Use of inhaled nitric oxide in preterm vs term/near-term neonates with pulmonary hypertension: results of the PaTTerN registry study

A multicenter epidemiological survey of iNO use in preterm infants in China

OBJECTIVE

To investigate the use of inhaled nitric oxide (iNO) in hospitalized preterm infants in China over 10 years and its clinical outcomes.

METHODS

A total of 616 premature infants who were administered iNO in the Neonatology Departments of 5 Class A tertiary hospitals in China for ten years from January 2013 to December 2022 were included retrospectively. Based on their enrollment periods, the patients were divided into two groups: Group 1 from January 2013 to December 2017 and Group 2 from January 2018 to December 2022, respectively. The perinatal characteristics, short-term clinical outcomes, and mortality rates were compared between these two groups.

RESULTS

The utilization of iNO in preterm infants grew annually over the past10 years; the utilization of iNO in Group 2 infants increased approximately one-fold when compared with Group 1 (1.52% vs. 0.80%, p < .001), and the increase was greater in gestational age (GA) < 34 weeks compared with 34-36 weeks preterm infants. Moreover, the iNO usage in Group 1 infants with GA < 34 weeks increased from 1.14% to 2.46% and 0.60% to 0.99% in 34-36 weeks preterm infants (p < .001) in Group 2, respectively. Apart from a smaller GA (32.9 w vs. 33.5 w, p < .001) and birth weight (BW, 1900 g vs. 2141 g, p < .001), the initial [14 parts per million (ppm) versus 10 ppm, p < .001] and maximum (15 ppm vs. 10 ppm, p < .001) doses of Group 2 were larger; however, their recent clinical outcomes did not improve with increasing iNO utilization (p > .05)as compared to Group 1, respectively. Although the overall iNO preterm mortality rates over the past 10 years were 25.8%, the mortality rates for preterm infants at 34-36 weeks were significantly lower than for preterm infants at GA < 34 weeks (15.4% vs. 33.8%, p < .001). Nonetheless, no improvement in mortality was observed in Group 2 preterm infants with GA < 34 weeks for the past 5 years when compared with Group 1 (32.9% vs. 35.8%, p > .05) infants, and significantly lower mortality rates were noticed in preterm infants with 34-36 weeks (11.2% vs. 22.7%, p < .001). Patients with hypoxic respiratory failure (HRF) or persistent pulmonary hypertension of the newborn (PPHN) iNO preterm infants did not show lower mortality rates with the increase of iNO use rate (p > .05). The overall mortality rates of preterm PPHN infants with iNO were lower than that of HRF (20.2% vs. 36.5%, p < .001), while the mortality rates of Group 2 preterm PPHN infants with iNO significantly lower than that of HRF (17.7% vs 36.0%, p < .001).

CONCLUSION

The iNO has been extensively used in Chinese preterm infants over the past 10 years, this increase was more significant in preterm infants with GA < 34 weeks. Moreover, preterm infants using iNO have lower GA and BW, larger initial and maximum doses, and more aggressive strategies in the last past 5 years. Although iNO use in preterm infants with GA of 34-36 weeks has significantly reduced mortality, mortality rates and short-term clinical outcomes of iNO in preterm infants <34 weeks of GA has no obvious improvement. Further studies are required to investigate the efficacy and safety of iNO in preterm infants <34 weeks of GA.

Retrospective study of preterm infants exposed to inhaled nitric oxide in Kaiser Permanente Southern California: morbidity, mortality and follow-up

OBJECTIVE

Describe characteristics of preterm infants exposed to inhaled nitric oxide (iNO) in Kaiser Permanente Southern California.

STUDY DESIGN

Case review of preterm infants <34-weeks exposed to iNO during 2010-2020 including respiratory and echocardiographic status, NICU course, and 12-month follow-up.

RESULTS

270 infants, 2.63% of births<34 weeks, (median, range: 26.1, 225/7-336/7 weeks gestation) were exposed to iNO. Median FiO2 at iNO initiation was 1.0 (IQR 0.94-1.0). Pulmonary hypertension (PH) was not associated with risk-adjusted 2 h oxygenation response or improved survival. Mortality to NICU discharge was 37.4%. Median cost of iNO was $7,695/patient. Discharged survivors experienced frequent rehospitalization (34.9%), use of supplemental oxygen, sildenafil, diuretics, bronchodilators, and steroids. Four infants had persistent PH. Five infants died after NICU discharge.

CONCLUSIONS

Preterm infants receiving iNO have high mortality and 1st year morbidity. As currently used, iNO may be an indicator of respiratory disease severity rather than mediator of improved outcomes.

Inhaled Nitric Oxide in Neonatal Pulmonary Hypertension

Pivotal trials investigating the use of inhaled nitric oxide (iNO) in the 1990s led to approval by the Food and Drug Administration in 1999. Inhaled nitric oxide is the only approved pulmonary vasodilator for persistent pulmonary hypertension of the newborn (PPHN). Selective pulmonary vasodilation with iNO in near-term and term neonates with PPHN is safe, and targeted use of iNO in less mature neonates with pulmonary hypertension (PH) can be beneficial. This review addresses a brief history of iNO, clinical features of neonatal PH, and the clinical application of iNO.

Neurodevelopmental outcomes of preterm neonates receiving rescue inhaled nitric oxide in the first week of age: a cohort study

OBJECTIVE

To assess the neurodevelopmental outcomes of preterm neonates who received inhaled nitric oxide (iNO) in the first week of age for hypoxaemic respiratory failure (HRF).

METHODS

In this retrospective cohort study, we included neonates born at <29 weeks gestational age (GA) between January 2010 and December 2018 who had a neurodevelopmental assessment at 18-24 months corrected age (CA) at one of the Canadian Neonatal Follow-Up Network clinics. The primary outcome was neurodevelopmental impairment (NDI). We performed propensity score-matched analysis to compare the outcomes of those who received and did not receive iNO.

RESULTS

Of the 5612 eligible neonates, 460 (8.2%) received iNO in the first week of age. Maternal age, receipt of antenatal corticosteroids, GA and birth weight were lower in the iNO group compared with the no-iNO group. Neonates in the iNO group had higher illness severity scores and higher rates of preterm prolonged rupture of membranes and were small for GA. Severe brain injury, bronchopulmonary dysplasia and mortality were higher in the iNO group. Of the 4889 survivors, 3754 (77%) neonates had follow-up data at 18-24 months CA. After propensity score matching, surviving infants who received rescue iNO were not associated with higher odds of NDI (adjusted OR 1.34; 95% CI 0.85 to 2.12).

CONCLUSIONS

In preterm neonates <29 weeks GA with HRF, rescue iNO use was not associated with worse neurodevelopmental outcomes among survivors who were assessed at 18-24 months CA.

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.

Practices and Outcomes from a Prospective, Multicenter Registry for Preterm Newborns with Pulmonary Hypertension

OBJECTIVE

To describe current treatment practices of preterm infants with early hypoxemic respiratory failure (HRF) and pulmonary hypertension (PH) and their association with patient outcomes.

STUDY DESIGN

We developed a prospective, observational, multicenter clinical registry of preterm newborns <34 weeks' gestation with HRF and PH, based on either clinical or echocardiographic evidence during the first 72 hours of life, from 28 neonatal intensive care units in the US from 2017 through 2022. The primary end point was mortality among those who did or did not receive PH-targeted treatment, and the secondary end points included comparisons of major morbidities. Variables were compared using t tests, Wilcoxon rank-sum tests, Fisher exact tests, and χ² tests.

RESULTS

We analyzed the results of 224 preterm infants enrolled in the registry. Of which, 84% (188/224) received PH-targeted treatment, most commonly inhaled nitric oxide (iNO). Early mortality in this cohort was high, as 33% (71/224) of this sample died in the first month of life, and 77% of survivors (105/137) developed bronchopulmonary dysplasia. Infants who received PH-targeted treatment had higher oxygenation indices at the time of enrollment (28.16 [IQR: 13.94, 42.5] vs 15.46 [IQR: 11.94, 26.15]; P = .0064). Patient outcomes did not differ between those who did or did not receive PH-targeted therapy.

CONCLUSIONS

Early-onset HRF with PH in preterm infants is associated with a high early mortality and a high risk of developing bronchopulmonary dysplasia. iNO is commonly used to treat early-onset PH in preterm infants with HRF. In comparison with untreated infants with lower oxygenation indices, iNO treatment in severe PH may prevent poorer outcomes.

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.

Association between immediate oxygenation response and survival in preterm infants receiving rescue inhaled nitric oxide therapy for hypoxemia from pulmonary hypertension: A systematic review and meta-analysis

PURPOSE

To investigate whether immediate response to inhaled nitric oxide (iNO) therapy is associated with reduced mortality in preterm infants with hypoxemic respiratory failure (HRF) and pulmonary hypertension (PH).

METHODS

A systematic review and meta-analysis of observational studies was conducted to examine the association between immediate response (improved oxygenation ≤6 h) compared to non-response, and all-cause mortality among preterm infants <34 weeks gestational age without congenital anomalies or genetic disorders who received iNO treatment. Adjusted and unadjusted odds ratio, were pooled using a random effects meta-analysis Hartung-Knapp-Sidik-Jonkman approach. Subgroup analyses were planned for infants with preterm premature rupture of membranes (PPROM) and those treated within 72 h after birth.

RESULTS

The primary analysis included 5 eligible studies, a total of 400 infants (196 responders; 204 non-responders). The studies were rated as low to moderate risk of bias based on the Quality in Prognostic Studies tool. Immediate iNO responsiveness was associated with reduced odds of mortality [odds ratio (OR) 0.22, 95 % confidence interval (95 % CI) (0.10-0.49)]. Although there was insufficient data for a subgroup analysis of infants with PPROM, infants treated with iNO within 72 h demonstrated consistent findings of reduced mortality [OR 0.21 95 % CI (0.13-0.36)]. Based on the GRADE approach, considering the risk of bias of included studies, the overall strength of evidence was rated as moderate.

CONCLUSION

There is evidence to suggest that immediate improvement in oxygenation following iNO therapy is associated with reduced odds of mortality before discharge in preterm infants with HRF and clinically suspected or confirmed PH.

Inhaled nitric oxide in preterm neonates with preterm prelabour rupture of membranes, a systematic review

AIM

To perform a systematic literature review to determine the effect of inhaled nitric oxide (iNO) on oxygenation, mortality and morbidity in preterm neonates with preterm prelabour rupture of membranes (PPROM) and early hypoxaemic respiratory failure (HRF).

METHODS

MEDLINE, Embase, Cochrane Central Register of Controlled Trials, ClinicalTrials.gov, Web of Science, Zetoc and ProQuest were searched. Studies including neonates <34 weeks' gestation with PPROM, oligohydramnios or pulmonary hypoplasia and HRF in the first 28 days of life treated with iNO were included. Studies were critically appraised and assessed for potential risk of bias using standardised checklists.

RESULTS

Six hundred and two records remained after duplicates were removed. Seven studies were included in the critical appraisal process. Quality of available evidence was very low to low. Six studies described an improvement in oxygenation after commencement of iNO. One hundred and three of 284 (36%) neonates exposed to iNO died. Seventy-seven of 92 (84%) neonates that had an echocardiogram performed before commencement of iNO had pulmonary hypertension (PH) present.

CONCLUSION

iNO may improve oxygenation when standard care fails. Improvement in oxygenation is likely associated with increase in survival. Survival may lead to an increase in morbidity. Efficacy of iNO in this cohort is likely secondary to relatively high prevalence of PH.

Pulmonary vasodilator strategies in neonates with acute hypoxemic respiratory failure and pulmonary hypertension

The management of acute hypoxemic respiratory failure (AHRF) in newborns continues to be a clinical challenge with elevated risk for significant morbidities and mortality, especially when accompanied with persistent pulmonary hypertension of the newborn (PPHN). PPHN is a syndrome characterized by marked hypoxemia secondary to extrapulmonary right-to-left shunting across the ductus arteriosus and/or foramen ovale with high pulmonary artery pressure and increased pulmonary vascular resistance (PVR). After optimizing respiratory support, cardiac performance and systemic hemodynamics, targeting persistent elevations in PVR with inhaled nitric oxide (iNO) therapy has improved outcomes of neonates with PPHN physiology. Despite aggressive cardiopulmonary management, a significant proportion of patients have an inadequate response to iNO therapy, prompting consideration for additional pulmonary vasodilator therapy. This article reviews the pathophysiology and management of PPHN in term newborns with AHRF while highlighting both animal and human data to inform a physiologic approach to the use of PH-targeted therapies.