Drug therapy for bronchopulmonary dysplasia

Inhaled bronchodilators for the prevention and treatment of chronic lung disease in preterm infants

BACKGROUND

Chronic lung disease (CLD) occurs frequently in preterm infants and is associated with respiratory morbidity. Bronchodilators have the potential effect of dilating small airways with muscle hypertrophy. Increased compliance and tidal volume, and decreased airway resistance, have been documented with the use of bronchodilators in infants with CLD. Therefore, bronchodilators are widely considered to have a role in the prevention and treatment of CLD, but there remains uncertainty as to whether they improve clinical outcomes. This is an update of the 2016 Cochrane review.

OBJECTIVES

To determine the effect of inhaled bronchodilators given as prophylaxis or as treatment for chronic lung disease (CLD) on mortality and other complications of preterm birth in infants at risk for or identified as having CLD.

SEARCH METHODS

An Information Specialist searched CENTRAL, MEDLINE, Embase, CINAHL and three trials registers from 2016 to May 2023. In addition, the review authors undertook reference checking, citation searching and contact with trial authors to identify additional studies.

SELECTION CRITERIA

We included randomised and quasi-randomised controlled trials involving preterm infants less than 32 weeks old that compared bronchodilators to no intervention or placebo. CLD was defined as oxygen dependency at 28 days of life or at 36 weeks' postmenstrual age. Initiation of bronchodilator therapy for the prevention of CLD had to occur within two weeks of birth. Treatment of infants with CLD had to be initiated before discharge from the neonatal unit. The intervention had to include administration of a bronchodilator by nebulisation or metered dose inhaler. The comparator was no intervention or placebo.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by Cochrane. Critical outcomes included: mortality within the trial period; CLD (defined as oxygen dependency at 28 days of life or at 36 weeks' postmenstrual age); adverse effects of bronchodilators, including hypokalaemia (low potassium levels in the blood), tachycardia, cardiac arrhythmia, tremor, hypertension and hyperglycaemia (high blood sugar); and pneumothorax. We used the GRADE approach to assess the certainty of the evidence for each outcome.

MAIN RESULTS

We included two randomised controlled trials in this review update. Only one trial provided useable outcome data. This trial was conducted in six neonatal intensive care units in France and Portugal, and involved 173 participants with a gestational age of less than 31 weeks. The infants in the intervention group received salbutamol for the prevention of CLD. The evidence suggests that salbutamol may result in little to no difference in mortality (risk ratio (RR) 1.08, 95% confidence interval (CI) 0.50 to 2.31; risk difference (RD) 0.01, 95% CI -0.09 to 0.11; low-certainty evidence) or CLD at 28 days (RR 1.03, 95% CI 0.78 to 1.37; RD 0.02, 95% CI -0.13 to 0.17; low-certainty evidence), when compared to placebo. The evidence is very uncertain about the effect of salbutamol on pneumothorax. The one trial with usable data reported that there were no relevant differences between groups, without providing the number of events (very low-certainty evidence). Investigators in this study did not report if side effects occurred. We found no eligible trials that evaluated the use of bronchodilator therapy for the treatment of infants with CLD. We identified no ongoing studies.

AUTHORS' CONCLUSIONS

Low-certainty evidence from one trial showed that inhaled bronchodilator prophylaxis may result in little or no difference in the incidence of mortality or CLD in preterm infants, when compared to placebo. The evidence is very uncertain about the effect of salbutamol on pneumothorax, and neither included study reported on the incidence of serious adverse effects. We identified no trials that studied the use of bronchodilator therapy for the treatment of CLD. Additional clinical trials are necessary to assess the role of bronchodilator agents in the prophylaxis or treatment of CLD. Researchers studying the effects of inhaled bronchodilators in preterm infants should include relevant clinical outcomes in addition to pulmonary mechanical outcomes.

Bronchodilators for the prevention and treatment of chronic lung disease in preterm infants

BACKGROUND

Chronic lung disease (CLD) occurs frequently in preterm infants. Bronchodilators have the potential effect of dilating small airways with muscle hypertrophy. Increased compliance and tidal volume and decreased pulmonary resistance have been documented with the use of bronchodilators in infants with CLD. Therefore, bronchodilators might have a role in the prevention and treatment of CLD.

OBJECTIVES

To determine the effect of bronchodilators given as prophylaxis or as treatment for CLD on mortality and other complications of preterm birth in infants at risk for or identified as having CLD.

SEARCH METHODS

On 2016 March 7, we used the standard strategy of the Cochrane Neonatal Review Group to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 2), MEDLINE (from 1966), Embase (from 1980) and the Cumulative Index to Nursing and Allied Health Literature (CINAHL; from 1982). We searched clinical trials databases, conference proceedings and the reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials. We applied no language restrictions.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials involving preterm infants were eligible for inclusion. Initiation of bronchodilator therapy for prevention of CLD had to occur within two weeks of birth. Treatment of patients with CLD had to be initiated before discharge from the neonatal unit. The intervention had to include administration of a bronchodilator by nebulisation, by metered dose inhaler (with or without a spacer device) or by intravenous or oral administration versus placebo or no intervention. Eligible studies had to include at least one of the following predefined clinical outcomes: mortality, CLD, number of days on oxygen, number of days on ventilator, patent ductus arteriosus (PDA), pulmonary interstitial emphysema (PIE), pneumothorax, intraventricular haemorrhage (IVH) of any grade, necrotising enterocolitis (NEC), sepsis and adverse effects of bronchodilators.

DATA COLLECTION AND ANALYSIS

We used the standard method described in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). Two review authors extracted and assessed all data provided by each study. We reported risk ratio (RR), risk difference (RD) and number needed to treat for an additional beneficial outcome (NNTB) with 95% confidence interval (CI) for dichotomous outcomes and mean difference (MD) for continuous data. We assessed the quality of the evidence by using the GRADE approach.

MAIN RESULTS

For this update, we identified one new randomised controlled trial investigating effects of bronchodilators in preterm infants. This study, which enrolled 73 infants but reported on 52 infants, examined prevention of CLD with the use of aminophylline. According to GRADE, the quality of the evidence was very low. One previously included study enrolled 173 infants to look at prevention of CLD with the use of salbutamol. According to GRADE, the quality of the evidence was moderate. We found no eligible trial that studied the use of bronchodilator therapy for treatment of individuals with CLD. Prophylaxis with salbutamol led to no statistically significant differences in mortality (RR 1.08, 95% CI 0.50 to 2.31; RD 0.01, 95% CI -0.09 to 0.11) nor in CLD (RR 1.03, 95% CI 0.78 to 1.37; RD 0.02, 95% CI -0.13 to 0.17). Results showed no statistically significant differences in other complications associated with CLD nor in preterm birth. Investigators in this study did not comment on side effects due to salbutamol. Prophylaxis with aminophylline led to a significant reduction in CLD at 28 days of life (RR 0.18, 95% CI 0.04 to 0.74; RD -0.35, 95% CI -0.56 to -0.13; NNTB 3, 95% CI 2 to 8) and no significant difference in mortality (RR 3.0, 95% CI 0.33 to 26.99; RD 0.08, 95% CI -0.07 to 0.22), along with a significantly shorter dependency on supplementary oxygen in the aminophylline group compared with the no treatment group (MD -17.75 days, 95% CI -27.56 to -7.94). Tests for heterogeneity were not applicable for any of the analyses, as each meta-analysis included only one study.

AUTHORS' CONCLUSIONS

Data are insufficient for reliable assessment of the use of salbutamol for prevention of CLD. One trial of poor quality reported a reduction in the incidence of CLD and shorter duration of supplementary oxygen with prophylactic aminophylline, but these results must be interpreted with caution. Additional clinical trials are necessary to assess the role of bronchodilator agents in prophylaxis or treatment of CLD. Researchers studying the effects of bronchodilators in preterm infants should include relevant clinical outcomes in addition to pulmonary mechanical outcomes. We identified no trials that studied the use of bronchodilator therapy for treatment of CLD.

Lung Injury and Bronchopulmonary Dysplasia in Newborn Infants

Bronchopulmonary dysplasia is the most common morbidity among surviving premature infants. Injury to the developing lung is the result of the interaction between a susceptible host and a number of contributing factors such as mechanical ventilation and infection. The resulting persistent impairment of pulmonary function and need for ongoing therapy are the underlying characteristics of bronchopulmonary dysplasia. Important insights into the pathogenesis of bronchopulmonary dysplasia have led to numerous therapies and preventive approaches. Although significant progress has been made, in order to further affect the incidence and severity of the disease, we need to further study (a) the genetically determined predisposing factors, (b) the relative contribution of the various pathogenetic pathways, and, most important, (c) how to best translate the knowledge gained from these studies into effective clinical approaches.

Bronchodilators for the prevention and treatment of chronic lung disease in preterm infants

BACKGROUND

Chronic lung disease (CLD) occurs frequently in preterm infants. Bronchodilators have the potential effect of dilating small airways with muscle hypertrophy. Increase in compliance and tidal volume and decrease in pulmonary resistance have been documented with use of bronchodilators in studies of pulmonary mechanics in infants with CLD. Therefore, it is possible that bronchodilators might have a role in the prevention and treatment of CLD.

OBJECTIVES

To determine the effect of bronchodilators given either prophylactically or as treatment for CLD on mortality and other complications of prematurity in preterm infants at risk for or having CLD.

SEARCH METHODS

For this update of the review, searches of The Cochrane Library, Issue 3, 2012; MEDLINE 1966; EMBASE; CINAHL; personal files and reference lists of identified trials were performed in March 2012. In addition Web of Science and abstracts from the Annual meetings of the Pediatric Academic Societies were searched electronically from 2000 to 2012 on PAS Abstracts2view(TM.) No language restrictions were applied.

SELECTION CRITERIA

Randomised controlled trials involving preterm infants were eligible for inclusion. Initiation of bronchodilator therapy had to occur within two weeks of birth for prevention of CLD. For treatment of CLD, treatment had to be initiated before discharge from the neonatal unit. The intervention had to include the administration of a bronchodilator either by nebulisation, metered dose inhaler (with or without a spacer device), intravenously or orally versus placebo or no intervention. Eligible studies had to include at least one of the predefined clinical outcomes (mortality, CLD, number of days on oxygen, number of days on ventilator, patent ductus arteriosus (PDA), pulmonary interstitial emphysema (PIE), pneumothorax, any grade of intraventricular haemorrhage (IVH), necrotising enterocolitis (NEC), sepsis and adverse effects of bronchodilators. Adverse effects of bronchodilators included hypokalaemia, tachycardia, cardiac arrhythmias, tremor, hypertension and hyperglycaemia).

DATA COLLECTION AND ANALYSIS

We used the standard method described in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). Two investigators extracted and assessed all data for each study. We reported risk ratio (RR) and risk difference (RD) with 95% confidence intervals (CI) for dichotomous outcomes and weighted mean difference (WMD) for continuous data.

MAIN RESULTS

In this update we identified four randomised controlled trials investigating the effects of bronchodilators in preterm infants. None of these studies fulfilled our inclusion criterion that clinical outcomes should be reported. One eligible study was previously found dealing with prevention of CLD; this study used salbutamol and enrolled 173 infants. No eligible studies were found dealing with treatment of CLD. Prophylaxis with salbutamol did not show a statistically significant difference in mortality (RR 1.08; 95% CI 0.50 to 2.31; RD 0.01; 95% CI -0.09 to 0.11) or CLD (RR 1.03; 95% CI 0.78 to 1.37; RD 0.02; 95% CI -0.13 to 0.17). No statistically significant differences were seen in other complications associated with CLD or preterm birth. No side effects due to salbutamol were commented on in this study.

AUTHORS' CONCLUSIONS

There are insufficient data to reliably assess the use of salbutamol for the prevention of CLD. Further clinical trials are necessary to assess the role of salbutamol or other bronchodilator agents in prophylaxis or treatment of CLD. Researchers studying the effects of bronchodilators in preterm infants should include relevant clinical outcomes in addition to pulmonary mechanical outcomes.

Current pharmacologic approaches for prevention and treatment of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a major complication of preterm birth and has serious adverse long-term health consequences. The etiology of BPD is complex, multifactorial, and incompletely understood. Contributing factors include ventilator-induced lung injury, exposure to toxic oxygen levels, and infection. Several preventive and therapeutic strategies have been developed with variable success. These include lung protective ventilator strategies and pharmacological and nutritional interventions. These strategies target different components and stages of the disease process and they are commonly used in combination. The purpose of this review is to discuss the evidence for current pharmacological interventions and identify future therapeutic modalities that appear promising in the prevention and management of BPD. Continued improved understanding of BPD pathogenesis leads to opportunities for newer preventive approaches. These will need to be evaluated in the setting of current clinical practice in order to assess their efficacy.

Adjunctive pharmacotherapy in neonates with respiratory failure

Whereas oxygen, continuous positive airway pressure (CPAP) and mechanical ventilation are the mainstays of treatment of pulmonary conditions in newborns, there are a number of adjunctive therapies that may improve the pulmonary function of these infants. These include the use of bronchodilators and diuretics given either systemically or through the inhaled route, mucolytic agents, and anti-inflammatory agents. This chapter gives an overview of the use of the most-studied agents including aerosolized bronchodilators, systemic and inhaled diuretics, and systemic and inhaled corticosteroids in the treatment and prevention of, where appropriate, respiratory distress syndrome, bronchopulmonary dysplasia, and meconium aspiration syndrome. Evidence on the use of mucolytic agents including acetylcysteine and deoxyribonuclease, and the anti-inflammatory agents including the macrolide antibiotics, cromolyn, pentoxyfylline, and recombinant human Clara cell protein are also reviewed.

Follow-up care for infants with chronic lung disease: a randomized comparison of community- and center-based models

OBJECTIVES

Premature infants with chronic lung disease benefit from comprehensive care, which typically is based in tertiary medical centers. When such centers are not easily accessible, alternative models of care are needed. The purpose of this work was to compare community-based follow-up, provided via telephone contacts, to traditional center-based follow-up of premature infants with chronic lung disease.

PATIENTS AND METHODS

After discharge from neonatal intensive care, 150 premature infants with chronic lung disease were randomly assigned to either community-based (n = 75) or center-based (n = 75) follow-up. In community-based follow-up, a nurse specialist maintained telephone contact with the infant's primary caregiver and health care providers. Center-based follow-up consisted of visits to a medical center-based multidisciplinary clinic staffed by a neonatologist, a nurse specialist, and a social worker. The outcomes of interest were Bayley Scales of Infant Development mental developmental index and psychomotor developmental index, Vineland Adaptive Behavioral Composite, and growth delay (weight for length <5th percentile) at 1-year adjusted age and respiratory rehospitalizations through 1-year adjusted age.

RESULTS

In each randomization group, 73 infants survived, and 69 were evaluated at 1-year adjusted age. The median mental development index (corrected for gestational age) was 90 for both groups. The median psychomotor developmental index was 82 for the center-based group and 81 for the community-based group. The median Vineland Adaptive Behavioral Composite was 100 and 102 for the center-based and community-based groups, respectively. In the center-based and community-based groups, respectively, the proportions with growth delay were 13% and 26%, and the proportions rehospitalized for respiratory illness were 33% and 29%.

CONCLUSIONS

Infants randomly assigned to community-based, as compared with those randomly assigned to center-based follow-up, had similar developmental and health outcomes. The former approach might be a preferred alternative for families in rural settings or families for whom access to a tertiary care medical center is difficult.

Pharmacological strategies in the prevention and management of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a disease of complex and multifactorial etiology and a major cause of morbidity in premature infants. Contributing factors include infection, exposure to toxic oxygen levels, and ventilator-induced lung injury, resulting in arrested lung development and impaired lung function. Several preventive and therapeutic strategies have been employed and include lung protective ventilator strategies, pharmacological and nutritional interventions. These strategies target different components and stages of the disease process, and their success has been variable. This review intends to bring together prior and current pharmacological interventions and future therapeutic modalities that appear promising in the prevention and management of BPD. Better understanding of the pathogenesis has given hope for newer treatment options. Newer studies need to be designed to assess the efficacy of combination therapies that target multiple steps of the disease process.

Bronchopulmonary dysplasia in preterm infants: pathophysiology and management strategies

Bronchopulmonary dysplasia (BPD) has classically been described as including inflammation, architectural disruption, fibrosis, and disordered/delayed development of the infant lung. As infants born at progressively earlier gestations have begun to survive the neonatal period, a 'new' BPD, consisting primarily of disordered/delayed development, has emerged. BPD causes not only significant complications in the newborn period, but is associated with continuing mortality, cardiopulmonary dysfunction, re-hospitalization, growth failure, and poor neurodevelopmental outcome after hospital discharge. Four major risk factors for BPD include premature birth, respiratory failure, oxygen supplementation, and mechanical ventilation, although it is unclear whether any of these factors is absolutely necessary for development of the condition. Genetic susceptibility, infection, and patent ductus arteriosus have also been implicated in the pathogenesis of the disease. The strategies with the strongest evidence for effectiveness in preventing or lessening the severity of BPD include prevention of prematurity and closure of a clinically significant patent ductus arteriosus. Some evidence of effectiveness also exists for single-course therapy with antenatal glucocorticoids in women at risk for delivering premature infants, surfactant replacement therapy in intubated infants with respiratory distress syndrome, retinol (vitamin A) therapy, and modes of respiratory support designed to minimize 'volutrauma' and oxygen toxicity. The most effective treatments for ameliorating symptoms or preventing exacerbation in established BPD include oxygen therapy, inhaled glucocorticoid therapy, and vaccination against respiratory pathogens.Many other strategies for the prevention or treatment of BPD have been proposed, but have weaker or conflicting evidence of effectiveness. In addition, many therapies have significant side effects, including the possibility of worsening the disease despite symptom improvement. For instance, supraphysiologic systemic doses of glucocorticoids lessen the incidence of BPD in infants at risk for the disease, and promote weaning of oxygen and mechanical ventilation in infants with established BPD. However, the side effects of systemic glucocorticoid therapy, most notably the recently recognized adverse effects on neurodevelopment, preclude their routine use for the prevention or treatment of BPD. Future research in BPD will most probably focus on continued incremental improvements in outcome, which are likely to be achieved through the combined effects of many therapeutic modalities.

Bronchodilators for the prevention and treatment of chronic lung disease in preterm infants

BACKGROUND

Chronic lung disease (CLD) occurs frequently in preterm infants (< 37 weeks gestational age) and has a multifactorial etiology. Bronchodilators have the potential effect of dilating small airways with muscle hypertrophy. Increase in compliance and tidal volume and decrease in pulmonary resistance have been documented with use of bronchodilators in short term studies of pulmonary mechanics in infants with CLD. Therefore it is possible that bronchodilators might have a role in the prevention and treatment of CLD.

OBJECTIVES

To evaluate the effect of bronchodilators, given prophylactically or as treatment for chronic lung disease, on mortality and other complications of preterm births.

SEARCH STRATEGY

The search strategy used to identify studies was according to the guidelines of the Cochrane Neonatal Review Group. Searches were made of MEDLINE 1966 to December 2000, EMBASE 1980 to January 2001, CINAHL 1982 to December 2000, the Cochrane Library Issue 1, 2001, personal files and reference lists of identified trials. The following terms were used: bronchopulmonary dysplasia, chronic lung disease, bronchodilator agents, adrenergic agents, anticholinergic agents, albuterol, aminophylline, atropine, caffeine, clenbuterol, cromakalim, ephedrine, epinephrine, fenoterol, hexoprenaline, ipratropium, isoetharine, isoproterenol, orciprenaline, procaterol, terbutaline, theophylline, tretoquinol.

LIMITS

newborn, infant; human, clinical trial or controlled clinical trial, meta analysis, multicenter study or randomised controlled trial. No language restrictions were applied.

SELECTION CRITERIA

Randomised controlled clinical trials involving preterm infants. Initiation of bronchodilator therapy had to occur within two weeks of birth for prevention of CLD. For treatment of CLD treatment should have been initiated before discharge from the neonatal unit. The intervention had to include the randomised administration of a bronchodilator either by nebulisation, metered dose inhaler with or without a spacer device, intravenously or orally, versus placebo or no intervention. Eligible studies had to include at least one of the following outcomes: mortality, CLD at 28 days or at 36 weeks corrected GA, number of days on oxygen, number of days on ventilator, patent ductus arteriosus (PDA), pulmonary interstitial emphysema (PIE), pneumothorax, any grade of intraventricular haemorrhage, necrotizing enterocolitis (NEC), sepsis and adverse effects of bronchodilators.

DATA COLLECTION AND ANALYSIS

We used the standard method for the Cochrane Collaboration as described in the Cochrane Collaboration handbook. Two investigators (GN, AO) extracted and assessed all data for each study. Any disagreement was resolved by discussion. Relative risk (RR) and risk difference (RD) with 95% confidence intervals (CI) are reported for dichotomous outcomes and mean difference (WMD) for continuous data.

MAIN RESULTS

One eligible study was found dealing with prevention of CLD; this study used salbutamol and enrolled 173 infants. No eligible studies were found dealing with treatment of CLD. Prophylaxis with salbutamol did not show a statistically significant difference in mortality [RR 1.08 (95% CI 0.50, 2.31); RD 0.01 (95% CI -0.09, 0.11)], CLD (mild, moderate or severe) [RR 1.03 (95% CI 0.78, 1.37); RD 0.02 (95% CI -0.13, 0.17)], need for iv dexamethasone [RR 0.77 (95% CI 0.49, 1.19); RD -0.08 (95% CI -0.22, 0.05)], respiratory infections [RR 0.61 (95% CI 0.27, 1.39); RD -0.06 (95% CI -0.16, 0.04)] or positive blood culture [RR 1.06 (95% CI 0.54, 2.06); RD 0.01 (95% CI -0.10, 0.12)]. There was no statistically significant difference in duration of ventilatory support [MD -1.63 days (95% CI -5.63, 2.37)], duration of oxygen supply [MD -2.82 days (95% CI -11.91, 6.27)] or age of weaning from respiratory support (defined as assisted ventilation or oxygen supplementation) [MD -2.87 days (95% CI -11.28, 5.54)]. No side effects due to salbutamol were commented on in this study.

REVIEWER'S CONCLUSIONS

There are insufficient data to reliably assess the use of salbutamol for the prevention of CLD. Further clinical trials are necessary to assess the role of salbutamol or other bronchodilator agents in prophylaxis or treatment of CLD.

A risk-benefit assessment of drugs used for neonatal chronic lung disease

Improvements in neonatal intensive care have resulted in more extremely low birthweight babies surviving who are at risk of developing chronic lung disease. The preterm lung is vulnerable as it is both structurally immature and deficient in surfactant and antioxidant defences. Mechanical ventilation and high inspired oxygen concentrations are often necessary for preterm babies to survive but they can cause pulmonary inflammation which leads to lung damage. Abnormal healing in the presence of ongoing inflammation leads to airways remodelling which can result in protracted respiratory problems in these babies. A commonly used definition for chronic lung disease is the requirement for supplemental oxygen beyond 36 weeks' postconception. Many drugs that are commonly used for chronic lung disease have not been subjected to proper randomised controlled trials but are widely used on the basis of small studies showing short term benefits. They can be broadly divided into 2 groups. First, there are preventative drugs that are administered early to reduce oxygen toxicity and pulmonary inflammation. Secondly, there are those administered in established chronic lung disease, designed to reduce respiratory morbidity. Pulmonary inflammation in the neonate is reduced by systemic corticosteroids. Corticosteroid therapy within the first 2 weeks of life enables earlier extubation of preterm babies with subsequent reduced chronic lung disease and improved neonatal survival when given between 7 and 14 days. However, there is an increased risk of gastrointestinal haemorrhage, metabolic derangement, ventricular hypertrophy and potential effects on long term growth and brain development. Diuretics and inhaled bronchodilators improve pulmonary compliance and reduce oxygen requirements in established chronic lung disease but probably have little effect in reducing the incidence. In babies with established chronic lung disease, home oxygen therapy enables earlier discharge and prophylaxis against respiratory syncytial virus can reduce morbidity from bronchiolitis. All of the above therapies have adverse effects that need to be considered before initiating treatment. Recently, new drugs have become available which may be beneficial. These include inhaled nitric oxide for reduction of ventilation-perfusion mismatching, recombinant human superoxide dismutase for protection against oxidative stress and alpha-1 proteinase inhibitor which may reduce airways remodelling. At present these therapies are undergoing clinical trials. Exogenous surfactant is beneficial in respiratory distress syndrome and may reduce the risk of chronic lung disease but there have been no randomised controlled trials of its use in established chronic lung disease. Drugs which have been tried unsuccessfully include erythromycin, ambroxol and mast cell stabilisers.

Aerosolized furosemide in the treatment of acute respiratory distress and possible bronchopulmonary dysplasia in preterm neonates

OBJECTIVE

To review the efficacy and safety of inhaled furosemide in the treatment of acute respiratory distress and possible bronchopulmonary dysplasia (BPD) in preterm neonates receiving ventilator and oxygen support.

DATA SOURCES

A MEDLINE search was performed from January 1966 to December 1998 using the key words inhaled or aerosolized furosemide, BPD, preterm, neonate, and infant newborn.

STUDY SELECTION AND DATA EXTRACTION

All clinical trials involving the use of inhaled furosemide in ventilator- and oxygen-dependent preterm neonates with acute respiratory distress and possible BPD were evaluated.

DATA SYNTHESIS

Inhaled furosemide 1 and 2 mg/kg has improved pulmonary function in preterm neonates without significant adverse effects. However, only a single dose of inhaled furosemide was used in these trials, and pulmonary functions were monitored for only two or four hours after administration.

CONCLUSIONS

Inhaled furosemide may be effective, but studies are needed to determine the optimal dosage regimen and long-term risks and benefits of its use in these patients.

Improved pulmonary distribution of recombinant human Cu/Zn superoxide dismutase, using a modified ultrasonic nebulizer

Prophylactic, intratracheal instillation of recombinant human Cu/Zn superoxide dismutase (rhSOD) has been shown to lessen lung injury produced by 48 h of hyperoxia and mechanical ventilation in neonatal piglets. However, instillation of small volumes of rhSOD intratracheally would not be expected to result in uniform pulmonary distribution. Aerosolization is a technique that may improve pulmonary distribution of drugs, but is limited by the poor efficiency of most nebulizers. A newly modified ultrasonic nebulizer was tested to assess pulmonary distribution of rhSOD compared to that achieved by intratracheal instillation. rhSOD was dual-labeled with technetium-99m (99mTc) and a fluorescent analog (permitting quantitative and qualitative assessments of pulmonary distribution), and administered to neonatal piglets by intratracheal instillation or by aerosolization. Intratracheal instillation of rhSOD to piglets when supine resulted in nonuniform distribution, with most of the drug being found in the right caudal lobe, and localized in airways. Placing animals in 30 degrees of Trendelenburg and administering half the dose in the left and half in the right lateral decubitus positions improved distribution, but alveolar deposition remained patchy. Aerosolization using a modified ultrasonic nebulizer uniformly delivered 45.8 +/- 3.8% of the rhSOD to the lungs that had been placed in the nebulizer. The rhSOD was still active and present in airways and alveoli in a homogeneous fashion. We conclude that intratracheal instillation of rhSOD in small volumes results in nonuniform pulmonary distribution, while aerosolization enhances rhSOD distribution and alveolar deposition. This has important implications for ongoing clinical trials of rhSOD for the prevention of acute and chronic lung injury in premature neonates.

The effect of early dexamethasone administration on bronchopulmonary dysplasia in preterm infants with respiratory distress syndrome

OBJECTIVES

This study was carried to evaluate the effect of early administration of dexamethasone on the incidence of bronchopulmonary dysplasia (BPD) and/or death in surfactant-treated preterm infants with respiratory distress syndrome (RDS).

STUDY DESIGN

In a multicenter, double-blind, placebo-controlled trial, 109 preterm infants with RDS and birth weights between 700 and 1600 gm, who were treated with mechanical ventilation and surfactant, were randomly assigned before 36 hours of life to receive dexamethasone (n = 55) or placebo (n = 54) for 12 days.

RESULTS

There were no differences in the incidence of BPD and/or death between groups. However, fewer patients in the dexamethasone group were oxygen-dependent at 36 weeks after conception (8% vs 33%, p < 0.05). The dexamethasone group had a lower incidence of necrotizing enterocolitis (0% vs 9%, p < 0.05). The incidence of arterial hypertension, hyperglycemia, and sepsis was not affected by the treatment. Basal and poststimulation serum cortisol levels did not differ between groups.

CONCLUSION

The administration of dexamethasone early in the course of RDS does not decrease the incidence of BPD and/or death in preterm infants. However, dexamethasone may reduce oxygen dependency at 36 weeks after conception.

The effects of hyperoxia, mechanical ventilation, and dexamethasone on pulmonary antioxidant enzyme activity in the newborn piglet

It has been previously shown that prophylactic, intravenous dexamethasone (DEX) and intratracheal recombinant human Cu/Zn superoxide dismutase (SOD) ameliorate lung injury in newborn piglets treated with 48 hr of hyperoxia and mechanical ventilation. DEX has many pharmacologic effects, including the possible induction of antioxidant enzyme systems. To investigate whether the effects of DEX are mediated by an increase in endogenous antioxidant enzyme activity, 5 groups of term newborn piglets were studied: Group 1 piglets were ventilated with room air for 48 hr; Group 2 animals were ventilated with 100% O2 for 48 hr; Group 3 animals were ventilated with room air for 48 hr and received DEX (0.7 mg/kg) every 12 h; Group 4 were ventilated with 100% O2 for 48 hr and also received DEX; Group 5 animals were no ventilated and were sacrificed at time 0. At the conclusion of the studies, bronchoalveolar lavage (BAL) was performed and the lungs were removed and homogenized. Lung tissue and BAL were analyzed for SOD, catalase, GPX activities, and total protein concentration. No significant differences in any of these assays were seen in either lung tissue or BAL in the 5 groups. These observations indicate that 48 hr of hyperoxia, mechanical ventilation, or dexamethasone treatment does not induce activity of SOD, catalase, or glutathione peroxidase (GPX) in the lungs of newborn piglets. Thus postnatal DEX appears to minimize neonatal lung injury by mechanisms that are independent of these enzymes.

Pathophysiology and treatment of bronchopulmonary dysplasia. Current issues

Although much has been learned about BPD in the 25 years since its initial description, BPD remains a significant complication of prematurity. Substantial advances into the understanding of its pathophysiology and pathogenesis have been made and are reflected in new therapeutic interventions. Much current research is directed towards the role of prevention, exploring new approaches for accelerating lung maturation with combined maternal steroid and thyrotropin releasing hormone (TRH) therapy, surfactant replacement therapy, high frequency oscillatory ventilation, antioxidant administration, manipulation of endogenous antioxidants, and other pharmacologic strategies to minimize lung injury. The impact of other technologies, such as synchronized intermittent mandatory ventilation, perfluorocarbon (liquid) ventilation, and perhaps inhaled nitric oxide therapy may become additional parts of the clinical regimen for some cases of severe neonatal respiratory failure. Less information is available on mechanisms which can hasten lung healing. Ongoing studies of inflammatory products, growth factors, and cytokines may lead to new therapies which will favorably influence the fibroproliferative phase of disease. In the meantime, the medical and social impact of BPD continues to remain a significant problem not only during infancy but also throughout life. Mildred Stahlman, MD, recently wrote that (a)s sanguine as the future looks for surfactant therapy, it may leave us with more very low-birth weight infants who survive, whose potential for normal pulmonary growth and development is unknown, and whose very immature organ systems, besides the lung, are still susceptible to metabolic, neurologic, and other problems. As more survivors are reaching young adulthood, respiratory and neurodevelopmental complications persist. Thus, as advances in the care of the premature newborn with respiratory distress have dramatically improved survival, the management of chronic lung disease and related problems remains a continuing challenge.

Delivery of micronized budesonide suspension by metered dose inhaler and jet nebulizer into a neonatal ventilator circuit

We compared the delivery of a micronized suspension of budesonide by a metered dose inhaler (MDI) with two different spacers (Aerochamber and Aerovent) and by two jet nebulizers (MAD2 and Ultravent) to a ventilated neonatal test-lung using a standard neonatal ventilator circuit. The combination of MDI and Aerochamber was significantly better at delivering budesonide to a filter in front of the test lung (14.2% of aerosolized dose) than were either the MDI and Aerovent (3.6%) or the Ultravent or MAD2 jet nebulizers (0.02% and 0.68% of initial reservoir dose). Of the droplets emerging from the MDI, Aerochamber, and ET tube, 18% of the initial dose was in droplets less than 4.7 microns. Assuming that the test-lung model accurately reflects in vivo deposition, the combination of MDI and Aerochamber appears to be an extremely effective way of delivering budesonide aerosol to ventilated newborn infants.