Effect of early adjunctive use of oral sildenafil and inhaled nitric oxide on the outcome of pulmonary hypertension in newborn infants. A feasibility study

Vasodilators for persistent pulmonary hypertension of the newborn: A network meta-analysis

OBJECTIVES

To compare the efficacy and safety of different vasodilators in the treatment of persistent pulmonary hypertension of the newborn (PPHN) by a Bayesian network meta-analysis.

METHODS

We searched databases (Cochrane, PubMed, Embase, and Web of Science) from January, 1990 up to December, 2023. Randomized controlled trials on the use of vasodilators in the treatment of PPHN. We extracted details of population, intervention, and outcome indicators. R and STATA software were used for data analysis. Sixteen articles were included, encompassing 776 neonates with PPHN. Among them, 12 articles were included in the quantitative analysis. The vasodilators included Sildenafil, Bosentan, Milrinone, Magnesium, Adenosine, and Tadalafil.

RESULTS

The Bayesian network meta-analysis results suggested that compared to placebo, Milrinone [OR = 0.125, 95% CI (0.0261, 0.562)], Sildenafil [OR = 0.144, 95% CI (0.0428, 0.420)], and Sildenafil_Milrinone [OR = 0.0575, 95% CI (0.00736, 0.364)] reduced the mortality, but the difference among the three was not significant. There was also no significant difference in the incidence of hypotension, the duration of mechanical ventilation, and the use of extracorporeal membrane oxygenation among the vasodilators. Compared to Bosentan, Adenosine was more effective in reducing the oxygenation index [MD = -12.78, 95% CI (-25.56, -0.03)], and Magnesium was less effective in reducing the oxygenation index than Sildenafil [MD = 5.19, 95% CI (1.23, 9.2)].

CONCLUSIONS

Milrinone, Sildenafil, and Sildenafil_Milrinone reduced the mortality of neonates with PPHN. More clinical trials are needed to verify the efficacy and safety of vasodilators in the treatment of PPHN.

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.

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.

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.

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.

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.

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.

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.

Oral drugs used to treat persistent pulmonary hypertension of the newborn

Introduction:Persistent Pulmonary Hypertension of the Newborn (PPHN) is a life-threatening neonatal condition, mostly treated with inhaled nitric oxide (iNO), intravenous prostaglandins, oral bosentan, sildenafil and tadalafil. However, the utility of non-oral agents is limited in PPHN for their side effects and inconvenient deliveries. Therefore, oral agents such as bosentan, sildenafil and tadalafil are becoming appealing for their satisfactory efficacy, easy mode of administration and acceptable side effects. Areas covered: We conducted a comprehensive search on Pubmed, Scopus, Web of Sciences concerning the use of bosentan, sildenafil and tadalafil to treat PPHN and summarized their efficacy, safety and pharmacokinetics. Expert opinion: Current randomized controlled trials (RCTs) have demonstrated the favorable responses and tolerable side effects of bosentan and sildenafil. Nevertheless, those RCTs are small and only one study has described the pharmacokinetics of sildenafil in neonates. Accordingly, bosentan, sildenafil and tadalafil remain off-label in clinical use. More well-designed RCTs with large samples and long-term follow-up and pharmacometrics studies are needed to demonstrate the efficacy, safety and pharmacokinetics of bosentan, sildenafil and tadalafil in PPHN.

Safety and effect of sildenafil on treating paediatric pulmonary arterial hypertension: a meta-analysis on the randomised controlled trials

BACKGROUND

Efficacy of sildenafil in treating paediatric pulmonary arterial hypertension is controversial. This systematic review aimed to explore the safety and effect of sildenafil on treating paediatric pulmonary arterial hypertension (PAH) through meta-analysis.

METHODS AND RESULTS

In this study, the electronic databases, including the Cochran Library database, EMBASE, and MEDLINE were systemically retrieved to identify the related randomised controlled trials (RCTs). Two reviewers had independently completed study selection, data collection, and assessment of the bias risk. Amongst 938 articles researched according to our retrieval strategy, 15 papers that involved 673 cases had been screened. Relative to control group, the sildenafil group had markedly reduced mortality (RR = 0.25, 95% CI: 0.12-0.51; p < 0.0001), but difference within the mortality was not statistically significant between high- and low-dose sildenafil groups (p = 0.152). Nonetheless, difference of the mean pulmonary arterial pressure between sildenafil as well as control group was of no statistical significance. Differences in the length of hospital stay and the incidences of pulmonary hypertensive crisis between children with PAH and controls were of no statistical significance. However, the summary estimate favoured that sildenafil reduced the duration of mechanical ventilation time, as well as the length of ICU stay and inotropic support.

CONCLUSIONS

Sildenafil therapy reduces the mortality of PAH patients, but its effects on the haemodynamic outcomes and other clinical outcomes are still unclear.

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.

Pharmacokinetic modeling of intravenous sildenafil in newborns with congenital diaphragmatic hernia

PURPOSE

We developed a pharmacokinetic model of intravenous sildenafil in newborns with congenital diaphragmatic hernia (CDH) to achieve a target plasma concentration of over 50 μg/l.

METHODS

Twenty-three CDH newborns with pulmonary hypertension (64 blood samples) received intravenous sildenafil. Patients received a loading dose of 0.35 mg/kg (IQR 0.16 mg/kg) for 3 h, followed by a continuous infusion of 1.5 mg/kg/day (IQR 0.1 mg/kg/day). For model development, non-linear mixed modeling was used. Inter-individual variability (IIV) and inter-occasion variability were tested. Demographic and laboratory parameters were evaluated as covariates. Normalized prediction distribution errors (NPDE) and visual predictive check (VPC) were used for model validation.

RESULTS

A two-compartment disposition model of sildenafil and a one-compartment disposition model of desmethyl sildenafil (DMS) was observed with IIV in sildenafil and DMS clearance and volume of distribution of sildenafil. NPDE and VPC revealed adequate predictability. Only postnatal age increased sildenafil clearance. This was partly compensated by a higher DMS concentration, which also has a therapeutic effect. In this small group of patients, sildenafil was tolerated well.

CONCLUSIONS

This model for sildenafil in CDH patients shows that concentration-targeted sildenafil dosing of 0.4 mg/kg in 3 h, followed by 1.6 mg/kg/day continuous infusion achieves appropriate sildenafil plasma levels.

Use of sildenafil in an infant with persistent pulmonary hypertension secondary to lung and renal hypoplasia - a case report

Background

Premature preterm rupture of membranes (PPROM) is reported to be associated with high rates of neonatal mortality and morbidity. Sildenafil has been used in infants with persistent pulmonary hypertension of newborn (PPHN) due to congenital diaphragmatic hernia (CDH) and bronchopulmonary dysplasia (BPD). Recently, Sildenafil has been evaluated as an alternative or adjunctive pulmonary vasodilator. This case report illustrates the use of early sildenafil for PPHN and right ventricular dysfunction in an unusual setting of lung and renal hypoplasia.

Case presentation

A male infant was born at 37 weeks with a birth weight of 2840 g. Rupture of membranes developed at approximately 24 weeks of gestational age (GA). Bilateral small kidneys (< 2 standard deviations below average) were detected on ultrasound (US) examination at 30 weeks of gestation. The baby developed pneumothorax and pulmonary hypertensive crisis towards the end of the first day. An echocardiogram showed a dilated right ventricle, moderate right ventricular systolic dysfunction, hypoplastic pulmonary arteries and a large patent ductus arteriosus with bidirectional flow. The patient was sedated, paralyzed, and inhaled nitric oxide was administered to decrease the pulmonary resistance. In anticipation of persistent pulmonary hypertension due to the hypoplastic lungs and small calibre of pulmonary arteries, sildenafil was started on day of life (DOL) 5 at a dosage of 0.25 mg/kg/dose Q8H and gradually increased to 2 mg/kg/dose Q8H on DOL 9. The patient was finally extubated on DOL 7 and weaned off of non-invasive respiratory support on DOL 26. Sildenafil was gradually weaned beginning on DOL 21 and discontinued on DOL 48. Repeat echocardiogram assessment at 3 months showed complete resolution of PHT and right ventricular dilatation.

Conclusions

We describe the early use of sildenafil in treating pulmonary hypertension associated with lung and renal hypoplasia in a non-CDH patient. Following this treatment the patient made a full recovery from right ventricular dysfunction.

Correlation between changes in brain natriuretic peptide and echocardiographic features in persistent pulmonary hypertension of newborn

Objective: To investigate the correlation between changes in brain natriuretic peptide (BNP) and echocardiographic features in persistent pulmonary hypertension of newborn (PPHN).Patients and methods: A total of 76 patients with PPHN treated in our hospital from March 2017 to February 2018 were divided into mild group (n = 33), moderate group (n = 22) and severe group (n = 21) according to the pulmonary arterial systolic pressure, and they were compared with 30 normal newborns (control group) during the same period. All newborns underwent echocardiography, the BNP level was detected, and the correlation between echocardiographic features and BNP changes was analyzed.Results: The BNP level in control group was significantly lower than those in PPHN groups, and it was constantly increased from mild group to severe group (p<.05). There were no significant differences in left atrial diameter (LA) and left ventricular diameter (LV) among groups (p>.05), while there were significant differences in the right atrial diameter (RA), right ventricular diameter (RV) and peak velocity of tricuspid regurgitation (VTR) (p<.05). BNP had no correlations with LA and LV (p>.05), but had positive correlations with RA, RV and VTR (r = 0.527, 0.503 and 0.524, p<.05).Conclusion: The BNP level of patients with PPHN increases with the increasing severity of disease. BNP has close correlations with echocardiographic features of neonatal patients. Predicting the BNP changes via echocardiography is of certain value in guiding the clinical treatment.

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 for pulmonary hypertension in neonates

BACKGROUND

Persistent pulmonary hypertension in the neonate (PPHN) is associated with high mortality. Currently, the therapeutic mainstay for PPHN consists of assisted ventilation and administration of inhaled nitric oxide (iNO). However, nitric oxide is costly, and its use may not be appropriate in resource-poor settings. Approximately 30% of patients fail to respond to iNO. High concentrations of phosphodiesterases in the pulmonary vasculature have led to the use of phosphodiesterase inhibitors such as sildenafil or milrinone.

OBJECTIVES

To assess the efficacy and safety of sildenafil for treatment of pulmonary hypertension in neonates.

SEARCH METHODS

We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 3), MEDLINE via PubMed (1966 to 18 April 2017), Embase (1980 to 18 April 2017), and the Cumulative Index to Nursing and Allied Health Literature (CINAHL; 1982 to 18 April 2017). We searched clinical trials databases, conference proceedings, and reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials.

SELECTION CRITERIA

We included randomised and quasi-randomised controlled trials of sildenafil compared with placebo or other pulmonary vasodilators, irrespective of dose, route, and duration of administration, in neonates with pulmonary hypertension, if investigators reported any of the prespecified outcomes.

DATA COLLECTION AND ANALYSIS

We assessed the methodological quality of trials regarding how bias was minimised at study entry, during study intervention, and at outcomes measurement. We extracted data on relevant outcomes; we estimated the effect size and reported it as risk ratio (RR), risk difference (RD), or mean difference (MD), as appropriate. We applied the I2 test of heterogeneity and used GRADE to assess the quality of evidence.

MAIN RESULTS

For this update, we identified two additional studies, for a total of five eligible trials that enrolled 166 infants. The methodological quality of these studies ranged from low to high risk of bias. Three studies were performed in resource-limited settings, where iNO and high-frequency ventilation were not available at the time of the study. One study compared sildenafil versus active controls, and another study evaluated sildenafil as adjuvant therapy to iNO. When comparing sildenafil with placebo, investigators noted significant reduction in mortality in the sildenafil alone group (three studies, 77 participants; typical RR 0.20, 95% confidence interval (CI) 0.07 to 0.56; I2 = 0% - none; typical RR -0.36, 95% CI -0.53 to -0.18; number needed to treat for an additional beneficial outcome 3, 95% CI 2 to 6; I2 = 39% - low). Trials reported no significant differences in mortality upon comparison of the sildenafil group versus the active control group (one study, 65 participants; typical RR 0.55, 95% CI 0.05 to 5.75), or when iNO was administered to both groups (one study, 24 participants; typical RR 1.27, 95% CI 0.26 to 6.28). Physiological parameters of oxygenation (oxygenation index, partial pressure of oxygen in arterial blood (PaO2)) suggested steady improvement after the first dose of sildenafil. None of the included trials identified any clinically important side effects. We rated the quality of evidence as low to very low owing to imprecision related to small sample size and unclear methodological features.

AUTHORS' CONCLUSIONS

Sildenafil used for treatment of pulmonary hypertension has potential for reducing mortality and improving oxygenation in neonates, especially in resource-limited settings where iNO is not available. However, large-scale randomised trials comparing sildenafil versus active controls (other pulmonary vasodilators) and providing follow-up for survivors are needed to assess the comparative effectiveness and long-term safety of sildenafil versus other pulmonary vasodilators.