Inhaled nitric oxide for oligohydramnios-induced pulmonary hypoplasia: a report of two cases and review of the literature

Treating very preterm European infants with inhaled nitric oxide increased in-hospital mortality but did not affect neurodevelopment at 5 years of age

AIM

We examined the outcomes of using inhaled nitric oxide (iNO) to treat very preterm born (VPT) infants across Europe.

METHODS

This was a sub-study of the Screening to Improve Health in Very Preterm Infants in Europe research. It focused on all infants born between 22 + 0 and 31 + 6 weeks/days of gestation from 2011 to 2012, in 19 regions in 11 European countries. We studied 7268 infants admitted to neonatal care and 5 years later, we followed up the outcomes of 103 who had received iNO treatment. They were compared with 3502 propensity score-matched controls of the same age who did not receive treatment.

RESULTS

All countries used iNO and 292/7268 (4.0%) infants received this treatment, ranging from 1.2% in the UK to 10.5% in France. There were also large regional variations within some countries. Infants treated with iNO faced higher in-hospital mortality than matched controls (odds ratio 2.03, 95% confidence interval 1.33-3.09). The 5-year follow-up analysis of 103 survivors showed no increased risk of neurodevelopmental impairment after iNO treatment.

CONCLUSION

iNO was used for VPT patients in all 11 countries. In-hospital mortality was increased in infants treated with iNO, but long-term neurodevelopmental outcomes were not affected in 103 5-year-old survivors.

The early use of inhaled nitric oxide in premature infants requiring respiratory support

Background: Earlier studies on the use of inhaled nitric oxide (iNO) for premature infants born at <34 weeks of gestation requiring respiratory support did not provide conclusive evidence of benefit. National guidelines generally discouraged the use in this population. More recent national guidelines endorsed the use of iNO in premature infants with hypoxic respiratory failure (HRF) associated with persistent pulmonary hypertension of the newborn (PPHN).Recent Studies: Two recently published observational studies evaluated the effect of administering iNO on oxygenation in the first week of life. These studies compared premature infants born at the gestational age (GA) of <34 weeks with HRF associated with PPHN to term and late preterm infants born at the GA of ≥34 weeks who received iNO. Both studies showed a similar effect of iNO on oxygenation in the two infant cohorts. The response rate in the premature infant cohort was 59% in the first study and 90% in the second. The mean response time was 9.2 h and 10.3 h, and the mean duration of therapy was 3.5 days and 8.2 days, respectively.Conclusion: The results of these studies support a trial of iNO in premature infants with persistent hypoxia despite optimum respiratory support. Obtaining a timely echocardiogram to exclude cardiac diseases and diagnose PPHN is logistically challenging for many clinicians, thus, a clinical diagnosis of PPHN might have to be made in these situations. Questions remain regarding the optimum dose of iNO and the duration of the initial iNO trial in these patients.KEY MESSAGESIn the most recently published studies, the improvement of oxygenation in iNO-treated infants born at <34 weeks of gestation with HRF and PPHN physiology was as effective as in infants born ≥34 weeks.These studies provide evidence supporting a trial of iNO in the subpopulation of premature infants with HRF associated with PPHN.

Current and emerging pharmacotherapies for the treatment of pulmonary arterial hypertension in infants

INTRODUCTION

Pulmonary hypertension (PH) is a complex condition that encompasses an array of underlying disease processes and affects a diverse population of infants, including those with congenital heart disease, congenital diaphragmatic hernia, persistent PH of the newborn, and those with lung disease such as bronchopulmonary dysplasia. While there are treatments available to adults with PH, limited data exists for infants, especially for the newer medications. Therapies that target the three main pathophysiologic pathways of pulmonary hypertension appear to benefit infants, but which are best for each individual disease process is unclear.

AREAS COVERED

A review of the therapies to treat pulmonary hypertension is covered in this article including the prostacyclin pathway, endothelin pathway, and the nitric oxide pathway. Other adjunctive treatments are also discussed. Findings are based on a PubMed literature search of research papers spanning 1990-2023 and a search of ongoing trials registered with clinicaltrials.gov.

EXPERT OPINION

Overall therapies seem to improve outcomes with most infants with PH. However, given the diverse population of infants with PH, it is imperative to understand the basis for the PH in individual patients and understand which therapies can be applicable. Further research into tailored therapy for the specific populations is warranted.

Controversies in neonatology: The efficacy of inhaled nitric oxide in preterm infants with persistent pulmonary hypertension

Introduction: There is limited and conflicting information in literature regarding use of inhaled nitric oxide (iNO) in preterm infants. In this study we examined the characteristics of preterm infants with persistent pulmonary hypertension (PHT) who responded and did not respond to iNO therapy . Material and Method: We retrospectively reviewed data of infants

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.

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.

Nitric Oxide in Pulmonary Hypoplasia: Results from the European iNO Registry

OBJECTIVES

The aim of this work was to describe treatment response and outcome data for preterm infants with pulmonary hypoplasia treated with inhaled nitric oxide (iNO). We hypothesised that an acute oxygenation response to iNO would be associated with survival.

DESIGN

A retrospective observational study design was used to identify cases of pulmonary hypoplasia in preterm infants <34 weeks' gestation reported to the European iNO Registry. Demographic and clinical data were collected including oxygenation and echocardiographic parameters. The primary outcome was acute oxygenation response defined as a reduction in fractional inspired oxygen of >0.15. Outcome data included chronic lung disease (CLD) and death.

RESULTS

Seventy-two infants with pulmonary hypoplasia were treated with iNO during a 10-year period (2007-2016). In total, 30/69 (43%) of the infants showed a significant improvement in oxygenation and were categorised as "responders." Thirty-one treated infants died, and 19 survivors developed CLD. Although there were no differences in demographics and baseline cardiorespiratory parameters between responders and non-responders, an acute response was significantly associated with survival. Neither pulmonary hypertension nor PPHN (persistent pulmonary hypertension of the newborn) physiology predicted the acute response to iNO or survival.

CONCLUSION

Although the acute oxygenation response to iNO therapy in pulmonary hypoplasia is comparable to other respiratory disorders in preterm infants, mortality in this group remains very high. An acute response is associated with survival and suggests that a short therapeutic trial of iNO therapy is warranted in this population. This study underscores the value of registries in evaluating therapies for rare neonatal disorders, although their limitations must be recognised.

The efficacy of inhaled nitric oxide treatment in premature infants with acute pulmonary hypertension

BACKGROUND

Although inhaled nitric oxide (iNO) therapy in term infants with pulmonary hypertension (PHT) has demonstrated definite benefit, the use of iNO in preterm infants remains inconclusive.

AIMS

To evaluate the impact of iNO treatment in premature infants with acute PHT.

STUDY DESIGN

Retrospective cohort.

SUBJECTS

Infants < 34 weeks' gestational age, admitted during 2010-2016 to two neonatal units, having treated with iNO for confirmed PHT. A positive response was defined by FiO₂ reduction ≥20% within 3-h post iNO initiation. Early PHT was defined when developed within the first 72 h of age.

OUTCOME MEASURES

The primary outcome was the evaluation of the acute response to iNO administration. Secondary outcomes included the comparison of neonatal characteristics and outcomes between positive and negative responders, and early or late PHT infants.

RESULTS

Of the 55 infants of our cohort, 39 (71%) had a positive response to iNO administration. No differences noted regarding bronchopulmonary dysplasia, intraventricular haemorrhage or other morbidities; however, positive responders had significantly higher survival rate in overall (77 vs 21%, p = 0.001) and within early PHT subgroup (74 vs 33%, p = 0.044). Regression analysis revealed that oligohydramnios (OR 2.834, 95%CI 1.652-6.070) and early PHT (OR 1.953, 95%CI 1.377-2.930) were significantly related with a positive response.

CONCLUSIONS

Preterm infants with confirmed acute PHT respond in significant proportion to the iNO administration, especially in the background of oligohydramnios or the development of early PHT.

Efficacy of inhaled nitric oxide in neonates with hypoxic respiratory failure and pulmonary hypertension: the Japanese experience

OBJECTIVE

To analyze data from a registry of Japanese neonates with hypoxic respiratory failure associated with pulmonary hypertension (PH) to compare the effectiveness of inhaled nitric oxide (iNO) in neonates born <34 weeks vs. ≥34 weeks gestational age (GA).

MATERIALS AND METHODS

iNO was administered according to approved Japanese product labeling. Study data were collected before iNO administration and at predefined intervals until discontinuation.

RESULTS

A total of 1,114 neonates were included (n=431, <34 weeks GA; n=675, ≥34 weeks GA; n=8, missing age data). Mean decrease from baseline oxygenation index (OI) was similar in both age groups. OI reduction was more pronounced in the <34 weeks subgroups with baseline OI ≥25. Survival rates were similar in the <34 weeks GA and ≥34 weeks GA groups stratified by baseline OI (OI<15, 89% vs. 93%; 15≤OI<25, 85% vs. 91%; 25≤OI≤40, 73% vs. 79%; OI>40, 64% vs. 66%).

CONCLUSION

iNO improved oxygenation in preterm neonates as effectively as in late preterm and term neonates, without negative impact on survival. If clinically significant PH is present, as measured by pulse oximetry or echocardiography, a therapeutic trial of iNO might be indicated for preterm neonates.

Outcomes of hypoxic respiratory failure at birth associated with previable rupture of membranes

OBJECTIVE

To characterize clinical outcomes of infants born after previable rupture of membranes (pROM, < 23 weeks gestation and latency period ≥ 2 weeks) in relation to refractory hypoxic respiratory failure (rHRF).

STUDY DESIGN

pROM neonates categorized as rHRF (FiO₂ > 0.6 for ≥ 2 h) and treated (high frequency ventilation + inhaled nitric oxide) were compared with no rHRF group. Primary outcome was survival until discharge. Factors associated with rHRF and mortality were identified.

RESULT

Overall, mortality and disability rates were 28% and 22%, respectively. Treated rHRF group (n = 32) had longer period of ROM, mortality was (31% vs. 14%; p = 0.20), with similar survival-without-disability (54% vs. 47%; p = 0.67). Higher gestational age at birth [1.57 (1.03,2.39)] and cesarean delivery [12.6 (1.22,125)] were associated with increased survival.

CONCLUSION

Birth after pROM is associated with high rates of adverse outcomes, independent of latency period. Following treatment, rHRF infants may have similar long-term outcomes as those without rHRF.

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.

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.

Early Use of Inhaled Nitric Oxide in Preterm Infants: Is there a Rationale for Selective Approach?

Background Inhaled nitric oxide (iNO) is being increasingly used in preterm infants < 34 weeks with hypoxemic respiratory failure (HRF) and/or pulmonary hypertension (PH). Objective To evaluate the risk factors, survival characteristics, and lung histopathology in preterm infants with PH/HRF. Methods Retrospective chart review was conducted to determine characteristics of 93 preterm infants treated with iNO in the first 28 days and compared with 930 matched controls. Factors associated with survival with preterm HRF and smooth muscle actin from nine autopsies were evaluated. Results Preterm neonates treated with iNO had a higher incidence of preterm prolonged rupture of membrane (pPROM ≥ 18 hours), oligohydramnios and delivered by C-section. In infants treated with iNO, antenatal steroids (odds ratio [OR],3.7; confidence interval [CI], 1.2-11.3; p = 0.02), pPROM (OR, 1.001; CI, 1.0-1.004; p = 0.3), and oxygenation response to iNO (OR, 3.7; CI, 1.08-13.1; p = 0.037) were associated with survival. Thirteen infants with all three characteristics had 100% (13/13) survival without severe intraventricular hemorrhage (IVH)/periventricular leukomalacia (PVL) compared with 48% survival (12/25, p = 0.004) and 16% severe IVH/PVL without any of these factors. Severity of HRF correlated with increased smooth muscle in pulmonary vasculature. Conclusion Preterm infants with HRF exposed to antenatal steroids and pPROM had improved oxygenation with iNO and survival without severe IVH/PVL. Precisely targeting this subset may be beneficial in future trials of iNO.

Maternal and neonatal outcomes following expectant management of preterm prelabour rupture of membranes before viability

AIM

To assess the contemporary maternal and neonatal outcomes following expectant management of preterm premature rupture of membranes (PPROM) prior to 24 weeks' gestation and to identify prognostic indicators of this morbid presentation.

METHODS

We performed a systematic review in the Pubmed and EMBASE databases to identify the primary (perinatal mortality, severe neonatal morbidity and serious maternal morbidity) and secondary (neonatal survival and morbidity) outcomes following expectant management of previable PPROM.

RESULTS

Mean latency between PPROM and delivery ranged between 20 and 43 days. Women with PPROM <24 weeks had an overall live birth rate of 63.6% and a survival-to-discharge rate of 44.9%. The common neonatal morbidities were respiratory distress syndrome, bronchopulmonary dysplasia and sepsis. The majority of neonatal deaths within 24 h post birth were associated with pulmonary hypoplasia, severe intraventricular haemorrhage and neonatal sepsis. The common maternal outcomes were chorioamnionitis and caesarean sections. The major predictors of neonatal survival were later gestational age at PPROM, adequate residual amniotic fluid levels, C-reactive protein <1 mg/dL within 24 h of admission and PPROM after invasive procedures.

CONCLUSION

Pregnancy latency and neonatal survival following previable PPROM has improved in recent years, although neonatal morbidity remains unchanged despite recent advances in obstetric and neonatal care. There is heterogeneity in management practices across centres worldwide.

Prolonged respiratory disorder predicts adverse prognosis in infants with end-stage kidney disease

BACKGROUND

Among comorbidities, pulmonary hypoplasia (PH) is known as a significant risk factor for mortality in infants with end-stage kidney disease (ESKD). However, the final outcomes of infants with both ESKD and PH are still not well defined, as the diagnosis modality, and definition of PH severity remain ambiguous.

METHODS

Children initiating peritoneal dialysis during infancy from 1990 to 2015 were followed until death, date of last contact, or the end of 2015. We examined the long-term outcome of children with congenital pulmonary disorders by studying infants with prolonged respiratory disorders of greater than 28 days duration after birth and evaluated risk factors for mortality.

RESULTS

Forty-six children were followed (median follow-up, 9.23 years), and classified as children without (n = 38; Group A) or with (n = 8; Group B) a prolonged respiratory disorder. Overall actuarial 5 year survival rate in this cohort was 79.5 %. The survival curve in Group B showed a significant decline compared with Group A. Prolonged respiratory disorder was significantly associated with mortality by multivariate analysis (hazard ratio, 8.32).

CONCLUSIONS

Infants who initiate peritoneal dialysis complicated by prolonged respiratory disorders have increased adverse risk factors for mortality; therefore, withholding aggressive treatment should be considered.

Inhaled nitric oxide therapy for pulmonary disorders of the term and preterm infant

The 21st century began with the FDA approval of inhaled nitric oxide therapy for the treatment of neonatal hypoxic respiratory failure associated with pulmonary hypertension in recognition of the 2 randomized clinical trials demostrating a significant reduction in the need for extracorporeal support in the term and near-term infant. Inhaled nitric oxide is one of only a few therapeutic agents approved for use through clinical investigations primarily in the neonate. This article provides an overview of the pertinent biology and chemistry of nitric oxide, discusses potential toxicities, and reviews the results of pertinent clinical investigations and large randomized clinical trials including neurodevelopmental follow-up in term and preterm neonates. The clinical investigations conducted by the Eunice Kennedy Shriver NICHD Neonatal Research Network will be discussed and placed in context with other pertinent clinical investigations exploring the efficacy of inhaled nitric oxide therapy in neonatal hypoxic respiratory failure.

Nitric Oxide and Other Novel Therapies for Pulmonary Hypertension

Pulmonary hypertension is an uncommon, yet devastating, syndrome with a complex underlying pathobiology. Hypoxia, inflammation, and increased shear stress appear to be the primary pathogenic events; however, mechanisms by which these processes lead to pulmonary hypertension remain incompletely understood. The ultimate increase in pulmonary vascular resistance is attributed to remodelling of the walls of resistance vessels, which can lead to encroachment on and reduction of the vascular lumen. The number of blood vessels per unit of cross-sectional area in the hypertensive lung is also reduced, which can contribute to increased vascular resistance. Regardless of its etiology, endothelial dysfunction underlies pulmonary hypertension, one manifestation of which is the attenuated production of bioactive nitric oxide. Nitric oxide administration can exert beneficial effects at various stages of the disease. Here we review the known pathobiology of pulmonary hypertension, with a principal focus on endothelial nitric oxide, and also summarize the data on nitric oxide replacement therapy and other novel therapies that relate to nitric oxide as one approach to treatment.

Management of hypoxemic respiratory failure and pulmonary hypertension in preterm infants

While diagnoses of hypoxemic respiratory failure (HRF) and pulmonary hypertension (PH) in preterm infants may be based on criteria similar to those in term infants, management approaches often differ. In preterm infants, HRF can be classified as 'early' or 'late' based on an arbitrary threshold of 28 postnatal days. Among preterm infants with late HRF, the pulmonary vascular abnormalities associated with bronchopulmonary dysplasia (BPD) represent a therapeutic challenge for clinicians. Surfactant, inhaled nitric oxide (iNO), sildenafil, prostacyclin and endothelin receptor blockers have been used to manage infants with both early and late HRF. However, evidence is lacking for most therapies currently in use. Chronic oral sildenafil therapy for BPD-associated PH has demonstrated some preliminary efficacy. A favorable response to iNO has been documented in some preterm infants with early PH following premature prolonged rupture of membranes and oligohydramnios. Management is complicated by a lack of clear demarcation between interventions designed to manage respiratory distress syndrome, prevent BPD and treat HRF. Heterogeneity in clinical phenotype, pathobiology and genomic underpinnings of BPD pose challenges for evidence-based management recommendations. Greater insight into the spectrum of disease phenotypes represented by BPD can optimize existing therapies and promote development of new treatments. In addition, better understanding of an individual's phenotype, genotype and biomarkers may suggest targeted personalized interventions. Initiatives such as the Prematurity and Respiratory Outcomes Program provide a framework to address these challenges using genetic, environmental, physiological and clinical data as well as large repositories of patient samples.

Treatment of premature infants with pulmonary hypertension and right ventricular dysfunction with milrinone: a case series

OBJECTIVE

Milrinone has been proposed as an effective treatment for pulmonary hypertension (PH) and right ventricular (RV) dysfunction. We aimed to determine the effect of milrinone therapy on clinical and echocardiography parameters of PH in preterm infants with elevated pulmonary pressures.

STUDY DESIGN

A retrospective case review was conducted on infants <32 weeks gestation who received milrinone for the treatment of PH and reduced RV function. Echocardiographic data were collected before and after treatment with milrinone, and serial clinical parameters were recorded over a 72h  period.

RESULT

Seven infants met the inclusion criteria with a median gestation and birth weight of 27.3 weeks and 1140 g, respectively. Four infants had a diagnosis of pulmonary hypoplasia with PH, and three infants were recipients in twin-to-twin transfusion syndrome who also developed PH. Nitric oxide was used in six infants before commencement of milrinone. Milrinone was commenced at a dose of 0.33 μg kg(-1) min(-1) to 0.5 μg kg(-1) min(-1) and continued for a median duration of 70 h. Use of milrinone was associated with a fall in oxygenation index and inhaled nitric oxide dose. Following an initial fall in blood pressure over the first 6 h, there was an increase in blood pressure over the subsequent 72 h. Echocardiographic data demonstrated an increase in indicators of myocardial performance and PH. One infant died before discharge.

CONCLUSION

This case series suggests that milrinone may be a useful therapy for premature infants with echocardiography findings of PH and/or RH dysfunction. This data support the need for a randomised control trial to confirm its efficacy.

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.

Neonatal survival after prolonged preterm premature rupture of membranes before 24 weeks of gestation

OBJECTIVE

To evaluate neonatal survival after prolonged preterm premature rupture of membranes (PROM) in the era of antenatal corticosteroids, surfactant, and inhaled nitric oxide.

METHODS

A single-center retrospective cohort study of neonates born from 2002-2011 after prolonged (1 week or more) preterm (less than 24 weeks of gestation) rupture of membranes was performed. The primary outcome was survival to discharge. Neonates whose membranes ruptured less than 24 hours before delivery (n=116) were matched (2:1) on gestational age at birth, sex, and antenatal corticosteroid exposure with neonates whose membranes ruptured 1 week or more before delivery (n=58). Analysis used conditional logistic regression for categorical data and Wilcoxon signed rank test for continuous data.

RESULTS

The prolonged preterm PROM exposed and unexposed cohorts had survival rates of 90% and 95%, respectively, although underpowered to assess the statistical significance (P=.313). Exposed neonates were more likely have pulmonary hypoplasia (26/58 exposed, 1/114 unexposed, P<.001), pulmonary hypertension (21/56 exposed, 10/112 unexposed, P<.001), and pulmonary air leak (21/58 exposed, 14/114 unexposed, P<.001). Gestational age at rupture (20.4 weeks exposed, 22.3 weeks unexposed, P=.189), length of rupture (3.7 weeks exposed, 6.4 weeks unexposed, P=.717), and lowest maximal vertical pocket before 24 weeks of gestation (0 cm exposed, 1.4 cm unexposed, P=.114) did not discriminate between survivors and nonsurvivors after exposure to prolonged preterm PROM.

CONCLUSION

With antenatal steroid exposure and aggressive pulmonary management, survival to discharge after prolonged preterm PROM was 90%. Pulmonary morbidities were common. Of note, the data were limited to women who remained pregnant 1 week or longer after rupture of membranes.

Guidelines for Rational and Cost-Effective Use of iNO Therapy in Term and Preterm Infants

Inhaled nitric oxide (iNO) is an effective but costly therapy for infants with hypoxemic respiratory failure. The approved and solidly evidence-based indication is for treatment of late preterm and term infants with persistent pulmonary hypertension of the newborn (PPHN); however, off-label use of iNO has become widespread. Although iNO treatment of infants with congenital diaphragmatic hernia constitutes one of the approved indications, available evidence from randomized trials suggests marginal if any efficacy. Rescue therapy in preterm infants with severe respiratory failure has been studied extensively and is not supported by data from a number of controlled trials. Such use is widespread, but should be discouraged. There may be a subgroup of such infants with pulmonary hypoplasia and documented PPHN who may benefit from this treatment, but the data are limited. Several studies have examined the use of iNO for prevention of chronic lung disease with inconsistent results. This promising application requires more study before it can be recommended. There may be a role of iNO in treating infants with pulmonary hypertension complicating severe bronchopulmonary dysplasia, but there are limited data on long term outcomes. Alternate therapies such as sildenafil may be beneficial in this specific population as well as in other causes of pulmonary hypertension. Rational use of this expensive treatment will maximize cost:benefit and avoid potential exposure to unknown adverse effects not balanced by documentable benefits.

Midtrimester preterm prelabour rupture of membranes (PPROM): expectant management or amnioinfusion for improving perinatal outcomes (PPROMEXIL - III trial)

Background

Babies born after midtrimester preterm prelabour rupture of membranes (PPROM) are at risk to develop neonatal pulmonary hypoplasia. Perinatal mortality and morbidity after this complication is high. Oligohydramnios in the midtrimester following PPROM is considered to cause a delay in lung development. Repeated transabdominal amnioinfusion with the objective to alleviate oligohydramnios might prevent this complication and might improve neonatal outcome.

Methods/Design

Women with PPROM and persisting oligohydramnios between 16 and 24 weeks gestational age will be asked to participate in a multi-centre randomised controlled trial. Intervention: random allocation to (repeated) abdominal amnioinfusion (intervention) or expectant management (control). The primary outcome is perinatal mortality. Secondary outcomes are lethal pulmonary hypoplasia, non-lethal pulmonary hypoplasia, survival till discharge from NICU, neonatal mortality, chronic lung disease (CLD), number of days ventilatory support, necrotizing enterocolitis (NEC), periventricular leucomalacia (PVL) more than grade I, severe intraventricular hemorrhage (IVH) more than grade II, proven neonatal sepsis, gestational age at delivery, time to delivery, indication for delivery, successful amnioinfusion, placental abruption, cord prolapse, chorioamnionitis, fetal trauma due to puncture. The study will be evaluated according to intention to treat. To show a decrease in perinatal mortality from 70% to 35%, we need to randomise two groups of 28 women (two sided test, β-error 0.2 and α-error 0.05).

Discussion

This study will answer the question if (repeated) abdominal amnioinfusion after midtrimester PPROM with associated oligohydramnios improves perinatal survival and prevents pulmonary hypoplasia and other neonatal morbidities. Moreover, it will assess the risks associated with this procedure.

Trial registration

NTR3492 Dutch Trial Register (http://www.trialregister.nl).

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.

Combination therapy for life-threatening pulmonary hypertension in a premature infant: first report on bosentan use

Premature infants with preterm premature rupture of membranes (PPROM) are at high risk of severe respiratory failure because of lung hypodysplasia associated with persistent pulmonary hypertension of the newborn (PPHN). We describe the clinical course of a 28-week gestation infant with PPROM from the 20th week and prolonged oligohydramnios before delivery, who developed refractory hypoxia treated with oral bosentan as adjunct therapy to inhaled nitric oxide (iNO) and oral sildenafil. Conclusion Our experience suggests that bosentan can be used in the premature infant with PPHN after PPROM. To the best of our knowledge, this is the first report of bosentan treatment in a premature infant.

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.

CPAP combined with inhaled nitric oxide for treatment of lung hypoplasia and persistent foetal circulation due to prolonged PPROM

BACKGROUND

Second trimester preterm premature rupture of the membranes (PPROM) before 24 weeks of gestation is associated with a high morbidity and mortality rate.

AIM

To demonstrate the efficacy of early continuous positive airway pressure (CPAP) combined with inhaled nitric oxide (iNO) for treatment of preterm infants with lung hypoplasia and persistent foetal circulation (PFC) due to very early PPROM and prolonged severe oligohydramnios.

METHODS

Seven infants with prolonged PPROM, lung hypoplasia, respiratory distress and persistent foetal circulation were intubated in the delivery room for subsequent surfactant and iNO application. As our new treatment strategy was to keep the period of mechanical ventilation as short as possible, all infants were switched on nasal CPAP combined with iNO within the first 24 hours.

RESULTS

Mean gestational age at PPROM was 19+6 weeks (range 14+2 to 23+6 weeks) and the average latency period between rupture of membranes and delivery was 10+3 weeks (7+3 to 16+4 weeks). Infants were born at 30+3 weeks of gestation (28+3 to 33+1 weeks) with an average birth weight of 1468g (884 to 2200g). In all neonates CPAP combined with iNO reversed PFC and 6 patients stabilised without the need for reintubation and mechanical ventilation. One infant had to be reintubated following 12 hours of CPAP combined with iNO due to respiratory insufficiency. All seven infants survived to discharge.

CONCLUSION

CPAP combined with iNO might be a promising approach for therapy of preterm infants with lung hypoplasia and persistent foetal circulation due to very early PPROM.

Contemporary neonatal outcome following rupture of membranes prior to 25 weeks with prolonged oligohydramnios

BACKGROUND

Prolonged oligohydramnios following early preterm prelabour rupture of membranes (PPROM) is traditionally associated with high neonatal mortality and significant risk of pulmonary hypoplasia. However, recent evidence points to an apparent improvement in outcome.

AIMS

To document current neonatal outcomes following rupture of membranes prior to 25 weeks with severe persistent oligohydramnios and a latency to delivery of at least 14 days.

METHODS

A retrospective case note analysis over a 28-month period at Saint Luc University Hospital, Brussels.

RESULTS

From 23 pregnancies that were complicated by PPROM prior to 25 weeks, 15 infants were born after 24 weeks with a latency of more than 14 days and persistent oligohydramnios. Nine infants (60%) had severe respiratory failure and clinical signs compatible with pulmonary hypoplasia. Seven of these infants (78%) responded to high frequency ventilation and inhaled nitric oxide therapy with good clinical outcome but two died from severe respiratory failure. Five infants showed no clinical signs of pulmonary hypoplasia and responded to conventional neonatal management. One of these infants died at 77 days of age of necrotising enterocolitis. One infant was not resuscitated and died within minutes of birth, following prior discussion with the perinatal team and the parents. Survivors in this high-risk group (73%) had low morbidity at the time of discharge.

SUMMARY

The favourable neonatal survival and morbidity figures are in keeping with recent published evidence. This study confirms improved outcome even amongst the highest risk infants with documented persistent oligohydramnios.

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.

The effect of prolonged rupture of membranes on circulating neonatal nucleated red blood cells

OBJECTIVES

To test the hypothesis that absolute nucleated red blood cells (ANRBC) counts are higher at birth in infants who were born after prolonged rupture of membranes (PROM, >24 hours).

STUDY DESIGN

Retrospective study of 31 infants admitted to the neonatal intensive care unit who were born after PROM, and pair matched for gestational age and Apgar scores with 31 no PROM controls. Venous ANRBC counts were obtained within 1 hour of life.

RESULTS

Groups did not differ in birthweight, gestational age, Apgar scores, and platelets counts. The ANRBC counts and hematocrit were significantly higher in infants who were born after PROM than in controls.

CONCLUSIONS

Infants born after PROM have higher ANRBC counts at birth than control infants. We suggest that increased fetal erythropoiesis exists in infants who are delivered after PROM. If correct, our interpretation supports the theory that fetal hypoxia and/or ischemia may result from PROM.

Effect of lung hypoplasia on birth-related changes in the pulmonary circulation in sheep

Lung hypoplasia (LH) is a serious cause of neonatal compromise, but little is known of its functional effects on the pulmonary circulation. Our aim was to characterize birth-related changes in the pulmonary circulation of newborn lambs with LH and to compare them with alterations in respiratory function. LH was induced in six ovine fetuses by the creation of a tracheo-amniotic shunt as well as amniotic fluid drainage starting at 105.6+/-1.5 (mean+/-SEM) days of gestation (term approximately 147 d). At 139.9+/-0.3 d, fetuses were exteriorized under anesthesia to implant vascular catheters and an ultrasonic flow probe around the left pulmonary artery. The lambs then were delivered and ventilated for 2 h, during which systemic and pulmonary artery pressures, left pulmonary blood flow, and measures of respiratory function were recorded. At autopsy, lungs were weighed and volume was measured at 20 cm H2O. In LH lambs, lung weight was 25% lower and respiratory system compliance was 30% lower than in controls. Mean pulmonary blood flow in LH lambs was 42% lower and pulmonary vascular resistance was 138% higher than in controls. Morphometry showed that volume density of pulmonary arteries in LH was 30% lower than in controls. We conclude that, in this LH model, changes in ventilatory indices were proportional to the change in lung size, whereas changes in the pulmonary circulation were greater than the change in lung size and were associated with reduced density of pulmonary arteries. LH severely impairs normal adaptation of the pulmonary circulation in the perinatal period.

Nitric oxide in preterm infant with pulmonary hypoplasia

Premature infants with hypoplastic lungs may have elevated pulmonary vascular resistance with right to left shunt across ductus arteriosus and/or foramen ovale. Inhaled nitric oxide (NO) being selective pulmonary vasodilator without significant effects on systemic circulation can potentially reverse this shunt. The authors herewith report a case of a premature infant with severe hypoxemic respiratory failure after preterm premature prolonged rupture of membranes leading to oligohydramnios and pulmonary hypoplasia that was treated successfully with NO and describe the neurodevelopmental outcome at 1 year of age.