Porcine versus bovine surfactant therapy for RDS in preterm neonates: pragmatic meta-analysis and review of physiopathological plausibility of the effects on extra-pulmonary outcomes

Blinding Assessments in Neonatal Ventilation Meta-Analyses: A Systematic Meta-Epidemiological Review

INTRODUCTION

Randomization and blinding are generally important in randomized trials. In neonatology, blinding of ventilation strategies is unfeasible if not impossible and we hypothesized that its importance has been overestimated, while the peculiarities of the neonatal patient and the specific outcomes have not been considered.

METHODS

For this meta-epidemiological review, we searched PubMed and Scopus databases in November 2023. We included all meta-analyses focusing on ventilation, published in past 5 years, and reporting either mortality or bronchopulmonary dysplasia (BPD) as an outcome. We extracted the information about how the authors had analyzed risk of bias and evidence certainty.

RESULTS

We screened 494 abstracts and included 40 meta-analyses. Overall, 13 of the 40 reviews assessed blinding properly. Australian and European authors were most likely to perform correct assessment of the blinding (p = 0.03) and the use of RoB 2.0 tool was also associated with proper assessment (p < 0.001). In multivariate regression, the use of RoB 2.0 was the only factor associated with a proper assessment (Beta 0.57 [95% confidence interval: 0.29-0.99]). GRADE ratings were performed in 25 reviews, and the authors downgraded the evidence certainty due to risk of bias in 19 of these and none of these reviews performed the blinding assessment correctly.

CONCLUSION

In past neonatal evidence syntheses, the role of blinding has been mostly overestimated, which has led to downgrading of evidence certainty. Objective outcomes (such as mortality and BPD) do not need to be downgraded due to lack of blinding, as the knowledge of the received intervention does not influence the outcome assessment.

Impact of Early Surfactant Administration on Ductus Arteriosus Assessed at 24 h in Preterm Neonates Less than 32 Weeks of Gestational Age

BACKGROUND AND OBJECTIVES

The purpose of this study was to investigate whether early surfactant administration affects the status of ductus arteriosus (DA) in preterm infants ≤ 32 weeks of gestational age (GA) within 24 h of birth.

MATERIALS AND METHODS

It is a prospective study conducted from 1 March 2022 to 31 December 2023 in a tertiary academic center. In-born infants ≤ 32 weeks of gestation (n = 88) were enrolled. The study group was further divided into surfactant (n = 44) and non-surfactant (n = 44) subgroups.

RESULTS

A total of 76% of the preterm infants who received surfactant therapy (RRR = 0.839) recorded an increase in Kindler score at 24 h of life (1 - RR = 1 - 0.24 = 76%). Surfactant administration was significantly associated with decreased pre-ductal diastolic pressure (29.9 mmHg vs. 34.8 mmHg, p = 0.0231), post-ductal diastolic pressure (28.7 mmHg vs. 32.2 mmHg, p = 0.0178), pre-ductal MAP (41.6 mmHg vs. 46.5 mmHg, p = 0.0210), and post-ductal MAP (41.0 mmHg vs. 45.3 mmHg, p = 0.0336). There were no significant changes in ductus arteriosus parameters at 24 h of life.

CONCLUSIONS

Early surfactant administration does not affect the status of ductus arteriosus in preterm infants ≤ 32 weeks of gestational age at 24 h of life.

Comparative effectiveness of calfactant and beractant in neonatal respiratory distress syndrome: A systemic review and meta-analysis

INTRODUCTION

Animal derived surfactants are considered to be the standard treatment for neonatal respiratory distress syndrome (NRDS). However, their comparative effectiveness remains inconclusive given the multiple prior studies with inconsistent results. Therefore, we conducted a systematic review and meta analysis to compare the effectiveness of two animal extract surfactants (calfactant and beractant) for the management of NRDS.

METHODS

We searched Pubmed, Scopus, and Google Scholar for studies comparing efficacy of calfactant and beractant for the treatment of NRDS. Mean differences (MD) and risk ratios (RR) with a 95% confidence interval (CI) were calculated using Review Manager.

RESULT

We found no significant difference between calfactnat and beractant groups in the primary outcomes: neonatal mortality before the age of 28 days (RR = 1.19, 95% CI = 0.97-1.46, p = 0.09), mortality before the hospital release (RR = 1.12, 95% Cl = 0.94-1.33, p = 0.22), oxygen requirement at 28 days of age (RR = 0.97, 95% CI = 0.90-1.05, p = 0.52), and death or oxygen need at 36 weeks postmenstrual age (RR = 0.99, 95% CI = 0.91-1.08, p = 0.81). The duration of supplementary oxygen was significantly lower in calfactant users (MD = -4.95, 95% CI = -7.60--2.30, p = 0.0002). Calfactant significantly lowered the duration of hospital stay, risk of pneumothorax and air leak syndrome whereas beractant users had lower risk of intraventricular hemorrhage (Grades 3 and 4).

CONCLUSION

There is no substantial difference in the efficacy of both surfactants in the prophylaxis and treatment of NRDS.

Meta-analysis of Lung Ultrasound Scores for Early Prediction of Bronchopulmonary Dysplasia

RATIONALE

Lung ultrasound scores (LUS) might be useful in monitoring neonates with chronic pulmonary insufficiency of prematurity and in predicting bronchopulmonary dysplasia (BPD). Given their ease of use, accuracy and lack of invasiveness, LUS have been the subject of several recent studies.

OBJECTIVE

We sought to clarify whether LUS provide an accurate and early (within the first two weeks of life) prediction of BPD in preterm infants of gestational age <32weeks.

METHODS

Systematic review and diagnostic accuracy meta-analysis following PRISMA-P, PRISMA and QUADAS guidelines. Studies designed to predict BPD in the first two weeks of life using LUS were selected. A classical LUS (calculated for 6 chest areas) and its extended version (eLUS, 10 chest areas) were tested.

RESULTS

Seven studies (1027 neonates) were meta-analyzed. LUS and eLUS showed good diagnostic accuracy in predicting BPD at 7 and 14 days of life (AUC 0.85-0.87, pooled sensitivity 70-80%, pooled specificity 80-87%). The diagnostic accuracy of LUS and eLUS did not differ at any timepoint (AUC difference always p >0.05). Repeating the analyses without outliers or with moderate-to-severe BPD as outcome yielded similar results. Meta-regressions showed that prenatal steroid prophylaxis and sex were not significant effect confounders.

CONCLUSIONS

LUS are accurate for early prediction of BPD and moderate-to-severe BPD, in an average population of preterm infants <32weeks' gestation. The diagnostic accuracy is similar for LUS and eLUS, so the use of the simpler score should be advocated. Registration. PROSPERO CRD42021233010.

Pulmonary surfactant: a unique biomaterial with life-saving therapeutic applications

Pulmonary surfactant is a complex lipoprotein mixture secreted into the alveolar lumen by type 2 pneumocytes, which is composed by tens of different lipids (approximately 90% of its entire mass) and surfactant proteins (approximately 10% of the mass). It is crucially involved in maintaining lung homeostasis by reducing the values of alveolar liquid surface tension close to zero at end-expiration, thereby avoiding the alveolar collapse, and assembling a chemical and physical barrier against inhaled pathogens. A deficient amount of surfactant or its functional inactivation is directly linked to a wide range of lung pathologies, including the neonatal respiratory distress syndrome. This paper reviews the main biophysical concepts of surfactant activity and its inactivation mechanisms, and describes the past, present and future roles of surfactant replacement therapy, focusing on the exogenous surfactant preparations marketed worldwide and new formulations under development. The closing section describes the pulmonary surfactant in the context of drug delivery. Thanks to its peculiar composition, biocompatibility, and alveolar spreading capability, the surfactant may work not only as a shuttle to the branched anatomy of the lung for other drugs but also as a modulator for their release, opening to innovative therapeutic avenues for the treatment of several respiratory diseases.

LISA/MIST: Complex clinical problems almost never have easy solutions

Over the last 10 years, new techniques to administer surfactant have been promoted, based on their presumed lesser invasiveness and they have been generally called LISA (less invasive surfactant administration). We believe that the clinical potential of LISA techniques is currently overestimated. LISA lacks biological and pathophysiological background justifying its potential benefits. Moreover, LISA has been investigated in clinical trials without previous translational data and these trials are affected by significant flaws. The available data from these trials only allow to conclude that LISA is better than prolonged, unrestricted invasive ventilation with loosely described parameters, a mode of respiratory support that should be anyway avoided in preterm infants. We urge the conduction of high-quality studies to understand how to choose and titrate analgesia/sedation and optimize surfactant administration in preterm neonates. We offer a comprehensive, evidence-based review of the clinical data on LISA, their biases and the lack of physiopathology background.

Surfactant therapies for pediatric and neonatal ARDS: ESPNIC expert consensus opinion for future research steps

Pediatric (PARDS) and neonatal (NARDS) acute respiratory distress syndrome have different age-specific characteristics and definitions. Trials on surfactant for ARDS in children and neonates have been performed well before the PARDS and NARDS definitions and yielded conflicting results. This is mainly due to heterogeneity in study design reflecting historic lack of pathobiology knowledge. We reviewed the available clinical and preclinical data to create an expert consensus aiming to inform future research steps and advance the knowledge in this area. Eight trials investigated the use of surfactant for ARDS in children and ten in neonates, respectively. There were improvements in oxygenation (7/8 trials in children, 7/10 in neonates) and mortality (3/8 trials in children, 1/10 in neonates) improved. Trials were heterogeneous for patients' characteristics, surfactant type and administration strategy. Key pathobiological concepts were missed in study design. Consensus with strong agreement was reached on four statements: 1. There are sufficient preclinical and clinical data to support targeted research on surfactant therapies for PARDS and NARDS. Studies should be performed according to the currently available definitions and considering recent pathobiology knowledge. 2. PARDS and NARDS should be considered as syndromes and should be pre-clinically studied according to key characteristics, such as direct or indirect (primary or secondary) nature, clinical severity, infectious or non-infectious origin or patients' age. 3. Explanatory should be preferred over pragmatic design for future trials on PARDS and NARDS. 4. Different clinical outcomes need to be chosen for PARDS and NARDS, according to the trial phase and design, trigger type, severity class and/or surfactant treatment policy. We advocate for further well-designed preclinical and clinical studies to investigate the use of surfactant for PARDS and NARDS following these principles.

Respiratory distress syndrome in preterm neonates in the era of precision medicine: A modern critical care-based approach

Respiratory distress syndrome (RDS) was recognized to be caused by primary surfactant deficiency almost 70 years ago and continuous positive airway pressure was introduced approximately 50 years ago. Since then, there have been many developments in neonatology; we know many things but others are still controversial. The more we know, the more questions arise. However, this review aims to indicate what is more needed to understand and how should be the modern approach to RDS in the era of precision medicine. The review is divided between new concepts and new tools. We will explain the interaction between steroids, CPAP and surfactant, as well as the surfactant catabolism and the diagnosis of NARDS; lung ultrasound and new tools to optimize CPAP will also be covered. How these concepts are integrated in the author's personal experience is also illustrated.

Molecular and biophysical mechanisms behind the enhancement of lung surfactant function during controlled therapeutic hypothermia

Therapeutic hypothermia (TH) enhances pulmonary surfactant performance in vivo by molecular mechanisms still unknown. Here, the interfacial structure and the composition of lung surfactant films have been analysed in vitro under TH as well as the molecular basis of its improved performance both under physiological and inhibitory conditions. The biophysical activity of a purified porcine surfactant was tested under slow and breathing-like dynamics by constrained drop surfactometry (CDS) and in the captive bubble surfactometer (CBS) at both 33 and 37 °C. Additionally, the temperature-dependent surfactant activity was also analysed upon inhibition by plasma and subsequent restoration by further surfactant supplementation. Interfacial performance was correlated with lateral structure and lipid composition of films made of native surfactant. Lipid/protein mixtures designed as models to mimic different surfactant contexts were also studied. The capability of surfactant to drastically reduce surface tension was enhanced at 33 °C. Larger DPPC-enriched domains and lower percentages of less active lipids were detected in surfactant films exposed to TH-like conditions. Surfactant resistance to plasma inhibition was boosted and restoration therapies were more effective at 33 °C. This may explain the improved respiratory outcomes observed in cooled patients with acute respiratory distress syndrome and opens new opportunities in the treatment of acute lung injury.

Surfactant use in late preterm infants: a survey among Belgian neonatologists

Specific recommendations on surfactant administration in late preterm (LPT) infants with pulmonary disease are lacking. We performed an online-based, nationwide survey amongst all (n = 102) Belgian neonatologists to identify the use of surfactant in LPT infants suffering from several respiratory pathologies. The survey used clearly defined clinical cases and resulted in a 86% response rate. Neonatologists adhere to the 200 mg/kg initial surfactant dosing scheme. Surfactant is widely used in respiratory distress syndrome (70.1%), but there is less unanimity on its use in meconium aspiration syndrome (58.0%), transient tachypnoea of the newborn (30.6%), congenital pneumonia (27.2%) and congenital diaphragmatic hernia (8.6%). Respondents adhere to the European guideline of a timely referral to a newborn intensive care unit (non-invasive ventilation and FiO₂ > 0.30 at 12 h of age), in order to minimise the risk of deterioration.Conclusion: We demonstrate a wide variety in the use of surfactant within LPT infants. The majority of Belgian neonatologists therefore urge for an investment in multi-centre trials on surfactant administration in LPT infants, in order to create an evidence-based practice as well as to reduce the strain on health care budgets.Trial registration: https://clinicaltrials.gov What is Known: • Any late preterm (LPT) infant with respiratory distress needs a timely referral to a neonatal intensive care unit in case of non-invasive ventilation and FiO₂ > 0.30 at 12 h of life, in order to minimise the risk of acute deterioration as well as chronic lung disease. • Any modest increase in morbidity in the sizeable group of LPT infants exerts a significant strain on health care budgets. What is New: • We report the attitudes and opinions of Belgian neonatologists about the use of surfactant in LPT infants suffering from several respiratory diseases. • Our survey demonstrates a significant variability in practice between neonatologists during treatment of respiratory pathologies in LPT infants. This highlights an urgent need for univocal therapeutic lines.

Nebulized versus invasively delivered surfactant therapy for neonatal respiratory distress syndrome: A systematic review and meta-analysis

BACKGROUND

Pulmonary surfactant (PS) is commonly used for the treatment of neonatal respiratory distress syndrome (NRDS), several randomized controlled trials (RCTs) have evaluated the role of nebulized versus invasively delivered PS, yet the results remained inconsistent. Therefore, we aimed to conduct this meta-analysis to evaluate the effects and safety of nebulized versus invasively delivered PS in the treatment of NRDS.

METHODS

We searched PubMed et al databases from inception date to May 15, 2020 for RCTs that compared nebulized vs invasively delivered PS. Two authors independently screened the studies and extracted data from the published articles. Summary odd ratios (OR) or mean differences (MDs) with 95% confidence intervals (CIs) were calculated for each outcome by means of fixed- or random-effects model.

RESULTS

Two RCTs with a total of 95 preterm neonates were identified, with 48 neonates received PS nebulization and 47 neonates undergone invasive PS administration. There was no significant difference in the SpO2 level (MD = -0.44, 95% CI -6.01 to 5.12) and the A/APaO2 level (MD = 0.01, 95% CI -0.02 to 0.05) 1 hour after treatment among 2 groups. But the duration of mechanical ventilation in the nebulization groups was significantly less than that of invasive group (MD = -30.70, 95% CI -41.45 to 19.95).

CONCLUSIONS

Given the limited evidences, the effects and safety of nebulized versus invasively delivered PS still need further verification.

Extrapulmonary Surfactant Therapy: Review of Available Data and Research/Development Issues

Since the discovery of surfactant, a large amount of knowledge has been accumulated about its biology and pharmacology. Surfactant is the cornerstone of neonatal respiratory critical care, but its proteins and phospholipids are produced in various tissues and organs, with possible roles only partially similar to that played in the alveoli. As surfactant research is focused mainly on its respiratory applications, knowledge about the possible role of surfactant in extrapulmonary disorders has never been summarized. Here we aim to comprehensively review the data about surfactant biology and pharmacology in organs other than the lung, especially focusing in the more promising surfactant extrapulmonary roles. We also review any preclinical or clinical data available about the therapeutic use of surfactant in these contexts. We offer a summary of knowledge and research/development milestones, as possible useful guidance for researchers of multidisciplinary background.