Frontiers in pulmonary hypertension in infants and children with bronchopulmonary dysplasia

Rho-kinase inhibitor prevents bleomycin-induced injury in neonatal rats independent of effects on lung inflammation

Bleomycin-induced lung injury is characterized in the neonatal rat by inflammation dominated by neutrophils and macrophages, inhibited distal airway and vascular development, and pulmonary hypertension, similar to human infants with severe bronchopulmonary dysplasia. Rho-kinase (ROCK) is known to mediate lung injury in adult animals via stimulatory effects on inflammation. We therefore hypothesized that inhibition of ROCK may ameliorate bleomycin-induced lung injury in the neonatal rat. Pups received daily intraperitoneal bleomycin or saline from Postnatal Days 1 through 14 with or without Y-27632, a ROCK inhibitor. Treatment with Y-27632 prevented bleomycin-induced pulmonary hypertension, as evidenced by normalized pulmonary vascular resistance, decreased right-ventricular hypertrophy, and attenuated remodeling of pulmonary resistance arteries. Bleomycin-induced changes in distal lung architecture, including septal thinning, inhibited alveolarization, and decreased numbers of peripheral arteries and capillaries, were partially or completely normalized by Y-27632. Treatment with Y-27632 or a CXCR2 antagonist, SB265610, also abrogated tissue neutrophil influx, while having no effect on macrophages. However, treatment with SB265610 did not prevent bleomycin-induced lung injury. Lung content of angiostatic thrombospondin-1 (TSP1) was increased significantly in the lungs of bleomycin-exposed animals, and was completely attenuated by treatment with Y-27632. Thrombin-stimulated TSP1 production by primary cultured rat pulmonary artery endothelial cells was also attenuated by Y-27632. Taken together, our findings suggest a preventive effect of Y-27632 on bleomycin-mediated injury by a mechanism unrelated to inflammatory cells. Our data suggest that improvements in lung morphology may have been related to indirect stimulatory effects on angiogenesis via down-regulation of TSP1.

B-type natriuretic peptide and mortality in extremely low birth weight infants with pulmonary hypertension: a retrospective cohort analysis

Background

B-type natriuretic peptide (BNP) is a strong predictor of mortality in adult patients with various forms of pulmonary hypertension (PH) and may be a strong prognostic marker in extremely low birth weight (ELBW) infants with bronchopulmonary dysplasia (BPD) associated PH as well. We sought to assess the relationship between BNP levels and all-cause mortality in a cohort of ELBW infants with BPD and PH.

Methods

We retrospectively identified ELBW infants with BPD and PH who had serum BNP levels measured as part of routine clinical care in the neonatal intensive care unit. Peak serum BNP levels were correlated with survival to discharge or death.

Results

Thirty-six ELBW infants (mean gestational age 26.0 ± 1.9 weeks and mean birth weight 740 ± 290 grams) with BPD and PH had available survival data and had serum BNP levels measured. Peak BNP level was significantly lower among infants who survived than among those who died (128 pg/ml, [IQR 23 to 463] vs. 997 pg/ml, [IQR 278 to 1770], P < 0.004). On multivariate Cox proportional hazard analysis, BNP predicted survival independent of age, gender, and BPD severity. Area under receiver operator characteristic analysis identified a BNP value of 220 pg/ml to have 90% sensitivity and 65% specificity in predicting mortality.

Conclusion

BNP estimation may be useful as a prognostic marker of all-cause mortality in ELBW infants with BPD associated PH.

Secondhand smoke exposure in preterm infants with bronchopulmonary dysplasia

OBJECTIVES

Preterm infants and children with bronchopulmonary dysplasia (BPD) often experience significant respiratory morbidities during the first two years of life. Second hand smoke (SHS) has been demonstrated to lead to respiratory morbidities in the general population. The objectives of this study were to assess the prevalence/impact of SHS on preterm infants and children with BPD.

METHODS

Subjects (n = 352) were recruited from the Johns Hopkins BPD outpatient clinic between January 2008 and August 2012. Second hand smoke exposure and respiratory morbidities were assessed through questionnaires and chart review.

RESULTS

Twenty-eight percent of preterm infants with BPD were exposed to SHS in the home setting, despite having significant lung disease. SHS was associated with multiple measures of socio-economic status, including lower household income (P < 0.001), lower caregiver education level (P = 0.013), and having public versus private insurance (P = 0.002). We found no difference in acute care use or chronic symptoms with SHS exposure. We observed trends that preterm infants who were exposed to SHS were more likely to be prescribed inhaled corticosteroids (P = 0.054) and were weaned off of supplemental oxygen over 2 months later (P = 0.13) than infants not exposed to SHS.

CONCLUSION

SHS exposure in preterm infants with BPD is common, even in those receiving supplemental oxygen and respiratory medications. Although there were no associations between respiratory outcomes and self-reported SHS exposure, trends toward increased use of inhaled steroids and a longer duration of supplemental oxygen use were noted. Further work is needed to determine more accurate means of assessing SHS risk in this vulnerable population.

Pulmonary hypertension in bronchopulmonary dysplasia: clinical findings, cardiovascular anomalies and outcomes

OBJECTIVE

Pulmonary hypertension (PH) worsens the prognosis of bronchopulmonary dysplasia (BPD). The following items have not been fully established for PH in BPD: clinical characterization, incidence of cardiovascular anomalies (CVAs), response to PH treatment, and outcome.

STUDY DESIGN

A review of clinical records, computed tomography (CT) images and catheterization data of 36 patients with PH-BPD referred to our PH Unit (March 2006 to December 2011) was performed. Twenty-nine patients without major congenital heart defects and with complete follow-up data were included.

RESULTS

The diagnosis of PH was made at a median age of 4.5 months (IQR 2.4-7.8), with an echocardiography estimated median right ventricular pressure/systemic pressure ratio of 70% (IQR 60-80%). CT scanning was performed in 21 patients and catheterization in 14 patients. CVAs were found in 19 patients (65.5%): aortopulmonary collaterals (n = 9), pulmonary vein stenosis (n = 7), ASD (n = 4), and PDA (n = 9). Hemodynamic data: PVRI 4.3 UW m(2) (2.7-7); PVRI/SVRI 0.44 (0.32-0.8); and transpulmonary gradient 28 mmHg (19-40). At a median follow-up of 35 months (IQR 21-91), 6 patients had undergone shunts closure, 22 received specific PH drugs, 3 spontaneously improved of their PH, and 8 (26%) had died.

CONCLUSION

PH in BPD is not always a transient condition; it can be diagnosed at later stages and can have a protracted course. The incidence of associated CVAs is high. Prompt diagnosis, detection, and treatment of CVAs, and specific drug therapy can improve the outcome in these patients, although the mortality rate remains high.

Bronchopulmonary dysplasia: the earliest and perhaps the longest lasting obstructive lung disease in humans

Bronchopulmonary dysplasia (BPD) is one of the most important sequelae of premature birth and the most common form of chronic lung disease of infancy. From a clinical standpoint BPD subjects are characterized by recurrent respiratory symptoms, which are very frequent during the first years of life and, although becoming less severe as children grow up, they remain more common than in term-born controls throughout childhood, adolescence and into adulthood. From a functional point of view BPD subjects show a significant airflow limitation that persists during adolescence and adulthood and they may experience an earlier and steeper decline in lung function during adulthood. Interestingly, patients born prematurely but not developing BPD usually fare better, but they too have airflow limitations during childhood and later on, suggesting that also prematurity per se has life-long detrimental effects on pulmonary function. For the time being, little is known about the presence and nature of pathological mechanisms underlying the clinical and functional picture presented by BPD survivors. Nonetheless, recent data suggest the presence of persistent neutrophilic airway inflammation and oxidative stress and it has been suggested that BPD may be sustained in the long term by inflammatory pathogenic mechanisms similar to those underlying COPD. This hypothesis is intriguing but more pathological data are needed. A better understanding of these pathogenetic mechanisms, in fact, may be able to orient the development of novel targeted therapies or prevention strategies to improve the overall respiratory health of BPD patients.

Health-care utilization and respiratory morbidities in preterm infants with pulmonary hypertension

OBJECTIVE

To assess health-care utilization and risk of respiratory morbidities in preterm infants with bronchopulmonary dysplasia (BPD) and pulmonary hypertension (PH).

STUDY DESIGN

Retrospective data were obtained from subjects (n=109) attending a BPD clinic. Subjects were stratified by the presence or absence of PH before and after 2 months of age. Analytic methods included t-tests, χ(2) tests and regression.

RESULT

Subjects with BPD and PH present after 2 months of age were hospitalized for 2.2 months longer than those without PH (P=0.02). These subjects were 4.5 times more likely to receive home supplemental oxygen or mechanical ventilation (P=0.03). No difference in the risk of respiratory morbidities after initial hospital discharge was seen with PH.

CONCLUSION

PH in preterm infants is associated with longer initial hospitalizations and a higher likelihood of requiring home respiratory support. This has implications for counseling families and reducing the medical, psychosocial, and economic burden of BPD and PH.

Long-term pulmonary outcomes of patients with bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the commonest cause of chronic lung disease in infancy. The incidence of BPD has remained unchanged despite many advances in neonatal care. BPD starts in the neonatal period but its effects can persist long term. Premature infants with BPD have a greater incidence of hospitalization, and continue to have a greater respiratory morbidity and need for respiratory medications, compared to those without BPD. Lung function abnormalites, especially small airway abnormalities, often persist. Even in the absence of clinical symptoms, BPD survivors have persistent radiological abnormalities and presence of emphysema has been reported on chest computed tomography scans. Concern regarding their exercise tolerance remains. Long-term effects of BPD are still unknown, but given reports of a more rapid decline in lung function and their suspectibility to develop chronic obstructive pulmonary disease phenotype with aging, it is imperative that lung function of survivors of BPD be closely monitored.

Pulmonary hypertension in bronchopulmonary dysplasia

Pulmonary hypertension (PH) is a common complication of neonatal respiratory diseases, including bronchopulmonary dysplasia (BPD), and recent studies have increased awareness that PH worsens the clinical course, morbidity and mortality of BPD. Recent evidence indicates that up to 18% of all extremely low-birth-weight infants will develop some degree of PH during their hospitalization, and the incidence rises to 25-40% of the infants with established BPD. Risk factors are not yet well understood, but new evidence shows that fetal growth restriction is a significant predictor of PH. Echocardiography remains the primary method for evaluation of BPD-associated PH, and the development of standardized screening timelines and techniques for identification of infants with BPD-associated PH remains an important ongoing topic of investigation. The use of pulmonary vasodilator medications, such as nitric oxide, sildenafil, and others, in the BPD population is steadily growing, but additional studies are needed regarding their long-term safety and efficacy.

An update on pharmacologic approaches to bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the most prevalent long-term morbidity in surviving extremely preterm infants and is linked to increased risk of reactive airways disease, pulmonary hypertension, post-neonatal mortality, and adverse neurodevelopmental outcomes. BPD affects approximately 20% of premature newborns, and up to 60% of premature infants born before completing 26 weeks of gestation. It is characterized by the need for assisted ventilation and/or supplemental oxygen at 36 weeks postmenstrual age. Approaches to prevention and treatment of BPD have evolved with improved understanding of its pathogenesis. This review will focus on recent advancements and detail current research in pharmacotherapy for BPD. The evidence for both current and potential future experimental therapies will be reviewed in detail. As our understanding of the complex and multifactorial pathophysiology of BPD changes, research into these current and future approaches must continue to evolve.