Thyrotropin-releasing hormone added to corticosteroids for women at risk of preterm birth for preventing neonatal respiratory disease

Thyrotropin-releasing hormone added to corticosteroids for women at risk of preterm birth for preventing neonatal respiratory disease

BACKGROUND

Thyrotropin-releasing hormones (TRH) added to prenatal corticosteroids has been suggested as a way to further reduce breathing problems and neonatal lung disease in infants born preterm.

OBJECTIVES

To assess the effects of giving prenatal TRH in addition to corticosteroids to women at risk of preterm birth for the prevention of neonatal respiratory disease.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 June 2013) and reference lists of retrieved studies. We also contacted trial authors.

SELECTION CRITERIA

Randomised controlled trials in women at sufficient risk of preterm birth to warrant the use of prenatal corticosteroids to promote lung maturity. TRH and corticosteroids were compared with corticosteroids, with or without placebo.

DATA COLLECTION AND ANALYSIS

All assessments of trial eligibility, risk of bias and data extractions were independently carried out by at least two review authors.

MAIN RESULTS

Over 4600 women were recruited into the 15 trials included in the review, however two trials did not contribute any outcome data to the review. The trials had a moderate risk of bias. Overall, prenatal TRH, in addition to corticosteroids, did not reduce the risk of death prior to hospital discharge (risk ratio (RR) 1.05, 95% confidence interval (CI) 0.86 to 1.27, six trials, 3694 infants), neonatal respiratory distress syndrome (average RR 1.05, 95% CI 0.91 to 1.22, nine trials, 3833 infants), or chronic lung disease (RR 1.01, 95% CI 0.85 to 1.19, five trials, 2511 infants), and did not improve any of the secondary fetal, neonatal or childhood outcomes assessed by intention-to-treat analyses.Indeed, the data showed prenatal TRH to have adverse effects for women and their infants. All side effects reported (nausea, vomiting, light headedness, urgency of micturition, facial flushing) were significantly more likely to occur in women receiving TRH. In the infants, prenatal TRH increased the risk of needing respiratory support (RR 1.16, 95% CI 1.03 to 1.29, three trials, 1969 infants), and of having a low Apgar score at five minutes (RR 1.48, 95% CI 1.14 to 1.92, three trials, 1969 infants). Only three trials provided data on childhood follow-up, and while one trial suggested poorer outcomes for infants who were exposed to prenatal TRH, the other two trials, that assessed infants using an established developmental instrument, showed no clear differences between groups in follow-up outcomes.Sensitivity analyses by trial quality, or subgroups with differing times from entry to birth, or different dose regimens of TRH, did not change these findings.

AUTHORS' CONCLUSIONS

Prenatal TRH in addition to corticosteroids, given to women at risk of preterm birth, does not improve infant outcomes and can cause maternal side effects.

Systematic Cochrane reviews in neonatology: a critical appraisal

BACKGROUND

There is a lack of up-to-date, systematic reviews that critically assess the role and potential limitations of evidence-based medicine (EBM) and systematic reviews in neonatology.

METHODS

We performed a systematic literature review of all Cochrane reviews published between 1996 and 2010 by the Cochrane Neonatal Review Group (CNRG). Main outcome parameter: assessment of the percentage of reviews that concluded that a certain intervention provides a benefit, the percentage of reviews that concluded that no benefit was seen, and the percentage of studies that concluded that the current level of evidence is inconclusive.

RESULTS

In total, 262 reviews were assessed, most of which included exclusively preterm infants (146/262). The majority of reviews assessed pharmacological interventions (145/262); other important fields included nutritional (46/262), and ventilatory issues (27/262). In 42/262 reviews, a clear recommendation in favor of a specific intervention was given, whereas 98/262 reviews concluded that certain interventions should not be performed. However, the largest proportion of reviews was inconclusive (122/262) and did not issue specific recommendations. The proportion of inconclusive reviews increased from 30% (1996-2000), to 50% (2001-2005), and finally to 58% for the years 2006-2010. Common reasons for inconclusive reviews were the small number of patients (105), insufficient data (94), insufficient methodological quality (87), and heterogeneity of studies (69).

CONCLUSION

There is an ongoing need for high-quality research in order to reduce the proportion of inconclusive meta-analyses in the field of neonatology. Funding and research agencies will play a vital role in selecting the most appropriate research programs.

Development of quality of care indicators from systematic reviews: the case of hospital delivery

BACKGROUND

The objective of this research is to generate quality of care indicators from systematic reviews to assess the appropriateness of obstetric care in hospitals.

METHODS

A search for systematic reviews about hospital obstetric interventions, conducted in The Cochrane Library, clinical evidence and practice guidelines, identified 303 reviews. We selected 48 high-quality evidence reviews, which resulted in strong clinical recommendations using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system. The 255 remaining reviews were excluded, mainly due to a lack of strong evidence provided by the studies reviewed.

RESULTS

A total of 18 indicators were formulated from these clinical recommendations, on antepartum care (8), care during delivery and postpartum (9), and incomplete miscarriage (1). Authors of the systematic reviews and specialists in obstetrics were consulted to refine the formulation of indicators.

CONCLUSIONS

High-quality systematic reviews, whose conclusions clearly claim in favour or against an intervention, can be a source for generating quality indicators of delivery care. To make indicators coherent, the nuances of clinical practice should be considered. Any attempt made to evaluate the extent to which delivery care in hospitals is based on scientific evidence should take the generated indicators into account.

RESPIRATORY DISTRESS SYNDROME

Respiratory Distress Syndrome (RDS) is due to immaturity of the lungs, primarily the surfactant synthesising system; hence, the risk of RDS is inversely proportional to gestational age. The incidence of RDS has been reduced by the routine use of both antenatal corticosteroids and postnatal surfactant, but still approximately one per cent of babies develop RDS. Hyaline membranes, formed from plasma proteins which have leaked onto the lung surface through damaged capillaries and endothelial cells, line the terminal airways. Hence, RDS has also been called hyaline membrane disease, but RDS is the preferred name as the presence of hyaline membranes can only be confirmed histologically. The aim of this review is to emphasize the pathophysiology of RDS and the clinical presentation and relevance of diagnostic techniques in the current population of very prematurely born infants, highlighting the differential diagnosis. In addition, the evidence base for prophylactic and management strategies including whether new therapies and techniques of respiratory support have positively impacted on outcomes are discussed. The mortality and long term morbidity associated with very premature birth are described. Our increasing understanding that the so-called new bronchopulmonary dysplasia (BPD) and associated chronic adverse respiratory outcomes in such infants can reflect antenatal events resulting in abnormal lung growth is highlighted.

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.

Postnatal thyroid hormones for respiratory distress syndrome in preterm infants

BACKGROUND

Preterm infants with respiratory distress syndrome are at increased risk of adverse neonatal and developmental outcomes. In animal research, thyroid hormones stimulate surfactant production and reduce the incidence and severity of respiratory distress when given antenatally.

OBJECTIVES

To determine whether thyroid hormone therapy used postnatally in preterm infants with suspected respiratory distress syndrome results in clinically important improvements in respiratory morbidity and subsequent improvements in neonatal and long term outcomes.

SEARCH STRATEGY

Searches were performed of The Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 1, 2006), MEDLINE (1966 - March 2006), PREMEDLINE (March 2006), EMBASE (1980 - March 2006), previous reviews including cross references, abstracts and conference proceedings, supplemented by requests to expert informants.

SELECTION CRITERIA

Trials that enrolled preterm infants with suspected respiratory distress syndrome and allocated infants thyroid hormone treatment compared to control commenced in the first 48 hours after birth.

DATA COLLECTION AND ANALYSIS

Independent assessment of trial quality and data extraction by each author. Synthesis of data using relative risk (RR) and weighted mean difference (WMD) using standard methods of the Cochrane Collaboration and its Neonatal Review Group.

MAIN RESULTS

Two studies enrolled preterm infants with respiratory distress. Amato (1988) allocated infants to L-thyroxine 50 mug/dose at 1 and at 24 hours or no treatment. Amato (1989) allocated infants to L-triiodothyronine 50 mug/day in two divided doses for two days or no treatment. Both studies had methodological concerns including quasi-random methods of patient allocation, no blinding of treatment or measurement and substantial post allocation losses. Neither study reported any significant benefits in neonatal morbidity or mortality from use of thyroid hormones. Meta-analysis of two studies (80 infants) found no significant difference in mortality to discharge (typical RR 1.00, 95% CI 0.47, 2.14). Amato 1988 reported no significant difference in use of mechanical ventilation (RR 0.64, 95% CI 0.38, 1.09). No significant effects were found in use of mechanical ventilation, duration of mechanical ventilation, air leak, CLD at 28 days in survivors, patent ductus arteriosus, intraventricular haemorrhage or necrotising enterocolitis. Neurodevelopment was not reported.

AUTHORS' CONCLUSIONS

There is no evidence from controlled clinical trials that postnatal thyroid hormone treatment reduces the severity of respiratory distress syndrome, neonatal morbidity or mortality in preterm infants with respiratory distress syndrome.

Bronchopulmonary dysplasia

Bronchopulmonary dysplasia is a chronic lung disease that affects premature babies and contributes to their morbidity and mortality. Improved survival of very immature infants has led to increased numbers of infants with this disorder. This increase puts a heavy burden on health resources since these infants need frequent re-admission to hospital in the first 2 years after birth and, even as adolescents, have lung-function abnormalities and persistent respiratory symptoms. Unlike the original description of the disease in 1967, premature infants can develop chronic oxygen dependency without severe, acute respiratory distress; this "new bronchopulmonary dysplasia" could be the result of impaired postnatal lung growth. Whether such infants subsequently have catch-up lung growth, especially if given corticosteroids postnatally, is unknown. No safe and effective preventive therapy has been identified, but promising new treatments directed either at reducing lung injury or improving lung growth are under study.

Disruption of rat forebrain development by glucocorticoids: critical perinatal periods for effects on neural cell acquisition and on cell signaling cascades mediating noradrenergic and cholinergic neurotransmitter/neurotrophic responses

Glucocorticoids are the consensus treatment for the prevention of respiratory distress in preterm infants, but there is evidence for increased incidence of neurodevelopmental disorders as a result of their administration. We administered dexamethasone (Dex) to developing rats at doses below or within the range of those used clinically, evaluating the effects on forebrain development with exposure in three different stages: gestational days 17-19, postnatal days 1-3, or postnatal days 7-9. At 24 h after the last dose, we evaluated biomarkers of neural cell acquisition and growth, synaptic development, neurotransmitter receptor expression, and synaptic signaling mediated by adenylyl cyclase (AC). Dex impaired the acquisition of neural cells, with a peak effect when given in the immediate postnatal period. In association with this defect, Dex also elicited biphasic effects on cholinergic presynaptic development, promoting synaptic maturation at a dose (0.05 mg/kg) well below those used therapeutically, whereas the effect was diminished or lost when doses were increased to 0.2 or 0.8 mg/kg. Dex given postnatally also disrupted the expression of adrenergic receptors known to participate in neurotrophic modeling of the developing brain and evoked massive induction of AC activity. As a consequence, disparate receptor inputs all produced cyclic AMP overproduction, a likely contributor to disrupted patterns of cell replication, differentiation, and apoptosis. Superimposed on the heterologous AC induction, Dex impaired specific receptor-mediated cholinergic and adrenergic signals. These results indicate that, during a critical developmental period, Dex administration leads to widespread interference with forebrain development, likely contributing to eventual, adverse neurobehavioral outcomes.

The Molecular Basis for Abnormal Human Lung Development

Our understanding of lung development in the past two decades has moved from an anatomical to a histological basis and, most recently, to a molecular basis. Tissue interactions specify tracheal and lung primordia formation, program branching morphogenesis of the airway epithelium and regulate epithelial differentiation. In addition, lung development is influenced by mechanical and humoral factors. The regulatory molecules involved in morphogenetic signaling include growth and transcription factors and extracellular matrix molecules. These morphogenetic signals are responsible for lung patterning and differentiation. We will provide a brief overview of molecular signaling during early respiratory formation, airway branching, pulmonary vascularization and epithelial differentiation. We will then review aberrant morphogenetic signaling in human lung abnormalities, such as tracheoesophageal fistula, congenital diaphragmatic hernia, pulmonary hyperplasia, alveolar capillary dysplasia, congenital cystic adenomatoid malformation and bronchopulmonary dysplasia.

Thyrotropin-releasing hormone added to corticosteroids for women at risk of preterm birth for preventing neonatal respiratory disease

BACKGROUND

Thyrotropin-releasing hormones (TRH) added to prenatal corticosteroids has been suggested as a way to further reduce breathing problems and neonatal lung disease in infants born preterm.

OBJECTIVES

To assess the effect of giving prenatal TRH in addition to corticosteroids to women at risk of very preterm birth for the prevention of neonatal respiratory disease.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register (July 2003), the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 3, 2003), MEDLINE (1965 to July 2003), EMBASE (1988 to July 2003), Current Contents (1997 to July 2003).

SELECTION CRITERIA

Randomised controlled trials in women at sufficient risk of preterm birth to warrant the use of prenatal corticosteroids to promote lung maturity. TRH and corticosteroids were compared with corticosteroids with or without placebo. The main outcomes considered were fetal and infant mortality, infant morbidity, childhood development and maternal morbidity.

DATA COLLECTION AND ANALYSIS

All assessments of trial eligibility, quality and data extractions were done by at least two authors independently.

MAIN RESULTS

Over 4600 women were recruited into the 13 included trials. Five trials were rated of high quality. Overall, prenatal TRH, in addition to corticosteroids, did not reduce the risk of neonatal respiratory disease or chronic oxygen dependence, and did not improve any of the fetal, neonatal or childhood outcomes assessed by intention to treat analyses.Indeed, the data showed prenatal TRH to have adverse effects for women and their infants. All side-effects monitored were more likely to occur in women receiving TRH. In the infants, prenatal TRH increased the risk of needing ventilation (relative risk (RR) 1.16, 95% confidence interval (CI) 1.03 to 1.29, 3 trials, 1969 infants), having a low Apgar score at five minutes (RR 1.48, 95% CI 1.14 to 1.92, 3 trials, 1969 infants) and, for the two trials providing data, was associated with poorer outcomes at childhood follow up. Sensitivity analyses by trial quality, or subgroups with differing times from entry to birth, or different dose regimens of TRH, did not change these findings.

REVIEWERS' CONCLUSIONS

Prenatal thyrotropin-releasing hormones, in addition to corticosteroids, given to women at risk of very preterm birth do not improve infant outcomes and can cause maternal side-effects.