Nitric oxide in preterm infant with pulmonary hypoplasia

Pulmonary hypertension with bronchopulmonary dysplasia: Aichi cohort study

BACKGROUND

The incidence of pulmonary hypertension (PH) associated with bronchopulmonary dysplasia (BPD) has not been investigated in regional cohorts. The aim of this study was to clarify the incidence of PH associated with BPD in all very low birthweight infants (VLBWIs) born during the study period in Aichi Prefecture, Japan.

METHODS

We conducted a retrospective observational cohort study of all VLBWIs born in Aichi Prefecture. The inclusion criteria were VLB, birth between 1 January 2015 and 31 December 2015, and admission to any neonatal intensive care unit in Aichi Prefecture. BPD28d and BPD36w were defined as the need for supplemental oxygen or any respiratory support at 28 days of age or 36 weeks of postmenstrual age (PMA). The primary outcome was the incidence of PH after 36 weeks' PMA (PH36w) in VLBWIs with BPD28d and BPD36w. The secondary outcomes were the clinical factors related to PH36w in BPD36w patients. Mann-Whitney U-test and Fisher's exact test were used for univariate analysis. Differences were considered statistically significant at P < 0.05. Risk ratio (RR) and 95% confidence interval (CI) were also evaluated.

RESULTS

A total of 441 patients were analyzed. A total of 217 and 131 patients met the definition of BPD28d and BPD36w, respectively. Nine patients were diagnosed with PH36w (4.2% and 6.9% of the BPD28d and BPD36w patients, respectively). The presence of oligohydramnios (RR, 2.71; 95% CI: 1.55-4.73, P = 0.014) and sepsis (RR, 3.62; 95% CI: 1.51-8.63, P = 0.025) was significant in the PH36w patients.

CONCLUSIONS

The incidence of PH36w was 4.2% and 6.9% in the BPD28d and BPD36w patients, respectively. Oligohydramnios and sepsis were significantly associated with PH36w in VLBWIs.

The Controversy Persists: Is There a Qualification Criterion to Utilize Inhaled Nitric Oxide in Pre-term Newborns?

Inhaled nitric oxide (iNO) use in premature newborns remains controversial among clinicians. In 2014, the American Academy of Pediatrics, Committee on Fetus and Newborn released a statement that the available data do not support routine iNO use in pre-term newborns. Despite the absence of significant benefits, 2016 California data showed that clinicians continue to utilize iNO in pre-term infants. With studies as recent as January 2017, the Cochrane review confirmed no major advantages of iNO in pre-term newborns. Still, it recognized that a subset of pre-term infants with pulmonary hypertension (PHTN) had not been separately investigated. Furthermore, recent non-randomized controlled trials have suggested that iNO may benefit specific subgroups of pre-term newborns, especially those with PHTN, prolonged rupture of membranes, and antenatal steroid exposure. Those pre-term infants who showed a clinical response to iNO had increased survival without disability. These findings underscore the need for future studies in pre-term newborns with hypoxemic respiratory failure and PHTN. This review will discuss the rationale for using iNO, controversies regarding the diagnosis of PHTN, and additional novel approaches of iNO treatment in perinatal asphyxia and neonatal resuscitation in the pre-term population < 34 weeks gestation.

Decreased OLA1 (Obg-Like ATPase-1) Expression Drives Ubiquitin-Proteasome Pathways to Downregulate Mitochondrial SOD2 (Superoxide Dismutase) in Persistent Pulmonary Hypertension of the Newborn

Persistent pulmonary hypertension of the newborn (PPHN) is a failure of pulmonary vascular resistance to decline at birth rapidly. One principal mechanism implicated in PPHN development is mitochondrial oxidative stress. Expression and activity of mitochondrial SOD2 (superoxide dismutase) are decreased in PPHN; however, the mechanism remains unknown. Recently, OLA1 (Obg-like ATPase-1) was shown to act as a critical regulator of proteins controlling cell response to stress including Hsp70, an obligate chaperone for SOD2. Here, we investigated whether OLA1 is causally linked to PPHN. Compared with controls, SOD2 expression is reduced in distal-pulmonary arteries (PAs) from patients with PPHN and fetal-lamb models. Disruptions of the SOD2 gene reproduced PPHN phenotypes, manifested by elevated right ventricular systolic pressure, PA-endothelial cells apoptosis, and PA-smooth muscle cells proliferation. Analyses of SOD2 protein dynamics revealed higher ubiquitinated-SOD2 protein levels in PPHN-lambs, suggesting dysregulated protein ubiquitination. OLA1 controls multiple proteostatic mechanisms and is overexpressed in response to stress. We demonstrated that OLA1 acts as a molecular chaperone, and its activity is induced by stress. Strikingly, OLA1 expression is decreased in distal-PAs from PPHN-patients and fetal-lambs. OLA1 deficiency enhanced CHIP affinity for Hsp70-SOD2 complexes, facilitating SOD2 degradation. Consequently, mitochondrial H₂O₂ formation is impaired, leading to XIAP (X-linked inhibitor of apoptosis) overexpression that suppresses caspase activity in PA-smooth muscle cells, allowing them to survive and proliferate, contributing to PA remodeling. In-vivo, ola1^-/- downregulated SOD2 expression, induced distal-PA remodeling, and right ventricular hypertrophy. We conclude that decreased OLA1 expression accounts for SOD2 downregulation and, therefore, a therapeutic target in PPHN treatments.

Factors influencing decision making in neonatology: inhaled nitric oxide in preterm infants

OBJECTIVE

We studied decision making regarding inhaled nitric oxide (iNO) in preterm infants with Pulmonary Hypertension (PH).

STUDY DESIGN

We asked members of the AAP-Society of Neonatal-Perinatal Medicine and Division-Chiefs to select from three management options- initiate iNO, engage parents in shared decision making or not consider iNO in an extremely preterm with PH followed by rating of factors influencing their decision.

RESULTS

Three hundred and four respondents (9%) completed the survey; 36.5% chose to initiate iNO, 42% to engage parents, and 21.5% did not consider iNO. Provider's prior experience, safety, and patient-centered care were rated higher by those who initiated or offered iNO; lack of effectiveness and cost considerations by participants who did not chose iNO.

CONCLUSIONS

Most neonatologists offer or initiate iNO therapy based on their individual experience. The minority who chose not to consider iNO placed higher value on lack of effectiveness and cost. These results demonstrate a tension between evidence and pathophysiology-based-therapy/personal experience.

Association of Early Inhaled Nitric Oxide With the Survival of Preterm Neonates With Pulmonary Hypoplasia

IMPORTANCE

Pulmonary hypoplasia affects a very small percentage of preterm neonates, but its presence is associated with high rates of mortality.

OBJECTIVE

To determine whether treatment with inhaled nitric oxide during the first week of life was associated with improved in-hospital survival in a cohort of extremely preterm neonates with pulmonary hypoplasia.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study used data from the Pediatrix Medical Group's Clinical Data Warehouse, a data set containing information from more than 350 neonatal intensive care units in 35 US states and Puerto Rico. Since inhaled nitric oxide was not randomly prescribed, we used 1-to-1 propensity score matching to reduce the imbalance of measured covariates between the 2 treatment groups. The initial, unmatched cohort included singleton neonates who were born between 22 and 29 weeks' gestation, had a birth weight of 400 g or more, were diagnosed with pulmonary hypoplasia as a cause of their respiratory distress, remained free of major anomalies, and were discharged between January 1, 2000, and December 31, 2014. We defined exposure as the initiation of inhaled nitric oxide on day t in days 0 to 7 of the life of a neonate. Each exposed neonate was matched 1-to-1 to a neonate who had not initiated inhaled nitric oxide on a given day.

MAIN OUTCOMES AND MEASURES

The primary outcome was mortality defined as death prior to transfer or discharge home. Secondary outcomes were any-stage necrotizing enterocolitis, retinopathy of prematurity requiring treatment, chronic lung disease, and periventricular leukomalacia.

RESULTS

Among 92 635 neonates in our study sample, we identified 767 (0.8%) with pulmonary hypoplasia who met all study inclusion criteria, of whom 185 (0.2%) were exposed to inhaled nitric oxide. Among 151 matched pairs of exposed and unexposed neonates, we did not identify a significant association between inhaled nitric oxide use and mortality (hazard ratio [HR], 0.79; 95% CI, 0.57-1.11). Subgroup analyses of neonates with and without persistent pulmonary hypertension (PPHN) likewise revealed no significant association between inhaled nitric oxide use and mortality (pulmonary hypoplasia with PPHN: HR, 0.67; 95% CI, 0.45-1.01; pulmonary hypoplasia without PPHN: HR, 1.11; 95% CI, 0.61-2.02), but these findings may have been influenced by ascertainment bias.

CONCLUSIONS AND RELEVANCE

Early treatment with inhaled nitric oxide is not associated with improved survival among extremely preterm neonates with pulmonary hypoplasia. Clinical trials are warranted to clarify the matter.

Diagnostic Approach to Pulmonary Hypertension in Premature Neonates

Bronchopulmonary dysplasia (BPD) is a form of chronic lung disease in premature infants following respiratory distress at birth. With increasing survival of extremely low birth weight infants, alveolar simplification is the defining lung characteristic of infants with BPD, and along with pulmonary hypertension, increasingly contributes to both respiratory morbidity and mortality in these infants. Growth restricted infants, infants born to mothers with oligohydramnios or following prolonged preterm rupture of membranes are at particular risk for early onset pulmonary hypertension. Altered vascular and alveolar growth particularly in canalicular and early saccular stages of lung development following mechanical ventilation and oxygen therapy, results in developmental lung arrest leading to BPD with pulmonary hypertension (PH). Early recognition of PH in infants with risk factors is important for optimal management of these infants. Screening tools for early diagnosis of PH are evolving; however, echocardiography is the mainstay for non-invasive diagnosis of PH in infants. Cardiac computed tomography (CT) and magnetic resonance are being used as imaging modalities, however their role in improving outcomes in these patients is uncertain. Follow-up of infants at risk for PH will help not only in early diagnosis, but also in appropriate management of these infants. Aggressive management of lung disease, avoidance of hypoxemic episodes, and optimal nutrition determine the progression of PH, as epigenetic factors may have significant effects, particularly in growth-restricted infants. Infants with diagnosis of PH are managed with pulmonary vasodilators and those resistant to therapy need to be worked up for the presence of cardio-vascular anomalies. The management of infants and toddlers with PH, especially following premature birth is an emerging field. Nonetheless, combination therapies in a multi-disciplinary setting improves outcomes for these infants.

Pulmonary hypoplasia

To survive the transition to extrauterine life, newborn infants must have lungs that provide an adequate surface area and volume to allow for gas exchange. The dynamic activities of fetal breathing movements and accumulation of lung luminal fluid are key to fetal lung development throughout the various phases of lung development and growth, first by branching morphogenesis, and later by septation. Because effective gas exchange is essential to survival, pulmonary hypoplasia is among the leading findings on autopsies of children dying in the newborn period. Management of infants born prematurely who had disrupted lung development, especially at the pre-glandular or canalicular periods, may be challenging, but limited success has been reported. Growing understanding of stem cell biology and mechanical development of the lung, and how to apply them clinically, may lead to new approaches that will lead to better outcomes for these patients.

Inhaled nitric oxide in preterm infants with prolonged preterm rupture of the membranes: a case series

The available evidence does not support the routine use of inhaled nitric oxide (iNO) in the care of premature infants. We present a case series of 22 preterm infants born after prolonged preterm premature rupture of membranes and oligohydramnios with respiratory failure. Oxygenation index decreased significantly after commencement of iNO.

Risk factors for pulmonary artery hypertension in preterm infants with moderate or severe bronchopulmonary dysplasia

BACKGROUND

Despite the potential importance of pulmonary artery hypertension (PAH) in preterm infants with bronchopulmonary dysplasia (BPD), little is known about the risk factors for PAH.

OBJECTIVES

To investigate the risk factors for PAH in preterm infants with BPD.

METHODS

Infants diagnosed with BPD were assigned to the PAH group or non-PAH group except for infants with mild BPD who had no PAH. PAH was diagnosed on the basis of echocardiograms demonstrating elevated right ventricle pressure beyond the postnatal age of 2 months. Logistic regression analysis was done for the multivariate assessment of the risk factors for PAH in preterm infants with moderate or severe BPD.

RESULTS

A total of 98 infants among 145 infants with BPD were divided into a PAH group (n = 25) or non-PAH group (n = 73), while the remaining 47 infants had mild BPD with no PAH. Among the study patients, survival rate of the PAH group was significantly lower than that of the non-PAH group. Infants with PAH had more severe cases of BPD and underwent longer durations of oxygen therapy, conventional or high-frequency ventilation, and hospitalization compared to those without PAH. Low 5-min Apgar scores (≤6; relative risk (RR) 6.2; 95% confidence interval (CI) 1.4-28.0; p = 0.017) and oligohydramnios (RR 7.7; 95% CI 2.0-29.6; p = 0.030) were found to be significant risk factors for PAH according to multivariate analysis.

CONCLUSIONS

The present study shows that oligohydramnios is a specific risk factor for PAH in preterm infants with moderate or severe BPD.

Early functional echocardiogram and inhaled nitric oxide: usefulness in managing neonates born following extreme preterm premature rupture of membranes (PPROM)

AIM

Poor neonatal outcome of preterm premature rupture of membranes (PPROM) < 24 weeks' gestational age (GA) is probably a result of abnormalities in both airway and vascular developments, ventilation perfusion mismatch, and possibly persistent pulmonary hypertension of the newborn (PPHN). Perinatal mortality of 50-90% has been reported in the past, with recent literature reporting significant improvement in neonatal survival. We report our 8-year experience in this group of infants using early diagnostic functional echocardiography (fECHO), high-frequency ventilation (HFV) and inhaled nitric oxide (iNO).

METHODS

The obstetric and neonatal databases were searched to identify babies with PPROM (< 20 weeks' gestation) or rupture earlier than 25 weeks for more than 14 days.

RESULTS

Twenty-six infants were identified, of whom 20 were admitted to the neonatal intensive care unit (NICU; mean GA 27.8 weeks, mean birth weight (BW) 1207 g). Early echocardiographic data were available in 12/15 infants requiring mechanical ventilation of whom 10 had evidence of PPHN. All infants who received iNO therapy survived to discharge and only two infants died. Survival to discharge was 69% for the whole cohort of infants and 90% for infants admitted to the NICU. In contrast, for the cohort from pre-iNO and -HFV era, the overall survival to discharge was 62% and 66% for the infants admitted to the NICU.

CONCLUSION

Premature infants with PPROM and presumed severe hypoxemic respiratory failure because of hypoplastic lungs often have significant PPHN and may show improvement in oxygenation after treatment with HFV and iNO. Early fECHO results in earlier identification and treatment of infants with PPHN in this high-risk group.

Inhaled nitric oxide for preterm premature rupture of membranes, oligohydramnios, and pulmonary hypoplasia

We sought to determine if inhaled nitric oxide (iNO) administered to preterm infants with premature rupture of membranes (PPROM), oligohydramnios, and pulmonary hypoplasia improved oxygenation, survival, or other clinical outcomes. Data were analyzed from infants with suspected pulmonary hypoplasia, oligohydramnios, and PPROM enrolled in the National Institute of Child Health and Development Neonatal Research Network Preemie Inhaled Nitric Oxide (PiNO) trial, where patients were randomized to receive placebo (oxygen) or iNO at 5 to 10 ppm. Outcome variables assessed were PaO (2) response, mortality, bronchopulmonary dysplasia (BPD), and severe intraventricular hemorrhage (IVH) or periventricular leukomalacia (PVL). Twelve of 449 infants in the PiNO trial met criteria. Six infants received iNO and six received placebo. The iNO group had a mean increase in PaO (2) of 39 +/- 50 mm Hg versus a mean decrease of 11 +/- 15 mm Hg in the control group. Mortality was 33% versus 67%, BPD (2/5) 40% versus (2/2) 100%, and severe IVH or PVL (1/5) 20% versus (1/2) 50% in the iNO and control groups, respectively. None of these changes were statistically significant. Review of a limited number of cases from a large multicenter trial suggests that iNO use in the setting of PPROM, oligohydramnios, and suspected pulmonary hypoplasia improves oxygenation and may decrease the rate of BPD and death without increasing severe IVH or PVL. However, the small sample size precludes definitive conclusions. Further studies are required to determine if iNO is of benefit in this specific patient population.

Inhaled nitric oxide in the treatment of preterm infants

Inhaled nitric oxide (iNO) has been used successfully in select term and near-term infants with respiratory failure. The use of iNO in the premature infant population, however, remains controversial. This article will review some of the current literature regarding the use of iNO in premature infants and discuss current recommendations and future research directions.

Characteristics of pulmonary hypertension in preterm neonates

OBJECTIVE

Characteristics of preterm infants who develop pulmonary hypertension (PHT) and their response to inhaled nitric oxide (iNO) are not well described. Our objective was to identify risk factors for PHT in infants <37 weeks gestational age (GA) and to evaluate their response to iNO.

STUDY DESIGN

A retrospective chart review was conducted in infants <37 weeks GA born from July/2000 to October/2005 who had an echocardiographic diagnosis of PHT in the first 4 weeks of life. A comparison non-PHT group was generated matched for GA and birth date. Data on prenatal and postnatal characteristics, response to iNO and mortality were collected.

RESULTS

Low Apgar scores, preterm premature rupture of membranes, oligohydramnios, pulmonary hypoplasia and sepsis were independently predictive of PHT. Mortality was significantly higher in the PHT group (26.2% versus 4.1%; P<0.0001) compared to the control group. Low birth weight, severe intraventricular hemorrhage and male sex were significantly associated with death in infants with PHT. Thirty-seven percent (23/61) of infants with PHT were treated with inhaled NO. Infants < 29-week GA had poor response to iNO and the response to iNO increased with GA (P<0.02).

CONCLUSIONS

Low Apgar scores, oligohydramnios and pulmonary hypoplasia are associated with the development of PHT in premature infants. The percentage of infants responding to iNO increases with advancing GA.