Prophylactic treatment of very premature infants with human surfactant

Reflections on the introduction of surfactant therapy for neonates with respiratory distress

When pulmonary surfactant was first detected in the 1950s by Pattle and Clements, many thousands of infants perished each year due to a respiratory illness termed hyaline membrane disease. Hyaline membranes are formed by plasma leaking through damaged endothelial barriers into the terminal bronchiolar: alveolar spaces. Since the leaking plasma lacks erythrocytes, these clots are opaque. Insightful research by Avery and Mead soon led to the suggestion that the neonatal respiratory distress syndrome (RDS) did not arise because of the presence of hyaline membranes, but rather was related to the lack of sufficient pulmonary surfactant, mainly as a result of immaturity. Unfortunately, initial attempts at treating RDS with aerosolized dipalmitoyl-phosphatidylcholine, the major single molecular component, proved unsuccessful. Almost 20 years later, it was demonstrated by Enhorning and Robertson that treating prematurely delivered rabbit pups with natural surfactant prevents respiratory failure. Initially, it appeared unlikely that animal surfactants could be used for therapy with human infants. However, in 1980, Fujiwara demonstrated that a modified bovine surfactant extract promoted gaseous exchange with infants suffering from RDS. Soon a number of bovine and porcine-modified surfactants and two wholly synthetic formulations were shown to alleviate RDS. The present review relates some of the key scientific findings and significant clinical contributions responsible for reducing the neonatal morbidity and mortality associated with RDS. It further describes some of the more recent findings on the biological, biophysical, and physiological significance of pulmonary surfactant in health and disease.

Revisiting surfactant protein D: an immune surveillance molecule bridging innate and adaptive immunity

Surfactant protein D (SP-D) is a C-type lectin that was originally discovered as a lung surfactant associated phospholipid recognising protein. It was originally shown to be of great importance in surfactant turnover and homeostasis in conjunction with another hydrophilic surfactant protein i.e. SP-A. In addition, it was found to agglutinate bacteria in suspension and likely a key defence molecule in the lungs. Since its early days of characterization in 1990s, SP-D has turned out to be a central player in the mucosal immunity as pulmonary as well as extrapulmonary innate immune molecule. The most exciting development has been characterization of its C-type lectin or carbohydrate recognition domain (CRDs) that exists in a homotrimeric form in native as well as recombinant versions. SP-D has a range of strategies to recognise pathogen-associated molecular patterns (PAMPs) and thus act as a soluble PAMP-recognizing receptor (PRR), and subsequent destruction of the pathogens directly, or indirectly via phagocytic cells. SP-D also recognizes a range of allergens, competes out with specific IgE antibodies, and downregulates histamine release by basophils and mast cells. These anti-microbial and anti-allergic properties of SP-D have been validated by in vivo murine models of infection and allergy. The SP-D gene deficient mice exhibit remarkable phenotypes where lungs are leaky, showing features of fibrosis and emphysema. One of the seminal discoveries in the field has been the observation that activated eosinophils (and other immune cells) can be induced into apoptotic pathways by SP-D. This raised the possibility that SP-D can be an innate immune surveillance molecule. Studies have revealed the ability of a recombinant fragment of human SP-D containing homotrimeric neck and CRD region to induce apoptosis via intrinsic as well as extrinsic pathways; in addition, it also seems capable of interfering with epithelial-to-mesenchymal transition. These studies have opened up enormous possibilities for setting up pre-clinical and clinical trials.

Prophylactic Oropharyngeal Surfactant for Preterm Newborns at Birth: A Randomized Clinical Trial

Importance

Preterm newborns at risk of respiratory distress syndrome are supported with continuous positive airway pressure (CPAP). Many newborns worsen despite CPAP and are intubated for surfactant administration, an effective therapy for treatment of respiratory distress syndrome. Endotracheal intubation is associated with adverse effects. Pharyngeal administration of surfactant to preterm animals and humans has been reported as an alternative.

Objective

To assess whether giving prophylactic oropharyngeal surfactant to preterm newborns at birth would reduce the rate of intubation for respiratory failure.

Design, Setting, and Participants

This unblinded, parallel-group randomized clinical trial (Prophylactic Oropharyngeal Surfactant for Preterm Infants [POPART]) was conducted from December 17, 2017, to September 11, 2020, at 9 tertiary neonatal intensive care units in 6 European countries. Newborns born before 29 weeks of gestation without severe congenital anomalies, for whom intensive care was planned, were eligible for inclusion. The data were analyzed from July 27, 2022, to June 20, 2023.

Intervention

Newborns were randomly assigned to receive oropharyngeal surfactant at birth in addition to CPAP or CPAP alone. Randomization was stratified by center and gestational age (GA).

Main Outcomes and Measures

The primary outcome was intubation in the delivery room for bradycardia and/or apnea or in the neonatal intensive care unit for prespecified respiratory failure criteria within 120 hours of birth. Caregivers were not masked to group assignment.

Results

Among 251 participants (mean [SD] GA, 26 [1.5] weeks) who were well matched at study entry, 126 (69 [54.8%] male) with a mean (SD) birth weight of 858 (261) grams were assigned to the oropharyngeal surfactant group, and 125 (63 [50.4%] male) with a mean (SD) birth weight of 829 (253) grams were assigned to the control group. The proportion of newborns intubated within 120 hours was not different between the groups (80 [63.5%) in the oropharyngeal surfactant group and 81 [64.8%] in the control group; relative risk, 0.98 [95% CI, 0.81-1.18]). More newborns assigned to the oropharyngeal surfactant group were diagnosed with and treated for pneumothorax (21 [16.6%] vs 8 [6.4%]; P = .04).

Conclusions and Relevance

This randomized clinical trial found that administration of prophylactic oropharyngeal surfactant to newborns born before 29 weeks' GA did not reduce the rate of intubation in the first 120 hours of life. These findings suggest that administration of surfactant into the oropharynx immediately after birth in addition to CPAP should not be routinely used.

Trial Registration

EudraCT: 2016-004198-41.

Historical perspective on surfactant therapy: Transforming hyaline membrane disease to respiratory distress syndrome

Lung surfactant is the first drug so far designed for the special needs of the newborn. In 1929, Von Neergard described lung hysteresis and proposed the role of surface forces. In 1955-1956, Pattle and Clements found direct evidence of lung surfactant. In 1959, Avery discovered that the airway's lining material was not surface-active in hyaline membrane disease (HMD). Patrick Bouvier Kennedy's death, among half-million other HMD-victims in 1963, stimulated surfactant research. The first large surfactant treatment trial failed in 1967, but by 1973, prediction of respiratory distress syndrome using surfactant biomarkers and promising data on experimental surfactant treatment were reported. After experimental studies on surfactant treatment provided insight in lung surfactant biology and pharmacodynamics, the first trials of surfactant treatment conducted in the 1980s showed a striking amelioration of severe HMD and its related deaths. In the 1990s, the first synthetic and natural surfactants were accepted for treatment of infants. Meta-analyses and further discoveries confirmed and extended these results. Surfactant development continues as a success-story of neonatal research.

Management Practices During Perinatal Respiratory Transition of Very Premature Infants

The present review considers some controversial management practices during extremely premature perinatal transition. We focus on perinatal prevention and treatment of respiratory distress syndrome (RDS) in immature infants. New concerns regarding antenatal corticosteroid management have been raised. Many fetuses are only exposed to potential adverse effects of the drug. Hence, the formulation and the dosage may need to be modified. Another challenge is to increase the fraction of the high-risk fetuses that benefit from the drug and to minimize the harmful effects of the drug. On the other hand, boosting anti-inflammatory and anti-microbial properties of surfactant requires further attention. Techniques of prophylactic surfactant administration to extremely immature infants at birth may be further refined. Also, new findings suggest that prophylactic treatment of patent ductus arteriosus (PDA) of a high-risk population rather than later selective closure of PDA may be preferred. The TREOCAPA trial (Prophylactic treatment of the ductus arteriosus in preterm infants by acetaminophen) evaluates, whether early intravenous paracetamol decreases the serious cardiorespiratory consequences following extremely premature birth. Lastly, is inhaled nitric oxide (iNO) used in excess? According to current evidence, iNO treatment of uncomplicated RDS is not indicated. Considerably less than 10% of all very premature infants are affected by early persistence of pulmonary hypertension (PPHN). According to observational studies, effective ventilation combined with early iNO treatment are effective in management of this previously fatal disease. PPHN is associated with prolonged rupture of fetal membranes and birth asphyxia. The lipopolysaccharide (LPS)-induced immunotolerance and hypoxia-reperfusion-induced oxidant stress may inactivate NO-synthetases in pulmonary arterioles and terminal airways. Prospective trials on iNO in the management of PPHN are indicated. Other pulmonary vasodilators may be considered as comparison drugs or adjunctive drugs. The multidisciplinary challenge is to understand the regulation of pregnancy duration and the factors participating the onset of extremely premature preterm deliveries and respiratory adaptation. Basic research aims to identify deficiencies in maternal and fetal tissues that predispose to very preterm births and deteriorate the respiratory adaptation of immature infants. Better understanding on causes and prevention of extremely preterm births would eventually provide effective antenatal and neonatal management practices required for the intact survival.

The highly packed and dehydrated structure of pre-formed unexposed human pulmonary surfactant isolated from amniotic fluid

By coating the alveolar air-liquid interface, lung surfactant overwhelms surface tension forces that, otherwise, would hinder the lifetime effort of breathing. Years of research have provided a picture of how highly hydrophobic and specialized proteins in surfactant promote rapid and efficient formation of phospholipid-based complex three-dimensional films at the respiratory surface, highly stable under the demanding breathing mechanics. However, recent evidence suggest that the structure and performance of surfactant typically isolated from bronchoalveolar lung lavages may be far from that of nascent, still unused, surfactant as freshly secreted by type II pneumocytes into the alveolar airspaces. In the present work, we report the isolation of lung surfactant from human amniotic fluid (amniotic fluid surfactant, AFS) and a detailed description of its composition, structure and surface activity in comparison to a natural surfactant (NS) purified from porcine bronchoalveolar lavages. We observe that the lipid/protein complexes in AFS exhibit a substantially higher lipid packing and dehydration than in NS. AFS shows melting transitions at higher temperatures than NS and a conspicuous presence of non-lamellar phases. The surface activity of AFS is not only comparable to that of NS under physiologically-meaningful conditions, but displays significantly higher resistance to inhibition by serum or meconium, agents that inactivate surfactant in the context of severe respiratory pathologies. We propose that AFS may be the optimal model to study the molecular mechanisms sustaining pulmonary surfactant performance in health and disease, and the reference material to develop improved therapeutic surfactant preparations to treat yet unresolved respiratory pathologies.

Bronchopulmonary dysplasia as a determinant of respiratory outcomes in adult life

Respiratory disease is unfortunately common in preterm infants with the archetype being bronchopulmonary dysplasia (BPD). BPD affects approximately 50,000 preterm infants in the U.S. annually with substantial morbidity and mortality related to its pathology (alveolar, airway, and pulmonary vasculature maldevelopment). Predicting the likelihood and severity of chronic respiratory disease in these children as they age is difficult and compounded by the lack of consistent phenotyping. Barriers to understanding the actual scope of this problem include few longitudinal studies, information limited by small retrospective studies and the ever-changing landscape of therapies in the NICU that affect long-term respiratory outcomes. Thus, the true burden of adult respiratory disease caused by premature birth is currently unknown. Nevertheless, limited data suggest that a substantial percentage of children with a history of BPD have long-term respiratory symptoms and persistent airflow obstruction associated with altered lung function trajectories into adult life. Small airway disease with variable bronchodilator responsiveness, is the most common manifestation of lung dysfunction in adults with a history of BPD. The etiology of this is unclear however, developmental dysanapsis may underlie the airflow obstruction in some adults with a history of BPD. This type of flow limitation resembles that of aging adults with chronic obstructive lung disease with no history of smoking. It is also unclear whether lung function abnormalities in people with a history of BPD are static or if these individuals with BPD have a more accelerated decline in lung function as they age compared to controls. While some of the more significant mediators of lung function, such as tobacco smoke and respiratory infections have been identified, more work is necessary to identify the best means of preserving lung function for individuals born prematurely throughout their lifespan.

Study protocol for the POPART study-Prophylactic Oropharyngeal surfactant for Preterm infants: A Randomised Trial

INTRODUCTION

Many preterm infants develop respiratory distress syndrome (RDS), a condition characterised by a relative lack of surfactant. Endotracheal surfactant therapy revolutionised the care of preterm infants in the 1990s. However, supporting newborns with RDS with continuous positive airway pressure (CPAP) and reserving endotracheal surfactant for those who develop respiratory failure despite CPAP yield better results than intubating all infants for surfactant. Half of preterm infants born before 29 weeks gestation initially managed with CPAP are intubated for surfactant. Intubation is difficult to learn and associated with adverse effects. Surfactant administration into the oropharynx has been reported in preterm animals and humans and may be effective. We wished to determine whether giving oropharyngeal surfactant at birth reduces the rate of endotracheal intubation for respiratory failure in preterm infants within 120 hours of birth.

METHODS AND ANALYSIS

Prophylactic Oropharyngeal surfactant for Preterm infants: A Randomised Trial (POPART, Eudract No. 2016-004198-41) is an investigator-led, unblinded, multicentre, randomised, parallel group, controlled trial. Infants are eligible if born at a participating centre before 29 weeks gestational age (GA) and there is a plan to offer intensive care. Infants are excluded if they have major congenital anomalies. Infants are randomised at birth to treatment with oropharyngeal surfactant (120 mg vial <26 weeks GA stratum; 240 mg vial 26-28⁺⁶ weeks GA stratum) in addition to CPAP or CPAP alone. The primary outcome is intubation within 120 hours of birth, for bradycardia and/or apnoea despite respiratory support in the delivery room or respiratory failure in the intensive care unit. Secondary outcomes include incidence of mechanical ventilation, endotracheal surfactant use, chronic lung disease and death before hospital discharge.

ETHICS AND DISSEMINATION

Approval for the study has been granted by the Research Ethics Committees at the National Maternity Hospital, Dublin, Ireland (EC31.2016) and at each participating site. The trial is being conducted at nine centres in six European countries. The study results will be submitted for publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

2016-004198-41; Pre-results.

Nasal high flow therapy for neonates: Current evidence and future directions

Nasal high flow (nHF) therapy is a commonly used method of providing non-invasive respiratory support for neonates. It has several potential mechanisms of action: continuous distending pressure, nasopharyngeal dead space washout, provision of heated and humidified gases and reduction of work of breathing. nHF is used in a number of clinical scenarios for preterm and term infants, including primary respiratory and post-extubation support. In recent years, large trials have generated evidence pertinent to these indications. Novel applications for nHF in neonates warrant further research: during endotracheal intubation, for initial delivery room stabilisation of preterm infants and in conjunction with minimally invasive surfactant therapy.

Review demonstrates that less invasive surfactant administration in preterm neonates leads to fewer complications

Surfactant treatment of neonatal respiratory distress syndrome (RDS) was introduced in Europe during the 1990s. Meta-analyses have indicated that using less invasive surfactant administration techniques on preterm neonates receiving continuous positive airway pressure (CPAP) results in improved survival rates without bronchopulmonary dysplasia. Surfactant should be administered early and ventilator settings adapted to changing oxygen requirements and lung mechanics. Side effects including initial bradycardia, oxygen desaturation, tube obstruction and isolated cases of pulmonary haemorrhage have been reported.

CONCLUSION

Less invasive surfactant therapy improves pulmonary outcomes in preterm neonates with RDS and should ideally be administered in combination with CPAP.

Radiologic Observations in Severe Neonatal Respiratory Distress Syndrome Treated with the Isolated Phospholipid Fraction of Natural Surfactant

Ten newborn babies with severe respiratory distress syndrome, all dependent on artificial ventilation, were treated via the airways with the isolated phospholipid fraction of bovine or porcine surfactant. After treatment with surfactant at a median age of 10.5h, there was in all patients a striking improvement of lung aeration in chest films, with a decrease in parenchymal fluid retention and in distension of bronchioli. These radiologic findings were associated with a dramatic improvement of oxygenation and a significant reduction of the right-to-left shunt. In spite of the rapid therapeutic response, four patients died from cerebral hemorrhage. One of the surviving patients developed bronchopulmonary dysplasia. Our findings document efficacy of this new surfactant preparation in the neonatal respiratory distress syndrome, but the long-term effects need to be further tested in randomized clinical trials.

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.

Acute and sustained effects of aerosolized vs. bolus surfactant therapy in premature lambs with respiratory distress syndrome

BACKGROUND

Surfactant (SF) instillation may produce acute deleterious effects on gas exchange and both systemic and cerebral hemodynamics. Our aim was to compare the effects of aerosolized SF (SF-aero) with those of bolus SF (SF-bolus) administration on gas exchange, lung mechanics, and cardiovascular function in premature lambs with respiratory distress syndrome (RDS).

METHODS

Fourteen preterm lambs (85% gestation) were randomly assigned to receive SF-aero or SF-bolus. Oxygenation index (OI), PaCO2, cardiovascular parameters, carotid blood flow (CBF), lung compliance (mean dynamic compliance), and tidal volume (VT) were measured every 30 min for 6 h. Biochemical and histological analyses were performed.

RESULTS

After delivery, lambs developed severe RDS (inspiratory fraction of oxygen: 1; pH < 7.15; PaCO2 > 80 mm Hg; PaO2 < 30 mm Hg, mean dynamic compliance < 0.08 ml/cm H2O/kg). By 60 min after treatment, both groups showed an improvement in OI, PaCO2, mean dynamic compliance, and VT that was maintained until the end of the experiment. PaCO2 and CBF increased significantly in the SF-bolus group during the first 15-30 min, without concomitant changes in cardiovascular parameters, whereas in the SF-aero group, PaCO2 and CBF decreased gradually. SF-aero induced less alveolar hemorrhage and inflammation.

CONCLUSION

SF-aero produced improvements in gas exchange and lung mechanics similar to those produced by bolus administration but with less lung injury and fewer cerebral hemodynamic changes.

Brain injury in chronically ventilated preterm neonates: collateral damage related to ventilation strategy

Brain injury is a frequent comorbidity in chronically ventilated preterm infants. However, the molecular basis of the brain injury remains incompletely understood. This article discusses the subtle (diffuse) form of brain injury that has white matter and gray matter lesions without germinal matrix hemorrhage-intraventricular hemorrhage, posthemorrhagic hydrocephalus, or cystic periventricular leukomalacia. This article synthesizes data that suggest that diffuse lesions to white matter and gray matter are collateral damage related to ventilator strategy. Evidence is introduced from the 2 large-animal, physiologic models of evolving neonatal chronic lung disease that suggest that an epigenetic mechanism may underlie the collateral damage.

Role of prophylactic surfactant in preterm infants

BACKGROUND

Respiratory distress syndrome (RDS) in preterm neonates is caused by a deficiency or dysfunction of pulmonary surfactant. The physiological function of surfactant includes the ability to lower surface tension, as well as the ability to rapidly adsorb and spread. A wide variety of surfactant products have been formulated and studied in clinical trials. The present study was designed to find out whether prophylactic administration of surfactant leads to a significant decrease in the risk of neonatal mortality and neonatal morbidity.

METHODS

This was an experimental study in which a total of 125 preterm newborns less than 34 weeks gestation were studied. One hundred preterm newborns (controls) less than 34 weeks gestation were managed in the conventional manner as per the existing protocols in the neonatal intensive care unit. Twenty-five consecutively delivered preterm newborns less than 34 weeks gestation were administered surfactant. Data regarding clinical outcomes including mortality and morbidity profile was collected and analysed.

RESULTS

The mean duration of ventilation in the ventilated babies in the control group and the surfactant group was 129.8 ± 43 hours and 85.7 ± 46 hours, respectively; the difference being statistically significant. In the surfactant group, four babies (16%) died and in the control group, 27 babies (27%) died. The difference was not statistically significant. The number of babies developing retinopathy of prematurity and needing laser treatment for retinopathy of prematurity was greater in the surfactant group.

CONCLUSION

Prophylactic administration of surfactant in preterm newborns of gestational age < 34 weeks is associated with a significant decrease in mean duration of ventilation and an increase in the incidence of retinopathy of prematurity.

Safety of surfactant administration before transport of premature infants

OBJECTIVE

To assess the safety of surfactant administration prior to transport of premature infants.

DESIGN/METHODS

We performed a retrospective review of 24- to 34-weeks premature infants admitted to the Newborn Intensive Care Unit (NICU) between July 1, 1999 and September 30, 2004. Outcome measures were the presence of hyperventilation (PCO2 <40 mm Hg) and/or pneumothorax on admission to the NICU. Factors associated with the presence of hyperventilation and pneumothorax were identified.

RESULTS

955 infants born at 24 to 34 weeks' gestation were admitted to the NICU during the study period. 217 (22.7%) received surfactant prior to transport within 48 hours of birth. The incidence of hyperventilation was 18.9%. Hyperventilated infants had longer transport times, lower birth weights, and lower PCO2 on blood gases obtained prior to transport. Pneumothorax occurred in six subjects (2.9%). Neonates with pneumothorax had lower APGAR scores.

CONCLUSIONS

We found the administration of surfactant prior to transport to be safe as evidenced by a low incidence of pneumothorax. Pneumothorax was more likely to occur in infants who needed significant resuscitation at birth. The incidence of hyperventilation appeared to be high and was inversely associated with birth weight.

Surfactants: past, present and future

In 1929 Kurt von Neergaard performed experiments suggesting the presence of pulmonary surfactant and its relevance to the newborn's first breath. Almost 25 years later, Richard Pattle, John Clements and Chris Macklin, each working on the effects of nerve gases on the lungs, contributed to the understanding of the physiology of pulmonary surfactant. About 5 years later Mary Ellen Avery and Jere Mead published convincing evidence that preterm neonates dying of hyaline membrane disease (respiratory distress syndrome, RDS) had a deficiency of pulmonary surfactant. The first trials of nebulized synthetic (protein-free) surfactant to prevent RDS were published soon after Patrick Bouvier Kennedy (son of President John F Kennedy) died of this disorder after treatment in Boston. These trials were unsuccessful; however, Goran Enhorning and Bengt Robertson in the early 1970s demonstrated that natural surfactants (containing proteins) were effective in an immature rabbit model of RDS. Soon after this Forrest Adams showed that a natural surfactant was also effective in an immature lamb model. Working with him was Tetsuro Fujiwara who 2 years later, after returning to Japan, published the seminal article reporting the responses of 10 preterm infants with RDS to a bolus of modified bovine surfactant. During the 1980s there were numerous randomized controlled trials of many different natural and synthetic surfactants, demonstrating reductions in pulmonary air leaks and neonatal mortality. Subsequently natural surfactants were shown to be superior to the protein-free synthetic products. Recently there have been a number of randomized trials comparing different natural surfactant preparations. Commercially available bovine surfactants may have similar efficacy but there is some evidence that a porcine surfactant used to treat RDS with an initial dose of 200 mg per kg is more effective than a bovine surfactant used in an initial dose of 100 mg per kg. Bovine and porcine surfactants have not been compared in trials of prophylaxis. Very recently a new synthetic surfactant with a surfactant protein mimic has been compared with other commercially available natural and synthetic surfactants in two trials. The new surfactant may be superior to one of the older protein-free synthetic surfactants but there is no evidence of its superiority over established natural products and it is currently not approved for clinical use. A number of other new synthetic surfactants have been tested in animal models or in treatment of adults with ARDS, but so far there have been no reports of treatment of neonatal RDS. Natural surfactants work best if given by a rapid bolus into the lungs but less invasive methods such as a laryngeal mask, pharyngeal deposition or rapid extubation to CPAP have showed promise. Unfortunately, delivery of surfactant by nebulization has so far been ineffective. Surfactant treatment has been tried in a number of other neonatal respiratory disorders but only infants with meconium aspiration seem to benefit although larger and more frequent doses are probably needed to demonstrate improved lung function. A surfactant protocol based upon early treatment and CPAP is suggested for very preterm infants. Earlier treatment may improve survival rates for these infants; however, there is a risk of increasing the prevalence of milder forms of chronic lung disease. Nevertheless, surfactant therapy has been a major contribution to care of the preterm newborn during the past 25 years.

Evolution of pulmonary surfactants for the treatment of neonatal respiratory distress syndrome and paediatric lung diseases

This review documents the evolution of surfactant therapy, beginning with observations of surfactant deficiency in respiratory distress syndrome, the basis of exogenous surfactant treatment and the development of surfactant-containing novel peptides patterned after SP-B. We critically analyse the molecular interactions of surfactant proteins and phospholipids contributing to surfactant function.

CONCLUSION

Peptide-containing surfactant provides clinical efficacy in the treatment of respiratory distress syndrome and offers promise for treating other lung diseases in infancy.

The evolution of neonatology

In 1960, the terms "neonatology" and "neonatologist" were introduced. Thereafter, an increasing number of pediatricians devoted themselves to full-time neonatology. In 1975, the first examination of the Sub-Board of Neonatal-Perinatal Medicine of the American Board of Pediatrics and the first meeting of the Perinatal Section of the American Academy of Pediatrics were held. One of the most important factors that improved the care of the neonate was the miniaturization of blood samples needed to determine blood gases, serum electrolytes, glucose, calcium, bilirubin, and other biochemical measurements. Another factor was the ability to provide nutrition intravenously, and the third was the maintenance of normal body temperature. The management of respiratory distress syndrome improved with i.v. glucose and correction of metabolic acidosis, followed by assisted ventilation, continuous positive airway pressure, antenatal corticosteroid administration, and the introduction of exogenous surfactant. Pharmacologic manipulation of the ductus arteriosus, support of blood pressure, echocardiography, and changes in the management of persistent pulmonary hypertension, including the use of nitric oxide and extracorporeal membrane oxygenation, all have influenced the cardiopulmonary management of the neonate. Regionalization of neonatal care; changes in parent-infant interaction; and technological changes such as phototherapy, oxygen saturation monitors, and brain imaging techniques are among the important advances reviewed in this report. Most remarkable, a 1-kg infant who was born in 1960 had a mortality risk of 95% but had a 95% probability of survival by 2000. However, errors in neonatology are acknowledged, and potential directions for the future are explored.

History of surfactant from 1980

The first successful trial of surfactant treatment for respiratory distress syndrome (RDS) was reported in 1980. Since then there have been numerous randomised trials demonstrating first, the efficacy of surfactant treatment in reducing pulmonary air leaks and increasing survival and second, assessing various other aspects of therapy. These studies show that multiple doses may be needed if surfactant is used to treat established RDS but early or prophylactic treatment is superior for infants with gestational ages less than 30 weeks. Natural surfactants (containing proteins) are more effective than synthetic products (protein free), the latter now being infrequently used. Natural surfactants vary and should not be considered to be equivalent in their effects. A porcine surfactant (poractant alfa) acts more rapidly than a bovine preparation (beractant) in infants with moderate to severe RDS. A meta-analysis of 5 comparative studies suggests that a dose of 200 mg/kg of poractant alfa is associated with lower mortality compared with 100 mg/kg of beractant. Chronic lung disease remains a problem but it is hoped that early treatment with surfactant combined with extubation to continuous positive airway pressure will reduce this complication of prematurity. The newer synthetic surfactants, containing analogues of surfactant protein B or C, have undergone some trials for treatment of RDS but comparative studies which have just been published do not show that they are superior to existing natural surfactants. However, as they are more resistant to inactivation they may have a role in treatment of adult or acute RDS. The last 25 years have seen a large increase in basic science research on surfactants with determination of the structure and function of the four surfactant proteins probably being the most important advances. Future studies will focus on widening the indications for surfactant treatment, developing non-invasive means of administration and assessing the role of the newer synthetic surfactants.

A randomized trial comparing beractant and poractant treatment in neonatal respiratory distress syndrome

AIM

To compare the effects of beractant and poractant in neonatal respiratory distress syndrome (RDS).

METHODS

Infants with RDS were randomized to receive beractant or poractant. The primary outcome measure was fraction of inspired oxygen (FiO2) requirement in the first 48 h after surfactant therapy.

RESULTS

58 infants completed the study. The mean gestational ages for the poractant and beractant groups were 29.6+/-3.6 and 29.3+/-2.9 wk, with average birthweights of 1394+/-699 and 1408+/-534 g, respectively. In the first 48 h, infants who received poractant had a lower FiO2 requirement compared to those who received beractant (p=0.018). The prevalence of patent ductus arteriosus (PDA) was lower in the group of infants that received poractant (17%) compared to the group that received beractant (45%) (p=0.02).

CONCLUSIONS

Infants with RDS treated with poractant had a lower FiO2 requirement during the first 48 h compared to infants who received beractant. Infants who received poractant also had fewer PDAs than infants who received beractant. The difference in FiO2 was not associated with a difference in age of first extubation, total intubation time, or incidence of bronchopulmonary dysplasia between groups.

Surfactant and Physiologic Responses of Preterm Lambs to Continuous Positive Airway Pressure

Although continuous positive airway pressure (CPAP) is used frequently for preterm infants, the relationships between the amount of surfactant and lung physiologic and injury responses to CPAP are unknown. Therefore, saturated phosphatidylcholine (Sat PC) was measured to quantify the surfactant necessary for preterm lambs to breathe successfully on a CPAP of 5 cm H(2)O (CPAP 5). Five of 21 lambs delivered at 130-136 days gestation failed to keep PCO(2) below 100 mm Hg by 2 hours. The lambs that failed had less than 1.9 micromol/kg Sat PC in bronchoalveolar fluid (approximately 3% the pool size at term), less surfactant secretion, and less large aggregate surfactant. Physiologic responses of other 132-day preterm lambs after 2 or 6 hours of CPAP 5, 8 cm H(2)O CPAP (CPAP 8), or mechanical ventilation were then characterized. At 6 hours, oxygenation and lung gas volumes were higher with CPAP 8 relative to the other groups and VE was decreased with CPAP 8 relative to CPAP 5. Lung dry/wet ratios were greater for the CPAP groups than for the mechanical ventilation group. A small amount of endogenous Sat PC is required for preterm lambs to breathe successfully with CPAP. CPAP 8 improves early newborn respiratory transition relative to CPAP 5.

Cost-effectiveness of exogenous surfactant therapy in pediatric patients with acute hypoxemic respiratory failure

OBJECTIVE

To determine whether the use of exogenous surfactant (Infasurf) in pediatric acute hypoxemic respiratory failure is cost-effective.

DESIGN

Deterministic cost-effectiveness analysis based on a Markov model. The model was calibrated using outcomes and resource utilization observed in a multiple-centered, prospective, randomized, controlled unblinded trial of Infasurf in pediatric acute hypoxemic respiratory failure. Costs were short-run direct costs estimated from the perspective of the hospital as provider. Primary outcomes were expected costs, expected survival rates, and incremental cost per life saved.

SETTING

Patients in the trial were treated in one of eight pediatric intensive care units of tertiary medical centers.

PATIENTS

Forty-two children with acute hypoxemic respiratory failure who were randomized to receive either standard therapy or exogenous surfactant in addition to standard therapy.

MEASUREMENTS AND MAIN RESULTS

Our baseline analysis suggests that for a 10-kg child, the Infasurf strategy is both less costly (62,922 US dollars vs. 74,006 US dollars) and more effective (survival: 90.3% vs. 85.1%) and therefore dominates standard treatment. Cost savings were realized in the model because patients in the surfactant group were more likely to leave the pediatric intensive care unit sooner. The Infasurf strategy continues to dominate for children up to 60 kg. At 70 kg, the cost to save an additional life using the Infasurf strategy is 79,805 US dollars, which is still cost-effective if the provider is willing to make this tradeoff.

CONCLUSIONS

For the majority of pediatric patients with acute hypoxemic respiratory failure, exogenous surfactant is cost-effective. If the use of this medication becomes standard care, a greater variety of packaging sizes could lead to decreased acquisition costs and increase the number of patients for whom this treatment is cost-effective.

Evidence of fetal pulmonary aspiration of intra-amniotic administered surfactant in animal experiment

INTRODUCTION

The instillation of surfactant into the airways of patients with respiratory distress syndrome (RDS), especially in the neonatal period, is a proven therapy. The preventive therapy of RDS through intra-amniotic injection of surfactant has been reported recently. It has not been conclusively shown, however, that the surfactant administered in this way actually reaches the fetal pulmonary airways.

OBJECTIVE

To study the distribution in fetal organs of a natural surfactant labeled with technetium-99m and injected through amniocentesis into the amniotic sac of guinea pigs in the last third of pregnancy.

METHODS

After stimulating fetal respiratory movements with aminophylline 0.3 ml of an aqueous suspension containing 0.75 mg of phospholipids of a natural bovine surfactant labeled with technetium-99m, together with 0.1 ml of the biological dye carmine indigo, were injected into the amniotic sac. One hour later fetuses were delivered by cesarean section. In those that were dye-stained, dosimetric and gammagraphic tests were applied to trachea, lungs, esophagus, stomach, heart, liver, kidneys and placenta.

RESULTS

Significant radio isotopic activity was found in both lungs of six treated fetuses, with a dose capture of between 1.0% and 5.3% of total dose. The level of activity in the stomachs was similar to that in the lungs (0.9% to 3.0% dose capture), whereas activity in other organs was negligible except in two placentae. No radio isotopic activity was found in non-injected control fetuses.

CONCLUSIONS

In the present animal model natural surfactant injected intra-amniotically is aspirated into the lungs within one hour.

Surfactant therapy in infants and children: three years experience in a pediatric intensive care unit

Despite the established success of surfactant application in neonates, the use of surfactant in older children is still a matter of discussion. We hypothesized that surfactant application in children with acute respiratory distress syndrome (ARDS) secondary to a pulmonary or systemic disease or after cardiac surgery improves pulmonary function. We also asked whether repeated treatment could further improve pulmonary function. To answer these questions, we measured oxygenation index (OI) and hypoxemia score after the first and after a second application of surfactant (50-100 mg/kg body wt) at least 24 h later. We enrolled 19 children (older than 4 weeks) for a retrospective chart review study, and six of them underwent cardiac surgery. Demographic data were extracted. OI and hypoxemia score were estimated before and 2 and 24 h after surfactant application. Lung injury score was calculated before and 24 h after surfactant application. Outcome measures included survival, duration of mechanical ventilation, and pediatric ICU and hospital stay. The median patient age was 9.0 (quarter percentile 3.7/25) months. The median weight was 8.4 (4.1/11.5) kg. The median lung injury score before the first surfactant application was 2.3 (2.3/2.6). Hospital duration and pediatric ICU stay for all patients was 31.0 (20.0/49.5) days and 27.0 (15.5/32.5) days, respectively. The duration of mechanical ventilation was 24.0 (18.5/31.0) days. The overall mortality was 53%. Twenty-four hours after the first surfactant application, pulmonary function significantly improved. The median OI was 14 (5.5/26) before and 7 (4.5/14.5) 24 h after surfactant application (P= 0.027). The hypoxemia score was 91.7 (69.9/154.2) before and 148.4 (99.2/167.6) 24 h after surfactant application (P = 0.0026). Seven children received a second application, which did not further improve pulmonary function. The lung injury score was not influenced by either surfactant application. We conclude that a single surfactant application improves pulmonary function in children with ARDS. A second application of surfactant showed no further benefit. Outcome was not affected in our study population.

Treatment with exogenous surfactant stimulates endogenous surfactant synthesis in premature infants with respiratory distress syndrome

OBJECTIVE

Treatment of preterm infants with respiratory distress syndrome (RDS) with exogenous surfactant has greatly improved clinical outcome. Some infants require multiple doses, and it has not been studied whether these large amounts of exogenous surfactant disturb endogenous surfactant metabolism in humans. We studied endogenous surfactant metabolism in relation to different amounts of exogenous surfactant, administered as rescue therapy for RDS.

DESIGN

Prospective clinical study.

SETTING

Neonatal intensive care unit in a university hospital.

PATIENTS

A total of 27 preterm infants intubated and mechanically ventilated for respiratory insufficiency.

INTERVENTIONS

Infants received a 24-hr infusion with the stable isotope [U-13C]glucose starting 5.3 +/- 0.5 hrs after birth. The 13C-incorporation into palmitic acid in surfactant phosphatidylcholine (PC) isolated from serial tracheal aspirates was measured. Infants received either zero (n = 5), one (n = 4), two (n = 15), or three (n = 3) doses of Survanta (100 mg/kg) when clinically indicated.

MEASUREMENTS AND MAIN RESULTS

Using multiple regression analysis, the absolute synthesis rate (ASR) of surfactant PC from plasma glucose increased with 1.3 +/- 0.4 mg/kg/day per dose of Survanta (p = .007) (mean +/- SEM). The ASR of surfactant PC from glucose was increased by prenatal corticosteroid treatment with 1.3 +/- 0.4 mg/kg/day per dose corticosteroid (p = .004), and by the presence of a patent ductus arteriosus with 2.1 +/- 0.7 mg/ kg/day (p = .01).

CONCLUSION

These data are reassuring and show for the first time in preterm infants that multiple doses of exogenous surfactant for RDS are tolerated well by the developing lung and stimulate endogenous surfactant synthesis.

Relationship between duration of preterm premature rupture of membranes and pulmonary maturation

OBJECTIVE

The purpose of this study was to evaluate the relationship between duration of preterm premature rupture of membranes (PPROM) before delivery and development of respiratory distress syndrome (RDS).

METHOD

One hundred and fifty-nine cases of PPROM with gestational ages between 24 and 37 weeks and birth weights between 1300 and 2100 g were studied retrospectively, out of which, 61 infants developed RDS. Subjects with factors known to affect RDS such as: maternal diabetes; hemorrhage; hypertension; fetal asphyxia; multifetal pregnancies; abnormal presentations; or cesarean deliveries were excluded from this study.

RESULTS

Out of 94 neonates, who had rupture of membranes (ROM) in less than 12 h, 41 cases (43.6%) developed RDS. Durations of ROM in 19 neonates were between 12 and 24 h and 6 of them (31.6%) developed RDS. In 21 cases whose ROM were between 24 and 48 h, RDS was seen in 4 (19%). However, in 25 subjects whose ROM was greater than 48 h, RDS presented in 10 cases. Statistical analysis, using Bartholomew's test, showed that there exists a reverse linear relationship between duration of ROM and RDS in the first 48 h. However, after 48 h, the risk of RDS increases, which may represent the effect of complications such as: chorioamnionitis; sepsis; and pulmonary hypoplasia on RDS.

CONCLUSION

Increasing the duration of PPROM, in the first 48 h, decreases the risk of RDS with a linear pattern.

Prophylactic natural surfactant extract for preventing morbidity and mortality in preterm infants

BACKGROUND

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

OBJECTIVES

To assess the effect of prophylactic intratracheal administration of natural surfactant extract in preterm newborns at risk for developing respiratory distress syndrome (RDS).

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 hand searching in the English language.

SELECTION CRITERIA

Randomized controlled trials which compared the effect of prophylactic natural surfactant administration (surfactant obtained from human or bovine sources, either modified with additional phospholipids or not) administered to high risk preterm newborns at or shortly after birth in order to prevent respiratory distress syndrome, other complications of prematurity, and mortality.

DATA COLLECTION AND ANALYSIS

Data regarding clinical outcomes including 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 reviewer. Data analysis was done in accordance with the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

All of the included studies note an initial improvement in respiratory status and a decrease in the risk of respiratory distress syndrome in infants who receive prophylactic natural surfactant extract. The meta-analysis supports a decrease in the risk of pneumothorax (typical relative risk 0.35, 95% CI 0.26, 0.49; typical risk difference -0.15, 95% CI -0.20, -0.11), a decrease in the risk pulmonary interstitial emphysema (typical relative risk 0.46, 95% CI 0.35, 0.60; typical risk difference -0.19, 95% CI -0.25, -0.13), a decrease in the risk of neonatal mortality (typical relative risk 0. 60, 95% CI 0.44, 0.83; typical risk difference -0.07, 95% CI -0.12, -0.03), and a decrease in the risk of bronchopulmonary dysplasia or death (typical relative risk 0.84, 95% CI 0.75, 0.93; typical risk difference -0.10, 95% CI -0.16, -0.04. No differences are reported in the risk of intraventricular hemorrhage, patent ductus arteriosus, necrotizing enterocolitis or retinopathy of prematurity. Few data are available on long-term followup of treated infants.

REVIEWER'S CONCLUSIONS

Prophylactic intratracheal administration of natural surfactant extract to infants judged to be at risk of developing respiratory distress syndrome (intubated infants <30 weeks gestation) has been demonstrated to improve clinical outcome. Infants who receive prophylactic natural surfactant extract have a decreased risk of pneumothorax, a decreased risk of pulmonary interstitial emphysema, a decreased risk of mortality, and a decreased risk of bronchopulmonary dysplasia or death.

Phagocyte-induced lipid peroxidation of lung surfactant

Surfactant therapy is given routinely to premature newborns with respiratory failure. However, alterations in surfactants have been shown to be a significant factor in some forms of respiratory failure in newborns in animal models of lung injury. To investigate whether antioxidant supplementation might help to protect exogenous surfactant from damage by oxygen free radicals, we examined the influence of vitamin E in combination with surfactant on superoxide production as estimated by the nitroblue tetrazolium reduction test, and measured surfactant peroxidation with a new colorimetric method with or without addition of superoxide dismutase (SOD) or vitamin E. Our results showed that surfactant interacts with free radicals; surfactant reduced superoxide production by neutrophils and was peroxidized when incubated with resting and with stimulated cells. Vitamin E supplementation decreased superoxide radical production and in a dose-dependent manner decreased surfactant peroxidation. The decrease in lipid peroxidation by SOD was not significant. These findings suggest that phagocytes induce lipid peroxidation of lung surfactant, a reaction that might be prevented by antioxidants.

Instillation of calf lung surfactant extract (calfactant) is beneficial in pediatric acute hypoxemic respiratory failure. Members of the Mid-Atlantic Pediatric Critical Care Network

OBJECTIVE

Prospective study of the efficacy of calf lung surfactant extract in pediatric respiratory failure.

DESIGN

Multi-institutional, prospective, randomized, controlled, unblinded trial.

SETTING

Eight pediatric intensive care units (ICU) of tertiary medical centers.

PATIENTS

Forty-two children with acute hypoxemic respiratory failure characterized by diffuse, bilateral pulmonary infiltrates, need for ventilatory support, and an oxygenation index of >7.

INTERVENTION

Instillation of intratracheal surfactant (80 mL/m2).

MEASUREMENTS AND MAIN RESULTS

Ventilator parameters, arterial blood gases, and derived oxygenation and ventilation indices were recorded before and at intervals after surfactant administration. Complications and outcome measures, including mortality, duration of mechanical ventilation, and length of pediatric ICU and hospital stay, were also examined. Patients who received surfactant demonstrated rapid improvement in oxygenation and, on average, were extubated 4.2 days (32%) sooner and spent 5 fewer days (30%) in pediatric intensive care than control patients. There was no difference in mortality or overall hospital stay. Surfactant administration was associated with no serious adverse effects.

CONCLUSIONS

Administration of calf lung surfactant extract, calfactant, appears to be safe and is associated with rapid improvement in oxygenation, earlier extubation, and decreased requirement for intensive care in children with acute hypoxemic respiratory failure. Further study is needed, however, before widespread use in pediatric respiratory failure can be recommended.

Recent developments in respiratory care pharmacology

Bronchoactive inhaled aerosol drugs target the respiratory tract directly and seek to minimize systemic exposure and reduce side effects. Common delivery devices such as the metered dose inhaler, the small volume nebulizer, or the dry powder inhaler each deliver approximately the same fraction of dose (10%) to the lungs, although their dose amounts are not equivalent. Major respiratory drug groups are reviewed, and include the beta-adrenergic and anticholinergic bronchodilators, mucolytic agents, corticosteroids, mediator antagonists, anti-infective agents, and exogenous surfactants. New agents in each group are identified and briefly described, along with the clinical use and most commonly observed side effects for each class of drugs.

Declining perinatal mortality in Finland between 1987 and 1994: contribution of different subgroups

OBJECTIVE

To examine the extent to which the decline in perinatal mortality is attributable to some subgroups, especially to certain birthweight or gestation groups.

STUDY DESIGN

A register study using the Finnish Medical Birth Register for years 1987 to 1994.

RESULTS

Of the overall reduction in perinatal mortality from 8.8 to 6.7 per 1000 births, 78% was due to stillbirths, compared with 22% due to early neonatal deaths. The decline in mortality among infants who weighed under 1500 g at birth was the major contributor (62%) to the overall reduction in perinatal mortality. The largest decline in mortality in the stillbirth group occurred among those weighing < 1000 g, while for early neonatal deaths the group most affected weighed 1000-1499 g. A similar pattern emerged when the gestation-week groups were examined.

CONCLUSION

The decline in perinatal mortality is attributable to stillbirths of very low birthweight. The most likely explanations for this result are the improved antenatal and neonatal care and the wider use of malformation screening.

Systematic review and meta-analysis of early postnatal dexamethasone for prevention of chronic lung disease

AIM

To review systematically the evidence to determine whether dexamethasone treatment of very low birthweight infants begun within 14 days of age prevents chronic lung disease (CLD) without clinically significant side effects.

METHODS

Randomised controlled trials of dexamethasone started within this time frame were identified through a search of electronic databases, proceedings of scientific meetings, and personal files. Meta-analyses using event rate ratio (ERR), event rate difference (ERD), and if significant, numbers needed to treat (NNT) for benefits and numbers needed to harm (NNH) for adverse effects were calculated. Weighted mean difference were used for continuous variables. Three prespecified subgroup analyses were performed for; (i) dexamethasone begun within 36 hours (hours) of birth; (ii) dexamethasone initiated between 7-14 days of age; or (iii) if surfactant treatment was used.

RESULTS

Ten studies were included in the review; six where dexamethasone was initiated within 36 hours of age, four studies for dexamethasone started between 7 and 14 days and six studies using surfactant. Mortality ERR and NNT with 95% confidence intervals for dexamethasone initiated at 7-14 days of age were 0.35 (0.16, 0.74) and 8 (4, 30). ERRs and NNTs for CLD at 28 days and 36 weeks of postmenstrual age were 0.71 (0.61, 0.84), 8 (5, 17), and 0.57 (0.44, 0.76), 10 (6, 23) in the overall analyses. When dexamethasone was started at 7 to 14 days of age ERR and NNT for CLD at 36 weeks were 0.63 (0.47, 0.85) and 3 (2, 9). Clinically significant side effects included increased risk of hypertension, hyperglycaemia, and increased time to regain birthweight.

CONCLUSIONS

These meta-analyses show a significant reduction in risk of CLD at 28 days and 36 weeks of postmenstrual age. In the subgroup where dexamethasone was started between 7 and 14 days of age mortality was significantly reduced. Caution is warranted in the routine use of dexamethasone because of lack of data on long term neurodevelopmental outcomes.

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.

Cytological changes in endotracheal aspirates associated with chronic lung disease

Endotracheal aspirates taken serially from mechanically ventilated premature infants born at < 28 weeks gestation between March 1992 and August 1993 were studied to determine whether early cytological changes would be a good predictor of lung damage in infants who develop chronic lung disease (CLD). CLD was diagnosed if the infant required supplemental oxygen at 36 weeks corrected gestational age. Fifty-five infants were enrolled in the study, five died and of the 50 infants remaining, 17 (34%) developed CLD. The infants with CLD had a significantly lower gestation (25.5 +/- 1.8 (mean +/- 1 SD) versus 26.2 +/- 0.9 weeks, p < 0.05), significantly more required surfactant (14/17 vs. 16/33, p < 0.05) and were ventilated for a significantly longer period (43.3 +/- 26.6 vs. 19.3 +/- 12.8 days, p < 0.0001). Endotracheal aspirate cytology showed that infants with CLD had significantly more degenerated columnar epithelial cells on day 3 (p = 0.001), and more neutrophils on day 10 (p = 0.007). Though not predictive of CLD, cytological changes consistent with bronchial epithelial and pulmonary damage followed by an inflammatory response were found in the tracheal aspirates of a group of infants clinically diagnosed with CLD.

Recent declines in New York City infant mortality rates

BACKGROUND

Although infant mortality rates have declined gradually in New York City for many years, the rate of that decline began to accelerate dramatically at the end of the 1980s.

OBJECTIVE

To analyze the recent accelerated decline in infant mortality for three race/ethnicity designations in New York City and to investigate whether shifts in birth weight distribution or changes in birth weight-specific death rates were more important in determining these declines between 1988 to 1989 and 1992 to 1993.

METHODS

Two complete cohorts of linked birth-death certificate files consisting of all live births in New York City in 1988 to 1989 and 1992 to 1993 were examined. For each cohort, separate multinomial logistic regressions were estimated by race/ethnicity to analyze the probability of a neonatal or postneonatal death relative to survival as a function of a spectrum of covariates. The coefficients from these regressions were used to construct direct and indirect standardization exercises to predict changes in infant mortality holding characteristics of the cohort, including birth weight distribution, constant over time, or holding the influence of determinants, including birth weight-specific death rates, constant over time.

RESULTS

For whites, Hispanics, and blacks, infant mortality rates declined by 27.4%, 24.8%, and 22.7%, respectively, between 1988 to 1989 and 1992 to 1993. For whites and blacks, the largest decreases occurred for neonatal mortality rates, whereas for Hispanics, postneonatal rates fell the greatest. Although infant mortality rates among very low birth weight infants (<1500 g) fell by 27.8%, 19.3%, and 16.6% for whites, Hispanics, and blacks, the greatest decreases in rates were seen among normal birth weight infants (>2500 g). Infant mortality rate declines for this category of infants reached 31%, 31.7%, and 31.3%, respectively, for whites, Hispanics, and blacks. Direct and indirect standardization exercises indicated that the most important factor in determining these declines were decreases in birth weight-specific death rates, not improvements in the birth weight distribution over time.

CONCLUSIONS

We conclude that the large decreases in infant mortality rates witnessed in New York City between 1988 to 1989 and 1992 to 1993 were attributable not to improvements in birth weight distribution of the population but to declines in birth weight-specific death rates and that normal birth weight infants showed the greatest improvement.

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.

Comparison of Infasurf (calf lung surfactant extract) to Survanta (Beractant) in the treatment and prevention of respiratory distress syndrome

OBJECTIVE

To compare the relative safety and efficacy of Infasurf (calf lung surfactant extract; ONY, Inc, Amherst, NY, IND #27169) versus Survanta (Beractant, Ross Laboratories, Columbus, OH) in reducing the acute severity of respiratory distress syndrome (RDS) when given at birth and to infants with established RDS.

DESIGN

A prospective, randomized, double-blind, multicenter clinical trial.

SETTING

Thirteen neonatal intensive care units participated in the treatment arm: seven of these concurrently participated in the prevention arm.

PATIENTS

The treatment arm enrolled infants of </=2000 g birth weight with established RDS, and the prevention arm enrolled infants of </=29 weeks' gestation with birth weights <1250 g.

INTERVENTION

Infants were randomly assigned to receive Infasurf (n = 303, treatment arm; n = 180, prevention arm) or Survanta (n = 305, treatment arm; n = 194, prevention arm) in accordance with the Survanta package insert instructions.

OUTCOME MEASURES

We projected a 25% reduction between groups in the need for a third dose of surfactant for infants with established RDS, and a 25% reduction in the need for a second dose of surfactant for infants who received prophylactic surfactant. Secondary outcomes included the severity of RDS measured by inspired oxygen concentrations and mean airway pressure, air leaks, complications associated with surfactant administration, and survival to 36 weeks' postmenstrual age without the need for oxygen supplementation.

RESULTS

In the treatment arm, there was no difference between groups in the number of infants requiring more than two doses of surfactant. The interval between doses was significantly longer for Infasurf, suggesting an increased duration of treatment effect. The inspired oxygen concentration and mean airway pressure were lower in the Infasurf infants during the first 48 hours in the treatment arm. In the prevention arm, there were no differences with respect to the number of surfactant doses. The dosing intervals were longer for Infasurf infants after the second dose. No difference in inspired oxygen or mean airway pressure was noted during the first 72 hours. There were no significant differences in the incidence of air leaks, complications associated with dosing, complications of prematurity, mortality, or survival without chronic lung disease in the prevention or treatment arm.

CONCLUSIONS

Infants treated with Infasurf have a modest benefit in the acute phase of RDS. Infasurf seems to produce a longer duration of effect than Survanta.

Calf's lung surfactant extract in acute hypoxemic respiratory failure in children

OBJECTIVE

Open-label trial of the safety and short-term efficacy of calf's lung surfactant in pediatric respiratory failure.

DESIGN

Multi-institutional, uncontrolled, observational trial.

SETTING

Six pediatric intensive care units of tertiary medical centers.

PATIENTS

Twenty-nine children with acute hypoxemic respiratory failure, characterized by diffuse, bilateral, pulmonary infiltrates, need for ventilator support, and an oxygenation index of > or = 7.

INTERVENTIONS

Up to four doses of intratracheal surfactant (80 mL/m2).

MEASUREMENTS AND MAIN RESULTS

Ventilator parameters, arterial blood gases, and derived oxygenation and ventilation indices were recorded before, and at intervals after, surfactant administration. Complications and outcome measures were also noted. There was immediate improvement in oxygenation and moderation of ventilator support associated with surfactant administration in 24 of 29 patients. A modest but statistically insignificant effect was seen with subsequent doses. The only complications occurred in three patients who developed airleaks, two of which were coincident with surfactant administration. The overall mortality rate was 14%, which compares favorably with other published series.

CONCLUSIONS

Administration of calf's lung surfactant appears to be safe and is associated with rapid improvement in oxygenation and moderation of ventilator support in children with acute hypoxemic respiratory failure. These results set the stage for a randomized, controlled study.

Retinopathy of prematurity and surfactant treatment

PURPOSE

Surfactant therapy in premature infants has reduced the severity of respiratory distress syndrome (RDS), thus leading to a reduction in mortality. However, the anticipated effect of surfactant therapy on the incidence and severity of retinopathy of prematurity (ROP) is ambiguous. The acute rise in PaO2 and the increased survival of low-birth-weight infants may augment the risk of ROP, whereas their improved health and respiratory status may lower it.

METHODS

We reviewed the findings of sequential ophthalmologic examinations performed in our neonatal intensive care unit. Premature infants of gestational age under 32 weeks and weighing less than 1500 g at birth who received surfactant treatment were compared with a group of historical controls consisting of premature infants of the same mean birth weight and gestational age who did not get this supplement.

RESULTS

ROP was present in 13 (65%) of the 20 surfactant-treated babies, and threshold disease was noted in six (30%). In the historical control group, 20 (77%) of 25 infants had ROP, of whom 10 (40%) were treated for threshold disease. These differences were not statistically significant.

CONCLUSION

Surfactant therapy was not associated with an increased incidence of ROP in our series.