Bosentan as Adjunctive Therapy for Persistent Pulmonary Hypertension of the Newborn: Results of the Randomized Multicenter Placebo-Controlled Exploratory Trial

Cardiac function in congenital diaphragmatic hernia

Cardiac function is known to play critical role in the pathophysiological progression and ultimate clinical outcome of patients with congenital diaphragmatic hernia (CDH). While often anatomically normal, the fetal and neonatal heart in CDH can suffer from both right and left ventricular dysfunction. Here we explore the abnormal fetal heart, early postnatal right and left ventricular dysfunction, the interplay between cardiac dysfunction and pulmonary hypertension, evaluation and echocardiographic assessment of the heart, and therapeutic strategies for managing and supporting the pathophysiologic heart and CDH. Further, we take a common clinical scenario and provide clinically relevant guidance for the diagnosis and management of this complex process.

Advances in the pharmacological management of bronchopulmonary dysplasia: an update of the literature

INTRODUCTION

Bronchopulmonary dysplasia (BPD) is the commonest adverse outcome of extremely prematurely born infants, and its incidence is increasing. Affected infants suffer chronic respiratory morbidity and are at risk of early onset of chronic obstructive pulmonary disease. It is, therefore, important that these infants are appropriately managed, with efficacious pharmacological treatments.

AREAS COVERED

Searches were made on Embase, PubMed, and the Cochrane database for ('treatment' or 'drug therapy/') and ('bronchopulmonary dysplasia' or 'chronic lung disease') and ('neonatology' or 'newborn' or 'prematurity' or 'baby') between 2019 and 2024. Corticosteroids, diuretics, caffeine, anti-asthmatics, nutritional supplements, and medications treating patent ductus arteriosus and pulmonary hypertension are discussed.

EXPERT OPINION

Dexamethasone is associated with adverse neurodevelopmental outcomes and impairment of adult lung function. Inhaled corticosteroids have not resulted in significant effects on BPD. Diuretics only result in short-term improvements in lung function and have side-effects. Evidence suggests it is better to wait and see than aggressively treat PDA; inhaled nitric oxide and sildenafil can improve oxygenation, but whether they improve long-term outcomes remains to be tested. Stem cells are a promising therapy, but further research is required. Appropriately designed trials are required to identify efficacious treatments for infants with BPD.

Comparison of Different Treatments of Persistent Pulmonary Hypertension of the Newborn: A Systematic Review and Network Meta-Analysis

OBJECTIVES

Persistent pulmonary hypertension of the newborn (PPHN) is a life-threatening disease. Despite being considered the gold standard treatment scheme, inhaled nitric oxide (iNO) is not readily available in settings with limited resources. Therefore, in recent years, research on related drugs is being actively pursued. Herein, we aimed to use random-effects network meta-analysis to evaluate the efficacy and associated mortality of different PPHN therapies.

DATA SOURCES

We electronically searched the PubMed, Embase, and Cochrane Library for data up to January 27, 2023.

STUDY SELECTION

Randomized controlled trials involving neonates with PPHN assessing efficacy and mortality of various treatments.

DATA EXTRACTION

Details of study population, treatments, and outcomes were extracted.

DATA SYNTHESIS

Direct pairwise comparisons and a network meta-analysis was performed under random effects. The ranking probability was further assessed based on the surface under the cumulative ranking curve (SUCRA). We analyzed 23 randomized clinical trials involving 902 newborns with PPHN. Sixteen different treatment strategies were compared with each other and conventional therapy (CON). A median concentration of 10-20 parts per million (ppm) iNO (MNO) coupled with sildenafil orally administered at a dose of 1-3 mg/kg/dose every 6-8 hours (OSID) demonstrated the best efficacy (MNO + OSID vs. CON: odds ratio [OR] = 27.53, 95% CI, 2.36-321.75; SUCRA = 0.818, ranking first; moderate quality). OSID combined with milrinone administered IV also performed well in terms of efficacy (OSID + milrinone vs. CON: OR = 25.13, 95% CI = 1.67-377.78; SUCRA = 0.811, ranking second; low quality) and mortality reduction (CON vs. OSID + milrinone: OR = 25.13, 95% CI = 1.67-377.78; SUCRA = 0.786, ranking last; low quality).

CONCLUSIONS

MNO + OSID is the most effective PPHN treatment. If iNO is not available, OSID + milrinone is preferred.

Meconium Aspiration Syndrome, Hypoxic-Ischemic Encephalopathy and Therapeutic Hypothermia-A Recipe for Severe Pulmonary Hypertension?

Hypoxic-ischemic encephalopathy (HIE) is the leading cause of mortality among term newborns globally. Infants born through meconium-stained amniotic fluid are at risk of developing meconium aspiration syndrome (MAS) and HIE. Simultaneous occurrence of MAS and HIE is a perilous combination for newborns due to the risk of persistent pulmonary hypertension of the newborn (PPHN). Moreover, therapeutic hypothermia (TH), which is the current standard of care for the management of HIE, may increase pulmonary vascular resistance (PVR) and worsen PPHN. Infants with MAS and HIE require close cardiorespiratory and hemodynamic monitoring for PPHN. Therapeutic strategies, including oxygen supplementation, ventilation, use of surfactant, inhaled nitric oxide and other pulmonary vasodilators, and systemic vasopressors, play a critical role in the management of PPHN in MAS, HIE, and TH. While TH reduces death or disability in infants with HIE, infants with MAS and HIE undergoing TH need close hemodynamic monitoring for PPHN.

Defining the Typical Course of Persistent Pulmonary Hypertension of the Newborn: When to Think Beyond Reversible Causes

OBJECTIVES

To describe the typical clinical course of reversible persistent pulmonary hypertension of the newborn (PPHN) from perinatal etiologies and compare that with the clinical course of PPHN due to underlying fetal developmental etiologies.

STUDY DESIGN

This was a single-center, retrospective cohort study of liveborn newborns either born or transferred to our facility for higher level of care between 2015 and 2020 with gestational age ≥35 weeks and a clinical diagnosis of PPHN in the electronic health record. Newborns with complex congenital heart disease and congenital diaphragmatic hernia were excluded. Using all data available at time of collection, newborns were stratified into 2 groups by PPHN etiology - perinatal and fetal developmental causes. Primary outcomes were age at initiation, discontinuation, and total duration of extracorporeal life support, mechanical ventilation, supplemental oxygen, inhaled nitric oxide, inotropic support, and prostaglandin E1. Our secondary outcome was age at echocardiographic resolution of pulmonary hypertension. Groups were compared by t-test. Time-to-event Kaplan Meier curves described and compared (log-rank test) discontinuation of each therapy.

RESULTS

Sixty-four (72%) newborns had perinatal etiologies whereas 24 (28%) had fetal developmental etiologies. The resolution of perinatal PPHN was more rapid compared with fetal developmental PPHN. By 10 days of age, more neonates were off inotropes (98% vs 29%, P < .01), decannulated from extracorporeal life support (100% vs 0%, P < .01), extubated (75% vs 37%, P < .01), and had echocardiographic resolution of PH (35% vs 7%, P = .02).

CONCLUSIONS

An atypical PPHN course, characterized by persistent targeted therapies in the second week of life, warrants further work-up for fetal developmental causes.

Targeted Therapies for Neonatal Pulmonary Hypertension: Beyond Nitric Oxide

Pulmonary hypertension in the neonatal population can be acute or chronic and carries significant risk for morbidity and mortality. It can be idiopathic but more often is associated with comorbid pulmonary and heart disease. There are several pharmacotherapeutics aimed at pulmonary vasodilation. This review highlights the most common agents as well as those on the horizon for the treatment of pulmonary hypertension in the neonate.

Randomized Controlled Trials of Pulmonary Vasodilator Therapy Adjunctive to Inhaled Nitric Oxide for Persistent Pulmonary Hypertension of the Newborn: A Systematic Review

Inhaled nitric oxide (iNO) is a pulmonary vasodilator considered standard of care to treat persistent pulmonary hypertension of the newborn. However, not all infants respond to iNO. The authors performed a systematic review to examine methodology, outcomes, and challenges of randomized controlled trials testing pulmonary vasodilator medications adjunctive to iNO. The 5 trials identified showed heterogeneity in eligibility criteria and outcomes assessed. No trial achieved recruitment goals, limiting conclusions regarding efficacy, safety, and pharmacology. Trial design consensus and alternative methodologic strategies such as deferred consent, real-world controls, nonrandomized database assessments, and Bayesian statistical approaches are needed.

Bosentan in the treatment of persistent pulmonary hypertension in newborns: a systematic review and meta-analysis

BACKGROUND

Persistent pulmonary hypertension of the newborn is a life-threatening condition that affects about 1-2 per 1,000 live births worldwide. Bosentan is an oral dual endothelin receptor antagonist that may have a beneficial effect on persistent pulmonary hypertension of the newborn by reducing pulmonary vascular resistance and improving oxygenation. However, its role in persistent pulmonary hypertension of the newborn remains unclear.

OBJECTIVES

To systematically evaluate the efficacy and safety of bosentan as an adjuvant therapy for persistent pulmonary hypertension of the newborn in newborns.

METHODS

We searched six English and two Chinese databases from their inception to 1 January 2023 following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We included randomised controlled trials and retrospective studies that compared bosentan with placebo or other drugs for persistent pulmonary hypertension of the newborn in newborns. We performed a meta-analysis using random-effects models and assessed the risk of bias and heterogeneity in the included studies.

RESULTS

We included 10 studies with a total of 550 participants. Bosentan significantly reduced the treatment failure rate (relative risk = 0.25, P < 0.001), pulmonary artery pressure (mean difference = -11.79, P < 0.001), and length of hospital stay (mean difference = -1.04, P = 0.003), and increased the partial pressure of oxygen (mean difference = 10.02, P < 0.001) and blood oxygen saturation (SpO2) (mean difference = 8.24, P < 0.001) compared with a placebo or other drugs. The occurrence of adverse reactions was not significantly different between bosentan and a placebo or other drugs.

CONCLUSIONS

Bosentan is effective in the treatment of persistent pulmonary hypertension of the newborn but adverse reactions such as abnormal liver function should be observed when using it.

Novel scoring tool of hypoxemic respiratory failure and pulmonary hypertension for defining severity of persistent pulmonary hypertension of newborn

OBJECTIVE

To obtain preliminary validity data for a hypoxemic respiratory failure/pulmonary hypertension (HRF/PH) score for classifying persistent pulmonary hypertension of the newborn (PPHN).

STUDY DESIGN

Retrospective chart review of 100 consecutive neonates admitted to a Children's hospital from 2016-2021 with PPHN, gestational age ≥34 weeks, and echocardiograms in the first week. We assessed the correlation between HRF/PH score and short-term outcomes using linear and logistic regressions.

RESULTS

HRF/PH scores ranged 2-12 (mean 8.5), and were classified mild (0-5), moderate (6-10), and severe (11-15), with 6%, 77% and 17% infants in respective categories. HRF/PH score category correlated with invasive ventilation, nitric oxide, high frequency ventilation, vasoactive infusions, extracorporeal life support and death. HRF/PH score category did not correlate with duration of support or length of stay.

CONCLUSION

The HRF/PH score offers a promising representation of disease severity for PPHN. The tool requires further validation in prospective studies and evaluation for long-term outcomes.

Successful Weaning From Veno-Venous Extracorporeal Membrane Oxygenation (VV-ECMO) After Initiation of Inhaled Epoprostenol in a Neonate With Refractory Persistent Pulmonary Hypertension of the Newborn (PPHN)

Despite improvements in the medical management of persistent pulmonary hypertension of the newborn (PPHN), a significant number of patients persist with inadequate gas exchange and are treated with extracorporeal membrane oxygenation (ECMO). Prolonged time to weaning ECMO can increase mortality risk. Therefore, multiple therapies are utilized for pulmonary hypertension treatment, including pharmacotherapy with pulmonary vasodilators, to improve the prognosis of these critical patients. We report a case of a 37 2/7-week neonate with severe PPHN refractory to triple pulmonary vasodilator therapy (inhaled nitric oxide (iNO), sildenafil, and milrinone) and required veno-venous (VV)-ECMO support to improve oxygenation. Our patient was successfully weaned from ECMO after the addition of inhaled epoprostenol (iEPO) therapy. This report indicates that inhaled prostacyclin therapy effectively helps refractory PPHN patients off extracorporeal life support (ECLS) and should be considered a valuable treatment.

Current and emerging pharmacotherapies for the treatment of pulmonary arterial hypertension in infants

INTRODUCTION

Pulmonary hypertension (PH) is a complex condition that encompasses an array of underlying disease processes and affects a diverse population of infants, including those with congenital heart disease, congenital diaphragmatic hernia, persistent PH of the newborn, and those with lung disease such as bronchopulmonary dysplasia. While there are treatments available to adults with PH, limited data exists for infants, especially for the newer medications. Therapies that target the three main pathophysiologic pathways of pulmonary hypertension appear to benefit infants, but which are best for each individual disease process is unclear.

AREAS COVERED

A review of the therapies to treat pulmonary hypertension is covered in this article including the prostacyclin pathway, endothelin pathway, and the nitric oxide pathway. Other adjunctive treatments are also discussed. Findings are based on a PubMed literature search of research papers spanning 1990-2023 and a search of ongoing trials registered with clinicaltrials.gov.

EXPERT OPINION

Overall therapies seem to improve outcomes with most infants with PH. However, given the diverse population of infants with PH, it is imperative to understand the basis for the PH in individual patients and understand which therapies can be applicable. Further research into tailored therapy for the specific populations is warranted.

Correlation of ABO blood groups with treatment response and efficacy in infants with persistent pulmonary hypertension of the newborn treated with inhaled nitric oxide

OBJECTIVE

Not all infants with persistent pulmonary hypertension of the newborn (PPHN) respond to inhaled nitric oxide (iNO) therapy, as it is known to improve oxygenation in only 50% to 60% of cases. In this study, we investigated whether ABO blood groups were a relevant factor affecting the improvement of oxygenation by nitric oxide (NO) therapy in infants with PPHN.

METHODS

This study was a retrospective, multicenter, and cohort-controlled trial that involved 37 medical units. Infants with PPHN who met the inclusion criteria and were treated with NO (a vasodilator) alone from July 1, 2015, to June 30, 2020, were selected and assigned into three groups: blood type A, blood type B, and blood type O (there were only 7 cases of blood type AB, with a small number of cases, and therefore, blood type AB was excluded for further analysis). The response to iNO therapy was defined as an increase in the ratio of the partial pressure of arterial oxygen (PaO2)/fraction of inspired oxygen (FiO2) > 20% from the basal value after treatment. Oxygenation was assessed mainly based on the two values, oxygenation index (OI) and PaO2/FiO2. The correlation of ABO blood groups with responses to iNO therapy and their influence on the efficacy of iNO therapy was analyzed based on the collected data.

RESULTS

The highest proportion of infants with PPHN who eventually responded to iNO therapy was infants with blood type O. Infants with blood type O more readily responded to iNO therapy than infants with blood type B. Oxygenation after iNO treatment group was optimal in the blood type O group and was the worst in the blood type A group among the three groups. Infants with blood type O showed better efficacy than those with blood types A and B.

CONCLUSION

ABO blood groups are correlated with responses to iNO therapy in infants with PPHN, and different blood groups also affect the efficacy of NO therapy in infants with PPHN. Specifically, infants with blood type O have a better response and experience the best efficacy to iNO therapy.

Pharmacotherapy for Pulmonary Hypertension in Infants with Bronchopulmonary Dysplasia: Past, Present, and Future

Approximately 8-42% of premature infants with chronic lung disease of prematurity, bronchopulmonary dysplasia (BPD), develop pulmonary hypertension (PH). Infants with BPD-PH carry alarmingly high mortality rates of up to 47%. Effective PH-targeted pharmacotherapies are desperately needed for these infants. Although many PH-targeted pharmacotherapies are commonly used to treat BPD-PH, all current use is off-label. Moreover, all current recommendations for the use of any PH-targeted therapy in infants with BPD-PH are based on expert opinion and consensus statements. Randomized Control Trials (RCTs) are needed to determine the efficacy of PH-targeted treatments in premature infants with or at risk of BPD-PH. Prior to performing efficacy RCTs, studies need to be conducted to obtain pharmacokinetic, pharmacodynamic, and safety data for any pharmacotherapy used in this understudied and fragile patient population. This review will discuss current and needed treatment strategies, identify knowledge deficits, and delineate both challenges to be overcome and approaches to be taken to develop effective PH-targeted pharmacotherapies that will improve outcomes for premature infants with or at risk of developing BPD-PH.

The use of milrinone in neonates with persistent pulmonary hypertension of the newborn - a randomised controlled trial pilot study (MINT 1)

OBJECTIVE

To assess the impact of milrinone administration on time spent on nitric oxide (iNO) in infants with acute pulmonary hypertension (aPH). We hypothesized that intravenous milrinone used in conjunction with iNO would reduce the time on iNO therapy and the time spent on invasive ventilation in infants ≥34 weeks gestation with a diagnosis of aPH. We aimed to assess the practicality of instituting the protocol and contributing to a sample size calculation for a definitive multicentre study.

STUDY DESIGN

This was a multicentre, randomized, double-blind, two arm pilot study, with a balanced (1:1) allocation. Infants with a gestation ≥34 weeks and a birth weight ≥2000 grams aPH, an oxygenation index of ≥10, and commenced on iNO were eligible. Participants on iNO were assigned to either a milrinone infusion (intervention) or a normal saline infusion (placebo) for up to 35 h. The primary outcome was time on iNO and feasibility of conducting the protocol.

RESULTS

The trial was terminated early after 4 years of enrollment due to poor recruitment. Four infants were allocated to the intervention arm and 5 to the placebo arm. The groups were well matched for baseline variables. No differences were seen in any of the primary or secondary outcomes.

CONCLUSION

Conducting an interventional trial in the setting of acute pulmonary hypertension in infants is not feasible using our current approach. Future studies in this area require alternative trial design to improve recruitment as this topic remains understudied in the neonatal field.

TRIAL REGISTRATION

www.isrctn.com ; ISRCTN:12949496; EudraCT Number:2014-002988-16.

Efficacy and safety of endothelin receptor antagonists, phosphodiesterase type 5 Inhibitors, and prostaglandins in pediatric pulmonary arterial hypertension: A network meta-analysis

Background

Pulmonary arterial hypertension (PAH) is a fatal disease characterized by pulmonary vascular remodeling and increased pulmonary artery pressure, leading to impaired lung oxygenation, right heart failure, and even death. Although great advances have been made in PAH-targeted medications for pediatric patients, the efficacy and safety of these treatments are controversial.

Methods

We retrieved relevant articles from electronic databases including PubMed, EMBASE, Web of Science, and Cochrane Library until 12 April 2022. To compare the effectiveness and safety of endothelin receptor antagonists (ERAs), phosphodiesterase type 5 Inhibitors (PDE-5i), and prostaglandins (ProA) in the treatment of pediatric PAH, we investigated six hemodynamic parameters, four respiratory parameters, intensive care unit (ICU) stay duration, length of hospital stay, and two safety outcomes.

Results

A total of 27 randomized controlled trials (RCTs) were included in the meta-analysis with 1,574 pediatric participants. The duration of mechanical ventilation was shorter for patients using bosentan, sildenafil, and ProsA, compared with that for patients using the placebo. Bosentan helped to shorten more time for mechanical ventilation than ProsA did, while ProsA was more effective than sildenafil in this respect. As for the length of stay in the ICU, patients administered by ProsA or sildenafil needed shorter ICU stay, compared to those using the placebo, while ProsA was more effective for shortening ICU stay time. In light of safety outcomes, there was a statistically significant difference between the sildenafil and the placebo group. Sildenafil surpassed ProsA in reducing the incidence of pulmonary hypertension (PH) crisis.

Conclusions

ERAs were more effective than ProsA in shortening the duration of mechanical ventilation, while ProsA were better for shortening the duration of mechanical ventilation and ICU stay than PDE-5i. PDE-5i were found to generate more benefits in decreasing the occurrence of PH crisis, though further investigation is warranted.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=351505.

Update on pre-ECMO evaluation and treatment for term infants in respiratory failure

The epidemiology, diagnostic and management approach to severe hypoxemic respiratory failure in the term and near-term neonate has evolved over time, as has the need for extracorporeal membrane oxygenation (ECMO) support in this patient population. Many patients who historically would have required ECMO support now respond to less invasive therapies, with patients requiring ECMO generally representing a higher risk and more heterogenous group of underlying diagnoses. This review will highlight these changes over time and the current available evidence for the diagnosis and management of these infants, as well as the current indications and relative contraindications to ECMO support when oxygen delivery cannot meet demand with less invasive management.

Effects of Inhaled Iloprost for the Management of Persistent Pulmonary Hypertension of the Newborn

OBJECTIVE

The study aimed to evaluate the effects of inhaled iloprost on oxygenation indices in neonates with persistent pulmonary hypertension of the newborn (PPHN).

STUDY DESIGN

We conducted a retrospective chart review of 30 patients with PPHN from January 2014 to November 2018, who did not respond to inhaled nitric oxide (iNO) alone and received inhaled iloprost. Twenty-two patients met the inclusion criteria and eight patients were excluded from the study (complex cardiac disease and extreme prematurity). Patients were categorized as responders or nonresponders (patients who required extracorporeal membrane oxygenation or died). Oxygenation index, mean airway pressure (MAP), and arterial partial pressure of oxygen (PaO₂) were recorded.

RESULTS

Among a total of 22 patients who were included in the study, 10 were classified as nonresponders as they required either extracorporeal membrane oxygenation or died. Gestational age and gender did not differ between responders and nonresponders. The median PaO₂ was lower (37 vs. 42 mm Hg; p < 0.05) and median MAP was higher (20 vs. 17 cm H₂O; p < 0.02) in nonresponders compared with responders just prior to initiating iloprost. Iloprost responders had a significant increase in median PaO₂ and decrease in median oxygenation index in the 24 hours after initiating treatment (p < 0.05), with no significant change in required mean airway pressure over that same period. There was no change in vasopressor use or clinically significant worsening of platelets count, liver, and kidney functions after initiating iloprost.

CONCLUSION

Inhaled iloprost is well tolerated and seems to have beneficial effects in improving oxygenation indices in neonates with PPHN who do not respond to iNO. There is a need of well-designed prospective trials to further ascertain the benefits of using inhaled iloprost as an adjunct treatment in neonates with PPHN who do not respond to iNO alone.

KEY POINTS

· Inhaled iloprost seems to have beneficial effects in improving oxygenation indices in PPHN.. · Inhaled iloprost is generally well tolerated in newborns with PPHN.. · There is a need for prospective randomized controlled trials to further ascertain the benefits of using inhaled iloprost..

Diagnosis & management of pulmonary hypertension in congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) contributes to neonatal morbidity and mortality worldwide. Pulmonary hypertension (PH) is a key component of CDH pathophysiology and critical consideration for management and therapeutic options. PH associated with CDH has traditionally been attributed to pulmonary vascular maldevelopment and associated lung parenchymal hypoplasia, leading to pre-capillary increase in pulmonary vascular resistance (PVR). However, there is increasing recognition that left ventricular hypoplasia, dysfunction and elevated end diastolic pressure may contribute to post-capillary pulmonary hypertension in CDH patients. The interplay of these mechanisms and associated dysfunction in the right and left ventricles results in variable hemodynamic phenotypes in CDH. Clinical assessment of individual phenotype may help guide personalized management strategies, including effective use of pulmonary vasodilators and extra-corporeal membrane oxygenation. Ongoing investigation of the underlying mechanisms of PH in CDH, and efficacy of physiology-based treatment approaches may support improvement in outcomes in this challenging condition.

Pulmonary hypertension in the newborn- etiology and pathogenesis

A disruption in the well-orchestrated fetal-to-neonatal cardiopulmonary transition at birth results in the clinical conundrum of severe hypoxemic respiratory failure associated with elevated pulmonary vascular resistance (PVR), referred to as persistent pulmonary hypertension of the newborn (PPHN). In the past three decades, the advent of surfactant, newer modalities of ventilation, inhaled nitric oxide, other pulmonary vasodilators, and finally extracorporeal membrane oxygenation (ECMO) have made giant strides in improving the outcomes of infants with PPHN. However, death or the need for ECMO occurs in 10-20% of term infants with PPHN. Better understanding of the etiopathogenesis of PPHN can lead to physiology-driven management strategies. This manuscript reviews the fetal circulation, cardiopulmonary transition at birth, etiology, and pathophysiology of PPHN.

Pulmonary vasodilator strategies in neonates with acute hypoxemic respiratory failure and pulmonary hypertension

The management of acute hypoxemic respiratory failure (AHRF) in newborns continues to be a clinical challenge with elevated risk for significant morbidities and mortality, especially when accompanied with persistent pulmonary hypertension of the newborn (PPHN). PPHN is a syndrome characterized by marked hypoxemia secondary to extrapulmonary right-to-left shunting across the ductus arteriosus and/or foramen ovale with high pulmonary artery pressure and increased pulmonary vascular resistance (PVR). After optimizing respiratory support, cardiac performance and systemic hemodynamics, targeting persistent elevations in PVR with inhaled nitric oxide (iNO) therapy has improved outcomes of neonates with PPHN physiology. Despite aggressive cardiopulmonary management, a significant proportion of patients have an inadequate response to iNO therapy, prompting consideration for additional pulmonary vasodilator therapy. This article reviews the pathophysiology and management of PPHN in term newborns with AHRF while highlighting both animal and human data to inform a physiologic approach to the use of PH-targeted therapies.

Case Report: Bosentan and Sildenafil Exposure in Human Milk - A Contribution From the ConcePTION Project

Introduction: Quantitative information on disposition of maternal medicines in human milk remains a major knowledge gap. This case report presents the clinical and pharmacokinetic data of a single mother-infant pair exposed to bosentan and sildenafil for the treatment of pulmonary arterial hypertension (PAH) during lactation.

Case presentation: A 43-year old mother was treated with sildenafil (20 mg, 3x/day) and bosentan (125 mg, 2x/day) for PAH. Her 21-months old infant received breastfeeding in combination with adequate complementary foods. Milk samples were collected over 24 h, at day 637 and 651 after delivery. The observed average steady-state concentrations of sildenafil (2.84 μg/L) and bosentan (49.0 μg/L) in human milk were low. The Daily Infant Dosage ingested by the nursing infant through human milk was 0.02 μg/kg/day for sildenafil and 0.29 μg/kg/day for bosentan at day 637, and 0.03 μg/kg/day and 0.60 μg/kg/day at day 651. The Relative Infant Dose calculated for an exclusively breastfed infant with an estimated milk intake of 150 ml/kg/day, was 0.06% for sildenafil and 0.24% for bosentan. General health outcome of the infant, reported by the mother, was uneventful until the sampling days.

Conclusion: Low medicine concentrations were found in human milk expressed 21 months after delivery after maternal intake of 20 mg sildenafil three times daily and 125 mg bosentan twice daily. General health of the nursing infant until sampling was reported as optimal by the mother.

Efficacy and safety of bosentan in the treatment of persistent pulmonary hypertension of the newborn: a Metaanalysis

OBJECTIVES

To systematically evaluate the efficacy and safety of bosentan in the treatment of persistent pulmonary hypertension of the newborn (PPHN).

METHODS

Chinese Journal Full-text Database, Weipu Database, Wanfang Data, China Biology Medicine disc, PubMed, Web of Science, Embase, and Cochrane Library were searched for literature on bosentan in the treatment of PPHN published up to August 31, 2021.

RESULTS

A total of 8 randomized controlled trials were included for Meta analysis. The results of the Meta analysis showed that compared with the control group, the bosentan treatment group had a significantly lower treatment failure rate (RR=0.23, P<0.001), a significantly greater reduction in pulmonary artery pressure [mean difference (MD)=-11.79, P<0.001)], significantly greater increases in oxygen partial pressure (MD=10.21, P=0.006) and blood oxygen saturation (MD=8.30, P<0.001), and a significantly shorter length of hospital stay (MD=-1.35, P<0.001). The descriptive analysis showed that the bosentan treatment group had a lower degree of tricuspid regurgitation than the control group after treatment. The main adverse reactions of bosentan treatment included abnormal liver function, anemia and edema. The results of subgroup analysis based on treatment regimen, research area, and drug dose were consistent with those before stratification.

CONCLUSIONS

Bosentan is effective in the treatment of PPHN. However, when using bosentan, attention should be paid to adverse reactions such as abnormal liver function.

Pulmonary Vasodilator Therapy in Persistent Pulmonary Hypertension of the Newborn

Inhaled nitric oxide (iNO) therapy had a transformational impact on the management of infants with persistent pulmonary hypertension of the newborn (PPHN). iNO remains the only approved pulmonary vasodilator for PPHN; yet 30% to 40% of patients do not respond or have incomplete response to iNO. Lung recruitment strategies with early surfactant administration and high-frequency ventilation can optimize the response to iNO in the presence of parenchymal lung diseases. Alternate pulmonary vasodilators are used commonly as rescue, life-saving measures, though there is a lack of high-quality evidence supporting their efficacy and safety. This article reviews the available evidence and future directions for research in PPHN.

Early diagnosis and targeted approaches to pulmonary vascular disease in bronchopulmonary dysplasia

Pulmonary hypertension has emerged as a life-threatening disease in preterm infants suffering from bronchopulmonary dysplasia (BPD). Its development is closely linked to respiratory disease, as vasculogenesis and alveologenesis are closely interconnected. Once clinically significant, BPD-associated pulmonary hypertension (BPD-PH) can be challenging to manage, due to poor reversibility and multiple comorbidities frequently associated. The pulmonary vascular disease process underlying BPD-PH is the result of multiple innate and acquired factors, and emerging evidence suggests that it progressively develops since birth and, in certain instances, may begin as early as fetal life. Therefore, early recognition and intervention are of great importance in order to improve long-term outcomes. Based on the most recent knowledge of BPD-PH pathophysiology, we review state-of-the-art screening and diagnostic imaging techniques currently available, their utility for clinicians, and their applicability and limitations in this specific population. We also discuss some biochemical markers studied in humans as a possible complement to imaging for the detection of pulmonary vascular disease at its early stages and the monitoring of its progression. In the second part, we review pharmacological agents currently available for BPD-PH treatment or under preclinical investigation, and discuss their applicability, as well as possible approaches for early-stage interventions in fetuses and neonates. IMPACT: BPD-associated PH is a complex disease involving genetic and epigenetic factors, as well as environmental exposures starting from fetal life. The value of combining multiple imaging and biochemical biomarkers is emerging, but requires larger, multicenter studies for validation and diffusion. Since "single-bullet" approaches have proven elusive so far, combined pharmacological regimen and cell-based therapies may represent important avenues for research leading to future cure and prevention.

Predicting treatment of pulmonary hypertension at discharge in infants with congenital diaphragmatic hernia

OBJECTIVE

To predict pulmonary hypertension (PH) therapy at discharge in a large multicenter cohort of infants with congenital diaphragmatic hernia (CDH).

STUDY DESIGN

Six-year linked records from Children's Hospitals Neonatal Database and Pediatric Health Information System were used; patients whose diaphragmatic hernia was repaired before admission or referral, who were previously home before admission or referral, and non-survivors were excluded. The primary outcome was the use of PH medications at discharge and the secondary outcome was an inter-center variation of therapies during inpatient utilization. Clinical factors were used to develop a multivariable equation randomly applied to 80% cohort; validated in the remaining 20% infants.

RESULTS

A total of 831 infants with CDH from 23 centers were analyzed. Overall, 11.6% of survivors were discharged on PH medication. Center, duration of mechanical ventilation, and duration of inhaled nitric oxide were associated with the use of PH medication at discharge. This model performed well in the validation cohort area under the receiver operating characteristic curve of 0.9, goodness-of-fit χ², p = 0.17.

CONCLUSIONS

Clinical variables can predict the need for long-term PH medication after NICU hospitalization in surviving infants with CDH. This information may be useful to educate families and guide the development of clinical guidelines.

Efficacy and Safety of IV Sildenafil in the Treatment of Newborn Infants with, or at Risk of, Persistent Pulmonary Hypertension of the Newborn (PPHN): A Multicenter, Randomized, Placebo-Controlled Trial

OBJECTIVE

To investigate the efficacy and safety of sildenafil added to inhaled nitric oxide (iNO) for newborn infants with persistent pulmonary hypertension of newborn (PPHN) or hypoxic respiratory failure (HRF) at risk of PPHN.

STUDY DESIGN

Part A of a multinational, randomized, double-blind, placebo-controlled trial. Infants ≤96 hours' old, >34 weeks of gestation, receiving iNO (10-20 ppm on ≥50% FiO₂) for PPHN or HRF at risk of PPHN, and oxygen index >15 to <60, were randomized (1:1) to intravenous (IV) sildenafil (loading: 0.1 mg/kg, over 30 minutes; maintenance: 0.03 mg/kg/h) or placebo, for up to 14 days. Coprimary end points were treatment failure rate (day 14/discharge) and time on iNO without treatment failure. Secondary end points included time on ventilation and oxygenation measures.

RESULTS

Of 87 infants screened, 29 were randomized to IV sildenafil and 30 to placebo; 13 discontinued treatment (sildenafil, n = 6; placebo: n = 7), including 3 deaths (sildenafil: n = 2; placebo: n = 1). Treatment failure rates did not differ with sildenafil (27.6%) vs placebo (20.0%; P = .4935). Mean time on iNO was not different with sildenafil (4.1 days) vs placebo (4.1 days; P = .9850). No differences were noted in secondary end points. Most common adverse events (AEs) with sildenafil (≥10% infants) were hypotension (n = 8/29), hypokalemia (n = 7/29), anemia, drug withdrawal syndrome (n = 4/29, each), and bradycardia (n = 3/29). One serious AE (hypotension) was considered treatment-related.

CONCLUSIONS

IV sildenafil added to iNO was not superior to placebo in infants with PPHN or HRF at risk of PPHN. A review of AEs did not identify any pattern of events indicative of a safety concern with IV sildenafil. Infants will have developmental follow-up (Part B). TRIAL REGISTRATION CLINICALTRIALS.GOV: NCT01720524.

Pathophysiology and Management of Persistent Pulmonary Hypertension of the Newborn

Persistent pulmonary hypertension of the newborn (PPHN) is a disorder of circulatory transition resulting in high pulmonary vascular resistance with extrapulmonary right-to-left shunts causing hypoxemia. There has been substantial gain in understanding of pathophysiology of PPHN over the past 2 decades, and biochemical pathways responsible for abnormal vasoconstriction of pulmonary vasculature are now better understood. Easy availability of bedside echocardiography helps in establishing early definitive diagnosis, understanding the pathophysiology and hemodynamic abnormalities, monitoring the disease process, and response to therapeutic intervention. There also has been significant advancement in specific management of PPHN targeted at deranged biochemical pathways and hemodynamic instability.

Hypotension in Preterm Infants (HIP) randomised trial

OBJECTIVE

To determine whether restricting the use of inotrope after diagnosis of low blood pressure (BP) in the first 72 hours of life affects survival without significant brain injury at 36 weeks of postmenstrual age (PMA) in infants born before 28 weeks of gestation.

DESIGN

Double-blind, placebo-controlled randomised trial. Caregivers were masked to group assignment.

SETTING

10 sites across Europe and Canada.

PARTICIPANTS

Infants born before 28 weeks of gestation were eligible if they had an invasive mean BP less than their gestational age that persisted for ≥15 min in the first 72 hours of life and a cerebral ultrasound free of significant (≥ grade 3) intraventricular haemorrhage.

INTERVENTION

Participants were randomly assigned to saline bolus followed by either a dopamine infusion (standard management) or placebo (5% dextrose) infusion (restrictive management).

PRIMARY OUTCOME

Survival to 36 weeks of PMA without severe brain injury.

RESULTS

The trial terminated early due to significant enrolment issues (7.7% of planned recruitment). 58 infants were enrolled between February 2015 and September 2017. The two groups were well matched for baseline variables. In the standard group, 18/29 (62%) achieved the primary outcome compared with 20/29 (69%) in the restrictive group (p=0.58). Additional treatments for low BP were used less frequently in the standard arm (11/29 (38%) vs 19/29 (66%), p=0.038).

CONCLUSION

Though this study lacked power, we did not detect major differences in clinical outcomes between standard or restrictive approach to treatment. These results will inform future studies in this area.

TRIAL REGISTRATION NUMBER

NCT01482559, EudraCT 2010-023988-17.

Pediatric Pulmonary Hypertension: Definitions, Mechanisms, Diagnosis, and Treatment

Pediatric pulmonary hypertension (PPH) is a multifactorial disease with diverse etiologies and presenting features. Pulmonary hypertension (PH), defined as elevated pulmonary artery pressure, is the presenting feature for several pulmonary vascular diseases. It is often a hidden component of other lung diseases, such as cystic fibrosis and bronchopulmonary dysplasia. Alterations in lung development and genetic conditions are an important contributor to pediatric pulmonary hypertensive disease, which is a distinct entity from adult PH. Many of the causes of pediatric PH have prenatal onset with altered lung development due to maternal and fetal conditions. Since lung growth is altered in several conditions that lead to PPH, therapy for PPH includes both pulmonary vasodilators and strategies to restore lung growth. These strategies include optimal alveolar recruitment, maintaining physiologic blood gas tension, nutritional support, and addressing contributing factors, such as airway disease and gastroesophageal reflux. The outcome for infants and children with PH is highly variable and largely dependent on the underlying cause. The best outcomes are for neonates with persistent pulmonary hypertension (PPHN) and reversible lung diseases, while some genetic conditions such as alveolar capillary dysplasia are lethal. © 2021 American Physiological Society. Compr Physiol 11:2135-2190, 2021.

Inadequate Dosage May Lead to the Recurrence of Postoperative Pulmonary Hypertension in Patients With Congenital Heart Disease

Background: Pulmonary arterial hypertension (PAH) associated with congenital heart disease (PAH-CHD) occurs predominantly among patients with uncorrected congenital heart disease (CHD). It is an intractable problem to control PAH continuously and stably after an operation.

Methods: 1) OPLS-DA combined with S-plot was used to retrospectively analyze the results of preoperative and postoperative PAH and 39 biochemical indicators of 235 patients admitted to Fuwai Yunnan Cardiovascular Hospital from January 2019 to December 2020. 2) Combined with Meta-analysis, the recurrence in postoperative PAH was analyzed in terms of operation factors, doses administered, and age factors.

Results: 1) 4 indicators (PAH, RBC, HGB, and CO₂) that reflect the prognosis of patients had been found by OPLS-DA combined with S-plot. 2) The recurrence rate of postoperative PAH was 37.02%. The comprehensive therapeutic effect of interventional closure was better than that of surgical operation. PAH was not significantly higher again in patients who received either the instruction dose or the literature dose. Postoperative combination therapy (bosentan and sildenafil) was more effective than bosentan alone. Recovery after treatment was better in infants than in the other four age groups.

Conclusion: OPLS-DA combined with S-plot was used for the first time to analyze clinical examination data. In this study, this method proved to be a feasible method for analyzing clinical data We recommend interventional closure as the first choice for patients with PAH-CHD. For postoperative oral therapy, we recommend the combination therapy (bosentan with sildenafil). To prevent the recurrence, the dose should be strictly prescribed according to the instructions, literature, or body surface area converted. Moreover, we recommend treatment at a young age in these patients.

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.

Persistent pulmonary hypertension of the newborn

Persistent pulmonary hypertension of the newborn (PPHN) is a significant clinical problem characterized by refractory and severe hypoxemia secondary to elevated pulmonary vascular resistance resulting in right-to-left extrapulmonary shunting of deoxygenated blood. PPHN is associated with diverse cardiopulmonary disorders and a high early mortality rate for infants with severe PPHN. Surviving infants with PPHN have an increased risk of long-term morbidities. PPHN physiology can be categorized by (1) maladaptation: pulmonary vessels have normal structure and number but have abnormal vasoreactivity; (2) excessive muscularization: increased smooth muscle cell thickness and increased distal extension of muscle to vessels that are usually not muscularized; and (3) underdevelopment: lung hypoplasia associated with decreased pulmonary artery number. Treatment involves adequate lung recruitment, optimization of cardiac output and left ventricular function, and pulmonary vasodilators such as inhaled nitric oxide. Infants who fail to respond to conventional therapy should be evaluated for lethal lung disorders including alveolar-capillary dysplasia, T-box transcription factor 4 gene, thyroid transcription factor-1, ATP-binding cassette A3 gene, and surfactant protein diseases.

Life-threatening PPHN refractory to nitric oxide: proposal for a rational therapeutic algorithm

Persistent pulmonary hypertension of the neonate (PPHN) refractory to inhaled nitric oxide still represents a frequent clinical challenge with negative outcomes in neonatal critical care. Several pulmonary vasodilators have become available thanks to improved understanding of pulmonary hypertension pathobiology. These drugs are commonly used in adults and there are numerous case series and small studies describing their potential usefulness in neonates, as well. New vasodilators act on different pathways, some of them can have additive effects and all have different pharmacology features. This information has never been summarized so far and no comprehensive pathobiology-driven algorithm is available to guide the treatment of refractory PPHN.Conclusion: We offer a rational clinical algorithm to guide the treatment of refractory PPHN based on expert advice and the more recent pathobiology and pharmacology knowledge. What is Known: • Refractory PPHN occurs in 30-40% of iNO-treated neonates and represents a significant clinical problem. Several pulmonary vasodilators have become available thanks to a better understanding of pulmonary hypertension pathobiology. What is New: • Available vasodilators have different pharmacology, mechanisms of action and may provide additive effect. We provide a rational clinical algorithm to guide the treatment of refractory PPHN based on expert advice and the more recent pathobiology and pharmacology knowledge.

Surf early to higher tides: surfactant therapy to optimize tidal volume, lung recruitment, and iNO response

Inhaled nitric oxide is approved by FDA for the management of hypoxemic respiratory failure in term and near-term infants. However, approximately a third of patients treated with inhaled nitric oxide fail to have a sustained improvement in oxygenation. Recruitment of the lung with surfactant enables optimal delivery of nitric oxide to the alveolar space leading to effective pulmonary vasodilation.

A Physiology-Based Pharmacokinetic Framework to Support Drug Development and Dose Precision During Therapeutic Hypothermia in Neonates

Therapeutic hypothermia (TH) is standard treatment for neonates (≥36 weeks) with perinatal asphyxia (PA) and hypoxic-ischemic encephalopathy. TH reduces mortality and neurodevelopmental disability due to reduced metabolic rate and decreased neuronal apoptosis. Since both hypothermia and PA influence physiology, they are expected to alter pharmacokinetics (PK). Tools for personalized dosing in this setting are lacking. A neonatal hypothermia physiology-based PK (PBPK) framework would enable precision dosing in the clinic. In this literature review, the stepwise approach, benefits and challenges to develop such a PBPK framework are covered. It hereby contributes to explore the impact of non-maturational PK covariates. First, the current evidence as well as knowledge gaps on the impact of PA and TH on drug absorption, distribution, metabolism and excretion in neonates is summarized. While reduced renal drug elimination is well-documented in neonates with PA undergoing hypothermia, knowledge of the impact on drug metabolism is limited. Second, a multidisciplinary approach to develop a neonatal hypothermia PBPK framework is presented. Insights on the effect of hypothermia on hepatic drug elimination can partly be generated from in vitro (human/animal) profiling of hepatic drug metabolizing enzymes and transporters. Also, endogenous biomarkers may be evaluated as surrogate for metabolic activity. To distinguish the impact of PA versus hypothermia on drug metabolism, in vivo neonatal animal data are needed. The conventional pig is a well-established model for PA and the neonatal Göttingen minipig should be further explored for PA under hypothermia conditions, as it is the most commonly used pig strain in nonclinical drug development. Finally, a strategy is proposed for establishing and fine-tuning compound-specific PBPK models for this application. Besides improvement of clinical exposure predictions of drugs used during hypothermia, the developed PBPK models can be applied in drug development. Add-on pharmacotherapies to further improve outcome in neonates undergoing hypothermia are under investigation, all in need for dosing guidance. Furthermore, the hypothermia PBPK framework can be used to develop temperature-driven PBPK models for other populations or indications. The applicability of the proposed workflow and the challenges in the development of the PBPK framework are illustrated for midazolam as model drug.

Variation in the definition of pulmonary hypertension and clinical indications for the use of nitric oxide in neonatal clinical trials

AIM

Pulmonary hypertension (PH) frequently complicates neonatal hypoxaemic respiratory failure, but is inconsistently defined. We aimed to describe the variation among randomised controlled trials (RCTs) of inhaled nitric oxide (iNO), in relation to the definition of PH and/or hypoxaemic respiratory failure used to select patients for trial inclusion.

METHODS

PubMed, Cochrane Library and ClinicalTrials.gov were systematically searched for RCTs of iNO in neonates. Included studies were assessed for clinical and/or echocardiography criteria used to define PH/hypoxaemic respiratory failure.

RESULTS

Thirty-two trials were included in this review, of which 23 enrolled infants ≥34 weeks' gestation. Echocardiographic diagnosis was used in 21 studies, but there was considerable variation in the echocardiographic parameters used to diagnose PH. The most commonly used indices included markers of tricuspid regurgitation and extrapulmonary shunt.

CONCLUSION

There is wide variation in the definition of PH used to select infants for inclusion into RCTs of iNO therapy in neonates. We recommend that an international consensus be reached on which parameters should be used and the thresholds defining severity of disease.

Persistent Pulmonary Hypertension of the Newborn: Pathophysiological Mechanisms and Novel Therapeutic Approaches

Persistent pulmonary hypertension of the newborn (PPHN) is one of the main causes of neonatal morbidity and mortality. It is characterized by sustained elevation of pulmonary vascular resistance (PVR), preventing an increase in pulmonary blood flow after birth. The affected neonates fail to establish blood oxygenation, precipitating severe respiratory distress, hypoxemia, and eventually death. Inhaled nitric oxide (iNO), the only approved pulmonary vasodilator for PPHN, constitutes, alongside supportive therapy, the basis of its treatment. However, nearly 40% of infants are iNO resistant. The cornerstones of increased PVR in PPHN are pulmonary vasoconstriction and vascular remodeling. A better understanding of PPHN pathophysiology may enlighten targeted and more effective therapies. Sildenafil, prostaglandins, milrinone, and bosentan, acting as vasodilators, besides glucocorticoids, playing a role on reducing inflammation, have all shown potential beneficial effects on newborns with PPHN. Furthermore, experimental evidence in PPHN animal models supports prospective use of emergent therapies, such as soluble guanylyl cyclase (sGC) activators/stimulators, l-citrulline, Rho-kinase inhibitors, peroxisome proliferator-activated receptor-γ (PPAR-γ) agonists, recombinant superoxide dismutase (rhSOD), tetrahydrobiopterin (BH4) analogs, ω-3 long-chain polyunsaturated fatty acids (LC-PUFAs), 5-HT2A receptor antagonists, and recombinant human vascular endothelial growth factor (rhVEGF). This review focuses on current knowledge on alternative and novel pathways involved in PPHN pathogenesis, as well as recent progress regarding experimental and clinical evidence on potential therapeutic approaches for PPHN.

Efficacy of Milrinone Plus Sildenafil in the Treatment of Neonates with Persistent Pulmonary Hypertension in Resource-Limited Settings: Results of a Randomized, Double-Blind Trial

BACKGROUND

The management of severe persistent pulmonary hypertension (PPHN) can be very challenging in many resource-limited centers without access to inhaled nitric oxide or extracorporeal membrane oxygenation.

OBJECTIVES

The current study aimed to investigate the efficacy of oral sildenafil and intravenous milrinone infusion and compare the effects of these drugs in combination versus as monotherapy in neonates with PPHN.

METHODS

A double-blind randomized controlled trial was conducted in which neonates with PPHN were divided into three groups of 20 patients each: group 1 received oral sildenafil starting at 0.5 mg/kg every 6 h to a target maintenance dose of 2 mg/kg every 6 h; group 2 received intravenous milrinone 0.5 μg/kg/min as a continuous infusion; and group 3 received both oral sildenafil and intravenous milrinone.

RESULTS

Post-treatment pulmonary artery systolic pressure was significantly lower in group 3 than in groups 1 and 2, which both received monotherapy (p = 0.031). The oxygenation index also decreased significantly in the dual-therapy group (p = 0.002) compared with the monotherapy groups. Combined use of both drugs demonstrated a beneficial synergistic effect with better outcomes and reduced mortality.

CONCLUSION

Dual therapy using sildenafil and milrinone was superior to monotherapy with either drug in neonates with severe PPHN and is recommended for use in resource-constrained settings.

REGISTRATION

Pan African Clinical Trial Registry identifier number PACTR201902691230243.

The Use of Cardiotonic Drugs in Neonates

There is a distinct lack of age-appropriate cardiotonic drugs, and adult derived formulations continue to be administered, without evidence-based knowledge on their dosing, safety, efficacy, and long-term effects. Dopamine remains the most commonly studied and prescribed cardiotonic drug in the neonatal intensive care unit (NICU), but evidence of its effect on endorgan perfusion still remains. Unlike adult and pediatric critical care, there are significant gaps in our knowledge on the use of various cardiotonic drugs in various forms of circulatory failure in the NICU.

Early postnatal echocardiographic assessment of pulmonary blood flow in newborns with congenital diaphragmatic hernia

Objective:

Echocardiography is the most important tool to assess infants with congenital diaphragmatic hernia (CDH) for pulmonary hypertension (PH). The pattern of blood flow in the pulmonary artery [described as time to peak velocity (TPV)/right ventricular ejection time (RVET) ratio] provides distinct information about pulmonary arterial pressure. The aim of our study was to investigate the correlation of TPV/RVET measurements with the most commonly used classification system for PH in CDH newborns and the association of these measurements with outcome parameters.

Methods:

Echocardiographic measurements were obtained in 40 CDH newborns within 6 h of life. The obtained measurements were correlated with the decision for or against extracorporeal membrane oxygenation (ECMO); early mortality; total duration of mechanical ventilation and total duration of oxygen supplementation.

Results:

The correlation coefficient between severity of PH and TPV/RVET measurements was −0.696 (P<0.001). Using receiver operating characteristic (ROC) analyses the optimal cutoff for TPV/RVET in order to predict the necessity for ECMO or early mortality without ECMO was 0.29 with a sensitivity of 86.7%, a specificity of 68%, a positive predictive value of 61.9% and a negative predictive value of 89.5%. Newborns with a TPV/RVET below the cutoff had a 5.9-fold risk for ECMO or early mortality, a significantly longer duration of mechanical ventilation (13.4 days vs. 7.4 days, P=0.003) and oxygen supplementation (22.4 days vs. 9.0 days, P=0.019), and a lower survival rate (76.2% vs. 100%, P=0.021).

Conclusions:

TPV/RVET is a feasible parameter to assess PH in CDH newborns with close correlation to outcome parameters.

Current and Future Treatments for Persistent Pulmonary Hypertension in the Newborn

Persistent pulmonary hypertension in newborn (PPHN) is a serious and possibly fatal syndrome characterized by sustained foetal elevation of pulmonary vascular resistance at birth. PPHN may manifest secondary to other conditions as meconium aspiration syndrome, infection and congenital diaphragmatic hernia. This MiniReview provides the reader with an overview of current and future treatment options for patients with PPHN without congenital diaphragmatic hernia. The study is based on systematic searches in the databases PubMed and Cochrane Library and registered studies on Clinicaltrials.gov investigating PPHN. Inhaled nitric oxide (iNO) is well documented for treatment of PPHN, but 30% fail to respond to iNO. Other current treatment options could be sildenafil, milrinone, prostaglandin analogues and bosentan. There are several ongoing trials with sildenafil, but evidence is lacking for the other treatments and/or for the combination with iNO. Currently, there is no evidence for effect in PPHN of other treatments, for example tadalafil, macitentan, ambrisentan, riociguat and selexipag used for pulmonary arterial hypertension in adults. Experimental studies in animal models for PPHN suggest effect of a series of approaches including recombinant human superoxide dismutase, L-citrulline, Rho-kinase inhibitors and peroxisome proliferator-activated receptor-γ agonists. We conclude that iNO is the most investigated and the only approved pulmonary vasodilator for infants with PPHN. In the iNO non-responders, sildenafil currently seems to be the best alternative either alone or in combination with iNO. Systematic and larger clinical studies are required for testing the other potential treatments of PPHN.

Approach to pulmonary vascular disease in the ICU

PURPOSE OF REVIEW

Pulmonary vascular disease (PVD) complicates the course of many cardiovascular, pulmonary and other systemic diseases in children. The physiological sequelae (pulmonary hypertension and elevated pulmonary vascular resistance) can overwhelm the right ventricle and lead to circulatory collapse. Despite the common end-point, the preceding pathophysiology is complex and variable and requires a tailored approach to diagnosis and management. In this article, we will review the most recent evidence and explore an approach to current controversies in the diagnosis and management of common or challenging patient subgroups.

RECENT FINDINGS

New methods of interpreting data derived from echocardiography and cardiac magnetic resonance imaging may assist in risk stratification and response to therapy. In specific patient subgroups, standard pharmacological therapies to reduce right ventricle afterload may be overutilized, ineffective and in some cases harmful. In the patient failing pharmacological therapy, new and novel techniques are being explored including temporary extracorporeal mechanical circulatory support, pumpless lung assist devices and novel surgical and catheterization procedures.

SUMMARY

PVD is a diverse entity, and attention to the underlying pathophysiology is essential for appropriate management. Despite significant advances in our understanding, the majority of data comes from small uncontrolled studies and must be interpreted with caution.

Continuous intravenous sildenafil as an early treatment in neonates with congenital diaphragmatic hernia

BACKGROUND

Pulmonary hypertension (PH) is an important contributor of morbidity and mortality in infants with congenital diaphragmatic hernia (CDH). Treatment options are limited, but sildenafil might improve oxygenation and PH in neonates with CDH.

OBJECTIVE

Aim of this study is to assess effects of intravenous sildenafil on oxygenation and PH in neonates with CDH.

METHODS

A retrospective chart review was performed in all neonates with CDH born in our institution between September 2012 and December 2014. Indication for sildenafil was an OI > 15, PH > 2/3 systemic pressure, or a difference in pre- and postductal oxygen saturation (≥8%). A sildenafil bolus was administered followed by a maintenance infusion of 1.6 mg/kg/d. Primary outcome was improved oxygenation after starting sildenafil. Patients were compared according to improvement in oxygenation (responder vs non-responder).

RESULTS

A total of 26 of 44 neonates were treated with intravenous sildenafil and in all sildenafil were initiated within the first 24 h of life (median age 3.1 h). Improved oxygenation was observed in 11 infants (42.3%). Among the 15 non-responders (57.6%) ECMO was started in 13 and two infants died without ECMO. Vasopressor support increased significantly during the first hours after commencing sildenafil in responders and non-responders. Echocardiographic indices demonstrated an effect on pulmonary arterial pressure within the first 24 h after starting sildenafil.

CONCLUSIONS

Treatment of neonates with intravenous sildenafil during the first day of life was associated with acute improvement in oxygenation in more than 40% of patients. However, a significant increase in vasopressor support was observed.

Beyond the inhaled nitric oxide in persistent pulmonary hypertension of the newborn

Persistent pulmonary hypertension (PPHN) is a consequence of failed pulmonary vascular transition at birth and leads to pulmonary hypertension with shunting of deoxygenated blood across the ductus arteriosus (DA) and foramen ovale (FO) resulting in severe hypoxemia, and it may eventually lead to life-threatening circulatory failure. PPHN is a serious event affecting both term and preterm infants in the neonatal intensive care unit. It is often associated with diseases such as congenital diaphragmatic hernia, meconium aspiration, sepsis, congenital pneumonia, birth asphyxia and respiratory distress syndrome. The diagnosis of PPHN should include echocardiographic evidence of increased pulmonary pressure, with demonstrable right-to-left shunt across the DA or FO, and the absence of cyanotic heart diseases. The mainstay therapy of PPHN includes treatment of underlying causes, maintenance of adequate systemic blood pressure, optimized ventilator support for lung recruitment and alveolar ventilation, and pharmacologic measures to increase pulmonary vasodilation and decrease pulmonary vascular resistance. Inhaled nitric oxide has been proved to treat PPHN successfully with improved oxygenation in 60-70% of patients and to significantly reduce the need for extracorporeal membrane oxygenation (ECMO). About 14%-46% of the survivors develop long-term impairments such as hearing deficits, chronic lung disease, cerebral palsy and other neurodevelopmental disabilities.

Effect of bosentan therapy in persistent pulmonary hypertension of the newborn

BACKGROUND

Persistent pulmonary hypertension of the newborn (PPHN) contributes to neonatal hypoxemia and is associated with a high mortality. Some PPHN patients are unresponsive to inhaled nitric oxide (iNO). Bosentan, an oral endothelin-1 receptor antagonist, reduces pulmonary vascular resistance and hence may play a role in the treatment of PPHN.

METHODS

A retrospective medical records review was performed in newborns who received oral bosentan as an adjunctive therapy for treatment of PPHN between January 2013 and February 2016 at the neonatal intensive care unit of Songklanagarind Hospital. The main outcomes were the effect of bosentan on oxygenation and hemodynamic status after commencement of treatment and the safety of bosentan.

RESULTS

Forty neonates at a median (IQR) gestation of 38 (36.8-40) weeks and an initial median (IQR) oxygen index (OI) of 29.2 (13.4-40.1) received bosentan therapy. Oral bosentan was commenced at a median (IQR) age of 27 (14.5-40.2) hours and the mean (SD) duration of treatment was 6.2 (3.1) days. The OI, alveolar-arterial oxygen difference (AaDO₂) and oxygen saturation (SpO₂) improved significantly at 2 h after treatment (p = 0.002, p = 0.01 and p < 0.001, respectively). In 21 (52.5%) neonates who received iNO and bosentan, the median OI (IQR) was 34.2 (29.0-42.6) with a significant decrease of OI at 6 h (p = 0.005) after treatment. In 19 (47.5%) neonates who received bosentan alone, the median OI (IQR) was 13.0 (9.8-30.9) with a significant decrease of OI in 2 h (p = 0.01) after treatment. The blood pressures before and after bosentan treatment were not statistically significantly different. The mortality rate was 12.5% (5/40).

CONCLUSION

Oral bosentan may be a safe and effective treatment to improve oxygenation in neonates with PPHN. Bosentan can be used as an adjuvant therapy with iNO and can be an alternative therapy option in mild-to-moderate PPHN.

Inotropes for Preterm Infants: 50 Years on Are We Any Wiser?

For almost half a century, inotropes have been administered to preterm infants with the ultimate goal of increasing their blood pressure. A number of trials, the majority of which focused on dopamine administration, have demonstrated increased blood pressure following inotrope administration in preterm infants and have led to continued use of inotropes in our neonatal units. We have also seen an increase in the number of potential agents available to the clinician. However, we now know that hypotension is a much broader concept than blood pressure alone, and our aim should instead be focused on improving end organ perfusion, specifically cerebral perfusion. Only a limited number of studies have incorporated the organ-relevant hemodynamic changes and long-term outcomes when assessing inotropic effects in neonates, the majority of which are observational studies or have a small sample size. In addition, important considerations, including the developing/maturing adrenergic receptors, polymorphisms of these receptors, and other differences in the pharmacokinetics and pharmacodynamics of preterm infants, are only recently being recognized. Certainly, there remains huge variation in practice. The lack of well-conducted randomized controlled trials addressing these relevant outcomes, along with the difficulty executing such RCTs, leaves us with more questions than answers. This review provides an overview of the various inotropic agents currently being used in the care of preterm infants, with a particular focus on their organ/cerebral hemodynamic effects both during and after transition.

Barriers to enrollment in a randomized controlled trial of hydrocortisone for cardiovascular insufficiency in term and late preterm newborn infants

OBJECTIVE

To analyze reasons for low enrollment in a randomized controlled trial (RCT) of the effect of hydrocortisone for cardiovascular insufficiency on survival without neurodevelopmental impairment (NDI) in term/late preterm newborns.

STUDY DESIGN

The original study was a multicenter RCT. Eligibility: ⩾34 weeks' gestation, <72 h old, mechanically ventilated, receiving inotrope. Primary outcome was NDI at 2 years; infants with diagnoses at high risk for NDI were excluded. This paper presents an analysis of reasons for low patient enrollment.

RESULTS

Two hundred and fifty-seven of the 932 otherwise eligible infants received inotropes; however, 207 (81%) had exclusionary diagnoses. Only 12 infants were randomized over 10 months; therefore, the study was terminated. Contributing factors included few eligible infants after exclusions, open-label steroid therapy and a narrow enrollment window.

CONCLUSION

Despite an observational study to estimate the population, very few infants were enrolled. Successful RCTs of emergent therapy may require fewer exclusions, a short-term primary outcome, waiver of consent and/or other alternatives.