethidium and Cell ROX deep red fluorescence. NgBR small interfering RNA and plasmid DNA were used to manipulate NgBR levels. Proliferation and wound healing were assessed by cell counts and scratch recovery assay, respectively. Acute ER stress was induced by tunicamycin. Differences of mitogen-activated protein kinase and Akt pathway activation in HTFL versus control PASMCs were evaluated. Results showed that HTFL PASMCs had decreased NgBR levels and increased proliferation, wound healing, ER stress, and ROS formation compared with controls. Knockdown of NgBR in control PASMCs generated a phenotype similar to HTFL, and overexpression in HTFL restored the defective phenotype to control. Decreased NgBR levels were associated with increased ROS formation in HTFL PASMCs. Subsequently, scavenging ROS decreased proliferation and wound healing. Mechanistically, ROS formation decreases NgBR expression, which induces ER stress. This leads to extracellular signal-regulated kinase pathway activation and PASMC phenotype alteration. Our data suggest that decreased NgBR expression in pulmonary hypertension of the newborn contributes to increased PASMC proliferation and oxidative stress, which lead to the pathogenesis of lung injury.

Safety of Selective Serotonin Reuptake Inhibitors in Pregnancy: A Review of Current Evidence

Selective serotonin reuptake inhibitors (SSRIs) are the most commonly prescribed antidepressant medications worldwide. However, over the past decade, their use during pregnancy, a period of extreme vulnerability to the onset of depression, has become highly concerning to patients and their healthcare providers in terms of safety to the developing fetus. Exposure to SSRIs in pregnancy has been associated with miscarriage, premature delivery, neonatal complications, birth defects-specifically cardiac defects-and, more recently, neurodevelopmental disorders in childhood, specifically autism spectrum disorders. Studies addressing the effect of individual SSRIs indicate a small but higher risk for birth defects with maternal fluoxetine and paroxetine use. Though the excess in absolute risk is small, it may still be of concern to some patients. Meanwhile, antenatal depression itself is associated with adverse perinatal outcomes, and discontinuing antidepressant treatment during pregnancy is associated with a high risk of relapse of depression. Whether the observed adverse fetal effects are related to the mother's medication use or her underlying maternal illness remains difficult to determine. It is important that every pregnant woman being treated with an SSRI (or considering such treatment) carefully weighs the risks of treatment against the risk of untreated depression for both herself and her child. The importance of recognizing a higher risk for the development of adverse outcomes lies in the potential for surveillance and possibly a timely intervention. Therefore, we recommend that pregnant women exposed to any SSRI in early pregnancy be offered options for prenatal diagnosis through ultrasound examinations and fetal echocardiography to detect the presence of birth defects. Tapering off or switching to other therapy in early pregnancy, if appropriate for the individual, may also be considered on a case-by-case basis.

Nitric oxide in paediatric respiratory disorders: novel interventions to address associated vascular phenomena?

Nitric oxide (NO) has a significant role in modulating the respiratory system and is being exploited therapeutically. Neonatal respiratory failure can affect around 2% of all live births and is responsible for over one third of all neonatal mortality. Current treatment method with inhaled NO (iNO) has demonstrated great benefits to patients with persistent pulmonary hypertension, bronchopulmonary dysplasia and neonatal respiratory distress syndrome. However, it is not without its drawbacks, which include the need for patients to be attached to mechanical ventilators. Notably, there is also a lack of identification of subgroups amongst abovementioned patients, and homogeneity in powered studies associated with iNO, which is one of the limitations. There are significant developments in drug delivery methods and there is a need to look at alternative or supplementary methods of NO delivery that could reduce current concerns. The addition of NO-independent activators and stimulators, or drugs such as prostaglandins to work in synergy with NO donors might be beneficial. It is of interest to consider such delivery methods within the respiratory system, where controlled release of NO can be introduced whilst minimizing the production of harmful byproducts. This article reviews current therapeutic application of iNO and the state-of-the-art technology methods for sustained delivery of NO that may be adapted and developed to address respiratory disorders. We envisage this perspective would prompt active investigation of such systems for their potential clinical benefit.

Maternal use of selective serotonin-reuptake inhibitors and risk of persistent pulmonary hypertension of the newborn

Use of selective serotonin reuptake inhibitors (SSRIs) in late pregnancy has been associated with persistent pulmonary hypertension of the newborn (PPHN), a rare condition with substantial infant mortality and morbidity. Although the increase in absolute risk is small on a population level, it may be of concern to many patients. It remains unclear the extent to which the increased risks reported for PPHN are explained by the underlying maternal illness rather than the use of SSRIs.

Intrauterine growth restriction - part 2

Small for gestational age (SGA) infants have been classically defined as having birth weight less than two standard deviations below the mean or less than the 10th percentile of a population-specific birth weight for specific gestational age, whereas intrauterine growth restriction (IUGR) has been defined as a rate of foetal growth that is less than normal for the population and for the growth potential of a specific infant. SGA infants have more frequent problems such as perinatal asphyxia, hypothermia, hypoglycaemia, polycythaemia and many more when compared with their appropriate for gestational age counterpart. They too have growth retardation and various major and subtle neurodevelopmental handicaps, with higher rates of perinatal and neonatal mortality. With the advent of newer technologies, even though the perinatal diagnosis of these SGA/IUGR foetuses has increased, but still perinatal morbidity and mortality rates are higher than normal foetuses and infants. In this part, we have covered neonatal IUGR classification, postnatal diagnosis, short-term and long-term complications faced by these IUGR infants.

Mechanism by which nuclear factor-kappa beta (NF-kB) regulates ovine fetal pulmonary vascular smooth muscle cell proliferation

Platelet activating factor (PAF) modulates ovine fetal pulmonary hemodynamic. PAF acts through its receptors (PAFR) in pulmonary vascular smooth muscle cells (PVSMC) to phosphorylate and induce nuclear translocation of NF-kB p65 leading to PVSMC proliferation. However, the interaction of NF-kB p65 and PAF in the nuclear domain to effect PVSMC cell growth is not clearly defined. We used siRNA-dependent translation initiation arrest to study a mechanism by which NF-kB p65 regulates PAF stimulation of PVSMC proliferation. Our hypotheses are: (a) PAF induces NF-kB p65 DNA binding and (b) NF-kB p65 siRNA attenuates PAF stimulation of PVSMC proliferation. For DNA binding, cells were fed 10 nM PAF with and without PAFR antagonists WEB 2170, CV 3988 or BN 52021 and incubated for 12 h. DNA binding was measured by specific ELISA. For NF-kB p65 siRNA effect, starved cells transfected with the siRNA were incubated for 24 h with and without 10 nM PAF. Cell proliferation was measured by DNA synthesis while expression of NF-kB p65 and PAFR protein was measured by Western blotting. In both studies, the effect of 10% FBS alone was used as the positive control. In general, PAF stimulated DNA binding which was inhibited by PAFR antagonists. siRNAs to NF-kB p65 and PAFR significantly attenuated cell proliferation compared to 10% FBS and PAF effect. Inclusion of PAF in siRNA-treated cells did not reverse inhibitory effect of NF-kB p65 siRNA on DNA synthesis. PAFR expression was inhibited in siRNA-treated cells. These data show that PAF-stimulation of PVSMC proliferation occurs via a PAFR-NF-kB p65 linked pathway.

Antidepressant use late in pregnancy and risk of persistent pulmonary hypertension of the newborn

IMPORTANCE

The association between selective serotonin reuptake inhibitor (SSRI) antidepressant use during pregnancy and risk of persistent pulmonary hypertension of the newborn (PPHN) has been controversial since the US Food and Drug Administration issued a public health advisory in 2006.

OBJECTIVE

To examine the risk of PPHN associated with exposure to different antidepressant medication classes late in pregnancy.

DESIGN AND SETTING

Cohort study nested in the 2000-2010 Medicaid Analytic eXtract for 46 US states and Washington, DC. Last follow-up date was December 31, 2010.

PARTICIPANTS

A total of 3,789,330 pregnant women enrolled in Medicaid from 2 months or fewer after the date of last menstrual period through at least 1 month after delivery. The source cohort was restricted to women with a depression diagnosis and logistic regression analysis with propensity score adjustment applied to control for potential confounders. EXPOSURES FOR OBSERVATIONAL STUDIES: SSRI and non-SSRI monotherapy use during the 90 days before delivery vs no use.

MAIN OUTCOMES AND MEASURES

Recorded diagnosis of PPHN during the first 30 days after delivery.

RESULTS

A total of 128,950 women (3.4%) filled at least 1 prescription for antidepressants late in pregnancy: 102,179 (2.7%) used an SSRI and 26,771 (0.7%) a non-SSRI. Overall, 7630 infants not exposed to antidepressants were diagnosed with PPHN (20.8; 95% CI, 20.4-21.3 per 10,000 births) compared with 322 infants exposed to SSRIs (31.5; 95% CI, 28.3-35.2 per 10,000 births), and 78 infants exposed to non-SSRIs (29.1; 95% CI, 23.3-36.4 per 10,000 births). Associations between antidepressant use and PPHN were attenuated with increasing levels of confounding adjustment. For SSRIs, odds ratios were 1.51 (95% CI, 1.35-1.69) unadjusted and 1.10 (95% CI, 0.94-1.29) after restricting to women with depression and adjusting for the high-dimensional propensity score. For non-SSRIs, the odds ratios were 1.40 (95% CI, 1.12-1.75) and 1.02 (95% CI, 0.77-1.35), respectively. Upon restriction of the outcome to primary PPHN, the adjusted odds ratio for SSRIs was 1.28 (95% CI, 1.01-1.64) and for non-SSRIs 1.14 (95% CI, 0.74-1.74).

CONCLUSIONS AND RELEVANCE

Evidence from this large study of publicly insured pregnant women may be consistent with a potential increased risk of PPHN associated with maternal use of SSRIs in late pregnancy. However, the absolute risk was small, and the risk increase appears more modest than suggested in previous studies.

Right ventricular echocardiographic indices predict poor outcomes in infants with persistent pulmonary hypertension of the newborn

AIMS

Infants with persistent pulmonary hypertension of the newborn (PPHN) have elevated pulmonary vascular resistance that can lead to right ventricular (RV) failure and death. Clinicians must decide which infants will fail conventional therapy and require transfer to extra corporeal membrane oxygenation (ECMO) centres, but accurate echocardiographic predictors have not been identified. We assessed echocardiographic measurements of RV pressure and function in predicting progression to death or ECMO in infants with PPHN.

METHODS AND RESULTS

Echocardiograms for infants ≥35-week gestation with a clinical diagnosis of PPHN were retrospectively reviewed. Traditional and strain echocardiographic measures were compared for those with or without the primary outcome of ECMO/cardiovascular death. Receiver operator curves identified cut points for measures that were significantly different. Of the 86 subjects analysed, 25 (29%) of the patients had the primary outcome of ECMO/death. The ECMO/death group had diminished tricuspid annular plane systolic excursion (TAPSE; P = 0.002) and RV global longitudinal peak strain (GLPS; P = 0.03), a predominant right-to-left shunt across the patent ductus arteriosus (PDA; P = 0.05), and an elevated oxygenation index (OI; P < 0.001). Sensitivity/specificity for TAPSE <4 mm was 56 and 85%, and for GLPS greater than or equal to -9% was 52 and 77%.

CONCLUSION

TAPSE, GLPS, and right-to-left PDA shunting were associated with progression to death/ECMO. RV free wall strain was not associated with the outcome, suggesting that diminished global strain better reflects clinical outcomes in this group. These thresholds may assist in the decision-making to transfer high-risk infants to ECMO centres.

A role for actin polymerization in persistent pulmonary hypertension of the newborn

Persistent pulmonary hypertension of the newborn (PPHN) is defined as the failure of normal pulmonary vascular relaxation at birth. Hypoxia is known to impede postnatal disassembly of the actin cytoskeleton in pulmonary arterial myocytes, resulting in elevation of smooth muscle α-actin and γ-actin content in elastic and resistance pulmonary arteries in PPHN compared with age-matched controls. This review examines the original histological characterization of PPHN with attention to cytoskeletal structural remodeling and actin isoform abundance, reviews the existing evidence for understanding the biophysical and biochemical forces at play during neonatal circulatory transition, and specifically addresses the role of the cortical actin architecture, primarily identified as γ-actin, in the transduction of mechanical force in the hypoxic PPHN pulmonary circuit.

Diffuse lung disease of infancy: a pattern-based, algorithmic approach to histological diagnosis

Diffuse lung disease (DLD) of infancy has multiple aetiologies and the spectrum of disease is substantially different from that seen in older children and adults. In many cases, a specific diagnosis renders a dire prognosis for the infant, with profound management implications. Two recently published series of DLD of infancy, collated from the archives of specialist centres, indicate that the majority of their cases were referred, implying that the majority of biopsies taken for DLD of infancy are first received by less experienced pathologists. The current literature describing DLD of infancy takes a predominantly aetiological approach to classification. We present an algorithmic, histological, pattern-based approach to diagnosis of DLD of infancy, which, with the aid of appropriate multidisciplinary input, including clinical and radiological expertise and ancillary diagnostic studies, may lead to an accurate and useful interim report, with timely exclusion of inappropriate diagnoses. Subsequent referral to a specialist centre for confirmatory diagnosis will be dependent on the individual case and the decision of the multidisciplinary team.