Pulmonary vasodilator therapy in the NICU: inhaled nitric oxide, sildenafil, and other pulmonary vasodilating agents

Novel insights into the potential applications of stem cells in pulmonary hypertension therapy

Pulmonary hypertension (PH) refers to a group of deadly lung diseases characterized by vascular lesions in the microvasculature and a progressive increase in pulmonary vascular resistance. The prevalence of PH has increased over time. Currently, the treatment options available for PH patients have limited efficacy, and none of them can fundamentally reverse pulmonary vascular remodeling. Stem cells represent an ideal seed with proven efficacy in clinical studies focusing on liver, cardiovascular, and nerve diseases. Since the potential therapeutic effect of mesenchymal stem cells (MSCs) on PH was first reported in 2006, many studies have demonstrated the efficacy of stem cells in PH animal models and suggested that stem cells can help slow the deterioration of lung tissue. Existing PH treatment studies basically focus on the paracrine action of stem cells, including protein regulation, exosome pathway, and cell signaling; however, the specific mechanisms have not yet been clarified. Apoptotic and afunctional pulmonary microvascular endothelial cells (PMVECs) and alveolar epithelial cells (AECs) are two fundamental promoters of PH although they have not been extensively studied by researchers. This review mainly focuses on the supportive communication and interaction between PMVECs and AECs as well as the potential restorative effect of stem cells on their injury. In the future, more studies are needed to prove these effects and explore more radical cures for PH.

Novel insights into minipuberty and GnRH: Implications on neurodevelopment, cognition, and COVID-19 therapeutics

In humans, the first 1000 days of life are pivotal for brain and organism development. Shortly after birth, gonadotropin-releasing hormone (GnRH) neurons in the hypothalamus are activated, a phenomenon known as minipuberty. This phenomenon, observed in all mammals studied, influences the postnatal development of the hypothalamic-pituitary-gonadal (HPG) axis and reproductive function. This review will put into perspective the results of recent studies showing that the impact of minipuberty extends beyond reproductive function, influencing sensory and cognitive maturation. Studies in mice have revealed the role of nitric oxide (NO) in regulating minipuberty amplitude, with NO deficiency linked to cognitive and olfactory deficits. Additionally, findings indicate that cognitive and sensory defects in adulthood in a mouse model of Down syndrome are associated with an age-dependent decline of GnRH production, whose origin can be traced back to minipuberty, and point to the potential therapeutic role of pulsatile GnRH administration in cognitive disorders. Furthermore, this review delves into the repercussions of COVID-19 on GnRH production, emphasizing potential consequences for neurodevelopment and cognitive function in infected individuals. Notably, GnRH neurons appear susceptible to SARS-CoV-2 infection, raising concerns about potential long-term effects on brain development and function. In conclusion, the intricate interplay between GnRH neurons, GnRH release, and the activity of various extrahypothalamic brain circuits reveals an unexpected role for these neuroendocrine neurons in the development and maintenance of sensory and cognitive functions, supplementing their established function in reproduction. Therapeutic interventions targeting the HPG axis, such as inhaled NO therapy in infancy and pulsatile GnRH administration in adults, emerge as promising approaches for addressing neurodevelopmental cognitive disorders and pathological aging.

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.

Implementation of an Inhaled Nitric Oxide Weaning Protocol and Stewardship in a Level 4 NICU to Decrease Inappropriate Use

OBJECTIVE

Inhaled nitric oxide (iNO) is an effective but expensive treatment of pulmonary hypertension in newborns, with limited data regarding weaning. Our institution implemented a multidisciplinary iNO weaning protocol and stewardship to reduce inappropriate use of iNO. The objective of this study was to evaluate our institutional iNO usage before and after implementation.

METHODS

Single-center study comparing a retrospective control group to a prospective cohort after implementation of an iNO weaning protocol. All infants in the neonatal intensive care unit (NICU) who received iNO during the study timeframe were included. The primary outcome was duration of iNO per course.

RESULTS

A total of 47 courses of iNO occurred during the pre-protocol timeframe compared with 37 courses in the post-protocol timeframe. Median iNO usage per course was 149 hours (IQR, 63-243) in the pre-protocol group versus 59 hours (IQR, 37-122) in the post-protocol group (p = 0.008). Length of stay was significantly longer in the pre-protocol group (p = 0.02), likely related to significantly longer ventilator days in the pre-protocol group (p = 0.02). Compliance with initiation of weaning when recommended per the protocol was 72%, and the incidence of successful weaning was 74%.

CONCLUSIONS

The implementation of an iNO weaning protocol in the NICU significantly decreased iNO usage by approximately 60% with no notable negative effects.

Persistent Pulmonary Hypertension: A Look Into the Future Therapy

Persistent pulmonary hypertension (PPHN) of the newborn is a lung parenchymal disorder that causes a wide range of hemodynamic changes in the newborn's systemic circulation. Arising from a multifactorial web of etiology, PPHN is one of the most common reasons for neonatal intensive care unit hospitalization and is associated with increased morbidity and mortality. Historically, multiple treatment modalities have been explored, ranging from oxygen and surfactant therapy to newer upcoming medications like magnesium sulfate and adenosine. This review article has discussed the pathogenesis of PPHN and its relationship with the clinical implications of PPHN, such as heart failure and so on. This article has also explored the diagnostic guidelines and analyzed the existing and the upcoming modalities for treating PPHN.

Approach to the Connection between Meconium Consistency and Adverse Neonatal Outcomes: A Retrospective Clinical Review and Prospective In Vitro Study

Whether meconium-stained amniotic fluid (MSAF) serves as an indicator of fetal distress is under debate; however, the presence of MSAF concerns both obstetricians and pediatricians because meconium aspiration is a major contributor to neonatal morbidity and mortality, even with appropriate treatment. The present study suggested that thick meconium in infants might be associated with poor outcomes compared with thin meconium based on chart reviews. In addition, cell survival assays following the incubation of various meconium concentrations with monolayers of human epithelial and embryonic lung fibroblast cell lines were consistent with the results obtained from chart reviews. Exposure to meconium resulted in the significant release of nitrite from A549 and HEL299 cells. Medicinal agents, including dexamethasone, L-Nω-nitro-arginine methylester (L-NAME), and NS-398 significantly reduced the meconium-induced release of nitrite. These results support the hypothesis that thick meconium is a risk factor for neonates who require resuscitation, and inflammation appears to serve as the primary mechanism for meconium-associated lung injury. A better understanding of the relationship between nitrite and inflammation could result in the development of promising treatments for meconium aspiration syndrome (MAS).

Sildenafil for pulmonary hypertension in neonates: An updated systematic review and meta-analysis

OBJECTIVES

To provide an updated review and meta-analysis on the efficacy and safety of sildenafil for treating persistent pulmonary hypertension in neonates (PPHN).

METHODS

PubMed/Medline, SCOPUS, Cochrane Central Register of Controlled Trials, and Web of Science were searched from the inception of publication to January 2021. The principal outcomes include oxygenation parameters, hemodynamic metrics and echocardiographic measurements, as well as adverse outcomes.

RESULTS

A total of eight studies were included with 216 term and premature neonates with PPHN. Compelling evidence showed the use of sildenafil could improve the prognosis of PPHN neonates, compared with baseline or placebo in neonates with PPHN, and a time-dependent pattern of the improvements can be observed. After 24 h of treatment, the Oxygenation index suggested a steady decrease (SD: -1.80, 95% confidence interval [CI]: -2.92, -0.67) and sildenafil exerted peak effects after 72 h of treatment (SD: -4.02, 95% CI: -5.45, -2.59). No clinically significant side effects were identified. Egger's test and funnel plots of the major outcomes were performed, and the publication bias was not significant.

CONCLUSION

Improvements were shown in oxygenation index, pulmonary arterial pressure, and adverse outcomes after using sildenafil for PPHN in neonates. However, future research with robust longitudinal or randomized controlled design is still needed.

Update on the use of sildenafil in neonatal pulmonary hypertension: a narrative review of the history, current administration, and future directions

Pulmonary hypertension (PH) is a life-threatening syndrome in neonates and has multiple and varied etiologies. However, few clinical studies have systematically evaluated the treatment regimens for this population. Phosphodiesterase (PDE) inhibitors, such as milrinone, tadalafil, dipyridamole, and sildenafil, are the most important regulators of vascular relaxation in the normal pulmonary vascular transition after birth, and these agents are widely used in the treatment of PH. Sildenafil, a representative PDE-5 inhibitor, has an important role as a single mode of therapy. However, the lack of evidence from pharmacokinetic and clinical trials has limited the emergence of standardized treatment regimens for sildenafil. There are also differing opinions among researchers regarding the best route of sildenafil administration. Due to the interindividual variability in the neonatal population, it is worth selecting the most suitable route of sildenafil administration according to the specific conditions of the neonatal population. These may be evaluated using the oxygenation index (OI), pulmonary artery pressure, mean blood pressure, and the serological index. This article reviews the clinical data on the use of sildenafil, focusing on the current and promising alternative routes of administration, which may affect subsequent clinical research in term and preterm neonates.

Roles of inflammation in the natural history of intracranial saccular aneurysms

Aneurysmal subarachnoid hemorrhage is caused by intracranial aneurysm (IA) rupture and results in high rates of mortality and morbidity. Factors contributing to IA generation, growth and rupture can involve genetics, injury, hemodynamics, environmental factors, and inflammation, in which inflammatory factors are believed to play central roles in the whole natural history. Inflammatory reactions that contribute to IA development may involve synthesis of many functional proteins and expression of genes induced by changes of blood flow, external stimuli such as smoking, internal balance such as hormonal status changes, and blood pressure. Meanwhile, inflammatory reactions itself can evoke inflammatory cytokines release and aggregation such as MMPs, MCP-1, TNF-α and ZO-1, directly or indirectly promoting aneurysm growth and rupture. However, the details of these inflammatory reactions and their action on inflammatory chemokines are still unknown. Moreover, some agents with the function of anti-inflammation, lipid-lowering, antihypertension or inflammatory factor inhibition may have the potential benefit to reduce the risk of aneurysm development or rupture in a group of population despite the underlying mechanism remains unclear. Consequently, we reviewed the potential inflammatory responses and their mechanisms contributing to aneurysm development and rupture and sought intervention targets that may prevent IA rupture or generation.

Bronchopulmonary dysplasia requiring tracheostomy: A review of management and outcomes

Bronchopulmonary Dysplasia (BPD) is a pulmonary disease affecting newborns, commonly those with prematurity or low birth weight. Its pathogenesis involves underdevelopment of lung tissue with subsequent limitations in ventilation and oxygenation, resulting in impaired postnatal alveolarization. Despite advances in care with improved survival, BPD remains a prevalent comorbidity of prematurity. In severe cases, management may involve mechanical ventilation via tracheostomy. BPD's demand for multidisciplinary care compounds the challenges in management of this condition. Here, we review existing literature: the history of disease, criteria for diagnosis, pathogenesis, and modes of treatment with a focus on the severe subtype: that which is associated with pulmonary hypertension (PAH) for which tracheostomy is often required to facilitate long-term mechanical ventilation. We review the current recommendations for tracheostomy and decannulation.

Frequent mutation of hypoxia-related genes in persistent pulmonary hypertension of the newborn

Aims

Persistent pulmonary hypertension of the newborn (PPHN) is characterized by sustained high levels of pulmonary vascular resistance after birth with etiology unclear; Arterial blood oxygen saturation of Tibetan newborns at high latitudes is higher than that of Han newborns at low latitudes, suggesting that genetic adaptation may allow sufficient oxygen to confer Tibetan populations with resistance to pulmonary hypertension; We have previously identified genetic factors related to PPHN through candidate gene sequencing; In this study, we first performed whole exome sequencing in PPHN patients to screen for genetic-related factors.

Methods and results

In this two-phase genetic study, we first sequenced the whole exome of 20 Tibetan PPHN patients and compared it with the published genome sequences of 50 healthy high-altitude Tibetanshypoxia-related genes, a total of 166 PPHN-related variants were found, of which 49% were from 43 hypoxia-related genes; considering many studies have shown that the differences in the genetic background between Tibet and Han are characterized by hypoxia-related genetic polymorphisms, so it is necessary to further verify whether the association between hypoxia-related variants and PPHN is independent of high-altitude life. During the validation phase, 237 hypoxia-related genes were sequenced in another 80 Han PPHN patients living in low altitude areas, including genes at the discovery stage and known hypoxia tolerance, of which 413 variants from 127 of these genes were shown to be significantly associated with PPHN.hypoxia-related genes.

Conclusions

Our results indicates that the association of hypoxia-related genes with PPHN does not depend on high-altitude life, at the same time, 21 rare mutations associated with PPHN were also found, including three rare variants of the tubulin tyrosine ligase-like family member 3 gene (TTLL3:p.E317K, TTLL3:p.P777S) and the integrin subunit alpha M gene (ITGAM:p.E1071D). These novel findings provide important information on the genetic basis of PPHN.

Impact of inhaled nitric oxide stewardship programme in a neonatal intensive care unit

AIM

Inhaled nitric oxide (iNO) is the most common, although expensive, therapy for persistent pulmonary hypertension of the newborn and hypoxaemic respiratory failure. With significant variation in iNO delivery practices amongst clinicians, this study aimed to assess the effectiveness of a stewardship programme in increasing clinician compliance with revised, standardised protocols and to measure the impact of compliance on iNO therapy use.

METHODS

Initiation and weaning protocols for iNO were introduced to the neonatal intensive care unit at The Centenary Hospital on 01 March 2016. A 2-year stewardship programme was utilised to assess protocol compliance and the resulting iNO usage impacts were measured. A combined retrospective and prospective study from 1 March 2014 to 28 February 2018 was conducted to compare the patterns of iNO utilisation between the pre- and post-stewardship cohorts.

RESULTS

The pre-stewardship cohort incorporated 18 neonates, receiving 19 iNO treatment episodes, and 18 neonates, receiving 21 iNO treatment episodes, in the post-stewardship cohort. No significant difference in patient demographics was determined. Compliance with the protocols improved from 61% in year 1 to 88% in year 2 of the stewardship programme. Significant reductions were observed in median total hours of iNO therapy per patient (P = 0.0014) and in median time from therapy initiation to initial wean (P < 0.0001). The cost of iNO therapy reduced 52% during the stewardship programme with no increase in adverse patient outcomes.

CONCLUSION

An iNO stewardship programme could be safely implemented in any NICU leading to increased protocol compliance with a beneficial reduction in iNO usage and cost.

Prostanoids and their analogues for the treatment of pulmonary hypertension in neonates

BACKGROUND

Persistent pulmonary hypertension of the newborn (PPHN) is a disease entity that describes a physiology in which there is persistence of increased pulmonary arterial pressure. PPHN is characterised by failure to adapt to a functional postnatal circulation with a fall in pulmonary vascular resistance. PPHN is responsible for impairment in oxygenation and significant neonatal mortality and morbidity. Prostanoids and their analogues may be useful therapeutic interventions due to their pulmonary vasodilatory and immunomodulatory effects.

OBJECTIVES

Primary objective• To determine the efficacy and safety of prostanoids and their analogues (iloprost, treprostinil, and beraprost) in decreasing mortality and the need for extracorporeal membrane oxygenation (ECMO) among neonates with PHSecondary objective• To determine the efficacy and safety of prostanoids and their analogues (iloprost, treprostinil, and beraprost) in decreasing neonatal morbidity (necrotizing enterocolitis (NEC), chronic lung disease (CLD), retinopathy of prematurity (ROP), intraventricular hemorrhage (IVH), periventricular leukomalacia (PVL), length of hospital stay, and duration of mechanical ventilation) and improving neurodevelopmental outcomes among neonates with PHComparisons• Prostanoids and their analogues at any dosage or duration used to treat PPHN versus 'standard treatment without these agents', placebo, or inhaled nitric oxide (iNO) therapy• Prostanoids and their analogues at any dosage or duration used to treat refractory PPHN as an 'add-on' therapy to iNO versus iNO alone SEARCH METHODS: We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2018, Issue 9), MEDLINE via PubMed (1966 to 16 September 2018), Embase (1980 to 16 September 2018), and the Cumulative Index to Nursing and Allied Health Literature (CINAHL; 1982 to 16 September 2018). We also searched clinical trials databases, conference proceedings of the Pediatric Academic Societies (1990 to 16 September 2018), and the reference lists of retrieved articles for randomized controlled trials and quasi-randomized trials. We contacted authors who have published in this field as discerned from the reference lists of identified clinical trials and review authors' personal files.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials evaluating prostanoids or their analogues (at any dose, route of administration, or duration) used in neonates at any gestational age less than 28 days' postnatal age for confirmed or suspected PPHN.

DATA COLLECTION AND ANALYSIS

We used the standard methods of Cochrane Neonatal to conduct a systematic review and to assess the methodological quality of included studies (neonatal.cochrane.org/en/index.html). Three review authors independently assessed the titles and abstracts of studies identified by the search strategy and obtained full-text versions for assessment if necessary. We designed forms for trial inclusion or exclusion and for data extraction. We planned to use the GRADE approach to assess the quality of evidence.

MAIN RESULTS

We did not identify any eligible neonatal trials evaluating prostanoids or their analogues as sole agents in the treatment of PPHN.

AUTHORS' CONCLUSIONS

Implications for practiceCurrently, no evidence shows the use of prostanoids or their analogues as pulmonary vasodilators and sole therapeutic agents for the treatment of PPHN in neonates (age 28 days or less).Implications for researchThe safety and efficacy of different preparations and doses and routes of administration of prostacyclins and their analogues in neonates must be established. Well-designed, adequately powered, randomized, multi-center trials are needed to address the efficacy and safety of prostanoids and their analogues in the treatment of PPHN. These trials should evaluate long-term neurodevelopmental and pulmonary outcomes, in addition to short-term outcomes.

Bronchopulmonary Dysplasia: When the Very Preterm Baby Comes Home

Many infants with severe bronchopulmonary dysplasia (BPD) can be safely managed with oxygen at home. This review covers criteria for home oxygen therapy, monitoring, and weaning protocols for oxygen therapy in the outpatient setting. Although most infants with BPD are weaned from oxygen within a year, they continue to have pulmonary function abnormalities into adolescence. These infants also require evaluation for pulmonary hypertension, systemic hypertension, and a strong focus on adequate nutritional needs for growth.

Sildenafil Exposure in the Neonatal Intensive Care Unit

OBJECTIVE

Pulmonary hypertension causes substantial morbidity and mortality in infants. Although Food and Drug Administration approved to treat pulmonary arterial hypertension in adults, sildenafil is not approved for infants. We sought to describe sildenafil exposure and associated diagnoses and outcomes in infants.

STUDY DESIGN

Retrospective cohort of neonates discharged from more than 300 neonatal intensive care units from 2001 to 2016.

RESULTS

Sildenafil was administered to 1,336/1,161,808 infants (0.11%; 1.1 per 1,000 infants); 0/35,977 received sildenafil in 2001 versus 151/90,544 (0.17%; 1.7 per 1,000 infants) in 2016. Among infants <32 weeks' gestational age (GA) with enough data to determine respiratory outcome, 666/704 (95%) had bronchopulmonary dysplasia (BPD). Among infants ≥32 weeks GA, 248/455 (55%) had BPD and 76/552 (14%) were diagnosed with meconium aspiration. Overall, 209/921 (23%) died prior to discharge.

CONCLUSION

The use of sildenafil has increased since 2001. Exposed infants were commonly diagnosed with BPD. Further studies evaluating dosing, safety, and efficacy of sildenafil are needed.

Sildenafil and Retinopathy of Prematurity in Preterm Infants with Bronchopulmonary Dysplasia

OBJECTIVE

To assess whether sildenafil is associated with worsening retinopathy of prematurity (ROP) in very low birth weight (VLBW) infants (≤1500 g) with bronchopulmonary dysplasia (BPD).

STUDY DESIGN

This retrospective case-control study included VLBW infants admitted to the neonatal intensive care unit between January 1, 2006, and December 31, 2012. Each infant treated with sildenafil was assigned 3 unexposed controls matched for gestational age, birth weight, and BPD diagnosis. Severe ROP was defined as stage ≥3 ROP. Worsening ROP was defined as increased stage of ROP within 8 weeks + 4 days after initiation of sildenafil or matched postmenstrual age.

RESULTS

Twenty-three exposed infants and 69 matched controls met the inclusion criteria for the study (mean birth weight, 715 ± 210 g; mean gestational age, 25 ± 1 weeks). The mean postmenstrual age at sildenafil treatment was 42 ± 8 weeks. Exposed infants had more days of respiratory support (mean, 208 ± 101 days vs 102 ± 33 days; P < .001). Exposed infants had a higher prevalence of severe ROP (26% [6 of 23] vs 7% [5 of 69]; OR, 6.4; 95% CI, 1.2-32.9; P = .026). Five exposed infants and 2 unexposed infants had severe ROP before starting sildenafil and were excluded from the analysis for worsening ROP. The rate of worsening ROP did not differ significantly between exposed infants and unexposed infants ((41% [7 of 17] vs 24% [12 of 51]; OR, 8.4; 95% CI, 0.9-78.6; P = .061).

CONCLUSION

Although sildenafil treatment was not statistically significantly associated with worsening of ROP, the raw difference in ROP rate is concerning. Larger studies are warranted to confirm this finding.

Reduced oxygen concentration for the resuscitation of infants with congenital diaphragmatic hernia

OBJECTIVE

To evaluate whether infants with congenital diaphragmatic hernia (CDH) can be safely resuscitated with a reduced starting fraction of inspired oxygen (FiO₂) of 0.5.

STUDY DESIGN

A retrospective cohort study comparing 68 patients resuscitated with starting FiO₂ 0.5 to 45 historical controls resuscitated with starting FiO₂ 1.0.

RESULTS

Reduced starting FiO₂ had no adverse effect upon survival, duration of intubation, need for ECMO, duration of ECMO, or time to surgery. Furthermore, it produced no increase in complications, adverse neurological events, or neurodevelopmental delay. The need to subsequently increase FiO₂ to 1.0 was associated with female sex, lower gestational age, liver up, lower lung volume-head circumference ratio, decreased survival, a higher incidence of ECMO, longer time to surgery, periventricular leukomalacia, and lower neurodevelopmental motor scores.

CONCLUSION

Starting FiO₂ 0.5 may be safe for the resuscitation of CDH infants. The need to increase FiO₂ to 1.0 during resuscitation is associated with worse outcomes.

A New Perspective on the Nitrate-Phosphodiesterase Type 5 Inhibitor Interaction

BACKGROUND

Nitrates and nitrate-containing compounds are vasodilators used for the treatment of angina and heart failure. Phosphodiesterase type 5 inhibitors used for the treatment of erectile dysfunction are also vasodilators, and when taken together with nitrates, synergistic effects that enhance hypotensive effects may occur. Phosphodiesterase type 5 inhibitors are therefore contraindicated in patients taking organic nitrates.

METHODS AND RESULTS

A literature review was performed to provide a historical overview of different phosphodiesterase type 5 inhibitors and nitrates and their interaction. The pharmacologic characteristics of phosphodiesterase type 5 inhibitors and nitrates are reviewed, and clinical recommendations for treating cardiovascular disease in men taking phosphodiesterase type 5 inhibitors are discussed. Pharmacologic and adverse drug reactions between nitrates and phosphodiesterase type 5 inhibitors are dependent on many variables. Organic nitrates remain an absolute contraindication in men treated with phosphodiesterase type 5 inhibitors. In general, nitrates may be taken 24 hours after the last dose of short-acting phosphodiesterase type 5 inhibitors and 48 hours after the last dose of long-acting phosphodiesterase type 5 inhibitors.

CONCLUSIONS

This literature review determined that the use of phosphodiesterase type 5 inhibitors with nitrates is a contraindication, with the duration between the last dose of phosphodiesterase inhibitor and nitrate use generally varying between short- and long-acting phosphodiesterase type 5 formulations. Patients receiving nitrates who wish to use phosphodiesterase type 5 inhibitors should be educated regarding the interaction and should be evaluated to determine whether nitrate treatment can be discontinued. Further research is needed to determine how soon phosphodiesterase type 5 inhibitors can be restarted after a patient has taken a nitrate and the effect of high and low phosphodiesterase type 5 inhibitor doses on the interaction effect.

CONTEMPORARY STRATEGY OF PULMONARY HYPERTENSION MANAGEMENT IN PEDIATRICS

Pulmonary hypertension (PH) in pediatrics is a polygenic multifactorial condition with extremely adverse prognosis. Selection of optimal management is a severe task. In absence of treatment the mean life duration in children is not higher one year. Last two decades, revolution in approaches to treatment improved the survival of this patients group. Recently, pediatricians and pediatric cardiologists have three drugs groups that act on the main pathogenetic chains of PH: endothelin pathway, nitric oxide pathway and prostacyclin pathway. At the moment, approaches to pediatric PH are based on the data obtained in the trials on adult patients. However, not long ago there were first randomized trials on children performed. The group of authors of current article presents a modern view on the problem of PH in children, and expert recommendations on children management. Class of recommendations and evidence level were set by the data obtained in pediatric population or on adult population with at least 10% of children included. To the strategy, developed by the Russian clinicians, laid the analysis of experience of the pathology treatment in Russian Federation, as the current practics and clinical guidelines on pediatric PH in Europe, and the recent trials published.

Association between oral sildenafil dosing, predicted exposure, and systemic hypotension in hospitalised infants

BACKGROUND

The relationship between sildenafil dosing, exposure, and systemic hypotension in infants is incompletely understood.

OBJECTIVES

The aim of this study was to characterise the relationship between predicted sildenafil exposure and hypotension in hospitalised infants.

METHODS

We extracted information on sildenafil dosing and clinical characteristics from electronic health records of 348 neonatal ICUs from 1997 to 2013, and we predicted drug exposure using a population pharmacokinetic model.

RESULTS

We identified 232 infants receiving sildenafil at a median dose of 3.2 mg/kg/day (2.0, 6.0). The median steady-state area under the concentration-time curve over 24 hours (AUC24,SS) and maximum concentration of sildenafil (Cmax,SS,SIL) were 712 ng×hour/ml (401, 1561) and 129 ng/ml (69, 293), respectively. Systemic hypotension occurred in 9% of the cohort. In multivariable analysis, neither dosing nor exposure were associated with systemic hypotension: odds ratio=0.96 (95% confidence interval: 0.81, 1.14) for sildenafil dose; 0.87 (0.59, 1.28) for AUC24,SS; 1.19 (0.78, 1.82) for Cmax,SS,SIL.

CONCLUSIONS

We found no association between sildenafil dosing or exposure with systemic hypotension. Continued assessment of sildenafil's safety profile in infants is warranted.

The Fetus Can Teach Us: Oxygen and the Pulmonary Vasculature

Neonates suffering from pulmonary hypertension of the newborn (PPHN) continue to represent an important proportion of patients requiring intensive neonatal care, and have an increased risk of morbidity and mortality. The human fetus has evolved to maintain a high pulmonary vascular resistance (PVR) in utero to allow the majority of the fetal circulation to bypass the lungs, which do not participate in gas exchange, towards the low resistance placenta. At birth, oxygen plays a major role in decreasing PVR to enhance pulmonary blood flow and establish the lungs as the organ of gas exchange. The failure of PVR to fall following birth results in PPHN, and oxygen remains the mainstay therapeutic intervention in the management of PPHN. Knowledge gaps on what constitutes the optimal oxygenation target leads to a wide variation in practices, and often leads to excessive oxygen use. Owing to the risk of oxygen toxicity, avoiding hyperoxemia is as important as avoiding hypoxemia in the management of PPHN. Current evidence supports maintaining arterial oxygen tension in the range of 50–80 mm Hg, and oxygen saturation between 90–97% in term infants with hypoxemic respiratory failure. Clinical studies evaluating the optimal oxygenation in the treatment of PPHN will be enthusiastically awaited.

Management of Congenital Diaphragmatic Hernia in Newborn - Paradigm Shift and Ethical Issues

Management of congenital diaphragmatic hernia (CDH) begins soon after it is detected, whether antenatally or postnatally. Assessment of the severity of the condition, associated congenital anomalies, maternal health and related issues, weight of the fetus/baby, mode of delivery, timing of delivery, immediate appropriate management of the baby with CDH at birth, appropriate utilization of available treatment modalities as well as infrastructure of the treating institute have an impact on the outcome of the neonate. Survival without significant long-term/permanent morbidity is considered as good outcome. With advances in antenatal diagnosis, several legal and ethical considerations have cropped up. While on one hand there are proponents of early antenatal diagnosis and medical termination of pregnancy (MTP), on the other hand there are several socio-cultural groups who look upon human life as precious and argue against MTP. There is an ongoing ethical battle between maternal vs. fetal rights; there is no way to put a lid on the controversy whether the mother be allowed to choose in favor of MTP after being aware of the anomalous fetus or, we must attempt to save every fetus irrespective of the antenatal diagnosis of life-threatening anomalies. Notwithstanding, appropriate assessment of the condition, thorough counseling and sound evidence-based decisions could avert ethical dilemma in most cases. This review article provides information about the various choices available in the diagnostic and treatment armamentarium, though it should be kept in mind that the entire spectrum of management strategies may not be universally available.

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.

Oral Sildenafil for Severe Pulmonary Hypertension Developing after Ibuprofen Use in a Neonate

BACKGROUND

Severe pulmonary hypertension may following ibuprofen administration for ductal closure.

CASE CHARACTERISTICS

An extremely preterm infant who developed severe pulmonary hypertension unresponsive to inhaled nitric oxide after ibuprofen administration.

OUTCOME

Pulmonary hypertension reversed after the administration of oral sildenafil, but the infant died due to complications related to bronchopulmonary dysplasia.

MESSAGE

Sildenafil may have a role in treatment of severe pulmonary hypertension after ibuprofen treatment for ductal closure.

Addressing the challenges of phenotyping pediatric pulmonary vascular disease

Pediatric pulmonary vascular disease (PVD) and pulmonary hypertension (PH) represent phenotypically and pathophysiologically diverse disease categories, contributing substantial morbidity and mortality to a complex array of pediatric conditions. Here, we review the multifactorial nature of pediatric PVD, with an emphasis on improved recognition, phenotyping, and endotyping strategies for pediatric PH. Novel tailored approaches to diagnosis and treatment in pediatric PVD, as well as the implications for long-term outcomes, are highlighted.

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

OBJECTIVE

To evaluate the efficacy, safety, and pharmacokinetics of the endothelin receptor antagonist bosentan as adjunctive therapy for neonates with persistent pulmonary hypertension of the newborn (PPHN).

STUDY DESIGN

This was a phase 3, multicenter, randomized, placebo-controlled exploratory trial (FUTURE-4). Eligible patients were >34 weeks gestation, <7 days old, receiving inhaled nitric oxide (iNO) treatment (≥4 hours), and had persistent respiratory failure (oxygenation index [OI] ≥12). After 2:1 randomization, bosentan 2 mg/kg or placebo was given by nasogastric tube twice daily for ≥48 hours and up to 1 day after iNO weaning.

RESULTS

Twenty-one neonates received a study drug (13 bosentan, 8 placebo). Compared with the placebo group, the group treated with bosentan had a higher median baseline OI and greater need for vasoactive agents. One treatment failure (need for extracorporeal membrane oxygenation) occurred in the group treated with bosentan. The time to weaning from iNO or mechanical ventilation was not different between the groups. Bosentan was well tolerated and did not adversely affect systemic blood pressure or hepatic transaminase levels. Anemia and edema were more frequent in patients receiving bosentan. Blood concentrations of bosentan were low and variable on day 1, and achieved steady state on day 5.

CONCLUSION

Adjunctive bosentan was well tolerated, but did not improve oxygenation or other outcomes in our patients with PPHN. This effect may be related to delayed absorption of bosentan on treatment initiation in critically ill neonates or to more severe illness of the neonates who received bosentan.

TRIAL REGISTRATION

ClinicalTrials.gov:NCT01389856.

Lung Circulation

The circulation of the lung is unique both in volume and function. For example, it is the only organ with two circulations: the pulmonary circulation, the main function of which is gas exchange, and the bronchial circulation, a systemic vascular supply that provides oxygenated blood to the walls of the conducting airways, pulmonary arteries and veins. The pulmonary circulation accommodates the entire cardiac output, maintaining high blood flow at low intravascular arterial pressure. As compared with the systemic circulation, pulmonary arteries have thinner walls with much less vascular smooth muscle and a relative lack of basal tone. Factors controlling pulmonary blood flow include vascular structure, gravity, mechanical effects of breathing, and the influence of neural and humoral factors. Pulmonary vascular tone is also altered by hypoxia, which causes pulmonary vasoconstriction. If the hypoxic stimulus persists for a prolonged period, contraction is accompanied by remodeling of the vasculature, resulting in pulmonary hypertension. In addition, genetic and environmental factors can also confer susceptibility to development of pulmonary hypertension. Under normal conditions, the endothelium forms a tight barrier, actively regulating interstitial fluid homeostasis. Infection and inflammation compromise normal barrier homeostasis, resulting in increased permeability and edema formation. This article focuses on reviewing the basics of the lung circulation (pulmonary and bronchial), normal development and transition at birth and vasoregulation. Mechanisms contributing to pathological conditions in the pulmonary circulation, in particular when barrier function is disrupted and during development of pulmonary hypertension, will also be discussed.

Advances in Neonatal Pulmonary Hypertension

Persistent pulmonary hypertension of the newborn (PPHN) is a surprisingly common event in the neonatal intensive care unit, and affects both term and preterm infants. Recent studies have begun to elucidate the maternal, fetal and genetic risk factors that trigger PPHN. There have been numerous therapeutic advances over the last decade. It is now appreciated that oxygen supplementation, particularly for the goal of pulmonary vasodilation, needs to be approached as a therapy that has risks and benefits. Administration of surfactant or inhaled nitric oxide (iNO) therapy at a lower acuity of illness can decrease the risk of extracorporeal membrane oxygenation/death, progression of disease and duration of hospital stay. Milrinone may have specific benefits as an 'inodilator', as prolonged exposure to iNO plus oxygen may activate phosphodiesterase (PDE) 3A. Additionally, sildenafil and hydrocortisone may benefit infants exposed to hyperoxia and oxidative stress. Continued investigation is likely to reveal new therapies such as citrulline and cinaciguat that will enhance NO synthase and soluble guanylate cyclase function. Continued laboratory and clinical investigation will be needed to optimize treatment and improve outcomes.

Pharmacological models and approaches for pathophysiological conditions associated with hypoxia and oxidative stress

Hypoxia is the failure of oxygenation at the tissue level, where the reduced oxygen delivered is not enough to satisfy tissue demands. Metabolic depression is the physiological adaptation associated with reduced oxygen consumption, which evidently does not cause any harm to organs that are exposed to acute and short hypoxic insults. Oxidative stress (OS) refers to the imbalance between the generation of reactive oxygen species (ROS) and the ability of endogenous antioxidant systems to scavenge ROS, where ROS overwhelms the antioxidant capacity. Oxidative stress plays a crucial role in the pathogenesis of diseases related to hypoxia during intrauterine development and postnatal life. Thus, excessive ROS are implicated in the irreversible damage to cell membranes, DNA, and other cellular structures by oxidizing lipids, proteins, and nucleic acids. Here, we describe several pathophysiological conditions and in vivo and ex vivo models developed for the study of hypoxic and oxidative stress injury. We reviewed existing literature on the responses to hypoxia and oxidative stress of the cardiovascular, renal, reproductive, and central nervous systems, and discussed paradigms of chronic and intermittent hypobaric hypoxia. This systematic review is a critical analysis of the advantages in the application of some experimental strategies and their contributions leading to novel pharmacological therapies.

Pediatric Pulmonary Hypertension: Guidelines From the American Heart Association and American Thoracic Society

Pulmonary hypertension is associated with diverse cardiac, pulmonary, and systemic diseases in neonates, infants, and older children and contributes to significant morbidity and mortality. However, current approaches to caring for pediatric patients with pulmonary hypertension have been limited by the lack of consensus guidelines from experts in the field. In a joint effort from the American Heart Association and American Thoracic Society, a panel of experienced clinicians and clinician-scientists was assembled to review the current literature and to make recommendations on the diagnosis, evaluation, and treatment of pediatric pulmonary hypertension. This publication presents the results of extensive literature reviews, discussions, and formal scoring of recommendations for the care of children with pulmonary hypertension.

Trends in treatment and in-hospital mortality for neonates with congenital diaphragmatic hernia

OBJECTIVE

We performed a retrospective cohort study in order to examine recent trends in use of post-partum treatments and in-hospital mortality for congenital diaphragmatic hernia (CDH).

STUDY DESIGN

Included were infants with CDH, born in 2003 to 2012 and hospitalized at ⩽7 days of age at one of 33 United States tertiary referral children's hospitals with extracorporeal membrane oxygenation (ECMO) programs. In-hospital mortality as well as use of ECMO, surfactant and a variety of vasodilators were examined for trends during the study period.

RESULT

Inclusion criteria were met by 3123 infants with CDH. Among 2423 term or near-term infants, odds of death decreased annually for those with isolated or complex CDH. For 700 premature or low-birth weight infants with CDH, in-hospital mortality did not change. Among treatments for CDH, increasing with time in the study cohort were use of milrinone and sildenafil individually, and use of multiple vasodilators during the hospitalization.

CONCLUSION

Survival improved in large subgroups of term or near-term infants with CDH in this 10-year multicenter cohort, temporally associated with increasing use of multiple vasodilators. Use of vasodilators for infants with CDH is increasing despite a lack of evidence supporting efficacy or safety. Prospective research is needed to clarify specific causal effects contributing to improving survival in these infants.

2015 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension

Guidelines summarize and evaluate all available evidence on a particular issue at the time of the writing process, with the aim of assisting health professionals in selecting the best management strategies for an individual patient with a given condition, taking into account the impact on outcome, as well as the risk–benefit ratio of particular diagnostic or therapeutic means. Guidelines and recommendations should help health professionals to make decisions in their daily practice. However, the final decisions concerning an individual patient must be made by the responsible health professional(s) in consultation with the patient and caregiver as appropriate.

Pulmonary hypertension in chronic lung disease of infancy

PURPOSE OF REVIEW

Advances in neonatal care have improved the survival of extremely preterm infants. Chronic lung disease (CLD) is a common complication of prematurity, seen in about a third of preterm babies. Further, pulmonary hypertension complicates the hospital course in about 18% of preterm infants, and the incidence is much higher in infants with established CLD. There is increasing interest in studying this population and understanding the underlying pathobiology behind the development of pulmonary hypertension, which could lead to better identification of at-risk patients as well as improved management strategies and therapeutic targets.

RECENT FINDINGS

Acknowledgement of this growing population of infants with pulmonary hypertension has led to modifications in the current WHO classification of pulmonary hypertension and the establishment of a subcategory for developmental lung disease with pulmonary hypertension. A number of recent publications have evaluated the use of targeted therapies in this population; however, there is a need for large controlled studies, to study the long-term efficacy and safety of these medications.

SUMMARY

This review will discuss the pathobiology of CLD with pulmonary hypertension and enumerate the current diagnostic and treatment modalities used by experts in the field. It will also suggest a diagnosis and management algorithm for infants suspected to have pulmonary hypertension in the newborn unit.

Genetic variation in CYB5R3 is associated with methemoglobin levels in preterm infants receiving nitric oxide therapy

BACKGROUND

In recent years, increasing numbers of preterm infants have been exposed to inhaled nitric oxide (iNO). This population has decreased methemoglobin (MetHb) reductase activity in their erythrocytes, which may increase the risk of MetHb toxicity. We sought to determine if genetic factors are associated with the observed variance in MetHb levels.

METHODS

A population of 127 preterm infants was genotyped for five single-nucleotide polymorphisms (SNPs) in the CYB5A and CYB5R3 genes. iNO dose and levels of MetHb were obtained by chart abstraction. ANOVA was performed to identify genetic associations with MetHb levels.

RESULTS

An association was found between the heterozygous genotype (GA) of rs916321 in the CYB5R3 gene and the mean of the first recorded MetHb levels in Caucasian infants (P = 0.01). This result remained significant after adjustment for the iNO dose (P = 0.009), gender (P = 0.03), multiple gestation (P = 0.03), birth weight (P = 0.02), and gestational age (P = 0.02). No significant associations were found with the other SNPs.

CONCLUSION

We demonstrate a novel genetic association with neonatal MetHb levels. Identification of genetic risk factors may be useful in determining which preterm infants are most at risk of developing MetHb toxicity with the use of iNO.

Pulmonary hypertension management in neonates

The management of pulmonary hypertension is multi-faceted, with therapies directed at supporting cardiovascular and pulmonary function, treating the underlying cause (if feasible), and preventing irreversible remodeling of the pulmonary vasculature. Recently, manipulation of signaling pathways and mediators contained within the pulmonary vascular endothelial cell has become a new target. This article will review the pathophysiology of pulmonary hypertension and the broad principles involved in its management, with specific emphasis on pharmacological therapies directed at the pulmonary vascular endothelium.

Sildenafil Treatment of Infants With Bronchopulmonary Dysplasia-Associated Pulmonary Hypertension

OBJECTIVE

This study had 2 goals: (1) to identify clinical and demographic characteristics associated with sildenafil exposure for infants with bronchopulmonary dysplasia (BPD)-associated pulmonary hypertension (PH); and (2) to characterize hospital-specific treatment frequency, age at first administration, and length of sildenafil treatment.

METHODS

This retrospective cohort study used data from the Pediatric Health Information System to determine variables associated with sildenafil exposure and between-hospital variations in sildenafil utilization patterns. The study included infants with BPD-PH who were discharged between January 1, 2006, and December 31, 2013.

RESULTS

Within 36 US pediatric hospitals, 3720 infants were diagnosed with BPD, of whom 598 (16%) also had a diagnosis of PH (BPD-PH). Among infants with BPD-PH, 104 infants (17%) received sildenafil. The odds for sildenafil treatment among infants born between 25 and 26 weeks' gestational age (GA) and <24 weeks' GA, respectively, were 2.26 (95% confidence interval [CI]: 1.20-4.24) and 3.21 (95% CI: 1.66-6.21) times those of infants born at 27 to 28 weeks' GA. Severity of BPD correlated with sildenafil exposure, with adjusted odds ratios (ORs) for moderate BPD (OR: 3.03 [95% CI: 1.03-8.93]) and severe BPD (OR: 7.56 [95% CI: 2.50-22.88]), compared with mild BPD. Greater rates of sildenafil exposure were observed among small for GA neonates (OR: 2.32 [95% CI: 1.21-4.46]). The proportion of infants with BPD-PH exposed to sildenafil varied according to hospital (median: 15%; 25th-75th percentile: 0%-25%), as did the median duration of therapy (52 days; 25th-75th percentile: 28-109 days).

CONCLUSIONS

The odds of sildenafil treatment were greatest among the most premature infants with severe forms of BPD. The frequency and duration of sildenafil exposure varied markedly according to institution. Patient-centered trials for infants with BPD-PH are needed to develop evidence-based practices.

Antenatal use of bosentan and/or sildenafil attenuates pulmonary features in rats with congenital diaphragmatic hernia

BACKGROUND

Lung hypoplasia, pulmonary persistent hypertension of the newborn and its morphological changes are the main features in congenital diaphragmatic hernia (CDH). This study was undertaken to investigate if antenatal use of sildenafil and/or bosentan attenuates vascular remodeling, promotes branching, and improves alveolarization in experimental nitrofeninduced CDH.

METHODS

Nitrofen (100 mg) was gavage-fed to pregnant rats at post conception day (PCD) 9 to induce CDH. The rats were randomized to 5 groups: 1) control; 2) nitrofen; 3) nitrofen+sildenafil 100 mg/kg per day at PCD 16-20; 4) nitrofen+bosentan 30 mg/kg per day, at PCD 16-20, and 5) nitrofen+bosentan+sildenafil, same doses and administration days. After cesarean delivery, the offsprings were sacrificed. The diaphragmatic defect and pulmonary hypoplasia were identified, and the lungs were dissected. Arterial wall thickness, bronchiolar density and alveolarization were assessed.

RESULTS

The offsprings with CDH were characterized by severe pulmonary hypoplasia (lung weight-to-body weight ratio: 0.0263 [95% confidence interval (CI) 0.0242-0.0278)] in the nitrofen group versus 0.0385 (95% CI 0.0355-0.0424) in the control group (P=0.0001). Pulmonary arterial wall thickness was decreased to 3.0 (95% CI 2.8-3.7) μm in the nitrofen+sildenafil group versus 5.0 (95% CI 4.1-4.9) μm in the nitrofen group (P=0.02). Terminal bronchioles increased to 13.7 (95% CI 10.7-15.2) μm in the nitrofen+bosentan group in contrast to 8.7 (95% CI 7.2-9.4) μm in the nitrofen group (P=0.002). More significant differences (P=0.0001) were seen in terminal bronchioles in the nitrofen+sildenafil+bosentan group than in the nitrofen group [14.0 (95% CI 12.5-15.4) μm versus 8.5 (95% CI 7.1-9.3) μm]. Pulmonary arterial wall thickness was also decreased in the former group.

CONCLUSIONS

In this rat model, antenatal treatment with sildenafil attenuates vascular remodeling. Bosentan promotes the development of terminal bronchioles in nitrofen-induced CDH.

Perinatal nitric oxide therapy prevents adverse effects of perinatal hypoxia on the adult pulmonary circulation

Adverse events in utero are associated with the occurrence of chronic diseases in adulthood. We previously demonstrated in mice that perinatal hypoxia resulted in altered pulmonary circulation in adulthood, with a decreased endothelium-dependent relaxation of pulmonary arteries, associated with long-term alterations in the nitric oxide (NO)/cyclic GMP pathway. The present study investigated whether inhaled NO (iNO) administered simultaneously to perinatal hypoxia could have potential beneficial effects on the adult pulmonary circulation. Indeed, iNO is the therapy of choice in humans presenting neonatal pulmonary hypertension. Long-term effects of neonatal iNO therapy on adult pulmonary circulation have not yet been investigated. Pregnant mice were placed in hypoxia (13% O₂) with simultaneous administration of iNO 5 days before delivery until 5 days after birth. Pups were then raised in normoxia until adulthood. Perinatal iNO administration completely restored acetylcholine-induced relaxation, as well as endothelial nitric oxide synthase protein content, in isolated pulmonary arteries of adult mice born in hypoxia. Right ventricular hypertrophy observed in old mice born in hypoxia compared to controls was also prevented by perinatal iNO treatment. Therefore, simultaneous administration of iNO during perinatal hypoxic exposure seems able to prevent adverse effects of perinatal hypoxia on the adult pulmonary circulation.

Subcutaneous treprostinil for pulmonary hypertension in chronic lung disease of infancy

Pulmonary arterial hypertension (PAH) associated with chronic lung disease of infancy can be a life-threatening disease affecting an increasing number of former premature infants. There is a need for improved delivery of targeted PAH therapies for this subgroup of patients who have severe and persistent PAH despite standard respiratory care for chronic lung disease. Currently infants who have severe PAH despite oral or inhaled therapy receive continuous intravenous prostanoid therapy (mostly epoprostenol), which is complicated because of the need for central venous access and associated catheter-related complications. We present a series of 5 infants who were successfully treated with a continuous infusion of subcutaneous treprostinil, which is a longer-acting prostanoid with similar hemodynamic effects. There were improvements in echocardiographic assessment of right ventricular function and estimated pulmonary hypertension, and in respiratory support required within weeks of therapy. Unlike commonly in adults, these 5 infants had no instances of severe site erythema, bleeding, bruising, or infection. In our experience with 5 former extremely preterm infants who had PAH associated with chronic lung disease, subcutaneous treprostinil was safe, efficacious, and well tolerated. We believe that subcutaneous treprostinil can be beneficial in a select group of former premature infants who have chronic lung disease and severe pulmonary arterial hypertension who have not responded adequately to conservative therapies.

Sildenafil for pulmonary hypertension complicating bronchopulmonary dysplasia

Sildenafil, a phospohodiesterase-5 inhibitor, is widely used to treat pulmonary hypertension in infants with bronchopulmonary dysplasia despite a lack of evidence to support either safety or efficacy and US FDA advice against its use.

Pulmonary Hypertension in Preterm Infants with Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD), the chronic lung disease of prematurity, is a significant contributor to perinatal morbidity and mortality. Premature birth disrupts pulmonary vascular growth and initiates a cascade of events that result in impaired gas exchange, abnormal vasoreactivity, and pulmonary vascular remodeling that may ultimately lead to pulmonary hypertension (PH). Even infants who appear to have mild BPD suffer from varying degrees of pulmonary vascular disease (PVD). Although recent studies have enhanced our understanding of the pathobiology of PVD and PH in BPD, much remains unknown with respect to how PH should be properly defined, as well as the most accurate methods for the diagnosis and treatment of PH in infants with BPD. This article will provide neonatologists and primary care providers, as well as pediatric cardiologists and pulmonologists, with a review of the pathophysiology of PH in preterm infants with BPD and a summary of current clinical recommendations for managing PH in this population.

Peroxisome proliferator activated receptor-γ-Rho-kinase interactions contribute to vascular remodeling after chronic intrauterine pulmonary hypertension

Peroxisome proliferator-activated receptor-γ (PPARγ) and Rho-kinase (ROCK) regulate smooth muscle cell (SMC) proliferation and contribute to vascular remodeling in adult pulmonary hypertension. Whether these pathways interact to contribute to the development of vascular remodeling in persistent pulmonary hypertension of the newborn (PPHN) remains unknown. We hypothesized that ROCK-PPARγ interactions increase SMC proliferation resulting in vascular remodeling in experimental PPHN. Pulmonary artery SMCs (PASMCs) were harvested from fetal sheep after partial ligation of the ductus arteriosus in utero (PPHN) and controls. Cell counts were performed daily for 5 days with or without PPARγ agonists and ROCK inhibition. PPARγ and ROCK protein expression/activity were measured by Western blot in normal and PPHN PASMCs. We assessed PPARγ-ROCK interactions by studying the effect of ROCK activation on PPARγ activity and PPARγ inhibition (siRNA) on ROCK activity and PASMC proliferation. At baseline, PPHN PASMC cell number was increased by 38% above controls on day 5. ROCK protein expression/activity were increased by 25 and 34% and PPARγ protein/activity decreased by 40 and 50% in PPHN PASMC. ROCK inhibition and PPARγ activation restored PPHN PASMC growth to normal values. ROCK inhibition increased PPARγ activity by 50% in PPHN PASMC, restoring PPARγ activity to normal. In normal PASMCs, ROCK activation decreased PPARγ activity and PPARγ inhibition increased ROCK activity and cell proliferation, resulting in a PPHN hyperproliferative PASMC phenotype. PPARγ-ROCK interactions regulate SMC proliferation and contribute to increased PPHN PASMC proliferation and vascular remodeling in PPHN. Restoring normal PPARγ-ROCK signaling may prevent vascular remodeling and improve outcomes in PPHN.