Safety and efficacy of inhaled nitric oxide treatment for premature infants with respiratory distress syndrome: follow-up evaluation at early school age

Inhaled nitric oxide (iNO) for preventing prematurity-related bronchopulmonary dysplasia (BPD): 7-year follow-up of the European Union Nitric Oxide (EUNO) trial

OBJECTIVES

Most studies of inhaled nitric oxide (iNO) for prevention of bronchopulmonary dysplasia (BPD) in premature infants have focused on short-term mortality and morbidity. Our aim was to determine the long-term effects of iNO.

METHODS

A 7-year follow-up was undertaken of infants entered into a multicenter, double-blind, randomized, placebo-controlled trial of iNO for prevention of BPD in premature infants born between 24 and 28 weeks plus six days of gestation. At 7 years, survival and hospital admissions since the 2-year follow-up, home oxygen therapy in the past year, therapies used in the previous month and growth assessments were determined. Questionnaires were used to compare general health, well-being, and quality of life.

RESULTS

A total of 305 children were assessed. No deaths were reported. Rates of hospitalization for respiratory problems (6.6 vs. 10.5%, iNO and placebo group, respectively) and use of respiratory medications (6.6 vs. 9.2%) were similar. Two patients who received iNO and one who received placebo had received home oxygen therapy. There were no significant differences in any questionnaire-documented health outcomes.

CONCLUSIONS

iNO for prevention of BPD in very premature infants with respiratory distress did not result in long-term benefits or adverse long-term sequelae. In the light of current evidence, routine use of iNO cannot be recommended for prevention of BPD in preterm infants.

Effect of Inhaled Nitric Oxide on Survival Without Bronchopulmonary Dysplasia in Preterm Infants: A Randomized Clinical Trial

IMPORTANCE

Bronchopulmonary dysplasia (BPD) occurs in approximately 40% of infants born at younger than 30 weeks' gestation and is associated with adverse pulmonary and neurodevelopmental outcomes.

OBJECTIVE

To test whether administration of inhaled nitric oxide to preterm infants requiring positive pressure respiratory support on postnatal days 5 to 14 improves the rate of survival without BPD.

DESIGN, SETTING, AND PARTICIPANTS

This intent-to-treat study was a randomized clinical trial performed at 33 US and Canadian neonatal intensive care units. Participants included 451 neonates younger than 30 weeks' gestation with birth weight less than 1250 g receiving mechanical ventilation or positive pressure respiratory support on postnatal days 5 to 14. Enrollment spanned from December 23, 2009, to April 23, 2012, and neurodevelopmental outcome studies were completed by April 4, 2014.

INTERVENTIONS

Placebo (nitrogen) or inhaled nitric oxide initiated at 20 ppm was decreased to 10 ppm between 72 and 96 hours after starting treatment and then to 5 ppm on day 10 or 11. Infants remained on the 5-ppm dose until completion of therapy (24 days).

MAIN OUTCOMES AND MEASURES

The primary outcome was the rate of survival without BPD at 36 weeks' postmenstrual age (PMA). Secondary outcomes included BPD severity, postnatal corticosteroid use, respiratory support, survival, and neurodevelopmental outcomes at 18 to 24 months' PMA.

RESULTS

In total, 222 infants (52.3% male [n = 116]) received placebo, and 229 infants (50.2% male [n = 115]) received inhaled nitric oxide. Their mean (SD) gestation was 25.6 (1.5) vs 25.6 (1.4) weeks, and their mean (SD) birth weight was 750 (164) vs 724 (160) g. Survival without BPD at 36 weeks' PMA was similar between the placebo and inhaled nitric oxide groups (31.5% [n = 70] vs 34.9% [n = 80]) (odds ratio, 1.17; 95% CI, 0.79-1.73). Rates for severe BPD (26.6% [55 of 207] vs 20.5% [43 of 210]) and postnatal corticosteroid use for BPD (41.0% [91 of 222] vs 41.5% [95 of 229]) and the mean (SD) days of positive pressure respiratory support (55 [40] vs 54 [42]), oxygen therapy (88 [41] vs 91 [59]), and hospitalization (105 [37] vs 108 [54]) were equivalent between the 2 groups. No differences in the incidence of common morbidities were observed. Respiratory outcomes on discharge to home, at 1 year, and at age 18 to 24 months' PMA and neurodevelopmental assessments at 18 to 24 months' PMA did not differ between groups.

CONCLUSIONS AND RELEVANCE

Inhaled nitric oxide, initiated at 20 ppm on postnatal days 5 to 14 to high-risk preterm infants and continued for 24 days, appears to be safe but did not improve survival without BPD at 36 weeks' PMA or respiratory and neurodevelopmental outcomes at 18 to 24 months' PMA.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00931632.

In Premature Newborns Intraventricular Hemorrhage Causes Cerebral Vasospasm and Associated Neurodisability via Heme-Induced Inflammasome-Mediated Interleukin-1 Production and Nitric Oxide Depletion

BACKGROUND

Intraventricular hemorrhage (IVH) occurs in 60-70% of neonates weighing 500-750 g and 10-20% of those weighing 1,000-1,500 g. All forms of IVH have been associated with neurocognitive deficits. Both subarachnoid and IVHs have been associated with delayed vasospasm leading to neurological deficits. Pathways linking hemoglobin release from blood clots to vasospasm include heme-induced activation of inflammasomes releasing interleukin-1 (IL-1) that can cause calcium dependent and independent vasospasm. Free hemoglobin is a potent scavenger of nitric oxide (NO). Depletion of NO, a potent endogenous vasodilator, has been associated with features of vasospasm.

HYPOTHESIS

In premature newborns, IVH causes cerebral vasospasm and associated neurodisability via heme-induced increased inflammasome-mediated IL-1 production and NO depletion.

CONFIRMATION OF HYPOTHESIS AND IMPLICATIONS

This hypothesis could be confirmed in the IVH animal model with visualization of any associated vasospasm by angiography and in newborns with IVH by transcranial Doppler ultrasonography and correlation with cerebrospinal fluid IL-1 and NO metabolite levels. Confirmation of the role of heme in activation of inflammasomes causing IL-1 production and NO binding could be achieved by measuring the effect of heme scavenging interventions on IL-1 levels and levels of NO metabolites. In addition to removal of the accumulated blood of an IVH by drainage, irrigation, and fibrinolytic therapy intrathecal application of vasodilators and heme scavenging agents like haptoglobin and haemopexin and systemic treatment with inhibitors of inflammasomes like telmisartan could be used to prevent and treat cerebral vasospasm, and thus reduce the risk of associated brain injury in premature neonates.

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.

Inhaled nitric oxide usage in preterm infants in the NICHD Neonatal Research Network: inter-site variation and propensity evaluation

OBJECTIVE

The use of inhaled nitric oxide (iNO) in preterm infants remains controversial. In October 2010, a National Institutes of Health consensus development conference cautioned against use of iNO in preterm infants. This study aims (1) to determine the prevalence and variability in use of iNO in the Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Research Network (NICHD NRN) before and after the consensus conference and (2) separately, to examine associations between iNO use and severe bronchopulmonary dysplasia (BPD) or death.

STUDY DESIGN

The NICHD NRN Generic Database collects data including iNO use on very preterm infants. A total of 13 centers contributed data across the time period 2008 to 2011. Infants exposed or not to iNO were compared using logistic regression, which included factors related to risk as well as their likelihood of being exposed to iNO.

RESULT

A total of 4885 infants were assessed between 2008 and 2011; 128 (2.6%) received iNO before day 7, 140 (2.9%) between day 7 and 28, and 47 (1.0%) at >28 days. Center-specific iNO use during 2008 to 2010 ranged from 21.9 to 0.4%; 12 of 13 sites reduced usage and overall NRN iNO usage decreased from 4.6 to 1.6% (P<0.001) in 2011. The use of iNO started between day 7 and day 14 was more prevalent among younger infants with more severe courses in week 1 and associated with increased risk of severe BPD or death (odds ratio 2.24; 95% confidence interval 1.23 to 4.07).

CONCLUSION

The variability and total use of iNO decreased in 2011 compared with 2008 to 2010. iNO administration started at ⩾ day 7 was associated with more severe outcomes compared with infants without iNO exposure.

Respiratory distress syndrome at birth is a risk factor for hospitalization for lower respiratory tract infections in infancy

BACKGROUND

Respiratory distress syndrome (RDS) and hospitalization for lower respiratory tract infection (LRTI; specifically, respiratory syncytial virus) are important causes of morbidity in infancy. Whether RDS at birth is an independent risk factor for LRTI is unknown. This study estimated the risk of LRTI-related hospitalization among late preterm infants with a history of RDS.

METHODS

The population-based cohort from Québec included all late preterm infants (32-36 weeks gestational age) born in 1996 to 1997. RDS was identified by International Classification of Diseases, Ninth Revision code 769, and a comparison cohort generated from all without RDS. A multivariable model estimated the adjusted odds ratio of LRTI-related hospitalization among late preterm infants with a history of RDS; and the incidence and increased risk of childhood chronic respiratory morbidity was calculated.

RESULTS

Of the 7488 late preterms, 459 (6.1%) had a history of RDS; 525 late preterms (7.0%) were hospitalized for LRTI in infancy, including 57 (12.4%) with RDS. The adjusted odds ratio for LRTI-related hospitalization associated with RDS was 1.6 (1.2-2.2). Other significant risk factors included male sex, or diagnosis of other respiratory conditions, diaphragm anomalies, bacteremia, intraventricular hemorrhage, congenital heart disease or respiratory system anomalies. Late preterm infants with a history of RDS were also at a significantly increased risk of childhood chronic respiratory morbidity.

CONCLUSIONS

Late preterms with a history of RDS are at a 60% increased risk of LRTI-related hospitalization in infancy compared with late preterm infants without RDS. Such infants may benefit from interventions decreasing the risk of contracting respiratory viruses causing acute LRTI.