A multicenter, randomized, controlled trial of lucinactant versus poractant alfa among very premature infants at high risk for respiratory distress syndrome

Total serum bilirubin level in umbilical cord blood and respiratory distress syndrome in very low birth weight infants

AIMS

To explore the association between total serum bilirubin (TSB) level in umbilical cord blood (UCB) and the occurrence and/or severity of respiratory distress syndrome (RDS) in very low birth weight (VLBW) infants.

METHODS

We performed a prospective study of 579 VLBW infants. The mean TSB level in UCB (1.8 mg/dL) was used to divide the cohort into two groups: neonates with levels <1.8 mg/dL and those with levels >1.8 mg/dL. Demographic and clinical characteristics of the 2 groups, including diagnosis of RDS, need for ventilation, peak fraction of inspired oxygen (FiO2), oxygenation index (OI), and duration of respiratory support, were compared.

RESULTS

Three hundred and twenty-four infants were included in the low-TSB group and 255 infants were included in the high-TSB group. RDS was less frequent in the high TSB group than in the low one (46.3% vs. 56.6%, P=0.01). A negative association between TSB level in UCB and the occurrence of RDS [odds ratio (OR)=0.620; 95% confidence interval (CI) 0.440-0.873, P=0.006] was observed. However, lower TSB in UCB was not associated with the maximum FiO2, OI, or duration of mechanical ventilation.

CONCLUSIONS

VLBW infants with low TSB levels in UCB were more likely to develop RDS. However, in conjunction with surfactant replacement therapy, no correlation was found between TSB levels in UCB and the severity of RDS. The negative association between high TSB in UCB and RDS warrants further investigation.

Myth: all surfactants are alike

There are several surfactant preparations available to the clinician, none of which are alike. They differ in their phospholipid and surfactant protein (SP) composition as well as dosing, yet they all have been shown to be clinically effective as surfactants. Head-to-head randomized clinical trials comparing surfactants have shown some advantages of preparations that contain SP-B and SP-C, primarily in short-term clinical outcomes. A new synthetic surfactant that contains a phospholipid mixture and a peptide resembling SP-B has shown promise as a potential alternative to animal-derived surfactants.

Bronchoalveolar lavage versus bolus administration of lucinactant, a synthetic surfactant in meconium aspiration in newborn lambs

This study was designed to study effects of lung lavage versus the classical bolus instillation with a peptide-based synthetic surfactant (lucinactant) in a model of Meconium Aspiration Syndrome (MAS). Eighteen newborn lambs received meconium and were randomized to: the experimental meconium installation (eMAS) group-lambs with eMAS kept on conventional mechanical ventilation (control); the SF-Bolus group-eMAS receiving a lucinactant bolus (30 mg/ml); or the D-SF-Lavage group-eMAS treated with dilute lucinactant bronchoalveolar lavage (10 mg/ml). Systemic and pulmonary arterial pressures, blood gases, and pulmonary mechanics were recorded for 180 min. In addition, the intrapulmonary distribution of the lucinactant was determined using dye-labeled microspheres. Following meconium instillation, severe hypoxia, hypercapnia, acidosis, and pulmonary hypertension developed, and dynamic compliance decreased (50% from baseline). After lung lavage with dilute lucinactant, gas exchange significantly improved versus bolus instillation (P < 0.05). Further, only in the lavage group did pulmonary arterial pressure return to basal values and dynamic compliance significantly increased. Both lung lavage and bolus techniques for the administration of lucinactant resulted in a non-uniform lung distribution. In conclusion, in newborn lambs with respiratory failure and pulmonary hypertension induced by meconium, lung lavage with dilute lucinactant seems to be an effective and safe alternative for treatment for MAS.

An open label, pilot study of Aerosurf® combined with nCPAP to prevent RDS in preterm neonates

BACKGROUND

Nasal continuous positive airway pressure (nCPAP) is an accepted mode of respiratory support for preterm infants with respiratory insufficiency. To avoid potential sequelae of endotracheal (ET) intubation and mechanical ventilation, prophylactic aerosolization of surfactant delivered via nCPAP has been attempted with limited success.

METHODS

To determine the feasibility and safety of prophylactic aerosolization of a peptide-containing synthetic surfactant, Aerosurf® (lucinactant for inhalation) was delivered by nCPAP to preterm infants at risk for respiratory distress syndrome (RDS). Neonates were enrolled into treatment group 1 (Aerosurf retreatment separated by at least 3 h) or treatment group 2 (Aerosurf retreatment separated by at least 1 h). A vibrating membrane nebulizer Aeroneb Pro® was used to aerosolize 20 mg/mL Aerosurf. All neonates received the initial 3-h treatment, and three retreatments were permitted within 48 h based on clinical response.

RESULTS

Seventeen infants were enrolled. Aerosurf was well tolerated, with transient desaturations observed during dosing without bradycardia or hypotension. Variability in output rates of the Aeroneb Pro was observed leading to different average dispensed drug volumes per treatment per patient. All infants survived; 29.4% required subsequent ET surfactant replacement therapy, 23.5% were diagnosed with RDS at 24 h, and 11.8% with bronchopulmonary dysplasia (BPD) at 28 days of life. Mean FiO₂ was 0.4 at baseline, and 0.32 at 4 h posttreatment.

CONCLUSIONS

Aerosurf can be safely administered via nCPAP in preterm infants at risk for RDS and may provide an alternative to surfactant administration via an ET tube. Further studies are required to evaluate this delivery approach.

Lipid polymorphism induced by surfactant peptide SP-B(1-25)

Pulmonary surfactant protein B (SP-B) is an essential protein for lowering surface tension in the alveoli. SP-B(1-25), a peptide comprised of the N-terminal 25 amino-acid residues of SP-B, is known to retain much of the biological activity of SP-B. Circular dichroism has shown that when SP-B(1-25) interacts with negatively charged lipid vesicles, it contains significant helical structure for the lipid compositions and peptide/lipid ratios studied here. The effect of SP-B(1-25) on lipid organization and polymorphisms was investigated via DSC, dynamic light scattering, transmission electron microscopy, and solid-state NMR spectroscopy. At 1-3 mol% peptide and physiologic temperature, SP-B(1-25) partitions at the interface of negatively charged PC/PG lipid bilayers. In lipid mixtures containing 1-5 mol% peptide, the structure of SP-B(1-25) remains constant, but (2)H and (31)P NMR spectra show the presence of an isotropic lipid phase in exchange with the lamellar phase below the T(m) of the lipids. This behavior is observed for both DPPC/POPG and POPC/POPG lipid mixtures as well as for both the PC and PG components of the mixtures. For 1-3 mol% SP-B(1-25), a return to a single lamellar phase above the lipid mixture T(m) is observed, but for 5 mol% SP-B(1-25) a significant isotropic component is observed at physiologic temperatures for DPPC and exchange broadening is observed in (2)H and (31)P NMR spectra of the other lipid components in the two mixtures. DLS and TEM rule out the formation of micellar structures and suggest that SP-B(1-25) promotes the formation of a fluid isotropic phase. The ability of SP-B(1-25) to fuse lipid lamellae via this mechanism, particularly those enriched in DPPC, suggests a specific role for the highly conserved N-terminus of SP-B in the packing of lipid lamellae into surfactant lamellar bodies or in stabilizing multilayer structures at the air-liquid interface. Importantly, this behavior has not been seen for the other SP-B fragments of SP-B(8-25) and SP-B(59-80), indicating a critical role for the proline rich first seven amino acids in this protein.

The management of evolving bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is associated with increased mortality and significant long-term cardiorespiratory and neurodevelopmental sequelae. Treatment of evolving BPD in the neonatal intensive care unit (NICU) is challenging due to the complex interplay of contributing risk factors which include preterm birth per se, supplemental oxygen, positive pressure ventilation, patent ductus arterious, and pre- and postnatal infection. Management of evolving BPD requires a multimodal approach including adequate nutrition, careful fluid management, effective and safe pharmacotherapy, and respiratory support aiming at minimal lung injury. Among pharmacological interventions, caffeine has the best risk-benefit profile. Systemic postnatal corticosteroids should be reserved to ventilated infants at highest risk of BPD who cannot be weaned from the ventilator. Several ongoing randomised trials are evaluating optimal oxygen saturation targets in preterm infants. The most beneficial respiratory support strategy to minimise lung injury remains unclear and requires further investigation.

Improved gas exchange and survival after KL-4 surfactant in newborn pigs with severe acute lung injury

OBJECTIVE

To determine the effectiveness of artificial surfactant therapy using KL-4 surfactant in newborn pigs with hydrochloric acid (HCl)-induced acute lung injury (ALI).

DESIGN

After induction of ALI via intratracheal HCl instillation, pigs were randomized to receive 5.8 ml/kg KL-4 surfactant or no surfactant prior to extubation to bubble CPAP.

SETTING

Clinical laboratory.

SUBJECTS

Spontaneously breathing newborn pigs (<1 week of age).

INTERVENTIONS

Treatment with KL-4 surfactant on bubble CPAP with PEEP of 6 cmH(2)O for 3.5 hr after extubation compared with controls.

MEASUREMENTS

Physiologic parameters and arterial blood gases were measured every 15 min. At the conclusion of the study, the lungs were excised for the analysis of histopathology and morphometric data.

MAIN RESULTS

Pigs treated with KL-4 surfactant had arterial blood gases with less acidosis (P < 0.001), higher P(a)O(2) levels (P < 0.001), and lower P(a)CO(2) levels (P < 0.001). Pigs treated with KL-4 surfactant had improved survival compared with controls (6/12 KL-4, 2/12 control, P < 0.05). Postmortem morphometric data demonstrated that pigs treated with KL-4 surfactant had larger (P < 0.05) exchange units in the caudal-dorsal lung as compared to relatively atelectatic region in the control animals.

CONCLUSIONS

In newborn pigs with severe HCl-induced ALI, treatment with KL-4 surfactant resulted in improved respiratory parameters, less dependent atelectasis, and improved short-term survival.

Complications among premature neonates treated with beractant and poractant alfa

OBJECTIVE

To compare the complications among preterm infants treated with two different natural surfactants.

METHODS

In a randomized clinical trial, 150 preterm infants with Respiratory distress syndrome (RDS) treated with exogenous surfactant, were enrolled in the study. Group A consisted of 79 neonates that received poractant (curosurf). Seventy one newborn infants in group B were treated with beractant (Survanta).

RESULTS

The mean gestational age for group A and B were 29.40+/-2.90 wk and 29.50+/-2.73 wk (P=0.82), respectively. The demographic and clinical variables were similar in both groups. The mean duration of intubation (as a primary outcome) was significantly shorter in infants treated with poractant (3.13+/-1.80 vs 4.06+/-2.7 days p=0.05). The mean duration of need for oxygen and hospitalization of patients in group A and B were 17.73+/-22.25 vs 19.14+/-17.85 days (p=0.67) and 24.89+/-26.41 vs 29.14+/-23.54 days (p= 0.32), respectively. There was no significant difference between groups with respect to mortality and morbidity, including pulmonary hemorrhage, intraventricular hemorrhage (IVH), patent ductus arteriosus, sepsis, and bronchopulmonary dysplasia (secondary outcome).

CONCLUSIONS

In this study, infants who received poractant had shorter duration of intubation than infants treated with beractant, without any difference in the duration of oxygen therapy or hospitalization. There was no significant superiority of poractant over beractant.

Surfactant in the preterm infant: what's going on

Surfactant treatment has been demonstrated to decrease pneumothorax and mortality in preterm infants. Natural surfactants are better than synthetic surfactants. Early rescue treatment with surfactant is better than late treatment, whereas the role of surfactant prophylaxis is under re-evaluation due to the actual large diffusion of antenatal steroid and nasal continuous positive airway pressure treatment which have changed the clinical characteristics of preterm infants with respiratory distress syndrome. It is possible that in the next future anti-inflammatory and anti-oxidant properties of exogenous natural surfactants may be improved through their combination with adequate agents with the aim of counteracting the pathogenetic role of inflammatory and oxidative lung injury injuries in the development of brochopulmonary dysplasia.

Nonventilatory strategies for patients with life-threatening 2009 H1N1 influenza and severe respiratory failure

Severe respiratory failure (including acute lung injury and acute respiratory distress syndrome) caused by 2009 H1N1 influenza infection has been reported worldwide. Refractory hypoxemia is a common finding in these patients and can be challenging to manage. This review focuses on nonventilatory strategies in the advanced treatment of severe respiratory failure and refractory hypoxemia such as that seen in patients with severe acute respiratory distress syndrome attributable to 2009 H1N1 influenza. Specific modalities covered include conservative fluid management, prone positioning, inhaled nitric oxide, inhaled vasodilatory prostaglandins, and extracorporeal membrane oxygenation and life support. Pharmacologic strategies (including steroids) investigated for the treatment of severe respiratory failure are also reviewed.

Accounting for multiple births in neonatal and perinatal trials: systematic review and case study

OBJECTIVES

To determine the prevalence in the neonatal literature of statistical approaches accounting for the unique clustering patterns of multiple births and to explore the sensitivity of an actual trial to several analytic approaches to multiples.

STUDY DESIGN

A systematic review of recent perinatal trials assessed the prevalence of studies accounting for clustering of multiples. The Nitric Oxide to Prevent Chronic Lung Disease (NO CLD) trial served as a case study of the sensitivity of the outcome to several statistical strategies. We calculated odds ratios using nonclustered (logistic regression) and clustered (generalized estimating equations, multiple outputation) analyses.

RESULTS

In the systematic review, most studies did not describe the random assignment of twins and did not account for clustering. Of those studies that did, exclusion of multiples and generalized estimating equations were the most common strategies. The NO CLD study included 84 infants with a sibling enrolled in the study. Multiples were more likely than singletons to be white and were born to older mothers (P < .01). Analyses that accounted for clustering were statistically significant; analyses assuming independence were not.

CONCLUSIONS

The statistical approach to multiples can influence the odds ratio and width of confidence intervals, thereby affecting the interpretation of a study outcome. A minority of perinatal studies address this issue.

A systematic review of the reporting of Data Monitoring Committees' roles, interim analysis and early termination in pediatric clinical trials

Background

Decisions about interim analysis and early stopping of clinical trials, as based on recommendations of Data Monitoring Committees (DMCs), have far reaching consequences for the scientific validity and clinical impact of a trial. Our aim was to evaluate the frequency and quality of the reporting on DMC composition and roles, interim analysis and early termination in pediatric trials.

Methods

We conducted a systematic review of randomized controlled clinical trials published from 2005 to 2007 in a sample of four general and four pediatric journals. We used full-text databases to identify trials which reported on DMCs, interim analysis or early termination, and included children or adolescents. Information was extracted on general trial characteristics, risk of bias, and a set of parameters regarding DMC composition and roles, interim analysis and early termination.

Results

110 of the 648 pediatric trials in this sample (17%) reported on DMC or interim analysis or early stopping, and were included; 68 from general and 42 from pediatric journals. The presence of DMCs was reported in 89 of the 110 included trials (81%); 62 papers, including 46 of the 89 that reported on DMCs (52%), also presented information about interim analysis. No paper adequately reported all DMC parameters, and nine (15%) reported all interim analysis details. Of 32 trials which terminated early, 22 (69%) did not report predefined stopping guidelines and 15 (47%) did not provide information on statistical monitoring methods.

Conclusions

Reporting on DMC composition and roles, on interim analysis results and on early termination of pediatric trials is incomplete and heterogeneous. We propose a minimal set of reporting parameters that will allow the reader to assess the validity of trial results.

Drug therapies in bronchopulmonary dysplasia: debunking the myths

Bronchopulmonary dysplasia (BPD), also known as chronic lung disease (CLD), is one of the most challenging complications in premature infants. The incidence of BPD has been increasing over the past two decades in parallel with an improvement in the survival of this population. Furthermore, the clinical characteristics and the natural history of infants affected by BPD have changed considerably, and newer definitions to clarify the term 'BPD' have also evolved since its first description more than four decades ago. Several drug therapies have also evolved, either to manage these infants' respiratory distress syndrome with an aim to prevent BPD or to manage the established condition. Although there is good evidence to support the 'routine' use of some therapies, many other therapies currently used in relation to BPD remain individual- or institution-specific, depending on beliefs and myths that we have adopted. In this article, we discuss the importance of defining BPD more objectively and the support--or lack thereof--for the drug therapies used in relation to BPD.

Accepting risk in clinical research: is the gene therapy field becoming too risk-averse?

Risk is an inescapable aspect of clinical research and is increasingly pertinent to the gene therapy field as the imperative for clinical trial activity grows. In recent years, the widely reported occurrence of serious adverse events (SAEs) in gene therapy studies, including trials for ornithine transcarbamylase (OTC) deficiency, X-linked severe combined immunodeficiency (SCID-X1), and rheumatoid arthritis, has heightened fear in public perceptions of gene therapy. Although it is essential to be cognizant of the risks involved in gene therapy research, there is a danger that gene therapy may become too risk-averse. If the field is to make progress, it is necessary to understand how risk is defined in gene therapy research, how understandings of risk differ, how risk is assessed, how decisions about risk are made, and how gene therapy risks are communicated to subjects and research participants during the informed consent process. In addition to minimizing the risks of clinical research through extensive preclinical safety studies, attention should be given to how decisions about risk and risk acceptability are made by researchers and subjects, and to the methods used to communicate risks to patients. Critical attention to risk will help ensure that the safety of subjects is protected, while also enabling research to develop better treatments for patients.

Protein-containing synthetic surfactant versus protein-free synthetic surfactant for the prevention and treatment of respiratory distress syndrome

BACKGROUND

Respiratory distress syndrome (RDS) is a significant cause of morbidity and mortality in preterm infants. RDS is caused by a deficiency, dysfunction, or inactivation of pulmonary surfactant. Numerous surfactants of either animal extract or synthetic design have been shown to improve outcomes. New surfactant preparations that include peptides or whole proteins that mimic endogenous surfactant protein have recently been developed and tested.

OBJECTIVES

To assess the effect of administration of synthetic surfactant containing surfactant protein mimics compared to protein free synthetic surfactant on the risk of mortality, chronic lung disease, and other morbidities associated with prematurity in preterm infants at risk for or having RDS.

SEARCH STRATEGY

Standard search methods of the Cochrane Neonatal Review Group were used. The search included MEDLINE (1966 - March 2009) and the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library) in all languages.

SELECTION CRITERIA

Randomized and quasi-randomized controlled clinical trials were considered for this review. Studies that enrolled preterm infants or low birth weight infants at risk for or having RDS who were treated with either a synthetic surfactant containing surfactant protein mimics or a protein free synthetic surfactant were included for this review. Studies of treatment or prevention of respiratory distress syndrome were included.

DATA COLLECTION AND ANALYSIS

Data regarding mortality, chronic lung disease and multiple secondary outcome measures were abstracted by the review authors. Statistical analysis was performed using Review Manager software. Categorical data were analyzed using relative risk, risk difference, and number needed to treat. 95% confidence intervals reported. A fixed effects model was used for the meta-analysis. Heterogeneity was assessed using the I(2) statistic.

MAIN RESULTS

One study was identified that compared protein containing synthetic surfactants (PCSS) to protein free synthetic surfactants. Infants who received protein containing synthetic surfactant compared to protein free synthetic surfactant did not demonstrate significantly different risks of prespecified primary outcomes: mortality at 36 weeks postmenstrual age (PMA) [RR 0.89 (95% CI 0.71, 1.11)], chronic lung disease at 36 weeks PMA [RR 0.89 (95% CI 0.78, 1.03)], or the combined outcome of mortality or chronic lung disease at 36 weeks PMA [RR 0.88 (95% CI 0.77, 1.01)]. Among the secondary outcomes, a decrease in the incidence of respiratory distress syndrome at 24 hours of age was demonstrated in the group that received PCSS [RR 0.83 (95% CI 0.72, 0.95).

AUTHORS' CONCLUSIONS

In the one trial comparing protein containing synthetic surfactants compared to protein free synthetic surfactant for the prevention of RDS, no statistically different clinical differences in death and chronic lung disease were noted. Clinical outcomes between the two groups were generally similar although the group receiving protein containing synthetic surfactants did have decreased incidence of respiratory distress syndrome. Further well designed studies comparing protein containing synthetic surfactant to the more widely used animal derived surfactant extracts are indicated.

Partitioning, dynamics, and orientation of lung surfactant peptide KL(4) in phospholipid bilayers

Lung surfactant protein B (SP-B) is a lipophilic protein critical to lung function at ambient pressure. KL(4) is a 21-residue peptide which has successfully replaced SP-B in clinical trials of synthetic lung surfactants. CD and FTIR measurements indicate KL(4) is helical in a lipid bilayer environment, but its exact secondary structure and orientation within the bilayer remain controversial. To investigate the partitioning and dynamics of KL(4) in phospholipid bilayers, we introduced CD(3)-enriched leucines at four positions along the peptide to serve as probes of side chain dynamics via (2)H solid-state NMR. The chosen labels allow distinction between models of helical secondary structure as well as between a transmembrane orientation or partitioning in the plane of the lipid leaflets. Leucine side chains are also sensitive to helix packing interactions in peptides that oligomerize. The partitioning and orientation of KL(4) in DPPC/POPG and POPC/POPG phospholipid bilayers, as inferred from the leucine side chain dynamics, is consistent with monomeric KL(4) lying in the plane of the bilayers and adopting an unusual helical structure which confers amphipathicity and allows partitioning into the lipid hydrophobic interior. At physiologic temperatures, the partitioning depth and dynamics of the peptide are dependent on the degree of saturation present in the lipids. The deeper partitioning of KL(4) relative to antimicrobial amphipathic alpha-helices leads to negative membrane curvature strain as evidenced by the formation of hexagonal phase structures in a POPE/POPG phospholipid mixture on addition of KL(4). The unusual secondary structure of KL(4) and its ability to differentially partition into lipid lamellae containing varying levels of saturation suggest a mechanism for its role in restoring lung compliance.

Penetration depth of surfactant peptide KL4 into membranes is determined by fatty acid saturation

KL(4) is a 21-residue functional peptide mimic of lung surfactant protein B, an essential protein for lowering surface tension in the alveoli. Its ability to modify lipid properties and restore lung compliance was investigated with circular dichroism, differential scanning calorimetry, and solid-state NMR spectroscopy. KL(4) binds fluid lamellar phase PC/PG lipid membranes and forms an amphipathic helix that alters lipid organization and acyl chain dynamics. The binding and helicity of KL(4) is dependent on the level of monounsaturation in the fatty acid chains. At physiologic temperatures, KL(4) is more peripheral and dynamic in fluid phase POPC/POPG MLVs but is deeply inserted into fluid phase DPPC/POPG vesicles, resulting in immobilization of the peptide. Substantial increases in the acyl chain order are observed in DPPC/POPG lipid vesicles with increasing levels of KL(4), and POPC/POPG lipid vesicles show small decreases in the acyl chain order parameters on addition of KL(4). Additionally, a clear effect of KL(4) on the orientation of the fluid phase PG headgroups is observed, with similar changes in both lipid environments. Near the phase transition temperature of the DPPC/POPG lipid mixtures, which is just below the physiologic temperature of lung surfactant, KL(4) causes phase separation with the DPPC remaining in a gel phase and the POPG partitioned between gel and fluid phases. The ability of KL(4) to differentially partition into lipid lamellae containing varying levels of monounsaturation and subsequent changes in curvature strain suggest a mechanism for peptide-mediated lipid organization and trafficking within the dynamic lung environment.

The effect of a C-terminal peptide of surfactant protein B (SP-B) on oriented lipid bilayers, characterized by solid-state 2H- and 31P-NMR

SP-B(CTERM), a cationic, helical peptide based on the essential lung surfactant protein B (SP-B), retains a significant fraction of the function of the full-length protein. Solid-state (2)H- and (31)P-NMR were used to examine the effects of SP-B(CTERM) on mechanically oriented lipid bilayer samples. SP-B(CTERM) modified the multilayer structure of bilayers composed of POPC, POPG, POPC/POPG, or bovine lipid extract surfactant (BLES), even at relatively low peptide concentrations. The (31)P spectra of BLES, which contains approximately 1% SP-B, and POPC/POPG with 1% SP-B(CTERM), look very similar, supporting a similarity in lipid interactions of SP-B(CTERM) and its parent protein, full-length SP-B. In the model systems, although the peptide interacted with both the oriented and unoriented fractions of the lipids, it interacted differently with the two fractions, as demonstrated by differences in lipid headgroup structure induced by the peptide. On the other hand, although SP-B(CTERM) induced similar disruptions in overall bilayer orientation in BLES, there was no evidence of lipid headgroup conformational changes in either the oriented or the unoriented fractions of the BLES samples. Notably, in the model lipid systems the peptide did not induce the formation of small, rapidly tumbling lipid structures, such as micelles, or of hexagonal phases, the observation of which would have provided support for functional mechanisms involving peptide-induced lipid flip-flop or stabilization of curved lipid structures, respectively.

Pitfalls, problems, and progress in bronchopulmonary dysplasia

Bronchopulmonary dysplasia is a chronic lung disease associated with premature birth and characterized by early lung injury. In this review we discuss some pitfalls, problems, and progress in this condition over the last decade, focusing mainly on the last 5 years, limited to studies in human neonates. Changes in the definition, pathogenesis, genetic susceptibility, and recent biomarkers associated with bronchopulmonary dysplasia will be discussed. Progress in current management strategies, along with novel approaches/therapies, will be critically appraised. Finally, recent data on long-term pulmonary and neurodevelopmental outcomes of infants with bronchopulmonary dysplasia will be summarized.

Animal-derived surfactants: where are we? The evidence from randomized, controlled clinical trials

Animal-derived surfactants, as well as synthetic surfactants, have been extensively evaluated in the treatment of respiratory distress syndrome (RDS) in preterm infants. Three commonly available animal-derived surfactants in the United States include beractant (BE), calfactant (CA) and poractant alfa (PA). Multiple comparative studies have been performed using these three surfactants. Prospective as well as retrospective studies comparing BE and CA have shown no significant differences in clinical or economic outcomes. Randomized, controlled clinical trials have shown that treatment with PA is associated with rapid weaning of oxygen and ventilatory pressures, fewer additional doses, cost benefits and survival advantage when compared with BE or CA. Recently, a study using an administrative database that included over 20,000 preterm infants has shown a significant decrease in mortality and cost benefits in favor of PA, when compared with BE or CA. Differences in outcomes between these animal-derived surfactants may be related to a higher amount of phospholipids and plasmalogens in PA. To date, animal-derived surfactants seem to be better than synthetic surfactants during the acute phase of RDS and in decreasing neonatal mortality. Further studies are needed comparing animal-derived surfactants with the newer generation of synthetic surfactants.

Synthetic surfactants: where are we? Evidence from randomized, controlled clinical trials

The benefits of exogenous synthetic or animal-derived surfactants for prevention or treatment of respiratory distress syndrome (RDS) are well established. Data from head-to-head trials comparing animal-derived surfactants primarily with the synthetic surfactant colfosceril suggest that the major clinical advantages afforded by the presence of surfactant protein (SP)-B and SP-C in animal-derived preparations relate to faster onset of action, a reduction in the incidence of RDS when used prophylactically, and a lower incidence of air leaks and RDS-related deaths. However, no benefits in terms of overall mortality or BPD have been shown in these head-to-head comparisons. Findings from trials of a new-generation synthetic surfactant containing a peptide that mimics SP-B, as well as their follow-up study suggest that its administration improves short-term clinical outcomes compared with colfosceril and results in survival through 1 year of age, which is at least comparable, if not perhaps superior, to that seen with animal-derived surfactants.

Animal-derived surfactants for the treatment and prevention of neonatal respiratory distress syndrome: summary of clinical trials

INTRODUCTION

Available literature suggests that the advantage of animal-derived surfactants over first-generation synthetic agents derives from the presence of surface-active proteins and their phospholipid content. Here we summarize the results of clinical trials comparing animal-derived surfactant preparations with other animal-derived surfactants and with both first-and second-generation synthetic surfactants.

METHODS

Published clinical trials of comparisons of animal-derived surfactants were summarized and compared. Comparisons emphasized differences in (1) key surfactant components attributed with efficacy and (2) differences in published outcomes.

RESULTS

For the most important outcomes, mortality and chronic lung disease, currently available natural surfactants are essentially similar in efficacy. When examining secondary outcomes (pneumothorax, ventilator weaning, and need for supplemental oxygen), it appears that both calfactant and poractant have an advantage over beractant. The weight of the evidence, especially for study design and secondary outcomes, favors the use of calfactant. However, the superiority of poractant over beractant, when the higher initial dose of poractant is used, strengthens the case for use of poractant as well.

CONCLUSIONS

Clinical trials suggest that the higher surfactant protein-B content in calfactant, and perhaps the higher phospholipid content in poractant (at higher initial dose), are the factors that most likely confer the observed advantage over other surfactant preparations.

A pilot randomized, controlled trial of later treatment with a peptide-containing, synthetic surfactant for the prevention of bronchopulmonary dysplasia

OBJECTIVE

Oxidant injury and lung inflammation in extremely premature infants are associated with the development of bronchopulmonary dysplasia. Surfactant dysfunction resulting from these events may contribute to the pathogenesis of bronchopulmonary dysplasia. Treatment with exogenous surfactant may decrease the incidence or severity of bronchopulmonary dysplasia. We conducted a masked, multicenter, multinational, randomized, controlled, pilot study to estimate the effects of treating infants at high risk for developing bronchopulmonary dysplasia with lucinactant, a synthetic, peptide-containing surfactant, on safety during dosing and the incidence of death or bronchopulmonary dysplasia.

METHODS

Preterm infants between 600 and 900 g requiring mechanical ventilation and a fraction of inspired oxygen of > or =0.30 between 3 and 10 days of age were randomly assigned to receive either sham air (placebo) or 1 of 2 doses of lucinactant (90 or 175 mg/kg total phospholipid) every 48 hours to a maximum of 5 doses, if they remained on mechanical ventilation.

RESULTS

Of 136 infants enrolled at 34 sites, 44 received placebo, 47 received 90 mg/kg total phospholipid, and 45 received 175 mg/kg total phospholipid. The 90 mg/kg group had a significantly higher percentage of boys (64%) compared with the placebo group (39%); no other significant differences in baseline characteristics among groups were present. Compared with placebo, both the 90 mg/kg and 175 mg/kg groups experienced a significantly higher incidence of desaturation and bradycardia during dosing. Twenty-four hours after dosing, the mean fraction of inspired oxygen was lower in both lucinactant groups (33%) compared with the placebo group (39%). The incidence of mortality or bronchopulmonary dysplasia was 66% in the placebo group, 79% in the 90 mg/kg group, and 58% in the 175 mg/kg group. These differences were not statistically significant. There were no statistical differences among groups for pneumothorax, pulmonary interstitial emphysema, intraventricular hemorrhage, periventricular leukomalacia, retinopathy of prematurity, or mortality.

CONCLUSIONS

There were trends toward lower oxygen requirements and toward a lower incidence of mortality or bronchopulmonary dysplasia at 36 weeks' postmenstrual age in infants who received the higher dose of lucinactant, and this warrants further investigation.

Review: Surfactant respiratory therapy using Surfaxin/sinapultide

Respiratory distress syndrome (RDS) is a leading cause of mortality and morbidity in preterm infants. Surfactant replacement therapy has been widely used to prevent and treat RDS in these newborns and has now become a standard of care. First-generation synthetic surfactants such as Exosurf did not contain any surfactant protein. This disadvantage was overcome with animal-derived surfactant preparations which contain specific proteins but has the limitation of being derived from animal sources. This has led to development of newer synthetic surfactants such as lucinactant (Surfaxin, Discovery Laboratories, Philadelphia) which contains the protein B mimic synthetic peptide, sinapultide. Recent phase 3 clinical trials with Surfaxin show promising results with similar efficacy as animal derived surfactants and yet avoiding the disadvantage associated with animal products. The purpose of this paper is to summarise results of recent clinical trials of Surfaxin use in newborns with RDS.

The helical structure of surfactant peptide KL4 when bound to POPC: POPG lipid vesicles

KL 4 is a 21-residue peptide employed as a functional mimic of lung surfactant protein B, which successfully lowers surface tension in the alveoli. A mechanistic understanding of how KL 4 affects lipid properties has proven elusive as the secondary structure of KL 4 in lipid preparations has not been determined at high resolution. The sequence of KL 4 is based on the C-terminus of SP-B, a naturally occurring helical protein that binds to lipid interfaces. The spacing of the lysine residues in KL 4 precludes the formation of a canonical amphipathic alpha-helix; qualitative measurements using Raman, CD, and FTIR spectroscopies have given conflicting results as to the secondary structure of the peptide as well as its orientation in the lipid environment. Here, we present a structural model of KL 4 bound to lipid bilayers based on solid state NMR data. Double-quantum correlation experiments employing (13)C-enriched peptides were used to quantitatively determine the backbone torsion angles in KL 4 at several positions. These measurements, coupled with CD experiments, verify the helical nature of KL 4 when bound to lipids, with (phi, psi) angles that differ substantially from common values for alpha-helices of (-60, -45). The average torsion angles found for KL 4 bound to POPC:POPG lipid vesicles are (-105, -30); this deviation from ideal alpha-helical structure allows KL 4 to form an amphipathic helix at the lipid interface.

Interactions of the C-terminus of lung surfactant protein B with lipid bilayers are modulated by acyl chain saturation

Lung surfactant protein B (SP-B) is critical to minimizing surface tension in the alveoli. The C-terminus of SP-B, residues 59-80, has much of the surface activity of the full protein and serves as a template for the development of synthetic surfactant replacements. The molecular mechanisms responsible for its ability to restore lung compliance were investigated with circular dichroism, differential scanning calorimetry, and (31)P and (2)H solid-state NMR spectroscopy. SP-B(59-80) forms an amphipathic helix which alters lipid organization and acyl chain dynamics in fluid lamellar phase 4:1 DPPC:POPG and 3:1 POPC:POPG MLVs. At higher levels of SP-B(59-80) in the POPC:POPG lipid system a transition to a nonlamellar phase is observed while DPPC:POPG mixtures remain in a lamellar phase. Deuterium NMR shows an increase in acyl chain order in DPPC:POPG MLVs on addition of SP-B(59-80); in POPC:POPG MLVs, acyl chain order parameters decrease. Our results indicate SP-B(59-80) penetrates deeply into DPPC:POPG bilayers and binds more peripherally to POPC:POPG bilayers. Similar behavior has been observed for KL(4), a peptide mimetic of SP-B which was originally designed using SP-B(59-80) as a template and has been clinically demonstrated to be successful in treating respiratory distress syndrome. The ability of these helical peptides to differentially partition into lipid lamellae based on their degree of monounsaturation and subsequent changes in lipid dynamics suggest a mechanism for lipid organization and trafficking within the dynamic lung environment.

Current perspectives in pulmonary surfactant--inhibition, enhancement and evaluation

Pulmonary surfactant (PS) is a complicated mixture of approximately 90% lipids and 10% proteins. It plays an important role in maintaining normal respiratory mechanics by reducing alveolar surface tension to near-zero values. Supplementing exogenous surfactant to newborns suffering from respiratory distress syndrome (RDS), a leading cause of perinatal mortality, has completely altered neonatal care in industrialized countries. Surfactant therapy has also been applied to the acute respiratory distress syndrome (ARDS) but with only limited success. Biophysical studies suggest that surfactant inhibition is partially responsible for this unsatisfactory performance. This paper reviews the biophysical properties of functional and dysfunctional PS. The biophysical properties of PS are further limited to surface activity, i.e., properties related to highly dynamic and very low surface tensions. Three main perspectives are reviewed. (1) How does PS permit both rapid adsorption and the ability to reach very low surface tensions? (2) How is PS inactivated by different inhibitory substances and how can this inhibition be counteracted? A recent research focus of using water-soluble polymers as additives to enhance the surface activity of clinical PS and to overcome inhibition is extensively discussed. (3) Which in vivo, in situ, and in vitro methods are available for evaluating the surface activity of PS and what are their relative merits? A better understanding of the biophysical properties of functional and dysfunctional PS is important for the further development of surfactant therapy, especially for its potential application in ARDS.

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.

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.

Protein containing synthetic surfactant versus animal derived surfactant extract for the prevention and treatment of respiratory distress syndrome

BACKGROUND

Respiratory distress syndrome (RDS) is a significant cause of morbidity and mortality in preterm infants. RDS is caused by a deficiency, dysfunction, or inactivation of pulmonary surfactant. Numerous surfactants of either animal extract or synthetic design have been shown to improve outcomes. New surfactant preparations that include peptides or whole proteins that mimic endogenous surfactant protein have recently been developed and tested.

OBJECTIVES

To assess the effect of administration of synthetic surfactant containing surfactant protein mimics compared to animal derived surfactant extract on the risk of mortality, chronic lung disease, and other morbidities associated with prematurity in preterm infants at risk for or having RDS.

SEARCH STRATEGY

Standard search methods of the Cochrane Neonatal Review Group were used. The search included MEDLINE (1966 - May 2007) and the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library) in all languages. In addition, published abstracts of the Society of Pediatric Research were searched electronically. For abstract books that did not include key words, the search was limited to the relevant sections on pulmonary and neonatology. The bibliography cited in each publication was obtained and searched in order to identify additional relevant articles.

SELECTION CRITERIA

Randomized and quasi-randomized controlled clinical trials were considered for this review. Studies that enrolled preterm infants or low birth weight infants at risk for or having RDS who were treated with either a synthetic surfactant containing surfactant protein mimics or an animal-derived surfactant preparation were included for this review. Studies that either attempted to treat or prevent respiratory distress syndrome were included.

DATA COLLECTION AND ANALYSIS

Primary outcome measures, including mortality, chronic lung disease and multiple secondary outcome measures were abstracted by the reviewers. Statistical analysis was performed using Review Manager software. Categorical data was analyzed using relative risk, risk difference, and number needed to treat. 95% confidence intervals reported. A fixed effects model was used for the meta-analysis. Heterogeneity was assessed using the I-squared statistic.

MAIN RESULTS

Two studies were identified that compared protein containing synthetic surfactants to animal derived surfactant preparations. In a meta-analysis of these two studies, infants who received protein containing synthetic surfactant compared to animal derived surfactant extract did not demonstrate significantly different risks of prespecified primary outcomes: mortality at 36 weeks [typical RR 0.81 (95% CI 0.64, 1.03)], chronic lung disease at 36 weeks [typical RR 0.99 (95% CI 0.84, 1.18)], or the combined outcome of mortality or chronic lung disease at 36 weeks [typical RR 0.96 (95% CI 0.82, 1.12)]. There were also no differences in any of the secondary outcomes regarding complications of prematurity between the two surfactant groups with the exception of necrotizing enterocolitis. A decrease in the risk of necrotizing enterocolitis was noted in infants who received protein containing synthetic surfactants compared to animal derived surfactant extract [typical RR 0.60 (95% CI 0.42, 0.86)]. However, this was a secondary outcome in both of the primary studies and there was moderate heterogeneity between the studies.

AUTHORS' CONCLUSIONS

In two trials of protein containing synthetic surfactants compared to animal derived surfactant extract, no statistically different clinical differences in death and chronic lung disease were noted. In general, clinical outcomes between the two groups were similar. Further well designed studies of adequate size and power will help confirm and refine these findings.

European consensus guidelines on the management of neonatal respiratory distress syndrome

Despite recent advances in the perinatal management of neonatal respiratory distress syndrome (RDS), controversies still exist. We report the recommendations of a European panel of expert neonatologists who developed consensus guidelines after critical examination of the most up-to-date evidence in 2007. Strong evidence exists for the role of antenatal steroids in RDS prevention, but it is not clear if repeated courses are safe. Many practices involved in preterm neonatal stabilization at birth are not evidence based, including oxygen administration and positive pressure lung inflation, and they may at times be harmful. Surfactant replacement therapy is crucial in management of RDS but the best preparation, optimal dose and timing of administration at different gestations is not always clear. Respiratory support in the form of mechanical ventilation may also be life saving but can cause lung injury, and protocols should be directed to avoiding mechanical ventilation where possible by using nasal continuous positive airways pressure. For babies with RDS to have the best outcome, it is essential that they have optimal supportive care, including maintenance of a normal body temperature, proper fluid management, good nutritional support, management of the ductus arteriosus and support of the circulation to maintain adequate blood pressure.

Protein containing synthetic surfactant versus animal derived surfactant extract for the prevention and treatment of respiratory distress syndrome

BACKGROUND

Respiratory distress syndrome (RDS) is a significant cause of morbidity and mortality in preterm infants. RDS is caused by a deficiency, dysfunction, or inactivation of pulmonary surfactant. Numerous surfactants of either animal extract or synthetic design have been shown to improve outcomes. New surfactant preparations that include peptides or whole proteins that mimic endogenous surfactant protein have recently been developed and tested.

OBJECTIVES

To assess the effect of administration of synthetic surfactant containing surfactant protein mimics compared to animal derived surfactant extract on the risk of mortality, chronic lung disease, and other morbidities associated with prematurity in preterm infants at risk for or having RDS.

SEARCH STRATEGY

Standard search methods of the Cochrane Neonatal Review Group were used. The search included MEDLINE (1966 - May 2007) and the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library) in all languages. In addition, published abstracts of the Society of Pediatric Research were searched electronically. For abstract books that did not include key words, the search was limited to the relevant sections on pulmonary and neonatology. The bibliography cited in each publication was obtained and searched in order to identify additional relevant articles.

SELECTION CRITERIA

Randomized and quasi-randomized controlled clinical trials were considered for this review. Studies that enrolled preterm infants or low birth weight infants at risk for or having RDS who were treated with either a synthetic surfactant containing surfactant protein mimics or an animal-derived surfactant preparation were included for this review. Studies that either attempted to treat or prevent respiratory distress syndrome were included.

DATA COLLECTION AND ANALYSIS

Primary outcome measures, including mortality, chronic lung disease and multiple secondary outcome measures were abstracted by the reviewers. Statistical analysis was performed using Review Manager software. Categorical data was analyzed using relative risk, risk difference, and number needed to treat. 95% confidence intervals reported. A fixed effects model was used for the meta-analysis. Heterogeneity was assessed using the I-squared statistic.

MAIN RESULTS

Two studies were identified that compared protein containing synthetic surfactants to animal derived surfactant preparations. In a meta-analysis of these two studies, infants who received protein containing synthetic surfactant compared to animal derived surfactant extract did not demonstrate significantly different risks of prespecified primary outcomes: mortality at 36 weeks [typical RR 0.81 (95% CI 0.64, 1.03)], chronic lung disease at 36 weeks [typical RR 0.99 (95% CI 0.84, 1.18)], or the combined outcome of mortality or chronic lung disease at 36 weeks [typical RR 0.96 (95% CI 0.82, 1.12)]. There were also no differences in any of the secondary outcomes regarding complications of prematurity between the two surfactant groups with the exception of necrotizing enterocolitis. A decrease in the risk of necrotizing enterocolitis was noted in infants who received protein containing synthetic surfactants compared to animal derived surfactant extract [typical RR 0.60 (95% CI 0.42, 0.86)]. However, this was a secondary outcome in both of the primary studies and there was moderate heterogeneity between the studies.

AUTHORS' CONCLUSIONS

In two trials of protein containing synthetic surfactants compared to animal derived surfactant extract, no statistically different clinical differences in death and chronic lung disease were noted. Further well designed studies of adequate size and power will be needed to confirm and refine these findings.

One-year follow-up of very preterm infants who received lucinactant for prevention of respiratory distress syndrome: results from 2 multicenter randomized, controlled trials

BACKGROUND

The benefits of exogenous surfactants for prevention or treatment of respiratory distress syndrome are well established, but there is a paucity of long-term follow-up data from surfactant-comparison trials.

OBJECTIVE

We sought to determine and compare survival and pulmonary and neurodevelopmental outcomes through 1 year corrected age of preterm infants who received lucinactant and other surfactants in the SELECT (Safety and Effectiveness of Lucinactant Versus Exosurf in a Clinical Trial) and STAR (Surfaxin Therapy Against Respiratory Distress Syndrome) trials individually and, secondarily, from analysis using combined data from these 2 trials.

METHODS

All infants from both trials who were randomly assigned to administration of lucinactant (175 mg/kg), colfosceril palmitate (67.5 mg/kg), beractant (100 mg/kg), or poractant alfa (175 mg/kg) were prospectively followed through 1 year corrected age, at which point masked assessment of outcomes was performed for surviving infants. One-year survival was a key outcome of interest. Other parameters assessed included rates of rehospitalization and respiratory morbidity and gross neurologic status. Data were analyzed by comparing the different surfactants within each trial and, in secondary analysis, combining data from both trials to compare lucinactant versus the animal-derived surfactants (beractant and poractant) used in these trials. Survival rates over time were compared by using the Wilcoxon test for survival through 1 year corrected age and logistic regression for comparison of fixed time points. The latter analyses were performed by using the prespecified approach, where loss to follow-up or withdrawal of consent was imputed as a death, and also using raw data. Other outcomes were analyzed by using the Cochran-Mantel-Haenszel test or logistic regression for categorical data, and analysis of variance on ranks was used for continuous data.

RESULTS

Very few cases were lost to follow-up in either trial (29 of 1546 enrolled in both trials [1.9%]). In the primary analysis of the SELECT trial comparing lucinactant to either colfosceril or beractant, there were no significant differences in the proportion of infants who were alive through 1 year corrected age. Fixed-time-point estimates of mortality at 1 year corrected age imputing loss to follow-up as a death were 28.1% for lucinactant, 31.0% for colfosceril, and 31.0% for beractant. By using raw data without imputing loss to follow-up as a death, mortality estimates at 1 year corrected age were computed to be 26.6%, 29.1%, and 28.3%, respectively. In the primary analysis of the STAR trial, significantly more infants treated with lucinactant were alive through 1 year corrected age compared with those who received poractant alfa. Fixed time estimates of mortality at 1 year corrected age imputing loss to follow-up as a death were 19.4% for lucinactant and 24.2% for poractant. These estimates using raw data that did not impute loss to follow-up as a death were 18.6% and 21.9%, respectively. In the combined analysis, survival through 1 year corrected age was higher for infants in the lucinactant group versus that of the infants in the animal-derived surfactants (beractant and poractant) group. The fixed-time-point estimates of mortality at 1 year corrected age imputing loss to follow-up as a death for lucinactant and animal-derived surfactants were 26.0% and 29.4%, respectively. However, the 1-year-corrected-age estimates using combined raw data were 24.6% for the lucinactant group and 26.7% for the animal-derived surfactant group. The incidence of postdischarge rehospitalizations, total number of rehospitalizations, incidence of respiratory illnesses, and total number of respiratory illnesses were generally similar among those in the treatment groups. Neurologic status at 1 year corrected age was essentially similar between infants who received lucinactant and those who received all other surfactants used in these 2 trials.

CONCLUSIONS

Findings from this 1-year follow-up of both lucinactant trials indicate that this new peptide-based synthetic surfactant is at least as good, if not superior, to animal-derived surfactants for prevention of respiratory distress syndrome and may be a viable alternative to animal-derived products.

Biochemical and pharmacological differences between preparations of exogenous natural surfactant used to treat Respiratory Distress Syndrome: role of the different components in an efficient pulmonary surfactant

The pharmaceutical application of exogenous natural pulmonary surfactant preparations has shown its efficiency in the therapeutical treatment of infants with Respiratory Distress Syndrome. At the same time, the use of these preparations in patients with Acute Respiratory Distress Syndrome, although not still an effective therapy, shows promising results. The analysis of composition, structure and surface activity of some of the different natural surfactant preparations available today for clinical use reveals important differences, a fact that opens horizons in the optimization of new effective formulations in the treatment of the Acute Respiratory Distress Syndrome. The purpose of this review is to carry out an updating of the current models interpreting the role of the main components of pulmonary surfactant as a reference to evaluate the biochemical composition of the preparations of exogenous natural pulmonary surfactant currently in use and their apparent pharmacological effect.

Aerosolized surfactants

PURPOSE OF REVIEW

To present existing data on the potential use of aerosolized surfactants for treatment of neonatal respiratory distress syndrome in the era of noninvasive ventilatory support.

RECENT FINDINGS

Current surfactant therapy requires endotracheal intubation and application of positive pressure ventilation. Instillation of the drug itself can be complicated by 'peridosing adverse events' including, but not limited to, desaturations, bradycardias, changes in blood pressure, drug reflux and even the need for reintubations. Increasing use of noninvasive ventilatory support for neonatal respiratory distress syndrome has motivated clinicians and researchers to look for alternate ways of introducing surfactants to patients. Aerosolized surfactants have been tested in animal models of respiratory distress syndrome. In addition, four small clinical studies have been performed to date. The effectiveness of this form of treatment requires further study, however, which will need to include optimizing the dose of aerosolized surfactant, choosing particle size, developing the best delivery system, and using a surfactant formulation that maintains its activity once aerosolized.

SUMMARY

Aerosolized surfactants for neonatal respiratory distress syndrome may prevent the need for endotracheal intubation. Appropriately designed randomized controlled studies are required to determine if this form of surfactant administration is as effective and safe as tracheal instillation.

Surfactant for respiratory distress syndrome: are there important clinical differences among preparations?

PURPOSE OF REVIEW

Respiratory distress syndrome is the leading cause of mortality and morbidity among infants born prematurely. The disorder arises from the developmental and biochemical abnormalities associated with preterm delivery. The decreased number of type II alveolar pneumocytes results in absent or reduced surfactant production, which leads to alveolar instability and a tendency to collapse during expiration and increased work of breathing necessitating the institution of supplemental oxygen therapy and positive pressure mechanical ventilation.

RECENT FINDINGS

Exogenous surfactant replacement therapy has been shown to be effective in the treatment of neonatal respiratory distress syndrome and has become a standard of care in neonatal intensive care units. A number of controversies still exist over a number of issues, however, such as the comparative effectiveness of one surfactant preparation over another, timing of administration, dosing volumes and short versus long-term benefits. Furthermore, the emergence of a newer generation of synthetic, peptide-containing surfactants has opened a new era in surfactant therapy which may have implications for future practice and research.

SUMMARY

This paper discusses these developments and analyses the effectiveness of surfactant therapy against respiratory distress syndrome by appraising the evidence produced from published trials and systemic reviews.

Long-term outcomes: what should the focus be?

The neonatal intervention trials of the 1980s and early 1990s focused primarily on short-term outcomes. Contemporary clinical trials have recognized the importance of longer-term outcomes but have rarely been powered to achieve that aim. This review discusses important and clinically relevant outcomes that future trials should be powered to address and identifies the challenges facing the neonatal clinical trials community. These challenges include consensus definitions of relevant outcomes that are objective and validated, variability among centers in populations and practices, and the need for predictive surrogate markers of long-term outcomes. Future trials must be designed and powered to address the potential for harm as well as the prospect of benefit.

Animal-derived surfactants versus past and current synthetic surfactants: current status

In this review, the authors assess major outcomes resulting from head-to-head comparison trials of animal-derived surfactants with previous and newer synthetic surfactants and among them. They also pay special attention to issues of study design and quality of the trials reviewed. Animal-derived surfactants that contain surfactant proteins (Survanta, Infasurf, and Curosurf) perform clinically better than Exosurf, a synthetic surfactant containing only phospholipids, primarily in outcomes related to acute management of respiratory distress syndrome (RDS; faster weaning and pneumothorax) but not in overall mortality or incidence of bronchopulmonary dysplasia (BPD). Trials comparing various animal-derived surfactants that provide different amounts of surface protein B (SP-B) or phospholipids have shown minor differences in outcomes related to the management of RDS or none at all. The exception is the suggestion of better survival using a high initial dose of Curosurf when compared with Survanta. This observation is based on analysis of trials of relatively lesser quality that have included a smaller number of infants than other surfactant comparisons, however. Data from recent trials comparing a new-generation synthetic surfactant that contains a peptide mimicking the action of SP-B, Surfaxin, have shown that it performs better than Exosurf (faster weaning and less BPD) and at least as well as the animal-derived surfactants Survanta and Curosurf. The ideal surfactant comparison trial to demonstrate which surfactant is better has yet to be conducted. Future surfactant comparison trials should pay particular attention to study design, be appropriately sized, and include long-term follow-up.

Criteria supporting the study of drugs in the newborn

BACKGROUND

Profound changes in the development and the maturation of neonates' organs and organ systems over variable periods of time potentially place neonates at increased risk and/or at different risks compared with adults or older children on exposure to pharmaceutical agents. Most studies of drugs in neonates focus on pharmacokinetic and pharmacodynamic end points and include insufficient numbers of patients to permit evaluation of safety. Only one fourth to one third of approved drugs have received adequate pediatric study to permit labeling for treatment of all appropriate pediatric populations.

OBJECTIVE

The initial goal of the Newborn Drug Prioritization Group was to develop a reproducible, objective process for evaluating drugs most in need of study in the neonatal population based on a universally acceptable priority ranking. The criteria would be applicable across therapeutic classes and would identify those drugs for which immediate study was most needed.

METHODS

Because the therapeutic requirements of the neonate are unique in comparison to older infants and children, the National Institute of Child Health and Human Development and the US Food and Drug Administration (FDA) developed the Newborn Drug Development Initiative to address the limited study of off-patent drugs in newborns. In March 2003, they convened a meeting of pediatric pharmacologists and pediatric specialists from the FDA, the American Academy of Pediatrics, the National Institutes of Health, and academic institutions to discuss how to increase the study of drugs for the newborn. One of the working groups was charged to develop generic criteria for overall prioritization of drugs for study in newborns. Because resources are limited, and not all drugs identified by the 4 clinically focused working groups can receive study at the same time, a process for priority ranking is necessary.

RESULTS

The panel identified 4 general categories containing different numbers of criteria as important for ranking drugs for priority investigation: (1) the disease and indication, including elements such as the potential for adverse outcomes, frequency in newborns, and level of evidence for treatment of newborns; (2) drug characteristics, including elements such as duration of dosing, lack of age-appropriate formulation, clinically relevant drug-drug and drug-disease interactions, and drug disposition in newborns; (3) feasibility and methodology for newborn studies, including both analytical considerations and clinical end points; and (4) the ethical basis for study, including elements to address benefit or harm due to exposure to the study drug, study methodology, and benefit of the new treatment relative to established standard therapy. Based on these categories, a list of criteria to warrant study of a drug in newborns was developed.

CONCLUSION

A process for judicious use of limited resources to rectify these deficiencies remains an urgent public health need.