Randomized, placebo-controlled trial of human surfactant given at birth versus rescue administration in very low birth weight infants with lung immaturity

Surfactant therapy guided by tests for lung maturity in preterm infants at risk of respiratory distress syndrome

BACKGROUND

Administration of various exogenous surfactant preparations has been shown to decrease lung injury and pneumothorax and improve survival in very preterm infants with respiratory distress syndrome (RDS). There is no consensus on the threshold for surfactant administration, to allow timely intervention and avoid over-treatment, also considering the invasiveness of the procedure and its cost. Rapid tests for lung maturity, which include the click test, lamellar body counts and stable microbubble test, might guide the identification of those infants needing surfactant administration.

OBJECTIVES

To assess the effects of surfactant treatment guided by rapid tests for surfactant deficiency in preterm infants at risk for or having RDS. Comparison 1: In preterm infants at risk for RDS, does surfactant treatment guided by rapid tests for surfactant deficiency compared to prophylactic surfactant administration to all high-risk infants minimize the need for surfactant treatment and prevent bronchopulmonary dysplasia and mortality? Comparison 2: In preterm infants who require early respiratory support, does surfactant treatment guided by rapid tests for surfactant deficiency compared to surfactant therapy provided to infants with RDS diagnosed on clinical and radiologic criteria minimize the need for surfactant treatment and prevent bronchopulmonary dysplasia and mortality?

SEARCH METHODS

We searched in October 2022 CENTRAL, PubMed, Embase and three additional trial registries. We also screened the reference lists of included studies and related systematic reviews for studies not identified by the database searches.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) and quasi-RCTs evaluating rapid tests after birth for surfactant deficiency in infants at high risk of RDS or requiring respiratory support. We specified two comparisons: 1)surfactant treatment guided by rapid tests for surfactant deficiency versus prophylactic surfactant administration to all high-risk infants in extremely preterm (less than 28 weeks' gestation) and very preterm (28 to 32 weeks' gestation); 2)surfactant treatment guided by rapid tests for surfactant deficiency versus surfactant therapy provided to preterm infants (less than 37 weeks' gestation) with RDS diagnosed on clinical and radiologic criteria.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. We used the fixed-effect model with risk ratio (RR) and risk difference (RD), with their 95% confidence intervals (CIs) for dichotomous data. Our primary outcomes were: neonatal mortality, mortality prior to hospital discharge, bronchopulmonary dysplasia and the composite outcome bronchopulmonary dysplasia or mortality. We used GRADE to assess the certainty of evidence.

MAIN RESULTS

We included three RCTs enrolling 562 newborn infants in this review. No studies compared surfactant treatment guided by rapid tests for surfactant deficiency versus prophylactic surfactant administration to all high-risk infants. Comparing surfactant therapy guided by rapid tests for surfactant deficiency versus surfactant therapy provided to infants with RDS diagnosed on clinical and radiologic criteria. No studies reported neonatal mortality. Compared with surfactant therapy provided to infants with RDS diagnosed on clinical and radiologic criteria, the evidence is very uncertain about the effect of surfactant treatment guided by rapid tests for surfactant deficiency on mortality prior to hospital discharge: RR 1.25, 95% CI 0.65 to 2.41, RD 0.01, 95% CI -0.03 to 0.05, 562 participants, 3 studies; I² for RR and RD = 75% and 43%, respectively; very low-certainty evidence. Surfactant treatment guided by rapid tests for surfactant deficiency may result in little to no difference in bronchopulmonary dysplasia: RR 0.90, 95% CI 0.61 to 1.32, RD -0.02, 95% CI -0.08 to 0.04, 562 participants, 3 studies; I² for RR and RD = 0%; low-certainty evidence. No studies reported the composite outcome bronchopulmonary dysplasia or mortality. Surfactant treatment guided by rapid tests for surfactant deficiency may result in little to no difference in surfactant utilization (RR 0.97, 95% CI 0.85 to 1.11, RD -0.02, 95% CI -0.10 to 0.06, 562 participants, 3 studies, I² for RR and RD = 63% and 65%, respectively, low-certainty evidence), and any pneumothorax (RR 0.53, 95% CI 0.15 to 1.92, RD -0.01, 95% CI -0.04 to 0.01, 506 participants, 2 studies, I² for RR and RD = 0%, low-certainty evidence) compared with surfactant therapy provided to infants with RDS diagnosed on clinical and radiologic criteria. No studies reported moderate to severe neurodevelopmental impairment. We identified two large ongoing RCTs.

AUTHORS' CONCLUSIONS

No studies compared surfactant treatment guided by rapid tests for surfactant deficiency to prophylactic surfactant administration to all high-risk infants. Low to very low-certainty evidence from three studies is available on surfactant therapy guided by rapid tests for surfactant deficiency versus surfactant therapy provided to infants with RDS diagnosed on clinical and radiologic criteria. No studies reported neonatal mortality, the composite outcome 'bronchopulmonary dysplasia or mortality', or neurodevelopmental outcomes. Compared with surfactant therapy provided to infants with RDS diagnosed on clinical and radiologic criteria, the evidence is very uncertain about the effect of surfactant treatment guided by rapid tests for surfactant deficiency on mortality prior to hospital discharge. Surfactant treatment guided by rapid tests for surfactant deficiency may result in little to no difference in bronchopulmonary dysplasia, surfactant utilization and any pneumothorax. The findings of the two large ongoing trials identified in this review are likely to have an important impact on establishing the effects of surfactant treatment guided by rapid tests for surfactant deficiency in preterm infants.

Clinical decision thresholds for surfactant administration in preterm infants: a systematic review and network meta-analysis

Background

The ideal threshold at which surfactant administration in preterm neonates with respiratory distress syndrome (RDS) is most beneficial is contentious. The aim of this systematic review was to determine the optimal clinical criteria to guide surfactant administration in preterm neonates with RDS.

Methods

The systematic review was registered in PROSPERO (CRD42022309433). Medline, Embase, CENTRAL and CINAHL were searched from inception till 16th May 2023. Only randomized controlled trials (RCTs) were included. A Bayesian random effects network meta-analysis (NMA) evaluating 33 interventions was performed. The primary outcome was requirement of invasive mechanical ventilation (IMV) within 7 days of life.

Findings

58 RCTs were included. In preterm neonates ≤30 weeks after adjusting for the confounding factor of modality of surfactant administration, an arterial alveolar oxygen tension ratio (aAO2) <0.36 (FiO2: 37-55%) was ranked the best threshold for decreasing the risk of IMV, very low certainty. Further, surfactant administration at an FiO2 40-45% possibly decreased mortality compared to rescue treatment when respiratory failure was diagnosed, certainty very low. The reasonable inference that could be drawn from these findings is that surfactant administration may be considered in preterm neonates of ≤30 weeks' with RDS requiring an FiO2 ≥ 40%. There was insufficient evidence for the comparison of FiO2 thresholds: 30% vs. 40%. The evidence was sparse for surfactant administration guided by lung ultrasound. For the sub-group >30 weeks, nebulized surfactant administration at an FiO2 < 30% possibly increased the risk of IMV compared to Intubate-Surfactant-Extubate at FiO2 < 30% and 40%, and less invasive surfactant administration at FiO2 40%, certainty very low.

Interpretation

Surfactant administration may be considered in preterm neonates of ≤30 weeks' with RDS if the FiO2 requirement is ≥40%. Future trials are required comparing lower FiO2 thresholds of 30% vs. 40% and that guided by lung ultrasound.

Funding

None.

Thresholds for surfactant use in preterm neonates: a network meta-analysis

OBJECTIVE

To perform a network meta-analysis of randomised controlled trials of different surfactant treatment strategies for respiratory distress syndrome (RDS) to assess if a certain fraction of inspired oxygen (FiO₂) is optimal for selective surfactant therapy.

DESIGN

Systematic review and network meta-analysis using Bayesian analysis of randomised trials of prophylactic versus selective surfactant for RDS.

SETTING

Cochrane Central Register of Controlled Trials, MEDLINE, Embase and Science Citation Index Expanded.

PATIENTS

Randomised trials including infants under 32 weeks of gestational age.

INTERVENTIONS

Intratracheal surfactant, irrespective of type or dose.

MAIN OUTCOME MEASURES

Our primary outcome was neonatal mortality, compared between groups treated with selective surfactant therapy at different thresholds of FiO₂. Secondary outcomes included respiratory morbidity and major complications of prematurity.

RESULTS

Of 4643 identified references, 14 studies involving 5298 participants were included. We found no statistically significant differences between 30%, 40% and 50% FiO₂ thresholds. A sensitivity analysis of infants treated in the era of high antenatal steroid use and nasal continuous positive airway pressure as initial mode of respiratory support showed no difference in mortality, RDS or intraventricular haemorrhage alone but suggested an increase in the combined outcome of major morbidities in the 60% threshold.

CONCLUSION

Our results do not show a clear benefit of surfactant treatment at any threshold of FiO₂. The 60% threshold was suggestive of increased morbidity. There was no advantage seen with prophylactic treatment. Randomised trials of different thresholds for surfactant delivery are urgently needed to guide clinicians and provide robust evidence.

PROSPERO REGISTRATION NUMBER

CRD42020166620.

Surfactant therapy guided by tests for lung maturity in preterm infants at risk of respiratory distress syndrome

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

To assess the effects of surfactant treatment guided by rapid tests for surfactant deficiency in preterm infants at risk for or having RDS.

Comparison 1: In preterm infants at risk for RDS, does surfactant treatment guided by rapid tests for surfactant deficiency compared to prophylactic surfactant administration to all high‐risk infants minimize the need for surfactant treatment and prevent bronchopulmonary dysplasia and mortality?

Comparison 2: In preterm infants who require early respiratory support, does surfactant treatment guided by rapid tests for surfactant deficiency compared to surfactant therapy provided to infants with RDS diagnosed on clinical and radiologic criteria minimize the need for surfactant treatment and prevent bronchopulmonary dysplasia and mortality?

Planned subgroup analysis: gestational age, disease severity, timing of testing and treatment, surfactant preparation, exposure to antenatal steroids.

Utility of large-animal models of BPD: chronically ventilated preterm lambs

This paper is focused on unique insights provided by the preterm lamb physiological model of bronchopulmonary dysplasia (BPD). Connections are also made to insights provided by the former preterm baboon model of BPD, as well as to rodent models of lung injury to the immature, postnatal lung. The preterm lamb and baboon models recapitulate the clinical setting of preterm birth and respiratory failure that require prolonged ventilation support for days or weeks with oxygen-rich gas. An advantage of the preterm lamb model is the large size of preterm lambs, which facilitates physiological studies for days or weeks during the evolution of neonatal chronic lung disease (CLD). To this advantage is linked an integrated array of morphological, biochemical, and molecular analyses that are identifying the role of individual genes in the pathogenesis of neonatal CLD. Results indicate that the mode of ventilation, invasive mechanical ventilation vs. less invasive high-frequency nasal ventilation, is related to outcomes. Our approach also includes pharmacological interventions that test causality of specific molecular players, such as vitamin A supplementation in the pathogenesis of neonatal CLD. The new insights that are being gained from our preterm lamb model may have important translational implications about the pathogenesis and treatment of BPD in preterm human infants.

Surfactant

Exogenous pulmonary surfactant, widely used in neonatal care, is one of the best-studied treatments in neonatology, and its introduction in the 1990s led to a significant improvement in neonatal outcomes in preterm infants, including a decrease in mortality. This chapter provides an overview of surfactant composition and function in health and disease and summarizes the evidence for its clinical use.

Delivery and performance of surfactant replacement therapies to treat pulmonary disorders

Lung surfactant is crucial for optimal pulmonary function throughout life. An absence or deficiency of surfactant can affect the surfactant pool leading to respiratory distress. Even if the coupling between surfactant dysfunction and the underlying disease is not always well understood, using exogenous surfactants as replacement is usually a standard therapeutic option in respiratory distress. Exogenous surfactants have been extensively studied in animal models and clinical trials. The present article provides an update on the evolution of surfactant therapy, types of surfactant treatment, and development of newer-generation surfactants. The differences in the performance between various surfactants are highlighted and advanced research that has been conducted so far in developing the optimal delivery of surfactant is discussed.

Early versus delayed selective surfactant treatment for neonatal respiratory distress syndrome

BACKGROUND

Clinical trials have confirmed that surfactant therapy is effective in improving the immediate need for respiratory support and the clinical outcome of premature newborns. Trials have studied a wide variety of surfactant preparations used either to prevent (prophylactic or delivery room administration) or treat (selective or rescue administration) respiratory distress syndrome (RDS). Using either treatment strategy, significant reductions in the incidence of pneumothorax, as well as significant improvement in survival, have been noted. It is unclear whether there are any advantages to treating infants with respiratory insufficiency earlier in the course of RDS.

OBJECTIVES

To compare the effects of early versus delayed selective surfactant therapy for newborns intubated for respiratory distress within the first two hours of life. Planned subgroup analyses included separate comparisons for studies utilizing natural surfactant extract and synthetic surfactant.

SEARCH METHODS

We searched the Oxford Database of Perinatal Trials, MEDLINE (MeSH terms: pulmonary surfactant; text word: early; limits: age, newborn: publication type, clinical trial), PubMed, abstracts, conference and symposia proceedings, expert informants, and journal handsearching in the English language. For the updated search in April 2012 we searched the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, 2012, Issue 1) and PubMed (January 1997 to April 2012).

SELECTION CRITERIA

Randomized and quasi-randomized controlled clinical trials comparing early selective surfactant administration (surfactant administration via the endotracheal tube in infants intubated for respiratory distress, not specifically for surfactant dosage) within the first two hours of life versus delayed selective surfactant administration to infants with established RDS were considered for review.

DATA COLLECTION AND ANALYSIS

Data regarding clinical outcomes were excerpted from the reports of the clinical trials by the review authors. Subgroup analyses were performed based on type of surfactant preparation, gestational age, and exposure to prenatal steroids. Data analysis was performed in accordance with the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

Six randomized controlled trials met selection criteria. Two of the trials utilized synthetic surfactant (Exosurf Neonatal) and four utilized animal-derived surfactant preparations.The meta-analyses demonstrate significant reductions in the risk of neonatal mortality (typical risk ratio (RR) 0.84; 95% confidence interval (CI) 0.74 to 0.95; typical risk difference (RD) -0.04; 95% CI -0.06 to -0.01; 6 studies; 3577 infants), chronic lung disease (typical RR 0.69; 95% CI 0.55 to 0.86; typical RD -0.04; 95% CI -0.06 to -0.01; 3 studies; 3041 infants), and chronic lung disease or death at 36 weeks (typical RR 0.83; 95% CI 0.75 to 0.91; typical RD -0.06; 95% CI -0.09 to -0.03; 3 studies; 3050 infants) associated with early treatment of intubated infants with RDS.Intubated infants randomized to early selective surfactant administration also demonstrated a decreased risk of acute lung injury including a decreased risk of pneumothorax (typical RR 0.69; 95% CI 0.59 to 0.82; typical RD -0.05; 95% CI -0.08 to -0.03; 5 studies; 3545 infants), pulmonary interstitial emphysema (typical RR 0.60; 95% CI 0.41 to 0.89; typical RD -0.06; 95% CI -0.10 to -0.02; 3 studies; 780 infants), and overall air leak syndromes (typical RR 0.61; 95% CI 0.48 to 0.78; typical RD -0.18; 95% CI -0.26 to -0.09; 2 studies; 463 infants).A trend toward risk reduction for bronchopulmonary dysplasia (BPD) or death at 28 days was also evident (typical RR 0.94; 95% CI 0.88 to 1.00; typical RD -0.04; 95% CI -0.07 to -0.00; 3 studies; 3039 infants). No differences in other complications of RDS or prematurity were noted.Only two studies reported on infants under 30 weeks' gestation. Decreased risk of neonatal mortality and chronic lung disease or death at 36 weeks' postmenstrual age was noted.

AUTHORS' CONCLUSIONS

Early selective surfactant administration given to infants with RDS requiring assisted ventilation leads to a decreased risk of acute pulmonary injury (decreased risk of pneumothorax and pulmonary interstitial emphysema) and a decreased risk of neonatal mortality and chronic lung disease compared to delaying treatment of such infants until they develop worsening RDS.

The role of surfactant in respiratory distress syndrome

The key feature of respiratory distress syndrome (RDS) is the insufficient production of surfactant in the lungs of preterm infants. As a result, researchers have looked into the possibility of surfactant replacement therapy as a means of preventing and treating RDS. We sought to identify the role of surfactant in the prevention and management of RDS, comparing the various types, doses, and modes of administration, and the recent development. A PubMed search was carried out up to March 2012 using phrases: surfactant, respiratory distress syndrome, protein-containing surfactant, protein-free surfactant, natural surfactant, animal-derived surfactant, synthetic surfactant, lucinactant, surfaxin, surfactant protein-B, surfactant protein-C.Natural, or animal-derived, surfactant is currently the surfactant of choice in comparison to protein-free synthetic surfactant. However, it is hoped that the development of protein-containing synthetic surfactant, such as lucinactant, will rival the efficacy of natural surfactants, but without the risks of their possible side effects. Administration techniques have also been developed with nasal continuous positive airway pressure (nCPAP) and selective surfactant administration now recommended; multiple surfactant doses have also reported better outcomes. An aerosolised form of surfactant is being trialled in the hope that surfactant can be administered in a non-invasive way. Overall, the advancement, concerning the structure of surfactant and its mode of administration, offers an encouraging future in the management of RDS.

Prophylactic versus selective use of surfactant in preventing morbidity and mortality in preterm infants

BACKGROUND

Surfactant therapy is effective in improving the outcome of very preterm infants. Trials have studied a wide variety of surfactant preparations used either to prevent or treat respiratory distress syndrome (RDS). In animal models, prophylactic surfactant leads to more homogeneous distribution and less evidence of lung damage. However, administration requires intubation and treatment of infants who will not go on to develop RDS. This is of particular concern with the advent of improved approaches to providing continuous distending pressure, particularly in the form of nasal continuous positive airway pressure (CPAP).

OBJECTIVES

To compare the effect of prophylactic surfactant administration to surfactant treatment of established RDS in very preterm infants at risk of RDS.

SEARCH METHODS

We updated the search of the Cochrane Central Register of Controlled Trials (The Cochrane Library), MEDLINE, EMBASE, CINAHL, and clinical trials.gov register in December 13, 2011.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials that compared the effects of prophylactic surfactant administration to surfactant treatment of established RDS in preterm infants at risk of RDS.

DATA COLLECTION AND ANALYSIS

Data regarding clinical outcomes were extracted from the reports of the clinical trials by the reviewers. Data analysis was done in accordance with the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

Eleven studies were identified that met inclusion criteria [nine without routine application of continuous positive air way pressure (CPAP) in the selective treatment group; two with routine application of CPAP in the selective treatment group]The meta-analysis of studies conducted prior to the routine application of CPAP demonstrated a decrease in the risk of air leak and neonatal mortality associated with prophylactic administration of surfactant. However, the analyses of studies that allowed for routine stabilization on CPAP demonstrated a decrease in the risk of chronic lung disease or death in infants stabilized on CPAP. When all studies were evaluated together, the benefits of prophylactic surfactant could no longer be demonstrated.

AUTHORS' CONCLUSIONS

Although the early trials of prophylactic surfactant administration to infants judged to be at risk of developing RDS compared to selective use of surfactant in infants with established RDS demonstrated a decreased risk of air leak and mortality, recent large trials that reflect current practice (including greater utilization of maternal steroids and routine post delivery stabilization on CPAP) do not support these differences and demonstrate less risk of chronic lung disease or death when using early stabilization on CPAP with selective surfactant administration to infants requiring intubation.

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.

Surfactant-replacement therapy for respiratory distress in the preterm and term neonate

Respiratory failure secondary to surfactant deficiency is a major cause of morbidity and mortality in preterm infants. Surfactant therapy substantially reduces mortality and respiratory morbidity for this population. Secondary surfactant deficiency also contributes to acute respiratory morbidity in late-preterm and term neonates with meconium aspiration syndrome, pneumonia/sepsis, and perhaps pulmonary hemorrhage; surfactant replacement may be beneficial for these infants. This statement summarizes indications, administration, formulations, and outcomes for surfactant-replacement therapy. The impact of antenatal steroids and continuous positive airway pressure on outcomes and surfactant use in preterm infants is reviewed. Because respiratory insufficiency may be a component of multiorgan dysfunction, preterm and term infants receiving surfactant-replacement therapy should be managed in facilities with technical and clinical expertise to administer surfactant and provide multisystem support.

Lung surfactants

PURPOSE

The pharmacology, clinical efficacy, and cost considerations of exogenous lung surfactants are reviewed.

SUMMARY

Exogenous pulmonary surfactants, along with advancements in ventilatory care, have significantly reduced the incidence of respiratory distress syndrome (RDS) and its related complications in infants. The following exogenous surfactants are approved for the prophylaxis and treatment (rescue) of neonatal RDS: beractant, a modified natural surfactant; calfactant and poractant, both natural surfactants; and colfosceril, a synthetic surfactant that is not currently available in the United States. Lucinactant, a synthetic surfactant, is under investigation and received approvable status from the Food and Drug Administration in February 2005. The surfactants are delivered directly to their site of action, and only small amounts reach the systemic circulation. Bioavailability to the distal airways and alveoli depends on the method of delivery, the stage and severity of pulmonary disease, and the properties of the particular surfactant. According to data from clinical trials, the use of exogenous surfactant therapy for rescue within the first two hours of life appears to be as efficacious as prophylaxis in most premature infants.

CONCLUSION

Comparative trials of surfactants have proven the efficacy of both synthetic and natural surfactants in the prevention and treatment of RDS. However, these trials have universally demonstrated greater reduction in the immediate need for ventilator support in infants who receive natural surfactants. Natural preparations cause less pneumothorax, bronchopulmonary dysplasia, and mortality compared with synthetic preparations. Synthetic agents offer the potential advantages of an unlimited supply with consistent pharmaceutical quality and no risk of transmitting infectious disease or causing immunologic sensitization.

From the archives of the AFIP: Lung disease in premature neonates: radiologic-pathologic correlation

Pulmonary disease is the most important cause of morbidity in preterm neonates, whose lungs are often physiologically and morphologically immature. Surfactant deficiency in immature lungs triggers a cascade of alveolar instability and collapse, capillary leak edema, and hyaline membrane formation. The term respiratory distress syndrome (RDS) has come to represent the clinical expression of surfactant deficiency and its nonspecific histologic counterpart, hyaline membrane disease. Historically, chest radiographs of infants with RDS predictably demonstrated decreased pulmonary expansion, symmetric generalized reticulogranular lung opacities, and air bronchograms. Refinements in perinatal medicine, including antenatal glucocorticoid administration, surfactant replacement therapy, and increasingly sophisticated ventilatory strategies have decreased the prevalence of RDS and air leak, altered familiar radiographic features, and lowered the threshold of potential viability to a gestational age of approximately 23 weeks. Alveolar paucity and pulmonary interstitial thickness in these profoundly premature neonates impair normal gas exchange and may necessitate prolonged mechanical ventilation, increasing the risk of lung injury. Bronchopulmonary dysplasia (BPD), alternatively termed chronic lung disease of infancy, is a disorder of lung injury and repair originally ascribed to positive-pressure mechanical ventilation and oxygen toxicity. Before the advent of surfactant replacement therapy, chest radiographs of infants with classic BPD demonstrated coarse reticular lung opacities, cystic lucencies, and markedly disordered lung aeration that reflected alternating regions of alveolar septal fibrosis and hyperinflated normal lung parenchyma. In the current era of surfactant replacement, BPD is increasingly a disorder of very low-birth-weight neonates with arrested alveolar and pulmonary vascular development, minimal alveolar septal fibrosis and inflammation, and more subtle radiographic abnormalities.

Overview of surfactant replacement trials

Clinical trials have evaluated the overall efficacy of surfactant therapy, as well as the relative efficacy of different surfactant preparations, the optimal timing of administration and the optimal dosage. Surfactant therapy leads to significant clinical improvement in infants at risk for, or having, respiratory distress syndrome (RDS). Clinical trials that compared the effects of synthetic or animal-derived surfactant preparations to placebo or no therapy demonstrate that surfactant therapy lead to rapid improvement in oxygenation, decreased ventilator support, decreased risk of pneumothorax, and mortality. Earlier treatment, prophylactic treatment of infants at high risk of developing RDS, and selective re-treatment leads to improved clinical outcome as well. Currently available animal-derived surfactants are superior to non-protein-containing synthetic surfactants. Ongoing evaluation will determine if important differences in animal-derived products are noted. Future trials will evaluate third-generation surfactant products and further refine what constitutes optimal use of surfactant.

Stable microbubble test and click test to predict respiratory distress syndrome in preterm infants not requiring ventilation at birth

AIMS

To determine the usefulness of the stable microbubble test (SMT) and of the click test (CT) on gastric aspirates obtained soon after birth to predict respiratory distress syndrome (RDS) in preterm babies not requiring ventilation at birth.

PATIENTS AND METHODS

The study was carried out with a cohort between 24 and 34 weeks of gestational age. Gastric secretions were collected before 1 hour of life and frozen for further analysis.

RESULTS

110 neonates were studied. For a cut-off value 10 microbubbles/mm2 (mb/mm2) the sensitivity and specificity to predict RDS were 73.9 % and 92%, respectively, in the SMT. The best SMT cut-off point to predict RDS was < or = 15 mb/mm2 (sensitivity = 82.6% specificity = 85.1%) if equal weight was given to false-positive and false-negative results. CT (104 samples) showed a sensitivity of 100% and a specificity of 45.1% to predict RDS. The overall accuracy of the SMT was better than the overall accuracy of the CT (87.5% vs. 64.4%; p < 0.001) to predict RDS.

CONCLUSIONS

The SMT is more accurate than the CT to predict RDS in infants below 35 weeks of gestational age and may be helpful to select patients to receive surfactant.

Surfactant therapy for respiratory distress syndrome in premature neonates: a comparative review

Exogenous surfactant therapy has been part of the routine care of preterm neonates with respiratory distress syndrome (RDS) since the beginning of the 1990s. Discoveries that led to its development as a therapeutic agent span the whole of the 20th century but it was not until 1980 that the first successful use of exogenous surfactant therapy in a human population was reported. Since then, randomized controlled studies demonstrated that surfactant therapy was not only well tolerated but that it significantly reduced both neonatal mortality and pulmonary air leaks; importantly, those surviving neonates were not at greater risk of subsequent neurological impairment. Surfactants may be of animal or synthetic origin. Both types of surfactants have been extensively studied in animal models and in clinical trials to determine the optimum timing, dose size and frequency, route and method of administration. The advantages of one type of surfactant over another are discussed in relation to biophysical properties, animal studies and results of randomized trials in neonatal populations. Animal-derived exogenous surfactants are the treatment of choice at the present time with relatively few adverse effects related largely to changes in oxygenation and heart rate during surfactant administration. The optimum dose of surfactant is usually 100 mg/kg. The use of surfactant with high frequency oscillation and continuous positive pressure modes of respiratory support presents different problems compared with its use with conventional ventilation. The different components of surfactant have important functions that influence its effectiveness both in the primary function of the reduction of surface tension and also in secondary, but nonetheless just as important, role of lung defense. With greater understanding of the individual surfactant components, particularly the surfactant-associated proteins, development of newer synthetic surfactants has been made possible. Despite being an effective therapy for RDS, surfactant has failed to have a significant impact on the incidence of chronic lung disease in survivors. Paradoxically the cost of care has increased as surviving neonates are more immature and consume a greater proportion of neonatal intensive care resources. Despite this, surfactant is considered a cost-effective therapy for RDS compared with other therapeutic interventions in premature infants.

Respiratory symptoms and lung function in relation to atopy in children born preterm

Respiratory morbidity is a major health problem among children. The aim of this study was to compare the background of respiratory problems of children born preterm with that of children born full-term, with special reference to atopy. The study comprised two cohorts of 10-year-old children: a group of 72 children born preterm with birth weights of less than 1,501 g, and a group of 65 children born full-term with birth weights of over 2,500 g. Histories of respiratory and atopic symptoms, and of risk factors for atopy, were collected with a questionnaire. Predisposition to atopy was verified by skin-prick testing and by measuring serum total and antigen-specific IgEs. Lung function was evaluated by spirometry testing. Children born preterm had significantly more wheezing. In them, the lifetime prevalence of wheezing was 43%, vs. 17% in children born full-term (P = 0.001; odds ratio, 3.71; 95% confidence interval, 1.67-8.25). In the full-term group, wheezing was associated with atopy: 64% of wheezers were atopic; in the preterm group, 23% of wheezers were atopic (difference between groups, P = 0.024). Children born preterm expired significantly lower spirometry values of forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1), FEV1/FVC ratio, forced expiratory flow after 50% of vital capacity has been exhaled (FEF50), and forced expiratory flow during middle half of FVC (FEF25-75). In the preterm group, wheezing, asthma, and low gestational age, but not atopy, were significantly associated with lower lung function values. Wheezers of the preterm group who still wheezed at age 10 were significantly more often atopic than those who no longer wheezed (62% vs. 9%, P = 0.006). In conclusion, we demonstrated a significant difference between groups in the association of atopy with respiratory problems. However, although atopy was not associated with a lifetime prevalence of respiratory symptoms in prematurely born children, an atopic predisposition in them was found to associate with persistence of wheezing.

Current surfactant use in premature infants

Exogenous surfactant therapy has been a significant advance in the management of preterm infants with RDS. It has become established as a standard part of the management of such infants. Both natural and synthetic surfactants lead to clinical improvement and decreased mortality, with natural surfactants having additional advantages over currently available synthetic surfactants. The use of prophylactic surfactant administered after initial stabilization at birth to infants at risk for RDS has benefits compared with rescue surfactant given to treat infants with established RDS. In infants who do not receive prophylaxis, earlier treatment (before 2 hours) has benefits over later treatment. The use of multiple doses of surfactant is a superior strategy to the use of a single dose, whereas the use of a higher threshold for retreatment seems to be as effective as a low threshold. Adverse effects of surfactant therapy are infrequent and usually not serious. Long-term follow-up of infants treated with surfactant in the neonatal period is reassuring. In the future we are likely to see the development of new types of surfactants. Further research is required to determine the optimal use of surfactant in conjunction with other respiratory interventions.

Expanded uses of surfactant therapy

There are few therapies for which the cumulative evidence of benefit is as much as that for surfactant therapy for RDS in premature infants. Exogenous surfactant therapy does seem to be beneficial for a number of non-RDS disorders. Although there are some trials supporting its use in MAS and ALI-ARDS, there are only a few small prospective, randomized, controlled trials supporting surfactant use in non-RDS disorders. Use of surfactant therapy for any disorder other than RDS must be considered "off the shelf" and experimental. Much work remains to be done to address the role of surfactant therapy in the myriad disorders discussed. Of import for each of the disorders is addressing the optimum type of surfactant to use, and the appropriate dose, method of delivery, and duration of treatment regimens.

Strategies for prevention of neonatal chronic lung disease

Chronic lung disease (CLD) of prematurity remains a substantial problem despite modern perinatal and neonatal care. CLD remains related to gestational age and lung immaturity, although it has become clear that severe initial lung disease is not a prerequisite for CLD to develop. Attempts to prevent CLD to date have not adequately addressed the multifactorial nature of the complex pathophysiology that leads to CLD. Thus, results have been modest at best. Prevention of CLD will require a multifaceted approach with specific interventions and care practices focused on different aspects of the pathway that leads to CLD. This review considers new information related to causation of CLD and the magnitude of the effect of prevention strategies tested to date. This article also advances the hypothesis that CLD is preventable with a global strategy of minimizing inciting events, optimizing management, and specific therapies aimed at intrinsic vulnerabilities.

Targeted early rescue surfactant in ventilated preterm infants using the click test

OBJECTIVE

To determine whether use of the click test, a rapid bedside test of surfactant function, results in earlier and more appropriate surfactant administration in ventilated preterm infants than does usual early rescue treatment.

STUDY DESIGN

Ventilated preterm infants (n = 126) with inspired oxygen >/=25% and mean airway pressure >/=7 cm H(2)O were randomized in gestational strata (<28 weeks and 28-36 weeks) to have surfactant therapy determined by the click test or by usual clinical and chest radiograph criteria. The treatment group had the click test performed on a tracheal aspirate as soon as possible after intubation and, if negative or equivocal (surfactant deficient), surfactant was given. The control group had surfactant given as soon as possible based on clinical and chest radiograph diagnoses of respiratory distress syndrome.

RESULTS

In infants of <28 weeks' gestation, use of the click test resulted in significantly earlier surfactant therapy (median time: 50 vs 159 minutes) and a reduction in the number of infants receiving surfactant (48% vs 79%). In infants of 28 to 36 weeks' gestation, there was no difference in time to surfactant (median time: 300 vs 268 minutes) or in the number of infants receiving surfactant. Neonatal morbidity and mortality were similar in click test and control groups.

CONCLUSIONS

Use of the click test in ventilated, extremely premature infants results in significantly earlier and more appropriately targeted administration of surfactant than does early rescue therapy based on clinical and radiograph criteria. A randomized trial of targeted early rescue surfactant therapy versus prophylactic surfactant therapy in infants of <28 weeks' gestation is warranted. The click test has the potential to improve clinical outcomes and reduce costs.

Prophylactic versus selective use of surfactant for preventing morbidity and mortality in preterm infants

BACKGROUND

This section is under preparation and will be included in the next issue.

OBJECTIVES

To compare the effect of prophylactic surfactant administration to surfactant treatment of established respiratory distress syndrome in premature infants.

SEARCH STRATEGY

Searches were made of the Oxford Database of Perinatal Trials, Medline (MeSH terms: pulmonary surfactant; limits: age groups, newborn infants), previous reviews including cross-references, abstracts, conference and symposia proceedings, expert informants, and journal handsearching in the English language.

SELECTION CRITERIA

Randomized controlled trials which compared the effects of prophylactic surfactant administration to surfactant treatment of established respiratory distress syndrome in premature infants were included in the analysis.

DATA COLLECTION AND ANALYSIS

Data regarding clinical outcomes including the incidence of pneumothorax, pulmonary interstitial emphysema, patent ductus arteriosus, necrotizing enterocolitis, intraventricular hemorrhage (any grade and severe intraventricular hemorrhage), bronchopulmonary dysplasia, mortality, bronchopulmonary dysplasia or death, and retinopathy of prematurity were excerpted from the reports of the clinical trials by the reviewers. Data analysis was done in accordance with the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

The majority of included studies noted an initial improvement in the respiratory status and a decrease in the incidence of respiratory distress syndrome in infants who received prophylactic surfactant. The meta-analysis supports a decrease in the incidence of pneumothorax, a decrease in the incidence of pulmonary interstitial emphysema, a decrease in the incidence of mortality and a decrease in the incidence of bronchopulmonary dysplasia or death associated with prophylactic administration of surfactant. No significant untoward effects of prophylactic surfactant administration are noted.

REVIEWER'S CONCLUSIONS

Prophylactic surfactant administration to infants judged to be at risk of developing respiratory distress syndrome (intubated infants less than 30-32 weeks gestation) has been demonstrated to improve clinical outcome. Infants who receive prophylactic surfactant have a decreased incidence of pneumothorax, a decreased incidence of pulmonary interstitial emphysema and a decreased incidence of mortality. However, it remains unclear exactly which criteria should be used to judge "at risk" infants who would require prophylactic surfactant administration.

Pulmonary function at school-age in surfactant-treated preterm infants

A follow-up study was conducted in 40 children who had been enrolled in a prospective randomized study of exogenous surfactant therapy for respiratory distress syndrome (RDS) (n = 22; S) or placebo (n = 18; P) to determine long-term pulmonary sequelae of surfactant treatment in premature infants with RDS. At follow-up, mean (SD) age was 6.63 (0.18) and 6.55 (0.23) years for S and P, respectively. Complete lung function tests (LFT) were attempted in all patients. Satisfactory data were obtained in 17/22 surfactant-treated and in 12/18 control children. There was no significant difference between groups for any of the parameters measured. Mean (SD) functional residual capacity (FRC) was 92% (16%) and 90% (21%) predicted, mean (SD) airway resistance (R(aw,exp)) was 122% (25%) and 127% (61%), and mean (SD) forced expiratory volume in 1 s (FEV1) was 104% (12%) and 99% (17%) predicted for S and P. Only maximal expiratory flow at 25% vital capacity (L/s) was significantly below the predicted range in S and P groups, with 74% (23%) and 77% (28%), respectively. To test bronchial hyperreactivity, a simple standardized running test was performed: 4 children in S and 5 in P showed a significant response as defined by clinical airway obstruction or changes in FEV1 and/or R(aw), with no significant difference between groups. Although we found no major abnormalities in lung function and no difference between S and P at early school-age, lack of cooperation during lung function tests makes further follow-up necessary.

Principles of surfactant replacement

Surfactant therapy is an established part of routine clinical management of babies with respiratory distress syndrome. An initial dose of about 100 mg/kg is usually needed to compensate for the well documented deficiency of alveolar surfactant in these babies, and repeated treatment is required in many cases. Recent experimental and clinical data indicate that large doses of exogenous surfactant may be beneficial also in conditions characterized by inactivation of surfactant, caused by, for example, aspiration of meconium, infection, or disturbed alveolar permeability with leakage of plasma proteins into the airspaces. The acute response to surfactant therapy depends on the quality of the exogenous material (modified natural surfactants are generally more effective than protein-free synthetic surfactants), timing of treatment in relation to the clinical course (treatment at an early stage of the disease is better than late treatment, and may reduce the subsequent need for mechanical ventilation), and mode of delivery (rapid instillation via a tracheal tube leads to more uniform distribution and is more effective than slow airway infusion). Treatment with aerosolized surfactant improves lung function in animal models of surfactant deficiency or depletion, but is usually associated with large losses of the nebulized material in the delivery system. Furthermore, data from experiments on immature newborn lambs indicate that treatment response may depend on the mode of resuscitation at birth, and that manual ventilation with just a few large breaths may compromise the effect of subsequent surfactant therapy. The widespread clinical use of surfactant has reduced neonatal mortality and lowered costs for intensive care in developed countries. The hydrophobic surfactant proteins SP-B and SP-C are probably essential for optimal biophysical and physiological activity of exogenous surfactants isolated from mammalian lungs, and the dose-effectiveness (in part reflecting resistance to inactivation) can be further improved by enrichment with SP-A. The development of new artificial surfactant substitutes, based on synthetic analogues of the native surfactant proteins, is an important challenge for future research.

Early versus late surfactant treatment in preterm infants of 27 to 32 weeks' gestational age: a multicenter controlled clinical trial

OBJECTIVE

To investigate whether early (<1 hour after birth) surfactant administration would be superior to late treatment (2-6 hours after birth) in preterm infants.

STUDY DESIGN

Randomized controlled multicenter clinical trial.

PATIENTS AND METHODS

Prenatal randomization of all infants of 27 to 32 weeks' gestational age stratified by center after parental informed consent. Early treatment: 100 mg/kg body weight bovine surfactant (SF-RI1, Alveofact; Dr K. Thomae, Biberach, Germany) to infants requiring intubation after birth. Late treatment: identical dosage to infants requiring intubation up to 6 hours of age with the fraction of inspired oxygen >0.4 at 2 to 6 hours after birth. Primary endpoint: the time on mechanical ventilation. Main secondary endpoints: mortality, bronchopulmonary dysplasia, intraventricular hemorrhage >/=grade III, and periventricular leukomalacia. Sample size calculation: at least 280 infants to prove superiority of either approach (alpha = 0.05; beta = 0.90).

RESULTS

Enrollment of 317 infants, 154 randomized to early surfactant treatment, 163 to late surfactant treatment. Study infants (all following data intent-to-treat groups: early versus late surfactant) were similar with respect to: gestational age, 29.5 +/- 1.6 weeks versus 29.7 +/- 1.6 weeks; birth weight, 1227 +/- 367 g versus 1269 +/- 334 g; and the rate of prenatal corticosteroids, 79.9% versus 72.8%. Duration of mechanical ventilation: 3 days (0-8) versus 2 days (0-6) (median, interquartile); further outcome variables: death or bronchopulmonary dysplasia (day 28) 25.9% versus 23.9%, mortality 3.2% versus 1.8%, intraventricular hemorrhage >/=grade III 6.5% versus 3.7%, and periventricular leukomalacia 5.2% versus 5.5% not differing statistically.

CONCLUSION

In preterm infants with a high rate of prenatal glucocorticoids, early surfactant administration was not found to be superior to late treatment in terms of relevant outcome variables.

Bronchopulmonary dysplasia. Impact of surfactant replacement therapy

Bronchopulmonary dysplasia is a major contributor to the morbidity and mortality of infants born prematurely. Surfactant replacement therapy has had a significant impact on the death rate from respiratory distress syndrome, yet the impact on bronchopulmonary dysplasia is minimal. Despite these findings, the overall incidence and severity of bronchopulmonary dysplasia are likely to decline over time as neonatal care continues to advance.

Comparison of two strategies for surfactant prophylaxis in very premature infants: a multicenter randomized trial

INTRODUCTION

Previous trials of surfactant therapy in premature infants have demonstrated a survival advantage associated with prophylactic therapy as an immediate bolus, compared with the rescue treatment of established respiratory distress syndrome. The optimal strategy for prophylactic therapy, however, remains controversial. When administered as an endotracheal bolus immediately after delivery, surfactant mixes with the absorbing fetal lung fluid and may reach the alveoli before the onset of lung injury. This approach, however, causes a brief delay in the initiation of standard neonatal resuscitation, including positive pressure ventilation, and is associated with a risk for surfactant delivery into the right main stem bronchus or esophagus. As an alternative approach, surfactant prophylaxis may be administered in small aliquots soon after resuscitation and confirmation of endotracheal tube position. Although this strategy has substantial logistical advantages in clinical practice, its efficacy has not been established.

OBJECTIVE

The purpose of this study was to determine whether the established benefits of the immediate bolus strategy for surfactant prophylaxis could still be achieved using a postventilatory aliquot strategy after initial standard resuscitation and stabilization.

DESIGN

Multicenter randomized clinical trial with patients randomized before delivery to immediate bolus or postventilatory aliquot therapy.

PARTICIPANTS

Inborn premature infants delivered to mothers at an estimated gestational age of 24[0/7] to 28[6/7] weeks.

INTERVENTIONS

Those infants who were randomized to the immediate bolus strategy were intubated as rapidly as possible after birth, and a 3-mL intratracheal bolus of calf lung surfactant extract (Infasurf) was administered before the initiation of positive pressure ventilation. Those infants who were randomized to the postventilatory aliquot strategy received standard resuscitation measures with intubation by 5 minutes of age, if not required earlier. At 10 minutes after birth, 3 mL of surfactant was administered in 4 divided aliquots of 0.75 mL each. Patients in both groups were eligible to receive up to three additional doses of surfactant as rescue therapy in the neonatal intensive care unit, if needed.

OUTCOME MEASURES

The primary outcome variable was survival to discharge to home. Secondary variables included neonatal complications and requirement for oxygen therapy at 36 weeks' postmenstrual age.

RESULTS

Among three centers, 651 infants were enrolled and randomized before delivery. Survival to discharge to home was similar for the two strategies for surfactant therapy as prophylaxis: 76% for the immediate bolus group and 80% for the postventilatory aliquot group. In a secondary analysis, the rate of supplemental oxygen administration at 36 weeks' postmenstrual age was 18% for the immediate bolus group and 13% for the postventilatory aliquot group.

CONCLUSIONS

Survival to discharge to home was similar with immediate bolus and postventilatory aliquot strategies for surfactant prophylaxis. Because of its logistical advantages in the delivery room and its beneficial effects on prolonged oxygen requirements, we recommend the postventilatory aliquot strategy for surfactant prophylaxis of premature infants delivered before 29 weeks' gestation.

School-age follow-up of prophylactic versus rescue surfactant trial: pulmonary, neurodevelopmental, and educational outcomes

BACKGROUND

Exogenous surfactant replacement has improved survival and reduced pulmonary complications of prematurity. Improved early outcomes for infants of <30 weeks' gestation treated with a strategy of prophylactic versus rescue surfactant, if needed, were demonstrated in a multicenter, randomized trial conducted between 1985 and 1988. We reevaluated a subset of survivors from this trial to determine the pulmonary and neurodevelopmental outcomes at school age.

METHODS

At 4.5 to 8 years of age, all survivors from one of the three centers were located, and 96% were evaluated. The original randomization included stratification by center and followed an intention-to-treat methodology in assessing the efficacy of prophylactic versus rescue treatment with surfactant. The follow-up test battery included a health-assessment questionnaire, spirometry, 88% saturation test, neurologic examination, and the McCarthy Scales of Children's Abilities (MSCA) and the Conners' Parent Rating Scale-48. Educational achievement was determined by school class placement and teachers' reports of achievement.

RESULTS

Of the 192 children originally enrolled, 154 survived. Evaluations were performed on 148 of these infants. An abnormal pulmonary history was found in 45 (30%) of the children: 16 (22%) in the prophylactic group and 29 (39%) in the rescue group. Formal pulmonary function was evaluated in 81 children; 29 (78%) in the prophylactic group and 33 (75%) in the rescue group were considered abnormal. No significant differences were found between the two groups on either cognitive or motor subscales of the MSCA, the Conners' Parent Rating Scale-48, the neurologic examination, the education services received in school, or the teacher ratings of below-average academic performance. Intelligence scores measured on the MSCA were low-normal for both groups. Some level of educational assistance was being provided to 72 (49%) of the cohort studied, and both groups had below average educational performance and increased needs for educational assistance.

CONCLUSIONS

Prophylactic surfactant administration to infants of <30 weeks' gestation was associated with fewer long-term clinical pulmonary complications than assignment to rescue administration. Formal pulmonary testing at school age did not reveal significant differences between treatment groups in those infants who could be tested. There also were no group differences found on neurologic, cognitive, behavioral, or educational assessments at school age.

A risk-benefit assessment of natural and synthetic exogenous surfactants in the management of neonatal respiratory distress syndrome

Alveolar surfactant is central to pulmonary physiology. Quantitative and qualitative surfactant abnormalities appear to be the primary aetiological factors in neonatal respiratory distress syndrome (RDS) and exogenous replacement of surfactant is a rational treatment. Available exogenous surfactants have a natural (mammal-derived lung surfactants) or synthetic origin. Pharmacodynamic and clinical studies have demonstrated that exogenous surfactants immediately improve pulmonary distensibility and gas exchange; however, this is achieved more slowly and with more failures with synthetic surfactants. The ensuing advantageous haemodynamic effects are not so striking and they include an inconvenient increased left to right ductal shunt. Two strategies of administration have been used: prophylactic or rescue therapy to treat declared RDS. All methods of instillation require intubation. In addition to the early benefits (improved gas exchange and reduced ventilatory support) the incidence of classical complications of RDS, especially air leak events, is decreased except for the uncommon problem of pulmonary haemorrhage. The incidence of bronchopulmonary dysplasia is neither uniformly nor significantly reduced although the severity appears to be lessened. The overall incidence of peri-intraventricular haemorrhages is not diminished although separate trials have shown a decreased rate. The most striking beneficial effect of exogenous surfactants is the increased survival (of about 40%) of treated very low birthweight neonates. A small number of adverse effects has been described. The long term outcome of survivor neonates with RDS treated with surfactants versus control neonates with RDS not treated with surfactants is similar in terms of physical growth, at least as good in terms of respiratory status, with a similar or slightly better neurodevelopmental outcome. There is not clear benefit of exogenous surfactant therapy in extremely premature infants (< 26 weeks gestational age, birthweight < 750 g). The potential risks of contamination, inflammatory and immunogenic reaction and the inhalation of platelet activating factor remain a theoretical concern of surfactant therapy which has not been confirmed in clinical practice. The optimal timing of treatment favours prophylaxis over rescue treatment and early rescue treatment rather than delayed therapy. Meta-analyses suggest the clinical superiority of natural surfactant extracts over a synthetic one (colfosceril palmitate). The economic impact of surfactant therapy is favourable and the costs per quality-adjusted life year (QALY) for surviving surfactant treated infants are low. In conclusion, the mid and long term benefit/risk ratio clearly favours the use of exogenous surfactants to prevent or to treat RDS in neonates who have a gestational age of > 26 weeks or a birthweight of > 750 g, especially with the prophylactic strategy using natural surfactant extracts.

Lung disease in premature neonates: impact of new treatments and technologies

Advances in perinatal medicine and neonatology have dramatically changed clinical outcomes for premature neonates and have ushered in a new era of radiological complexity. "Portable" chest radiographs continue to be the mainstay in diagnostic imaging of fragile newborns, but radiologists may be confronted with new and unexpected radiological expressions of once-familiar disease processes. Familiarity with the radiological impact of emerging treatments in premature neonates is essential for accurate film interpretation.

Effect of neonatal surfactant therapy on lung function at school age in children born very preterm

Our aim was to evaluate long-term effects of exogenous surfactant therapy on pulmonary functional outcome in children born very preterm. We examined 40 children aged 7-12 years who were born before 30 weeks of gestation with an immature surfactant system, and were randomized to one of three treatment groups: human surfactant given at birth (prophylactic), human surfactant given after development of neonatal respiratory distress syndrome (rescue), and placebo (air) treatment. Spirometric parameters of preterm born children were compared with those of 20 children born at term. In addition, spirometric parameters were monitored twice daily for 4 weeks using a home spirometer. All spirometric parameters were significantly lower in the preterm groups than in the controls, except for the forced vital capacity (FVC) in the prophylactically treated group. Bronchial obstruction was found in 53% of the prophylactically treated group, in 36% of the rescue group, in 67% of the placebo group, and in 0% of the control group. Peak expiratory flow (PEF) and FVC values were higher in those children who received surfactant compared with the placebo group (P < 0.05). In 16 children (40%) born preterm, a beta2-agonist induced an increase in PEF > or = 15% at least three times during 2 weeks of home monitoring; eight children (20%) had abnormal diurnal PEF variation. Multiple regression analysis indicated that the independent variables associated with favorable outcomes in spirometric parameters were surfactant therapy (P = 0.012-0.045) and short intubation time after birth (P = 0.0009-0.0044). Bronchial obstruction, responsiveness to a beta2-agonist, and high diurnal PEF variation are common in children born before 30 gestational weeks. Surfactant supplementation reducing the need for mechanical ventilation or supplementary oxygen after birth may decrease the severity of immaturity related bronchial obstruction in childhood.

Approaching the management of the neonatal intensive care unit graduate through history and physical assessment

NICU graduates, often ex-premature infants, offer unusual challenges to the primary care provider. History and physical assessment require an organized approach with meticulous attention to detail. These infants are at high risk for multiple problems including growth delays, nutrition and feeding problems, pulmonary sequelae, neurological sequelae and developmental delays, vision and hearing disturbances, as well as abnormalities in parent-infant bonding. This article emphasizes particular aspects of the history and physical examination that signify pathophysiology and sequelae common to the NICU graduate.

Manual ventilation with a few large breaths at birth compromises the therapeutic effect of subsequent surfactant replacement in immature lambs

The reason why some infants with respiratory distress syndrome fail to respond to surfactant, or respond only transiently, is incompletely understood. We hypothesized that resuscitation with large breaths at birth might damage the lungs and blunt the effect of surfactant. Five pairs of lamb siblings were delivered by cesarean section at 127-128 d of gestation. One lamb in each pair was randomly selected to receive six manual inflations of 35-40 mL/kg ("bagging") before the start of mechanical ventilation, a volume roughly corresponding to the inspiratory capacity of lamb lungs after prophylactic surfactant supplementation. Both siblings were given rescue porcine surfactant, 200 mg/kg, at 30 min of age. Blood gases and deflation pressure-volume (P-V) curves of the respiratory system were recorded until the lambs were killed at 4 h. The P-V curves became steeper after surfactant in the control group, but no such effect was seen in those subjected to bagging. At 4 h, inspiratory capacity and maximal deflation compliance were almost three times higher (p < 0.01) in the controls than in the bagged lambs. The latter were also more difficult to ventilate and tended to have less well expanded alveoli and more widespread lung injury in histologic sections. We conclude that a few inflations with volumes that are probably harmless in other circumstances might, when forced into the surfactant-deficient lung immediately at birth, compromise the effect of subsequent surfactant rescue treatment. Our findings challenge current neonatal resuscitation practice of rapidly establishing a normal lung volume by vigorous manual ventilation.

A multicenter randomized masked comparison trial of synthetic surfactant versus calf lung surfactant extract in the prevention of neonatal respiratory distress syndrome

OBJECTIVE

To compare the efficacy and safety of a synthetic surfactant (Exosurf Neonatal, Burroughs Wellcome Co) and a surfactant extract of calf lung lavage (Infasurf, IND #27,169, ONY, Inc) in the prevention of neonatal respiratory distress syndrome (RDS).

DESIGN AND SETTING

Ten-center randomized masked comparison trial.

PATIENTS

Premature infants (n = 871) <29 weeks gestational age by best obstetric estimate.

INTERVENTIONS

Infants were randomly assigned to a course of treatment with Exosurf Neonatal (n = 438) or Infasurf (n = 433) at birth, and if still intubated, at 12 and 24 hours of age. Crossover treatment was allowed within 72 hours of age if severe respiratory failure (defined as two consecutive a/A PO2 ratios </=.10) persisted after three doses of the randomized surfactant.

PRIMARY OUTCOME MEASURES

Three primary outcome measures of efficacy [the incidence of RDS; the incidence of RDS death; and the incidence of survival without bronchopulmonary dysplasia at 28 days after birth] were compared using linear regression techniques.

RESULTS

Of 871 randomized infants, 18 infants did not receive treatment with a study surfactant, and 25 infants did not meet all eligibility criteria. The primary analysis of efficacy was performed in the 846 eligible infants and analysis of safety outcomes in the 853 infants who received study surfactant. Demographic characteristics did not differ between the two treatment groups. Compared with Exosurf, Infasurf treatment resulted in a 62% decrease in the incidence of RDS (Infasurf, 16% vs Exosurf, 42%) and a 70% decrease in RDS death (Infasurf, 1.7% vs Exosurf, 5.4%) but did not increase the incidence of survival without bronchopulmonary dysplasia at 28 days. Treatment with Infasurf resulted in significant improvement in several secondary outcome measures. Infasurf-treated infants had lower average FIO2 (Infasurf, .33 [SEM] vs Exosurf, .42; difference .08; 95% confidence interval [CI], .06 to .11) and average mean airway pressure (Infasurf, 6.0 cm H2O vs Exosurf, 7.1 cm H2O; difference 1.1 cm H2O; 95% CI, .7 to 1.6 cm H2O) for the first 72 hours of life. Crossover surfactant treatment was significantly less frequent in the Infasurf compared with the Exosurf group (Infasurf, 1% vs Exosurf, 6%). Complications (bradycardia, clinical airway obstruction, and transcutaneous arterial desaturation) associated with second and third, but not initial, surfactant treatments were observed more frequently in the Infasurf treatment group. Infasurf-treated infants had significantly less air leak (</=7 days) (Infasurf, 8% vs Exosurf, 14%; adjusted relative risk [ARR] .55; 95% CI, .37 to .81). Severe intraventricular hemorrhage (IVH) (grade 3 and 4) did not differ between the two groups (Infasurf, 11.8% vs Exosurf, 8.3%; ARR 1.41; 95% CI, .94 to 2.09) but total IVH occurred more frequently in Infasurf-treated infants (Infasurf, 39.0% vs Exosurf, 29.9%; ARR, 1.30; 95% CI, 1.08 to 1.57).

CONCLUSION

Significant reductions in the incidence of RDS, the severity of early respiratory disease, the incidence of pulmonary air leaks associated with RDS, and the mortality attributable to RDS suggest that Infasurf is a more effective surfactant preparation than Exosurf Neonatal in the prophylaxis of RDS. However, Infasurf prophylaxis as used in this study was also associated with a greater risk of total but not severe IVH.

Mortality, severe respiratory distress syndrome, and chronic lung disease of the newborn are reduced more after prophylactic than after therapeutic administration of the surfactant Curosurf

OBJECTIVE

To test the hypothesis that prophylactic treatment with the surfactant Curosurf (Chiesi Farmaceutici SPA, Parma, Italy) improves survival and respiratory problems more than rescue treatment.

DESIGN

Meta-analysis of three prophylaxis versus rescue treatment trials, conducted in four countries.

METHODS

A meta-analysis was performed with the original, individual data of mortality, severe respiratory distress syndrome, and chronic lung disease of 671 newborns as outcomes. The random-effects logistic model (accounting for the trial-within-country structure) was applied and adjusted for imbalances in covariates.

RESULTS

The probability of each outcome differed between the countries, but the actual treatment effect itself did not. The adjusted odds ratios (ORs) and confidence intervals (CIs) for prophylaxis versus rescue were as follows: mortality: OR, .47; 95% CI, .30 to .73; severe RDS: OR, .50; 95% CI, .33 to .74; and chronic lung disease of the newborn in the survivors at day 28 after birth: OR, .54; 95% CI, .34 to .86. Gender, birth weight, gestational age, and prenatal administration of glucocorticosteroids were significant confounding covariates.

CONCLUSION

The analysis shows that for the porcine surfactant Curosurf, prophylactic administration of surfactant has significant advantages over rescue therapy.

Comparison of mortality risk: a score for very low birthweight infants

AIM

To develop and evaluate a score which quantifies mortality risk in very low birthweight (VLBW) infants (birthweight below 1500 g) at admission to the neonatal intensive care unit.

METHODS

Five hundred and seventy two VLBW infants admitted from 1978 to 1987 were randomly assigned to a cohort (n = 396) for score development and a cohort (n = 176) for score validation. Two hundred and ninety four VLBW infants admitted from 1988 to 1991 were used to compare risk adjusted mortality between the two eras.

RESULTS

Using multiple regression analysis, birthweight, Apgar score at 5 minutes, base excess at admission, severity of respiratory distress syndrome, and artificial ventilation were predictive of death in the development cohort. According to regression coefficients, a score ranging from 3 to 40 was developed. At a cutoff of 21, it predicted death in the validation cohort with a sensitivity of 0.85, a specificity of 0.73, and a correct classification rate of 0.76. The area under the receiver operating characteristic curve was 0.86. There was no significant difference in risk severity and in risk adjusted mortality between the eras 1978-87 and 1988-91.

CONCLUSION

The present score is robust, easily obtainable at admission, and permits early randomisation based on mortality risk.

Appropriate surfactant usage in 1996

Surfactant therapy has been proven effective in the prevention and treatment of respiratory distress syndrome. Over 6,000 infants have been studied in randomized controlled trials. These studies have demonstrated that both prophylactic administration of surfactant and administration of surfactant to premature infants with established respiratory distress syndrome will decrease the risk of pneumothorax and decrease the risk of mortality. Currently, over 50% of very low birth weight infants in North America receive some sort of surfactant preparation. However, many questions remain regarding optimal usage of surfactant preparations. Recent randomized controlled trials have evaluated issues regarding surfactant dosage, treatment strategy, method of administration, and surfactant preparation. Initial doses in the range of 100-200 mg/kg with repeat doses to selected infants who relapse appears to be the best approach to therapy. Prophylactic surfactant therapy leads to a small but statistically significant reduction in the risk of pneumothorax and mortality. The clinical relevance of these advantages and the cost effectiveness of this care remains under debate. A variety of methods of administration have been used in randomized controlled trials. Trials which compare these methods of administration demonstrate the adequacy of currently tested bolus administration. However, other methods of administration, such as slow infusion of surfactant leads to uneven distribution of surfactant and poor response. Both synthetic surfactants and natural surfactant extracts have been proven effective in the care of these infants. However, randomized controlled trials which directly compare these two preparations demonstrate a small advantage to the use of natural surfactant extracts. Natural surfactant extracts improve initial ventilatory status and decrease the risk of pneumothorax. Surfactant replacement therapy has proven to be effective in the treatment of very low birth weight premature infants. Current clinical trials support the early institution of treatment either prophylactically or as soon as possible in intubated babies with signs of respiratory distress syndrome. Repeat treatment may be important in optimizing outcome due to surfactant inactivation. Currently available natural surfactant extracts improve early clinical outcome and decrease pneumothorax compared to the available synthetic preparations.

The influence of the wider use of surfactant therapy on neonatal mortality among blacks and whites

BACKGROUND

Surfactant therapy reduces morbidity and mortality among premature infants with the respiratory distress syndrome (RDS). Fetal pulmonary surfactant matures more slowly in white than in black fetuses, and therefore RDS is more prevalent among whites than among blacks. We reasoned that the increased use of surfactant after its approval by the Food and Drug Administration (FDA) in 1990 might have reduced neonatal mortality more among whites than among blacks.

METHODS

We merged vital-statistics information for all 1563 infants with very low birth weights (500 to 1500 g) born from 1987 through 1989 or in 1991 and 1992 to residents of St. Louis with clinical data from the four neonatal intensive care units in the St. Louis area; we then compared neonatal mortality during two periods, one before and one after the FDA's approval of surfactant for clinical use (1987 through 1989 and 1991 through 1992).

RESULTS

The use of surfactant increased by a factor of 10 between 1987 through 1989 and 1991 through 1992. The neonatal mortality rate among all very-low-birth-weight infants decreased 17 percent, from 220.3 deaths per 1000 very-low-birth-weight babies born alive (in 1987 through 1989) to 183.9 per 1000 (in 1991 through 1992; P = 0.07). This decrease was due to a 41 percent reduction in the mortality rate among white newborns with very low birth weights (from 261.5 per 1000 to 155.5 per 1000; P = 0.003). In contrast, among black infants, the mortality rate for very-low-birth-weight infants did not change significantly (195.6 per 1000 and 196.8 per 1000). The relative risk of death among black newborns with very low birth weights as compared with white newborns with similar weights was 0.7 from 1987 through 1989 and 1.3 from 1991 through 1992 (P = 0.02). The differences in mortality were not explained by differences in access to surfactant therapy, by differences in mortality between black and white infants who received surfactant, or by differences in the use of antenatal corticosteroid therapy.

CONCLUSIONS

After surfactant therapy for RDS became generally available, neonatal mortality improved more for white than for black infants with very low birth weights.

Exogenous surfactant use in neonates

OBJECTIVE

To review exogenous surfactant use in the treatment of respiratory distress syndrome (RDS) in premature neonates.

DATA SOURCES

A MEDLINE search and extensive review of journals was conducted to identify the information for this review from 1983 to 1995 using the following key words: prematurity, surfactant, clinical trials, beractant, Survanta, colfosceril, Exosurf, and neonatal respiratory distress syndrome.

STUDY SELECTION AND DATA EXTRACTION

All articles were considered for possible inclusion in the review. Emphasis was placed on controlled studies involving beractant and colfosceril palmitate.

DATA SYNTHESIS

Results of published clinical trials using beractant or colfosceril palmitate in premature infants at risk for RDS have shown improvement in the need for supplemental oxygen and ventilatory support over the course of RDS and a reduction in pneumothorax. However, there was little impact on the incidence of intraventricular hemorrhage. Clinical trials studying the treatment of established RDS have also shown similar improvements. In a comparison of prophylactic versus late treatment, no distinct advantage of preventive treatment was found, except among infants less than 26-28 weeks gestation. Single versus multiple-dose studies have shown no specific advantage of more than two doses of colfosceril palmitate. A comparison trial of beractant and colfosceril palmitate has shown no difference in outcome. Long-term follow-up studies have been encouraging among infants being treated with exogenous surfactant.

CONCLUSIONS

The use of beractant and colfosceril palmitate in premature infants has clearly decreased morbidity and mortality associated with RDS. Only one trial has compared the efficacy of beractant with that of colfosceril in the treatment of RDS. There does not appear to be a distinct advantage of one product over another. Early treatment of infants at highest risk for RDS, those less than 26-28 weeks gestation, seems to be beneficial over waiting for RDS to progress in severity. Further research needs to be performed to determine the optimal dosing and timing of these agents, as well as comparative trials studying efficacy. Criteria for use of these products need to be further defined to decrease the incidence of unnecessary treatment.

Prophylaxis of respiratory distress syndrome by treatment with modified porcine surfactant at birth: a multicentre prospective randomized trial

The objective of this prospective, multicentre trial, carried out at 18 third level hospitals in Italy, was to evaluate efficacy of modified porcine surfactant (Curosurf), administered at birth to prevent the development of respiratory distress syndrome (RDS) in premature infants. 287 babies with a gestational age of 24-30 weeks were randomized to prophylactic treatment with Curosurf (80 mg/ml; dose 20 mg/kg) or to a control group receiving no surfactant treatment in the delivery-room. Babies in both groups were eligible for rescue treatment with surfactant (200 mg/kg) if they developed clinical symptoms of RDS and required mechanical ventilation. The main end-point was to obtain, in the prophylaxis group, a 30% reduction in the incidence of grade 3-4 RDS. Median gestational age was 28 weeks in both groups and mean birth weight 1010 and 1002 g, respectively for prophylaxis and control babies. There was a 32% reduction in the incidence of grade 3-4 RDS in the prophylaxis group (p < 0.05). This was associated with a significant reduction in mean maximum fraction of inspired oxygen (0.57 vs 0.66%; p < 0.01), a decreased incidence of pulmonary interstitial emphysema (7 vs 14%; p < 0.05) and a lowered mortality (21 vs 35%; p < 0.01). Combined unfavourable outcome (mortality + bronchopulmonary dysplasia and/or grade 3-4 intraventricular hemorrhage and/or grade 2-4 retinopathy of prematurity) was significantly lower in the prophylaxis than in the second group (41 vs 58%; p < 0.01). The favourable effects of prophylactic treatment were equally recorded in all the age groups, including the babies with the lowest gestational age (24-25 weeks). Multiple and logistic regression analysis confirmed that high gestational age and surfactant prophylaxis were, independently, associated with a lower degree of RDS (p = 0.0001 and p = 0.0008, respectively) and a lower mortality (p = 0.0001 and p = 0.0045, respectively). We conclude that prophylaxis with modified natural surfactant effectively prevents RDS in newborn babies between 24 and 30 weeks' gestation.

Respiratory mechanics before and after late artificial surfactant rescue

OBJECTIVE

To assess the effect of late administration of synthetic surfactant (Exosurf) on the ventilatory function of premature infants with hyaline membrane disease (HMD).

METHODOLOGY

Prospective non-randomized study in the Neonatal Intensive Care Unit (NICU) of a major referral hospital. The patients included two groups of premature infants with a birthweight between 750 and 2000 g who developed HMD. In group 1 with moderate to severe HMD, 2 x 5 mL/kg doses of Exosurf were given 12 h apart (first dose given at a mean age of 18.7 +/- 3.4 h [mean +/- s.e.m.]). In group 2 with milder HMD, no surfactant was given.

RESULTS

Significant reductions (P < 0.05) in the fraction of inspired oxygen (FIO2) occurred 6 h after surfactant administration (24 h of life) and by 48 h (64 h of life) in group 2. These improvements in gas exchange preceded improvements in passive respiratory compliance which occurred 24 h after surfactant (42 h of life) and by 72 h (88 h of life) in group 2 (P < 0.01). In both groups pulmonary resistance increased and was significant (P < 0.05) by 48 h (66 h of life) in group 1.

CONCLUSIONS

Synthetic surfactant given as late as a mean age 18.7 +/- 3.4 h still improves gas exchange but these early improvements cannot be completely explained by modifications of respiratory compliance.

Glutathione metabolism in newborns: evidence for glutathione deficiency in plasma, bronchoalveolar lavage fluid, and lymphocytes in prematures

Respiratory distress in premature newborns is associated with deficiency of surfactant in the bronchoalveolar lining fluid; this may be influenced by a local deficiency of antioxidants. Severe L-buthionine-S,R-sulfoximine-induced depletion of glutathione (GSH, a major antioxidant) in rodents is associated with lung type 2 cell lamellar body damage and decreased concentrations in lung and bronchoalveolar lavage fluid (BALF) of phosphatidyl choline (a major component of surfactant). At birth, prematurely born newborns (30-34 weeks) had lower peripheral venous plasma GSH concentrations than term (> 36 weeks) babies; these levels decreased further with increasing prematurity (< 27 weeks, with respiratory distress). On day 2, the peripheral venous plasma GSH concentrations reached a nadir, and the lowest levels were found in the most premature newborns. Lymphocyte GSH concentrations were lowest on day 2 and day 7, and in prematures (< 27 weeks, with respiratory distress) remained below adult lymphocyte GSH levels for at least 4 weeks. At birth, prematures (< 27 weeks, with respiratory distress) had a central plasma arterio-venous (A-V) GSH gradient across the lung (an estimate of lung uptake of GSH) of 0.72 +/- 0.15 (mean +/- SD) mumol/L; on day 2, the A-V gradient did not change significantly (0.49 +/- 0.09 mumol/L). At birth, these prematures had markedly decreased BALF GSH concentrations (compared with adult levels), and they were not significantly changed during the first 4 weeks of life. These results suggest that GSH deficiency is present in prematures and that it increases with the degree of prematurity. At birth, GSH deficiency will compromise the lungs' defense against oxidative stress injury. Oxidative stress is likely to increase if hyperoxic treatment is given for respiratory distress in these infants.

Porcine surfactant replacement therapy in newborns of 25-31 weeks' gestation: a randomized, multicentre trial of prophylaxis versus rescue with multiple low doses. The French Collaborative Multicentre Study Group

The aim of the study was to determine if prophylaxis with multiple low doses of porcine surfactant would increase survival, without bronchopulmonary dysplasia, compared with rescue therapy, for respiratory distress syndrome in newborns of 25-31 weeks' gestation. Compared with rescue therapy (n = 122), prophylaxis (n = 134) decreased the need for oxygenation and ventilatory support within 3-72 h. It did not, however, increase survival without bronchopulmonary dysplasia (60% versus 46%) (odds ratio (OR) = 1.53, 95% confidence interval (CI) = 0.90-2.61). Furthermore, prophylaxis decreased the incidence of severe peri-intraventricular haemorrhage (3% versus 16%) (OR = 0.28, 95% CI = 0.09-0.84) and retinopathy of prematurity (2% versus 11%) (OR = 0.18, CI = 0.04-0.78). We conclude that prophylaxis did not increase survival without bronchopulmonary dysplasia. The decreased incidence of severe peri-intraventricular haemorrhage and retinopathy of prematurity after prophylaxis requires further study.