Inhaled nitric oxide for respiratory failure in preterm infants

Nature of the Ru-NO Coordination Bond: Kohn-Sham Molecular Orbital and Energy Decomposition Analysis

We have analyzed structure, stability, and Ru-NO bonding of the trans-[RuCl(NO)(NH3)4]2+ complex by using relativistic density functional theory. First, we focus on the bond dissociation energies associated with the three canonical dissociation modes leading to [RuCl(NH3)4]++NO+, [RuCl(NH3)4]2++NO, and [RuCl(NH3)4]3++NO-. The main objective is to understand the Ru-NO+ bonding mechanism in the conceptual framework of Kohn-Sham molecular orbital theory in combination with a quantitative energy decomposition analysis. In our analyses, we have addressed the importance of the synergism between Ru-NO+ σ-donation and π-backdonation as well as the so-called negative trans influence of the Cl- ligand on the Ru-NO bond. For completeness, the Ru-NO+ bonding mechanism is compared with that of the corresponding Ru-CO bond.

Inhaled nitric oxide for respiratory failure in preterm infants

BACKGROUND

Inhaled nitric oxide (iNO) is effective in term infants with hypoxic respiratory failure. The pathophysiology of respiratory failure and the potential risks of iNO differ substantially in preterm infants, necessitating specific study in this population.

OBJECTIVES

To determine effects of treatment with inhaled nitric oxide (iNO) on death, bronchopulmonary dysplasia (BPD), intraventricular haemorrhage (IVH) or other serious brain injury and on adverse long-term neurodevelopmental outcomes in preterm newborn infants with hypoxic respiratory failure.Owing to substantial variation in study eligibility criteria, which decreases the utility of an overall analysis, we divided participants post hoc into three groups: (1) infants treated over the first three days of life because of defects in oxygenation, (2) preterm infants with evidence of pulmonary disease treated routinely with iNO and (3) infants treated later (after three days of age) because of elevated risk of BPD.

SEARCH METHODS

We used standard methods of the Cochrane Neonatal Review Group. We searched MEDLINE, Embase, Healthstar and the Cochrane Central Register of Controlled Trials in the Cochrane Library through January 2016. We also searched the abstracts of the Pediatric Academic Societies.

SELECTION CRITERIA

Eligible for inclusion were randomised and quasi-randomised studies in preterm infants with respiratory disease that compared effects of iNO gas versus control, with or without placebo.

DATA COLLECTION AND ANALYSIS

We used standard methods of the Cochrane Neonatal Review Group and applied the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to assess the quality of evidence.

MAIN RESULTS

We found 17 randomised controlled trials of iNO therapy in preterm infants. We grouped these trials post hoc into three categories on the basis of entry criteria: treatment during the first three days of life for impaired oxygenation, routine use in preterm babies along with respiratory support and later treatment for infants at increased risk for bronchopulmonary dysplasia (BPD). We performed no overall analyses.Eight trials providing early rescue treatment for infants on the basis of oxygenation criteria demonstrated no significant effect of iNO on mortality or BPD (typical risk ratio (RR) 0.94, 95% confidence interval (CI) 0.87 to 1.01; 958 infants). Four studies examining routine use of iNO in infants with pulmonary disease reported no significant reduction in death or BPD (typical RR 0.94, 95% CI 0.87 to 1.02; 1924 infants), although this small effect approached significance. Later treatment with iNO based on risk of BPD (three trials) revealed no significant benefit for this outcome in analyses of summary data (typical RR 0.92, 95% CI 0.85 to 1.01; 1075 infants).Investigators found no clear effect of iNO on the frequency of all grades of IVH nor severe IVH. Early rescue treatment was associated with a non-significant 20% increase in severe IVH.We found no effect on the incidence of neurodevelopmental impairment.

AUTHORS' CONCLUSIONS

iNO does not appear to be effective as rescue therapy for the very ill preterm infant. Early routine use of iNO in preterm infants with respiratory disease does not prevent serious brain injury or improve survival without BPD. Later use of iNO to prevent BPD could be effective, but current 95% confidence intervals include no effect; the effect size is likely small (RR 0.92) and requires further study.

Methemoglobin and nitric oxide therapy in Ugandan children hospitalized for febrile illness: results from a prospective cohort study and randomized double-blind placebo-controlled trial

BACKGROUND

Exposure of red blood cells to oxidants increases production of methemoglobin (MHb) resulting in impaired oxygen delivery to tissues. There are no reliable estimates of methemoglobinemia in low resource clinical settings. Our objectives were to: i) evaluate risk factors for methemoglobinemia in Ugandan children hospitalized with fever (study 1); and ii) investigate MHb responses in critically ill Ugandan children with severe malaria treated with inhaled nitric oxide (iNO), an oxidant that induces MHb in a dose-dependent manner (study 2).

METHODS

Two prospective studies were conducted at Jinja Regional Referral Hospital in Uganda between 2011 and 2013. Study 1, a prospective cohort study of children admitted to hospital with fever (fever cohort, n = 2089 children 2 months to 5 years). Study 2, a randomized double-blind placebo-controlled parallel arm trial of room air placebo vs. 80 ppm iNO as an adjunctive therapy for children with severe malaria (RCT, n = 180 children 1-10 years receiving intravenous artesunate and 72 h of study gas). The primary outcomes were: i) masimo pulse co-oximetry elevated MHb levels at admission (>2 %, fever cohort); ii) four hourly MHb levels in the RCT.

RESULTS

In the fever cohort, 34 % of children admitted with fever had elevated MHb at admission. Children with a history of vomiting, delayed capillary refill, elevated lactate, severe anemia, malaria, or hemoglobinopathies had increased odds of methemoglobinemia (p < 0.05 in a multivariate model). MHb levels at admission were higher in children who died (n = 89) compared to those who survived (n = 1964), p = 0.008. Among children enrolled in the iNO RCT, MHb levels typically plateaued within 12-24 h of starting study gas. MHb levels were higher in children receiving iNO compared to placebo, and MHb > 10 % occurred in 5.7 % of children receiving iNO. There were no differences in rates of study gas discontinuation between trial arms.

CONCLUSIONS

Hospitalized children with evidence of impaired oxygen delivery, metabolic acidosis, anemia, or malaria were at risk of methemoglobinemia. However, we demonstrated high-dose iNO could be safely administered to critically ill children with severe malaria with appropriate MHb monitoring.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01255215 (Date registered: December 5, 2010).

Antenatal insults modify newborn olfactory function by nitric oxide produced from neuronal nitric oxide synthase

Newborn feeding, maternal, bonding, growth and wellbeing depend upon intact odor recognition in the early postnatal period. Antenatal stress may affect postnatal odor recognition. We investigated the exact role of a neurotransmitter, nitric oxide (NO), in newborn olfactory function. We hypothesized that olfactory neuron activity depended on NO generated by neuronal NO synthase (NOS). Utilizing in vivo functional manganese enhanced MRI (MEMRI) in a rabbit model of cerebral palsy we had shown previously that in utero hypoxia-ischemia (H-I) at E22 (70% gestation) resulted in impaired postnatal response to odorants and poor feeding. With the same antenatal insult, we manipulated NO levels in the olfactory neuron in postnatal day 1 (P1) kits by administration of intranasal NO donors or a highly selective nNOS inhibitor. Olfactory function was quantitatively measured by the response to amyl acetate stimulation by MEMRI. The relevance of nNOS to normal olfactory development was confirmed by the increase of nNOS gene expression from fetal ages to P1 in olfactory epithelium and bulbs. In control kits, nNOS inhibition decreased NO production in the olfactory system and increased MEMRI slope enhancement. In H-I kits the MEMRI slope did not increase, implicating modification of endogenous NO-mediated olfactory function by the antenatal insult. NO donors as a source of exogenous NO did not significantly change function in either group. In conclusion, olfactory epithelium nNOS in newborn rabbits probably modulates olfactory signal transduction. Antenatal H-I injury remote from delivery may affect early functional development of the olfactory system by decreasing NO-dependent signal transduction.

Inhaled nitric oxide for respiratory failure in preterm infants

BACKGROUND

Inhaled nitric oxide (iNO) is effective in term infants with hypoxic respiratory failure. The pathophysiology of respiratory failure and the potential risks of iNO differ substantially in preterm infants, necessitating study in this population.

OBJECTIVES

To determine the effect of treatment with iNO on death, bronchopulmonary dysplasia (BPD), intraventricular hemorrhage (IVH), and neurodevelopmental disability in preterm newborn infants with respiratory disease.

SEARCH STRATEGY

Standard methods of the Cochrane Neonatal Review Group were used. MEDLINE, EMBASE, Healthstar and the Cochrane Central Register of Controlled Trials (The Cochrane Library) were searched covering the years from 1985 to 2010. In addition, the abstracts of the Pediatric Academic Societies were also searched.

SELECTION CRITERIA

Randomized and quasi-randomized studies in preterm infants with respiratory disease that compared the effects of iNO gas to control, with or without placebo were eligible.

DATA COLLECTION AND ANALYSIS

Standard methods of the Cochrane Neonatal Review Group were used.

MAIN RESULTS

Fourteen randomized controlled trials of inhaled nitric oxide therapy in preterm infants were found. The trials have been grouped post hoc into three categories depending on entry criteria; entry in the first three days of life based on oxygenation criteria, routine use in preterm babies with pulmonary disease, and later enrolment based on an increased risk of BPD. No overall analyses were performed.Nine trials of early rescue treatment of infants based on oxygenation criteria demonstrated no significant effect of iNO on mortality or BPD. Three studies with routine use of iNO in infants with pulmonary disease also demonstrated no significant reduction in death or BPD [typical RR 0.93 (95% CI 0.86 to 1.01)] although this small effect approached significance. Later treatment with iNO based on the risk of BPD (two trials) demonstrated no significant benefit for this outcome in analyses which are possible using summary data.There is no clear effect of iNO on the frequency of all grades of IVH or of severe IVH. Early rescue treatment was associated with a non-significant 20% increase in severe IVH.No effect on the incidence of neurodevelopmental impairment was found.

AUTHORS' CONCLUSIONS

iNO as rescue therapy for the very ill preterm infant does not appear to be effective. Early routine use of iNO in preterm infants with respiratory disease does not affect serious brain injury or improve survival without BPD. Later use of iNO to prevent BPD might be effective, but requires further study.

Nitric oxide plays a key role in myelination in the developing brain

Inhaled nitric oxide (iNO) is one of the most promising therapies used in neonates, but there is little information available about its effect on the developing brain. We explored the effects of both iNO and endogenous NO on developing white matter in rodents. Rat or mouse pups and their mothers were placed in a chamber containing 5 to 20 ppm of NO for 7 days after birth. Neonatal exposure to iNO was associated with a transient increase in central nervous system myelination in rats and C57BL/6 mice without any deleterious effects at low doses (5 ppm) or behavioral consequences in adulthood. Exposure to iNO was associated with a proliferative effect on immature oligodendrocytes and a subsequent promaturational effect. The role of endogenous NO in myelination was investigated in animals treated with the nitric oxides synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME) in the neonatal period; this led to protracted myelination defects and subsequent behavioral deficits in adulthood. These effects were reversed by rescuing L-NAME-treated animals with iNO. Thus, we demonstrate considerable effect of both exogenous and endogenous NO on myelination in rodents. These data point to potential new avenues for neuroprotection in human perinatal brain damage.

Neuroprotective effect of inhaled nitric oxide on excitotoxic-induced brain damage in neonatal rat

Background

Inhaled nitric oxide (iNO) is one of the most promising therapies used in neonates. However, little information is known about its impact on the developing brain submitted to excitotoxic challenge.

Methodology/Principal Findings

We investigated here the effect of iNO in a neonatal model of excitotoxic brain lesions. Rat pups and their dams were placed in a chamber containing 20 ppm NO during the first week of life. At postnatal day (P)5, rat pups were submitted to intracranial injection of glutamate agonists. At P10, rat pups exposed to iNO exhibited a significant decrease of lesion size in both the white matter and cortical plate compared to controls. Microglia activation and astrogliosis were found significantly decreased in NO-exposed animals. This neuroprotective effect was associated with a significant decrease of several glutamate receptor subunits expression at P5. iNO was associated with an early (P1) downregulation of pCREB/pAkt expression and induced an increase in pAkt protein concentration in response to excitotoxic challenge (P7).

Conclusion

This study is the first describe and investigate the neuroprotective effect of iNO in neonatal excitotoxic-induced brain damage. This effect may be mediated through CREB pathway and subsequent modulation of glutamate receptor subunits expression.

Respiratory function during infancy in survivors of the INNOVO trial

RATIONALE

Despite encouraging reports suggesting that inhaled nitric oxide (iNO) appear to improve outcome in hypoxemic term and near term infants by improving oxygenation and reducing need for ECMO, the long-term benefits of iNO remain unclear. This study aimed to compare lung function at approximately 1 year in infants who were and were not randomly allocated to iNO as part of their neonatal management for severe respiratory failure at birth. Furthermore, results were compared to lung function of healthy infants.

METHODS

Maximal expiratory flow at functional residual capacity (V'maxFRC) was measured at approximately 1 year of age (corrected for any prematurity) in survivors of the INNOVO trial. Results were expressed as Z-scores, adjusted for sex and body size, based on data from healthy controls using identical techniques.

RESULTS

Technically satisfactory results were obtained in 30 infants (53% < 34 weeks gestation), 19 of whom were randomized to receive iNO V'maxFRC. Z-score was significantly reduced in infants with prior respiratory failure, whether or not they had been allocated to iNO (mean (SD) Z-score: -2.0 (1.2) and -2.6 (1.1), respectively, 95% CI difference; iNO vs. no iNO: -0.3; 1.6, P = 0.2). There was significant respiratory morbidity in both groups during the first year of life.

CONCLUSIONS

These results suggest that airway function remains reduced at 1 year of age following severe respiratory failure at birth, whether or not iNO is administered.

Chronic lung disease in newborns

Chronic lung disease (CLD) or bronchopulmonary dysplasia (BPD) occurs in preterm infants who require respiratory support in the first few days of birth. Apart from prematurity, oxygen therapy and assisted ventilation, factors like intrauterine/postnatal infections, patent ductus arteriosus, and genetic polymorphisms also contribute to its pathogenesis. The severe form of BPD with extensive inflammatory changes is rarely seen nowadays; instead, a milder form characterized by decreased alveolar septation due to arrest in lung development is more common. A multitude of strategies, mainly pharmacological and ventilatory, have been employed for prevention and treatment of BPD. Unfortunately, most of them have not been proved to be beneficial. A comprehensive protocol for management of BPD based on the current evidence is discussed here.

Pediatric acute lung injury

Among ventilated children, the incidence of acute lung injury (ALI) was 9%; of that latter group 80% developed the acute respiratory distress syndrome (ARDS). The population-based prevalence of pediatric ARDS was 5.5 cases/100.000 inhabitants. Underlying diseases in children were septic shock (34%), respiratory syncytial virus infections (16%), bacterial pneumonia (15%), near-drowning 9%, and others. Mortality ranged from 18% to 27% for ALI (including ALI-non ARDS and ARDS) and from 29% to 50% for ARDS. Mortality was only 3%-11% in children with ALI-non ARDS. As risk factors, oxygenation indices and multi-organ failure have been identified. New insights into the pathophysiology (for example the interplay between intraalveolar coagulation/fibrinolysis and inflammation and the genetic polymorphism for the angiotensin-converting enzyme) offer new therapeutic options. Lung protective mechanical ventilation with optimal lung recruitment is the mainstay of supportive therapy. New therapeutic modalities refer to corticosteroid and surfactant treatment. Well-designed follow up studies are needed.

What is new in ventilation strategies for the neonate?

A large number of ventilation strategies are now available for the neonate. This review has focused on new information, that is, studies published since 2000 and the implication of their results for current clinical practice. Meta-analysis of randomised trials has demonstrated that assist control and synchronous intermittent mandatory ventilation (SIMV) shortens the duration of ventilation only if started in the recovery rather than the early stage of respiratory disease. A recent randomised trial demonstrated pressure-regulated volume control ventilation may also have no advantages if started early. Weaning by SIMV with pressure support is better (reducing oxygen dependency) than SIMV alone. Meta-analysis of volume-targeted ventilation demonstrated significant reductions in the duration of ventilation and pneumothorax, but the trials were small and of different designs. Volume guarantee may provide more consistent blood gas control. The level of volume targeting appears to be crucial to the success of this technique. Meta-analysis of randomised trials of prophylactic high-frequency oscillation trials has shown a modest reduction in bronchopulmonary dysplasia. Randomised trials have failed to confirm the advantages of nasal continuous positive airway pressure (NCPAP) seen in various non-randomised studies; however, the randomised trials reported to date have been small. Inhaled nitric oxide (NO) does not improve the outcome of prematurely born infants with severe respiratory failure, but early low-dose prolonged iNO appears to have benefits that merit further testing. More randomised trials with long-term outcomes are required to identify the optimal ventilation strategy(ies) for the neonate.

How has research in the past 5 years changed my clinical practice

This article discusses how research in the past 5 years into management strategies influencing respiratory outcomes has changed (or not changed) the author's clinical practice. Changes include using inhaled nitric oxide but no longer systemic pulmonary vasodilators in term born infants with pulmonary hypertension. Use of postnatal steroids is now restricted to systemic administration in infants with severe respiratory failure and who are ventilator dependent beyond 2 weeks of age. Infants with bronchopulmonary dysplasia, unless they have pulmonary hypertension, are maintained at oxygen saturation levels of 90-92% rather than >/=95%. Supine sleeping is instituted in prematurely born infants without contraindications several weeks prior to neonatal discharge to reinforce to parents the importance of supine sleeping their baby at home. Further research is required to identify the optimal respiratory support strategy, particularly for very immature infants.

Inhaled nitric oxide for respiratory failure in preterm infants

BACKGROUND

Inhaled nitric oxide (iNO) has been proven to be effective in term infants with hypoxic respiratory failure. The pathophysiology of respiratory failure, and the potential risks, differ substantially in preterm infants. Therefore, analysis of the efficacy and toxicities of iNO in infants born before 35 weeks is necessary.

OBJECTIVES

To determine the effect of treatment with iNO on the rates of death, bronchopulmonary dysplasia (BPD), intraventricular haemorrhage (IVH), or neurodevelopmental disability in preterm newborn infants (< 35 weeks gestation) with respiratory disease.

SEARCH STRATEGY

Standard methods of the Cochrane Neonatal Review Group were used. MEDLINE, EMBASE, Healthstar and the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library) were searched, using the following keywords: nitric oxide, clinical trial, and newborn covering the years from 1985 to 2006. In addition, the abstracts of the Pediatric Academic Societies were also searched.

SELECTION CRITERIA

Randomised and quasi-randomised studies in preterm infants with respiratory disease that compared the effects of administration of iNO gas compared to control, with or without placebo are included in this review.

DATA COLLECTION AND ANALYSIS

Data regarding clinical outcomes including death, BPD (defined as oxygen dependence at 36 weeks postmenstrual age), IVH, periventricular leukomalacia (PVL), long term neurodevelopmental outcome and short term effects on oxygenation were excerpted from the trial reports by the investigators. Standard methods of the Cochrane Neonatal Review Group were used. Two investigators extracted, assessed and coded separately all data for each study. Any disagreement was resolved by discussion.

MAIN RESULTS

Eleven randomised controlled trials of inhaled nitric oxide therapy in preterm infants were found. The trials have been grouped post hoc into three categories depending on the entry criteria; entry in the first three days of life based on oxygenation criteria (Kinsella 1999; Hascoet 2004; INNOVO 2005; Van Meurs 2004; Mercier 1999; Dani 2006), routine use in intubated preterm babies (Schreiber 2003; Kinsella 2006) and later enrolment based on an increased risk of BPD (Subhedar 1997; Ballard 2006). The usefulness of the overall analyses was considered limited by the differing characteristics of the studies, and only subgroup analyses were performed. Trials of early rescue treatment of infants based on oxygenation criteria demonstrated no significant effect of iNO on mortality or BPD. The subgroup of studies with routine use of iNO in intubated preterm infants demonstrated a marginally significant reduction in the combined outcome of death or BPD [typical RR 0.91 (95% CI 0.84, 0.99); typical RD -0.06 (95% CI -0.12, -0.01)]. Later treatment with iNO based on the risk of BPD demonstrated no significant benefit for this outcome in our analysis. Studies of early rescue treatment with iNO demonstrated a trend toward increased risk of severe IVH, whereas the subgroup of studies with routine use in intubated preterm infants seems to show a reduction in the risk of having either a severe IVH or PVL [typical RR 0.70 (95% CI 0.53, 0.91); typical RD -0.07 (95% CI -0.12, -0.02)]. Later iNO treatment of infants at risk of BPD is given after the major risk period for IVH, and does not appear to lead to progression of old lesions. Two studies (Schreiber 2003; INNOVO 2005) presented data on long term neurodevelopmental outcome. The early routine treatment study (Schreiber 2003) showed an improved outcome at two years corrected age, while the rescue treatment study (INNOVO 2005) showed no effect of iNO.

AUTHORS' CONCLUSIONS

iNO as rescue therapy for the very ill ventilated preterm infant does not appear to be effective and may increase the risk of severe IVH. Later use of iNO to prevent BPD also does not appear to be effective. Early routine use of iNO in mildly sick preterm infants may decrease serious brain injury and may improve survival without BPD. Further studies are needed to confirm these findings, to define groups most likely to benefit, and to describe long term outcomes.

Neurodevelopmental outcomes of premature infants with severe respiratory failure enrolled in a randomized controlled trial of inhaled nitric oxide

OBJECTIVES

We hypothesized that inhaled nitric oxide (iNO) would not decrease death or neurodevelopmental impairment (NDI) in infants enrolled in the National Institute of Child Health and Human Development Preemie iNO Trial (PiNO) trial, nor improve neurodevelopmental outcomes in the follow-up group.

STUDY DESIGN

Infants <34 weeks of age, weighing <1500 g, with severe respiratory failure were enrolled in the multicenter, randomized, controlled trial. NDI at 18 to 22 months corrected age was defined as: moderate to severe cerebral palsy (CP; Mental Developmental Index or Psychomotor score Developmental Index <70), blindness, or deafness.

RESULTS

Of 420 patients enrolled, 109 who received iNO (52%) and 98 who received placebo (47%) died. The follow-up rate in survivors was 90%. iNO did not reduce death or NDI (78% versus 73%; relative risk [RR], 1.07; 95% CI, 0.95-1.19), or NDI or Mental Developmental Index <70 in the follow-up group. Moderate-severe CP was slightly higher with iNO (RR, 2.41; 95% CI, 1.01-5.75), as was death or CP in infants weighing <1000 g (RR, 1.22; 95% CI, 1.05-1.43).

CONCLUSIONS

In this extremely ill cohort, iNO did not reduce death or NDI or improve neurodevelopmental outcomes. Routine iNO use in premature infants should be limited to research settings until further data are available.

Evidence-based use of adjunctive therapies to ventilation

Respiratory distress is the most common reason for admission to newborn intensive care units. Over the past two decades, we have witnessed a revolution in the therapies that are used to manage neonates who have pulmonary disorders. Multiple adjunctive agents have also been used in an attempt to mitigate the course of neonatal lung disease. The disorders we discuss include respiratory distress syndrome, chronic lung disease/bronchopulmonary dysplasia, persistent pulmonary hypertension of the newborn, meconium aspiration syndrome, and transient tachypnea of the newborn. We review the evidence that either supports or refutes the use of adjunctive therapies for these disorders.

Matching ventilatory support strategies to respiratory pathophysiology

Neonates can suffer from various diseases that impact differently on lung function according to the specific pulmonary pathophysiology. As a consequence, the optimal respiratory support will vary according to disorder. Most randomized trials have only included prematurely born infants who have respiratory distress syndrome (RDS) or infants who have severe respiratory failure. Meta-analysis of the results has demonstrated that for the prematurely born infant who has RDS, prophylactic high-frequency oscillatory ventilation only results in a modest reduction in bronchopulmonary dysplasia, and patient-triggered ventilation (assist/control or synchronized intermittent mandatory ventilation) reduces the duration of ventilation if started in the recovery phase. Whether the newer triggered modes are more efficacious remains to be appropriately tested. In term infants who have severe respiratory failure, extracorporeal membrane oxygenation increases survival, but inhaled nitric oxide only reduces the need for extracorporeal membrane oxygenation. Research is required to identify the optimum respiratory strategy for infants who have other respiratory disorders, particularly bronchopulmonary dysplasia.

Progress in Discovery and Evaluation of Treatments to Prevent Bronchopulmonary Dysplasia

BACKGROUND

Recent improvements in the survival of extremely preterm infants have been accompanied by evolution in the pathogenesis and histopathology of bronchopulmonary dysplasia (BPD). Although oxygen and barotrauma-induced injury remain important contributing factors, pulmonary developmental arrest appears to play an equally important causal role in prolonged respiratory illness, especially among the most immature surviving preterm newborns. To date, clinical trials have failed to demonstrate a substantial benefit of a single treatment or preventive strategy for BPD.

OBJECTIVES

To evaluate the current evidence in favor of treatments that might prevent BPD.

METHODS

Review of clinical studies of preventive treatment strategies for BPD.

RESULTS

High frequency oscillatory ventilation, permissive hypercapnea, and inhaled nitric oxide might offer benefit to infants at risk of BPD. These and other potential preventive therapies for BPD, such as superoxide dismutase, inositol, and alpha(1)-proteinase inhibitor, deserve further study.

CONCLUSIONS

Although some current treatments offer promise, no preventive therapy for BPD has proven safe and effective, except for intramuscular vitamin A. Additional studies of respiratory technologies, management strategies, and protective molecules are needed.