Targeted Therapy for Pulmonary Hypertension in Premature Infants

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.

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.

Case report: High-dose epoprostenol therapy in pediatric patients with pulmonary hypertension and developmental lung disease

Pulmonary hypertension (PH) with developmental lung disease is a life-threatening disease and accounts for 10%-12% of pediatric PH patients. Administration of specific pulmonary vasodilators to pediatric PH patients has brought about improvement of their long-term prognosis. Intravenous epoprostenol therapy is a gold standard therapy for severe idiopathic pulmonary arterial hypertension (IPAH), but there are few reports demonstrating the efficacy of epoprostenol for pediatric PH patients with developmental lung disease, especially when treating with high doses of epoprostenol. Two cases of pediatric PH patients with alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) and congenital diaphragmatic hernia (CDH) with bronchopulmonary dysplasia (BPD), respectively, treated with epoprostenol above 100 ng/kg/min are presented. In these two cases, severe PH was improved significantly by an aggressive increase of the epoprostenol infusion rate with administration of oral pulmonary vasodilators and appropriate respiratory management, without any significant adverse effects. High-dose epoprostenol therapy may be one of the therapeutic options in pediatric PH patients with developmental lung disease.

The Clinical and Cost Utility of Cardiac Catheterizations in Infants with Bronchopulmonary Dysplasia

OBJECTIVE

To evaluate the cost-utility of catheterization-obligate treatment in preterm infants with pulmonary hypertension, as compared with empiric initiation of sildenafil based on echocardiographic findings alone.

STUDY DESIGN

A Markov state transition model was constructed to simulate the clinical scenario of a preterm infant with echocardiographic evidence of pulmonary hypertension associated with bronchopulmonary dysplasia (BPD) and without congenital heart disease under consideration for the initiation of pulmonary vasodilator therapy via one of two modeled treatment strategies-empiric or catheterization-obligate. Transitional probabilities, costs and utilities were extracted from the literature. Forecast quality-adjusted life-years was the metric for strategy effectiveness. Sensitivity analyses for each variable were performed. A 1000-patient Monte Carlo microsimulation was used to test the durability of our findings.

RESULTS

The catheterization-obligate strategy resulted in an increased cost of $10 778 and 0.02 fewer quality-adjusted life-years compared with the empiric treatment strategy. Empiric treatment remained the more cost-effective paradigm across all scenarios modeled through one-way sensitivity analyses and the Monte Carlo microsimulation (cost-effective in 98% of cases).

CONCLUSIONS

Empiric treatment with sildenafil in infants with pulmonary hypertension associated with BPD is a superior strategy with both decreased costs and increased effectiveness when compared with catheterization-obligate treatment. These findings suggest that foregoing catheterization before the initiation of sildenafil is a reasonable strategy in preterm infants with uncomplicated pulmonary hypertension associated with BPD.

Pharmacotherapy in Bronchopulmonary Dysplasia: What Is the Evidence?

Bronchopulmonary Dysplasia (BPD) is a multifactorial disease affecting over 35% of extremely preterm infants born each year. Despite the advances made in understanding the pathogenesis of this disease over the last five decades, BPD remains one of the major causes of morbidity and mortality in this population, and the incidence of the disease increases with decreasing gestational age. As inflammation is one of the key drivers in the pathogenesis, it has been targeted by majority of pharmacological and non-pharmacological methods to prevent BPD. Most extremely premature infants receive a myriad of medications during their stay in the neonatal intensive care unit in an effort to prevent or manage BPD, with corticosteroids, caffeine, and diuretics being the most commonly used medications. However, there is no consensus regarding their use and benefits in this population. This review summarizes the available literature regarding these medications and aims to provide neonatologists and neonatal providers with evidence-based recommendations.

Life-threatening bronchopulmonary dysplasia: a British Paediatric Surveillance Unit Study

OBJECTIVES

To assess the minimum incidence of life-threatening bronchopulmonary dysplasia (BPD), defined as need for positive pressure respiratory support or pulmonary vasodilators at 38 weeks corrected gestational age (CGA), in infants born <32 weeks gestation in the UK and Ireland; and to describe patient characteristics, management and outcomes to 1 year.

METHODS

Prospective national surveillance study performed via the British Paediatric Surveillance Unit from June 2017 to July 2018. Data were collected in a series of three questionnaires from notification to 1 year of age.

RESULTS

153 notifications met the case definition, giving a minimum incidence of 13.9 (95% CI: 11.8 to 16.3) per 1000 live births <32 weeks' gestation. Median gestation was 26.1 (IQR 24.6-28) weeks, and birth weight 730 g (IQR 620-910 g). More affected infants were male (95 of 153, 62%; p<0.05). Detailed management and outcome data were provided for 94 infants. Fifteen died at median age 159 days (IQR 105-182) or 49.6 weeks CGA (IQR 43-53). Median age last receiving invasive ventilation was 50 days (IQR 22-98) and total duration of pressure support for surviving infants 103 (IQR 87-134) days. Fifty-seven (60.6%) received postnatal steroids and 22 (23.4%) pulmonary vasodilators. Death (16%) and/or major neurodevelopmental impairment (37.3%) or long-term ventilation (23.4%) were significantly associated with need for invasive ventilation near term and pulmonary hypertension.

CONCLUSIONS

This definition of life-threatening BPD identified an extremely high-risk subgroup, associated with serious morbidity and mortality. Wide variability in management was demonstrated, and future prospective study, particularly in key areas of postnatal steroid use and pulmonary hypertension management, is required.

Neonatal and Postneonatal Pulmonary Hypertension

During transition at birth with ventilation of the lungs, pulmonary vascular resistance (PVR) decreases from high fetal values, leading to an 8 to 10-fold increase in pulmonary blood flow (Qp). In some infants, this transition does not occur, resulting in pulmonary hypertension (PH). In infants, PH can present as: (a) primary PH in term neonates (idiopathic), (b) PH secondary to lung disease or hypoplasia in term infants, (c) acute PH in preterm infants with respiratory distress syndrome (RDS), (d) chronic PH with bronchopulmonary dysplasia (BPD) in preterm infants and (e) post-neonatal PH. A hemodynamically significant patent ductus arteriosus (PDA) can exacerbate PH in preterm infants due to increased Qp. Pulmonary vein stenosis (PVS) can complicate BPD with PH. Diagnosis of PH is based on clinical features, echocardiography and, in some intractable cases, cardiac catheterization. Therapy of PH includes oxygen, invasive or non-invasive ventilation, correction of acidosis, surfactant and selective and non-selective pulmonary vasodilators such as inhaled nitric oxide and sildenafil, respectively. Early closure of a hemodynamically significant PDA has the potential to limit pulmonary vascular remodeling associated with BPD and PH. The role of thiamine in pathogenesis of PH is also discussed with the recent increase in thiamine-responsive acute pulmonary hypertension in early infancy. Recognition and prompt therapy of PH can prevent right ventricular dysfunction, uncoupling and failure.

Pulmonary vasodilator therapy in persistent pulmonary hypertension of the newborn

A review of the physiology of persistent pulmonary hypertension of the newborn is provided, followed by a critical review of many of the agents that have been employed to treat this condition. In addition, the authors speculate on what type of pharmacologic therapy may prove useful in the future.