Cromolyn sodium for the prevention of chronic lung disease in preterm infants

Cromolyn sodium for the prevention of chronic lung disease in preterm infants

BACKGROUND

This is an update of a review last published by Cochrane in June 2012 entitled "Cromolyn sodium for the prevention of chronic lung disease in preterm infants", which included two studies. This 2016 update identified no further studies.Chronic lung disease (CLD) frequently occurs in preterm infants and has a multifactorial aetiology including inflammation. Cromolyn sodium is a mast cell stabiliser that inhibits neutrophil activation and neutrophil chemotaxis and therefore may have a role in the prevention of CLD.

OBJECTIVES

To determine the effect of prophylactic administration of cromolyn sodium on the incidence of CLD at 28 days or 36 weeks' postmenstrual age (PMA), mortality, or the combined outcome of mortality and CLD at 28 days or 36 weeks' PMA in preterm infants.

SEARCH METHODS

We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL 2016, Issue 4), MEDLINE via PubMed (1966 to 12 May 2016), Embase (1980 to 12 May 2016), and CINAHL (1982 to 12 May 2016). We searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials.

SELECTION CRITERIA

We included randomised or quasi-randomised controlled clinical trials involving preterm infants. Initiation of cromolyn sodium administration was during the first two weeks of life. The intervention had to include administration of cromolyn sodium by nebuliser or metered dose inhaler with or without spacer device versus placebo or no intervention. Eligible studies had to include at least one of the following outcomes: overall mortality, CLD at 28 days, CLD at 36 weeks' PMA, or the combined outcome mortality and CLD at 28 days.

DATA COLLECTION AND ANALYSIS

We used the standard method for Cochrane as described in the Cochrane Handbook for Systematic Reviews of Interventions. We reported risk ratio (RR) and risk difference (RD) with 95% confidence intervals (CI) for dichotomous outcomes and mean difference (MD) with 95% CI for continuous data. The meta-analysis used a fixed-effect model. We examined heterogeneity using the I2 statistic. We assessed the quality of evidence for the main comparison at the outcome level using the GRADE approach.

MAIN RESULTS

We identified two eligible studies with small numbers of infants enrolled (64 infants). Prophylaxis with cromolyn sodium did not result in a statistically significant effect on the combined outcome of mortality and CLD at 28 days (typical RR 1.05, 95% CI 0.73 to 1.52; typical RD 0.03, 95% CI -0.20 to 0.27; 2 trials, 64 infants; I2 = 0% for both RR and RD); mortality at 28 days (typical RR 1.31, 95% CI 0.52 to 3.29; I2 = 73% typical RD 0.06, 95% CI -0.13 to 0.26; I2 = 87%; 2 trials, 64 infants) (very low quality evidence); CLD at 28 days (typical RR 0.93, 95% CI 0.53 to 1.64; I2 = 40%; typical RD -0.03, 95% CI -0.27 to 0.20; I2 = 38%; 2 trials, 64 infants) or at 36 weeks' PMA (RR 1.25, 95% CI 0.43 to 3.63; RD 0.08, 95% CI -0.29 to 0.44; 1 trial, 26 infants). There was no significant difference in CLD in survivors at 28 days (typical RR 0.97, 95% CI 0.58 to 1.63; typical RD -0.02, 95% CI -0.29 to 0.26; I2 = 0% for both RR and RD; 2 trials, 50 infants) or at 36 weeks' PMA (RR 1.04, 95% CI 0.38 to 2.87; RD 0.02, 95% CI -0.40 to 0.43; 1 trial, 22 infants). Prophylaxis with cromolyn sodium did not show a statistically significant difference in overall neonatal mortality, incidence of air leaks, necrotising enterocolitis, intraventricular haemorrhage, sepsis, and days of mechanical ventilation. There were no adverse effects noted. The quality of evidence according to GRADE was very low for one outcome (mortality to 28 days) and low for all other outcomes. The reasons for downgrading the evidence was due to design (risk of bias in one study), inconsistency between the two studies (high I2 values for mortality at 28 days for both RR and RD), and lack of precision of estimates (small sample sizes). Further research does not seem to be justified.

AUTHORS' CONCLUSIONS

There is currently no evidence from randomised trials that cromolyn sodium has a role in the prevention of CLD. Cromolyn sodium cannot be recommended for the prevention of CLD in preterm infants.

Genome-wide transcriptional profiling reveals connective tissue mast cell accumulation in bronchopulmonary dysplasia

RATIONALE

Bronchopulmonary dysplasia (BPD) is a major complication of premature birth. Risk factors for BPD are complex and include prenatal infection and O(2) toxicity. BPD pathology is equally complex and characterized by inflammation and dysmorphic airspaces and vasculature. Due to the limited availability of clinical samples, an understanding of the molecular pathogenesis of this disease and its causal mechanisms and associated biomarkers is limited.

OBJECTIVES

Apply genome-wide expression profiling to define pathways affected in BPD lungs.

METHODS

Lung tissue was obtained at autopsy from 11 BPD cases and 17 age-matched control subjects without BPD. RNA isolated from these tissue samples was interrogated using microarrays. Standard gene selection and pathway analysis methods were applied to the data set. Abnormal expression patterns were validated by quantitative reverse transcriptase-polymerase chain reaction and immunohistochemistry.

MEASUREMENTS AND MAIN RESULTS

We identified 159 genes differentially expressed in BPD tissues. Pathway analysis indicated previously appreciated (e.g., DNA damage regulation of cell cycle) as well as novel (e.g., B-cell development) biological functions were affected. Three of the five most highly induced genes were mast cell (MC)-specific markers. We confirmed an increased accumulation of connective tissue MC(TC) (chymase expressing) mast cells in BPD tissues. Increased expression of MC(TC) markers was also demonstrated in an animal model of BPD-like pathology.

CONCLUSIONS

We present a unique genome-wide expression data set from human BPD lung tissue. Our data provide information on gene expression patterns associated with BPD and facilitated the discovery that MC(TC) accumulation is a prominent feature of this disease. These observations have significant clinical and mechanistic implications.

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.

Current perspectives on the prevention and management of chronic lung disease in preterm infants

Chronic lung disease (CLD) or bronchopulmonary dysplasia is a recognized sequel of preterm birth. With improving survival of infants at lower gestational ages, the incidence is on the rise. Pathological features of CLD include alveolar maldevelopment, with or without areas of pulmonary fibrosis. Assisted ventilation, infection/inflammation, oxygen administration, and fluid overload are the major risk factors in the evolution of CLD.Interventions, including the treatment of maternal infection, administration of prenatal glucocorticoids, and postnatal surfactant replacement therapy, improve the survival of preterm infants; however, their effect on CLD is difficult to determine. Strategies that have been effective in reducing CLD are the administration of retinol (vitamin A), high frequency oscillatory ventilation, and administration of glucocorticoids. Previous concerns regarding neurological problems associated with high frequency ventilation have not been substantiated in recent studies. Current recommendations do not advise the routine use of glucocorticoids due to concerns regarding long-term neurodevelopment. Therapies that were found to be ineffective in reducing the incidence of CLD include prenatal thyrotropin, cromolyn sodium (sodium cromoglycate), alpha-1 antitrypsin, superoxide dismutase, tocopherol (vitamin E), ascorbic acid (vitamin C), allopurinol, ambroxol, inositol, inhaled bronchodilators, and fluid restriction. Strategies that may be effective in reducing lung injury and subsequent CLD include avoiding assisted ventilation, lung protective ventilatory maneuvers, permissive hypercapnia, prevention of infection, early aggressive nutrition, and the treatment of a patent ductus arteriosus. The use of inhaled glucocorticoids improves pulmonary dynamics but long-term effects are unknown. The management of infants with established CLD has not been studied adequately, and the role of various ventilatory strategies for infants with established CLD is not clear. Adequate oxygenation should be maintained to prevent hypoxic episodes. Diuretics are helpful during acute decompensation; however, their long-term impact has not been well studied. Provision of adequate nutrition, immunization (routine and against respiratory syncytial virus), follow-up, and monitoring are the key elements in the long-term management of infants with CLD. Future research priorities should be to identify strategies to prevent/treat inflammation and promote the healing processes in the injured lung. The long-term effects of lung-protective ventilation strategies need to be studied.

Update on Cochrane data on paediatric respiratory diseases

INTRODUCTION

Systematic reviews seek to describe and summarise the best evidence for a given intervention by pooling data from relevant quality clinical trials. The Cochrane Collaboration has fostered the development and dissemination of systematic reviews throughout the world. We have identified and summarised The Cochrane systematic reviews of relevance to the paediatric pulmonologist.

METHODS

We performed an expert search of the Cochrane Database of Systematic Reviews using a combination of medical subject headings and free text terms relating to paediatric respiratory disease.

RESULTS

The search identified 120 systematic reviews with interventions specific to children with some relevance to pulmonary disease, and 327 reviews with interventions relating to pulmonary disease in adults and children. After pragmatic exclusions, 81 reviews were sorted by disease and 59 of these are discussed in detail.

CONCLUSIONS

There are now many systematic reviews that make a positive contribution to paediatric pulmonology. The majority of reviews (69%) found evidence that either confirmed or refuted an accepted practice. The remaining reviews concluded that the evidence for an accepted practice is poor and sometimes wholly absent. Clinicians must be aware that lack of evidence of effect is not the same as evidence of lack of effect. Caution must be exercised before applying the conclusions of systematic reviews based upon adult data to childhood disease.