Long-term follow-up of premature infants treated with prophylactic, intratracheal recombinant human CuZn superoxide dismutase

Targeted Therapies for Neonatal Pulmonary Hypertension: Beyond Nitric Oxide

Pulmonary hypertension in the neonatal population can be acute or chronic and carries significant risk for morbidity and mortality. It can be idiopathic but more often is associated with comorbid pulmonary and heart disease. There are several pharmacotherapeutics aimed at pulmonary vasodilation. This review highlights the most common agents as well as those on the horizon for the treatment of pulmonary hypertension in the neonate.

The post-cardiac arrest syndrome: A case for lung-brain coupling and opportunities for neuroprotection

Systemic inflammation and multi-organ failure represent hallmarks of the post-cardiac arrest syndrome (PCAS) and predict severe neurological injury and often fatal outcomes. Current interventions for cardiac arrest focus on the reversal of precipitating cardiac pathologies and the implementation of supportive measures with the goal of limiting damage to at-risk tissue. Despite the widespread use of targeted temperature management, there remain no proven approaches to manage reperfusion injury in the period following the return of spontaneous circulation. Recent evidence has implicated the lung as a moderator of systemic inflammation following remote somatic injury in part through effects on innate immune priming. In this review, we explore concepts related to lung-dependent innate immune priming and its potential role in PCAS. Specifically, we propose and investigate the conceptual model of lung-brain coupling drawing from the broader literature connecting tissue damage and acute lung injury with cerebral reperfusion injury. Subsequently, we consider the role that interventions designed to short-circuit lung-dependent immune priming might play in improving patient outcomes following cardiac arrest and possibly other acute neurological injuries.

Bronchopulmonary Dysplasia: An Update of Current Pharmacologic Therapies and New Approaches

Bronchopulmonary dysplasia (BPD) remains the most prevalent long-term morbidity of surviving extremely preterm infants and is associated with significant health care utilization in infancy and beyond. Recent advances in neonatal care have resulted in improved survival of extremely low birth weight (ELBW) infants; however, the incidence of BPD has not been substantially impacted by novel interventions in this vulnerable population. The multifactorial cause of BPD requires a multi-pronged approach for prevention and treatment. New approaches in assisted ventilation, optimal nutrition, and pharmacologic interventions are currently being evaluated. The focus of this review is the current state of the evidence for pharmacotherapy in BPD. Promising future approaches in need of further study will also be reviewed.

A Pathogenic Relationship of Bronchopulmonary Dysplasia and Retinopathy of Prematurity? A Review of Angiogenic Mediators in Both Diseases

Bronchopulmonary dysplasia (BPD) and retinopathy of prematurity (ROP) are common and significant morbidities of prematurely born infants. These diseases have in common altered and pathologic vascular formation in the face of incomplete organ development. Therefore, it is reasonable to question whether factors affecting angiogenesis could have a joint pathogenic role for both diseases. Inhibition or induced expression of a single angiogenic factor is unlikely to be 100% causative or protective of either of BPD or ROP. It is more likely that interactions of multiple factors leading to disordered angiogenesis are present, increasing the likelihood of common pathways in both diseases. This review explores this possibility by assessing the evidence showing involvement of specific angiogenic factors in the vascular development and maldevelopment in each disease. Theoretical interactions of specific factors mutually contributing to BPD and ROP are proposed and, where possible, a timeline of the proposed relationships between BPD and ROP is developed. It is hoped that future research will be inspired by the theories put forth in this review to enhance the understanding of the pathogenesis in both diseases.

Ventilation strategies for preventing oxidative stress-induced injury in preterm infants with respiratory disease: an update

Reactive oxygen and nitrogen species are produced by several inflammatory and structural cells of the airways. The lungs of preterm newborns are susceptible to oxidative injury induced by both reactive oxygen and nitrogen species. Increased oxidative stress and imbalance in antioxidant enzymes may play a role in the pathogenesis of inflammatory pulmonary diseases. Preterm infants are frequently exposed to high oxygen concentrations, infections or inflammation; they have reduced antioxidant defense and high free iron levels which enhance toxic radical generation. Multiple ventilation strategies have been studied to reduce injury and improve outcomes in preterm infants. Using lung protective strategies, there is the need to reach a compromise between satisfaction of gas exchange and potential toxicities related to over-distension, derecruitment of lung units and high oxygen concentrations. In this review, the authors summarize scientific evidence concerning oxidative stress as it relates to resuscitation in the delivery room and to the strategies of ventilation.

Mouse lung development and NOX1 induction during hyperoxia are developmentally regulated and mitochondrial ROS dependent

Animal models demonstrate that exposure to supraphysiological oxygen during the neonatal period compromises both lung and pulmonary vascular development, resulting in a phenotype comparable to bronchopulmonary dysplasia (BPD). Our prior work in murine models identified postnatal maturation of antioxidant enzyme capacities as well as developmental regulation of mitochondrial oxidative stress in hyperoxia. We hypothesize that consequences of hyperoxia may also be developmentally regulated and mitochondrial reactive oxygen species (ROS) dependent. To determine whether age of exposure impacts the effect of hyperoxia, neonatal mice were placed in 75% oxygen for 72 h at either postnatal day 0 (early postnatal) or day 4 (late postnatal). Mice exposed to early, but not late, postnatal hyperoxia demonstrated decreased alveolarization and septation, increased muscularization of resistance pulmonary arteries, and right ventricular hypertrophy (RVH) compared with normoxic controls. Treatment with a mitochondria-specific antioxidant, (2-(2,2,6,6-tetramethylpiperidin-1-oxyl-4-ylamino)-2-oxoethyl)triphenylphosphonium chloride (mitoTEMPO), during early postnatal hyperoxia protected against compromised alveolarization and RVH. In addition, early, but not late, postnatal hyperoxia resulted in induction of NOX1 expression that was mitochondrial ROS dependent. Because early, but not late, exposure resulted in compromised lung and cardiovascular development, we conclude that the consequences of hyperoxia are developmentally regulated and decrease with age. Attenuated disease in mitoTEMPO-treated mice implicates mitochondrial ROS in the pathophysiology of neonatal hyperoxic lung injury, with potential for amplification of ROS signaling through NOX1 induction. Furthermore, it suggests a potential role for targeted antioxidant therapy in the prevention or treatment of BPD.

Drug therapy for the prevention and treatment of bronchopulmonary dysplasia

INTRODUCTION

As more infants are surviving at younger gestational ages, bronchopulmonary dysplasia (BPD) remains as a frequent neonatal complication occurring after preterm birth. The multifactorial nature of the disease process makes BPD a challenging condition to treat. While multiple pharmacologic therapies have been investigated over the past two decades, there have been limited advances in the field. Often multiple therapies are used concurrently without clear evidence of efficacy, with potential for significant side effects from drug-drug interactions.

METHODS

Systematic literature review.

CONCLUSION

Although there is physiologic rationale for the use of many of these therapies, none of them has single-handedly altered the incidence, severity, or progression of BPD. Future research should focus on developing clinically significant end-points (short and long term respiratory assessments), investigating biomarkers that accurately predict risk and progression of disease, and creating appropriate stratification models of BPD severity. Applying a multi-modal approach to the study of new and existing drugs should be the most effective way of establishing the optimal prevention and treatment regimens for BPD.

The role of genetic polymorphisms in antioxidant enzymes and potential antioxidant therapies in neonatal lung disease

SIGNIFICANCE

Oxidative stress is involved in the development of newborn lung diseases, such as bronchopulmonary dysplasia and persistent pulmonary hypertension of the newborn. The activity of antioxidant enzymes (AOEs), which is impaired as a result of prematurity and oxidative injury, may be further affected by specific genetic polymorphisms or an unfavorable combination of more of them.

RECENT ADVANCES

Genetic polymorphisms of superoxide dismutase and catalase were recently demonstrated to be protective or risk factors for the main complications of prematurity. A lot of research focused on the potential of different antioxidant strategies in the prevention and treatment of lung diseases of the newborn, providing promising results in experimental models.

CRITICAL ISSUES

The effect of different genetic polymorphisms on protein synthesis and activity has been poorly detailed in the newborn, hindering to derive conclusive results from the observed associations with adverse outcomes. Therapeutic strategies that aimed at enhancing the activity of AOEs were poorly studied in clinical settings and partially failed to produce clinical benefits.

FUTURE DIRECTIONS

The clarification of the effects of genetic polymorphisms on the proteomics of the newborn is mandatory, as well as the assessment of a larger number of polymorphisms with a possible correlation with adverse outcome. Moreover, antioxidant treatments should be carefully translated to clinical settings, after further details on optimal doses, administration techniques, and adverse effects are provided. Finally, the study of genetic polymorphisms could help select a specific high-risk population, who may particularly benefit from targeted antioxidant strategies.

Antioxidant strategies and respiratory disease of the preterm newborn: an update

Preterm newborns are challenged by an excessive oxidative burden, as a result of several perinatal stimuli, as intrauterine infections, resuscitation, mechanical ventilation, and postnatal complications, in the presence of immature antioxidant capacities. "Oxygen radical disease of neonatology" comprises a wide range of conditions sharing a common pathway of pathogenesis and includes bronchopulmonary dysplasia (BPD) and other main complications of prematurity. Antioxidant strategies may be beneficial in the prevention and treatment of oxidative stress- (OS-) related lung disease of the preterm newborn. Endotracheal supplementation or lung-targeted overexpression of superoxide dismutase was proved to reduce lung damage in several models; however, the supplementation in preterm newborn failed to reduce the risk of BPD, although long-term respiratory outcomes were improved. Also melatonin administration to small cohorts of preterm newborns suggested beneficial effects on lung OS. The possibility to identify single nucleotide polymorphism affecting the risk of BPD may help to identify specific populations with particularly high risk of OS-related diseases and may pose the basis for individually targeted treatments. Finally, surfactant replacement may lead to local anti-inflammatory and antioxidant effects, thanks to specific enzymatic and nonenzymatic antioxidants naturally present in animal surfactants.

The protective role of MnTBAP in oxidant-mediated injury and inflammation in a rat model of lung contusion

BACKGROUND

Lung contusion (LC) is a unique direct and focal insult that is considered a major risk factor for the initiation of acute lung injury and acute respiratory distress syndrome. We have shown recently that consumption of nitric oxide (due to excess superoxide) resulting in peroxynitrite formation leads to decreased vascular reactivity after LC. In this study, we set out to determine whether the superoxide scavenger Mn (III) tetrakis (4-benzoic acid) porphyrin chloride (MnTBAP) plays a protective role in alleviating acute inflammatory response and injury in LC.

METHODS

Nonlethal, closed-chest, bilateral LC was induced in a rodent model. Administration of the superoxide dismutase mimetic MnTBAP concurrently in LC in rats was performed, and bronchoalveolar lavage (BAL) and lung samples were analyzed for degree of injury and inflammation at 5 and 24 h after the insult. The extent of injury was assessed by the measurement of cells and albumin with cytokine levels in the BAL and lungs. Lung samples were subjected to H&E and superoxide staining with dihydro-ethidium. Protein-bound dityrosine and nitrotyrosine levels were quantified in lung tissue by tandem mass spectrometry.

RESULTS

The degrees of lung injury after LC as determined by BAL albumin levels were significantly decreased in the MnTBAP-administered rats at all the time points when compared to the corresponding controls. The release of proinflammatory cytokines and BAL neutrophils was significantly less in the rats administered MnTBAP after LC. Administration of MnTBAP decreased tissue damage and decreased necrosis and neutrophil-rich exudate at the 24-h time point. Staining for superoxide anions showed significantly greater intensity in the lung samples from the LC group compared to the LC+ MnTBAP group. High-performance liquid chromatography/tandem mass spectrometry revealed that MnTBAP treatment significantly attenuated dityrosine and nitrotyrosine levels, consistent with decreased oxidant injury.

CONCLUSION

Superoxide dismutase mimetic-MnTBAP reduced permeability and oxidative injury in LC and may have a therapeutic role in diminishing inflammation in LC.

[Oxidative stress in the neonatal lung disease]

Oxidative stress is a risk factor for bronchopulmonary dysplasia in the preterm newborn. Antioxidant defense is impaired in the preterm newborn. Oxidative stress is also involved in cell growth and development. The relationship between oxidative stress and cell growth needs to be understood before antioxidant therapy can be routinely introduced. Several antioxidant therapies have been unsuccessfully tried until now. This review highlights the importance of oxygen free radicals in the pathogenesis of bronchopulmonary dysplasia.

Superoxide dismutase improves oxygenation and reduces oxidation in neonatal pulmonary hypertension

RATIONALE

Hyperoxic ventilation in the management of persistent pulmonary hypertension of the newborn (PPHN) can result in the formation of reactive oxygen species, such as superoxide anions, which can inactivate nitric oxide (NO) and cause vasoconstriction and oxidation.

OBJECTIVE

To compare the effect of intratracheal recombinant human superoxide dismutase (rhSOD) and/or inhaled NO (iNO) on systemic oxygenation, contractility of pulmonary arteries (PAs), and lung reactive oxygen species (isoprostane, 3-nitrotyrosine) levels in neonatal lambs with PPHN.

METHODS

Six newborn lambs with PPHN (induced by antenatal ductal ligation) were killed at birth. Twenty-six PPHN lambs were ventilated for 24 h with 100% O(2) alone (n = 6) or O(2) combined with rhSOD (5 mg/kg intratracheally) at birth (n = 4), rhSOD at 4 h of age (n = 5), iNO (20 ppm, n = 5), or rhSOD + iNO (n = 6). Contraction responses of fifth-generation PAs to norepinephrine and KCl, lung isoprostane levels, and 3-nitrotyrosine fluorescent intensity were measured.

RESULTS

Systemic oxygenation was impaired in PPHN lambs and significantly improved (up to threefold) in both rhSOD groups with or without iNO. Oxygenation improved more rapidly with the combination of rhSOD + iNO compared with either intervention alone. Norepinephrine- and KCl-induced contractions and lung isoprostane levels were significantly increased by 100% O(2) compared with nonventilated newborn lambs with PPHN. Both rhSOD and iNO mitigated the increased PA contraction response and lung isoprostane levels. Intratracheal rhSOD decreased the enhanced lung 3-nitrotyrosine fluorescence observed with iNO therapy.

CONCLUSION

Intratracheal rhSOD and/or iNO rapidly increase oxygenation and reduce both vasoconstriction and oxidation in newborn lambs with PPHN. This has important implications for clinical trials of rhSOD and iNO in newborn infants with PPHN.

Perfluorochemical liquids enhance delivery of superoxide dismutase to the lungs of juvenile rabbits

Previous studies suggest acute lung injury (ALI) in premature newborns is associated with relative deficiency of antioxidant enzymes that may be ameliorated by recombinant human superoxide dismutase (rhSOD). Perfluorochemicals (PFCs) are distributed homogeneously and support gas exchange in diseased lungs. We investigated whether PFCs could provide an effective delivery system for rhSOD. Juvenile rabbits were lung-lavaged, treated with surfactant, and randomized: group I: fluorescently labeled rhSOD (5 mg/kg in 2 mL/kg saline); group II: fluorescently labeled rhSOD (5 mg/kg in 18 mL/kg PFC). Animals were ventilated with oxygen for 4 h; the lungs were harvested for analysis of SOD distribution and oxidative injury. Cardiopulmonary indices remained stable and similar between groups. Qualitative assessment (QA) showed a more homogeneous lung SOD distribution in group II and a better histologic profile. QA of lung SOD distribution showed significant increase in SOD concentrations in group II (7.37 +/- 1.54 microg/mg protein) compared with group I (1.65 +/- 0.23 microg/mg protein). Oxidative injury as assessed by normalized protein carbonyl was 149.1 +/- 26.8% SEM in group II compared with 200.5 +/- 7.3% SEM in group I. Plasma SOD was significantly higher in group II. Administration of rhSOD with or without PFCs does not compromise cardiovascular function or impede lung recovery after ALI. PFCs enhance rhSOD delivery to the lungs by 400% while decreasing lung oxidative damage by 25% compared with rhSOD alone. These data suggest that PFCs optimize lung rhSOD delivery and might enhance the beneficial effects of rhSOD in preventing acute and chronic lung injury.

Antioxidant defenses in the preterm lung: role for hypoxia-inducible factors in BPD?

Pulmonary antioxidants and their therapeutic implications have been extensively studied during past decades. The purpose of this review is to briefly summarize the key findings of these studies as well as to elaborate on some novel approaches with respect to potential preventive treatments for neonatal chronic lung disease bronchopulmonary dysplasia (BPD). Such new ideas include, for example, modification of transcription factors governing the hypoxic response pathways, important in angiogenesis, cell survival, and glycolytic responses. The fundamental strategy behind that approach is that fetal lung normally develops under hypoxic conditions and that this hypoxic, growth-favoring environment is interrupted by a premature birth. Importantly, during fetal lung development, alveolar development appears to be dependent on vascular development. Therefore, enhancement of signaling factors that occur during hypoxic fetal life ('continued fetal life ex utero'), including angiogenic responses, could potentially lead to improved lung growth and thereby alleviate the alveolar and vascular hypoplasia characteristic of BPD.

Pulmonary antioxidant defenses in the preterm newborn with respiratory distress and bronchopulmonary dysplasia in evolution: implications for antioxidant therapy

Preterm neonates with respiratory distress are exposed not only to the relative hyperoxia ex utero, but also to life-saving mechanical ventilation with high inspired oxygen (O2) concentrations, which is considered a major risk factor for the development of bronchopulmonary dysplasia, also referred to as chronic lung disease of infancy. O2 toxicity is mediated through reactive oxygen species (ROS). ROS are constantly generated as byproducts of normal cellular metabolism, but their production is increased in various pathological states, and also upon exposure to exogenous oxidants, such as hyperoxia. Antioxidants, either enzymatic or nonenzymatic, protect the lung against the deleterious effects of ROS. Expression of various pulmonary antioxidants is developmentally regulated in many species so that the expression is increased toward term gestation, as if in anticipation of birth into an O2-rich extrauterine environment. Therefore, the lungs of prematurely born infants may be ill-adapted for protection against ROS. While premature birth interrupts normal lung development, the clinical condition necessitating the administration of high inhaled O2 concentrations may lead to permanent impairment of alveolar development. An understanding of the processes involved in lung growth, especially in alveolarization and vascularization, as well as in repair of injured lung tissue, may facilitate development of strategies to enhance these processes.

Changes of free radical of liver and intestine in premature rat with hyperoxia-induced chronic lung disease

AIM: To investigate dynamic changes of free radical of liver and intestine in premature infant with hyperoxia-induced chronic lung disease (CLD).

METHODS: Superoxide dismutase (SOD) activity, concentration of malondialdehyde (MDA) in the liver, intestine and lung specimen on d 1, 3, 7, 14 and 21 in 40 premature rat with hyperoxia-induced CLD and 40 control premature rats were assayed with double wavelength scanning by spectrophotometer.

RESULTS: In model group, level of MDA in the liver and intestine was increased on day 14 (122±9 moL/g vs 68±7 moL/g, 117±9 moL/g vs 68±9 moL/g, P < 0.01), and then was decreased but still maintained at a higher level than that in control group at day 21 (P < 0.05). Level of MDA in the lung was increased on day 3, and reached a peak level on day 7 (94±12 mol/ g vs 24±5 mol/g, P < 0.001), and still maintained at a higher level than that in control group at day 21 (P < 0.01), but there was no significant difference in SOD activity among any groups (P>0.05).

CONCLUSION: Damage of free radicals in the liver and intestine can be induced by CLD in premature infant, but the time of occurrence is very delayed in the lung.

Pulmonary outcome at 1 year corrected age in premature infants treated at birth with recombinant human CuZn superoxide dismutase

OBJECTIVE

To examine whether treatment of premature infants with intratracheal recombinant human CuZn superoxide dismutase (r-h CuZnSOD) reduces bronchopulmonary dysplasia and improves pulmonary outcome at 1 year corrected age.

DESIGN

Three hundred two premature infants (600-1200 g birth weight) treated with exogenous surfactant at birth for respiratory distress syndrome were randomized to receive either intratracheal r-h CuZnSOD (5 mg/kg in 2 mL/kg saline) or placebo every 48 hours (as long as intubation was required) for up to 1 month of age. Short-term, as well as longer-term pulmonary outcome was assessed.

RESULTS

There were no differences between groups in the incidence of death or the development of bronchopulmonary dysplasia (oxygen requirement with an Edwards chest radiograph score of >or=3) at 28 days of life or 36 weeks' postmenstrual age. r-h CuZnSOD was well-tolerated and not associated with significant increases in any adverse event. At a median of 1 year corrected age, health assessments and physical examinations were performed on 209 (80%) surviving infants, with complete data available on 189 infants. Thirty-seven percent of placebo-treated infants had repeated episodes of wheezing or other respiratory illness severe enough to require treatment with asthma medications such as bronchodilators and/or corticosteroids compared with 24% of r-h CuZnSOD-treated infants, a 36% reduction. In infants <27 weeks' gestation, 42% treated with placebo received asthma medications compared with 19% of r-h CuZnSOD-treated infants, a 55% decrease. Infants <27 weeks' gestation who received r-h CuZnSOD also had a 55% decrease in emergency department visits and a 44% decrease in subsequent hospitalizations. Growth measurements and the results of physical examinations were comparable between groups.

CONCLUSIONS

These data indicate that treatment at birth with r-h CuZnSOD may reduce early pulmonary injury, resulting in improved clinical status when measured at 1 year corrected age. r-h CuZnSOD appears to be a safe and effective therapy that improves pulmonary outcome in high-risk premature infants.

Bronchopulmonary dysplasia-oxidative stress and antioxidants

There is increasing evidence that oxidative stress is implicated in the development of bronchopulmonary dysplasia. Several important factors contribute to augmented oxidative stress in the newborn and especially the preterm infant: first, because of its immaturity, the lung of preterm infants is frequently exposed to oxygen therapy and hyperoxia. Second, the antioxidant defense and its ability to be induced during an hyperoxic challenge are impaired. Third, the preterm infant has an increased susceptibility to infection and inflammation, which increases oxidative stress. Fourth, free iron, which catalyzes the production of toxic reactive oxygen species, can be detected in preterm infants. The molecular and cellular mechanisms for free radical-induced injury are now understood in more detail, and it is clear that oxidative stress plays an important role in triggering apoptosis, in serving as second messenger and in signal transduction. This new insight might lead to novel and efficient therapies. So far, there has been no significant breakthrough regarding antioxidant therapies. Care should, however, be exercised in supplementing the preterm infant with antioxidants since this may affect growth and development.

Role of oxidant injury in the pathogenesis of neonatal lung disease

Bronchopulmonary dysplasia (BPD) is a chronic lung disease that develops in newborn infants treated with oxygen and mechanical ventilation for a primary lung disorder. With significant improvements in survival of many critically ill infants, BPD has become an extremely important complication of newborn intensive care. The pathogenesis of BPD is complex and involves a variety of causative factors. However, increasing evidence has suggested that an oxidative insult could be an extremely important component of the injury process. Premature infants are especially sensitive to oxidant injury since they are exposed to supraphysiological concentrations of oxygen at birth while endogenous antioxidant enzyme activity may be relatively deficient.

CONCLUSION

Superoxide dismutase is an antioxidant enzyme that has been shown in numerous basic and clinical studies to protect cells against oxidant injury.

Antioxidants as therapy in the newborn: some words of caution

Reactive oxygen and nitrogen species are considered to play a major role in the pathogenesis of a wide range of human disorders. This may be a particularly important pathogenetic mechanism in the newborn nursery. The phrase "oxygen radical disease of prematurity" has been coined to collectively describe a wide range of neonatal disorders based on the belief that premature newborns are deficient in antioxidant defenses at a time when they are subjected to acute and chronic oxidant stresses. This belief has led to a number of clinical trials of antioxidant therapies being undertaken in neonatal patients. The realization that reactive oxygen species play a critical role in neonatal illnesses has only recently been paralleled by an increased understanding of their physiologic roles. A major concern is that effective scavenging of reactive oxygen species, to attenuate their toxic effects, will also inhibit essential cellular functions such as growth in potential target organs such as lung, brain, intestine, and retina.

Superoxide dismutase for preventing chronic lung disease in mechanically ventilated preterm infants

BACKGROUND

Free oxygen radicals have been implicated in the pathogenesis of chronic lung disease in preterm infants. Superoxide dismutase is a naturally occurring enzyme which provides a defence against such oxidant injury. Exogenously administered superoxide dismutase has been tested in clinical trials to prevent chronic lung disease in preterm infants.

OBJECTIVES

To determine if exogenously administered superoxide dismutase is efficacious in the prevention of chronic lung disease in preterm infants who are mechanically ventilated, and efficacious in decreasing the following outcomes: bronchopulmonary dysplasia, intraventricular hemorrhage, periventricular leukomalacia, retinopathy of prematurity, necrotizing enterocolitis, patent ductus arteriosus and mortality. To determine the frequency and nature of adverse effects of superoxide dismutase.

SEARCH STRATEGY

We searched Medline (1966 - 2000) and the Cochrane Controlled Trials Register (CCTR) using the following keywords: [bronchopulmonary dysplasia OR chronic lung disease] AND superoxide dismutase, limited to human studies in newborn infants (infant, newborn). We hand searched the reference lists of articles located and the abstracts of the Society for Pediatric Research (USA) (published in Pediatric Research) from 1980 - 2000.

SELECTION CRITERIA

Randomized controlled trials where subjects were preterm infants who had developed or were at risk of developing respiratory distress syndrome requiring assisted ventilation and who were randomly allocated to receive either superoxide dismutase (in any form, by any route) or placebo or no treatment. We included studies which reported any of the following outcomes: chronic lung disease, bronchopulmonary dysplasia, any intraventricular hemorrhage, intraventricular hemorrhage grades III/IV, patent ductus arteriosus, periventricular leukomalacia, retinopathy of prematurity, necrotizing enterocolitis, neonatal mortality, death prior to discharge and neurodevelopmental outcome.

DATA COLLECTION AND ANALYSIS

We extracted and assessed separately all data for each study and entered final data into RevMan. We did not perform subgroup analyses (which were originally planned) because only two studies were eligible for inclusion. We assessed the methodological quality of the studies by assessing the risk for bias. We pooled the outcomes of infants who had developed bronchopulmonary dysplasia at 28 days with those who had died at 28 days to derive the combined outcome of bronchopulmonary dysplasia or death at 28 days. Similarly we pooled the outcomes of infants who had respiratory problems after discharge with those who had died prior to discharge to derive the combined outcome of respiratory problems after discharge or death. We used the standard method of the Cochrane Neonatal Review Group for statistical analysis, using a fixed effect model.

MAIN RESULTS

Two randomized controlled trials were included for analysis. No differences were found in either study or in the pooled data in death prior to discharge, oxygen dependency at 36 weeks corrected age, oxygen dependency at 28 days of life or in other outcomes. In one study (Rosenfeld 1984), survivors who had been treated with superoxide dismutase had a shorter duration of continuous positive airway pressure (4.9 vs 9.7 days), a lower frequency of respiratory problems after discharge (relative risk 0.33, 95% confidence limits 0.11, 0.96) and a lower frequency of chest radiograph abnormalities (relative risk 0.30, 95% confidence limits 0.11, 0.87) compared to survivors who received placebo. A third study was available only in abstract form and will be evaluated for inclusion after publication.

REVIEWER'S CONCLUSIONS

Based on currently available published trials, there is insufficient evidence to draw firm conclusions about the efficacy of superoxide dismutase in preventing chronic lung disease of prematurity. Data from a small number of treated infants suggest that it is well tolerated and has no serious adverse effects.