Lamellar body counts on gastric aspirates for prediction of respiratory distress syndrome

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

BACKGROUND

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

OBJECTIVES

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

SEARCH METHODS

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

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

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

MAIN RESULTS

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

AUTHORS' CONCLUSIONS

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

Biochemical and Lung Function Test Accuracy for Predicting the Need for Surfactant Therapy in Preterm Infants: A Systematic Review

INTRODUCTION

We evaluate the accuracy of postnatal biochemical and lung function tests performed within 3 h from birth for predicting surfactant need in preterm infants ≤34 weeks' gestation receiving noninvasive respiratory support for respiratory distress syndrome (RDS).

METHODS

We systematically searched MEDLINE, Embase, The Cochrane Library, PROSPERO, and clinicaltrials.gov databases for studies published from 2000 to November 10, 2021, cross-referencing relevant literature and contacting experts. We included diagnostic accuracy studies and systematic reviews of biochemical or lung function tests identifying the need for surfactant in preterm neonates ≤34 weeks' with RDS not intubated at birth. The authors individually assessed the risk of bias following a tailored QUADAS-2 tool.

RESULTS

Eight studies, including 810 infants, met the inclusion criteria. Four tests were included: the click test, the stable microbubble test, the lamellar body count on gastric aspirates, and the forced oscillation technique. The reference standards were transparent criteria for distinguishing the infants according to oxygen requirement, which reflected the current criteria for surfactant therapy. The risk of bias was judged high because of the population selection and exclusion of participants from the analysis. There were no serious concerns regarding blinding and applicability. The individual study sensitivity and specificity range from 0.60 to 1 and from 0.51 to 0.91, respectively. It was not appropriate to combine the accuracy estimates in a meta-analysis because of the heterogeneity of the study characteristics.

CONCLUSIONS

Current evidence is insufficient to recommend biochemical and lung function tests for tailoring surfactant therapy.

Predicting respiratory distress syndrome at birth using a fast test based on spectroscopy of gastric aspirates: 2. Clinical part

AIM

To evaluate the accuracy of our new rapid point-of-care (POC) test for lung maturity. The method as we describe in an accompanying article was developed with the purpose of improving the outcome from respiratory distress syndrome (RDS). The test enables the delivery of surfactant in infants with immature lungs already at birth and ensures that infants with mature lungs are not treated unnecessarily.

METHODS

Fresh gastric aspirate (GAS) was sampled at birth in a cohort of preterm infants with gestational ages ranging between 24 and 31 completed weeks for lung surfactant measurement as lecithin-sphingomyelin ratio (L/S). L/S was prospectively compared with RDS development. The clinical outcome was blinded for the investigators of L/S. The time for analysis was <15 minutes.

RESULTS

GAS was obtained from 72 infants. Forty-four (61%) developed RDS. The cut-off for L/S was 3.05; predicting RDS with a sensitivity of 91% and specificity of 79%.

CONCLUSION

The new improved spectroscopic L/S method of lung maturity on GAS has high sensitivity. The method is designed for use as a POC test at birth, and a spectroscopic prototype has been developed for bedside use. Clinical trials with this new lung maturity test are planned.

Estimation of early life endogenous surfactant pool and CPAP failure in preterm neonates with RDS

Background

It is not known if the endogenous surfactant pool available early in life is associated with the RDS clinical course in preterm neonates treated with CPAP. We aim to clarify the clinical factors affecting surfactant pool in preterm neonates and study its association with CPAP failure.

Methods

Prospective, pragmatic, blind, cohort study. Gastric aspirates were obtained (within the first 6 h of life and before the first feeding) from 125 preterm neonates with RDS. Surfactant pool was measured by postnatal automated lamellar body count based on impedancemetry, without any pre-analytical treatment. A formal respiratory care protocol based on European guidelines was applied. Clinical data and perinatal risk factors influencing RDS severity or lamellar body count were real-time recorded. Investigators performing lamellar body count were blind to the clinical data and LBC was not used in clinical practice.

Results

Multivariate analysis showed gestational age to be the only factor significantly associated with lamellar body count (standardized β:0.233;p = 0.023). Lamellar body count was significantly higher in neonates with CPAP success (43.500 [23.750–93.750]bodies/μL), than in those failing CPAP (20.500 [12.250–49.750] bodies/μL;p = 0.0003).LBC had a moderate reliability to detect CPAP failure (AUC: 0.703 (0.615–0.781);p < 0.0001; best cut-off: ≤30,000 bodies/μL). Upon adjustment for possible confounders, neither lamellar body count, nor its interaction factor with gestational age resulted associated with CPAP failure.

Conclusions

Early postnatal lamellar body count on gastric aspirates in CPAP-treated preterm neonates with RDS is significantly influenced only by gestational age. Lamellar bodies are not associated with CPAP failure. Thus, the endogenous surfactant pool available early in life only has a moderate reliability to predict CPAP failure.

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

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

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

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

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

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

Preventing Continuous Positive Airway Pressure Failure: Evidence-Based and Physiologically Sound Practices from Delivery Room to the Neonatal Intensive Care Unit

Routine use of continuous positive airway pressure (CPAP) to support preterm infants with respiratory distress is an evidenced-based strategy to decrease incidence of bronchopulmonary dysplasia. However, rates of CPAP failure remain unacceptably high in very premature neonates, who are at high risk for developing bronchopulmonary dysplasia. Using the GRADE framework to assess the quality of available evidence, this article reviews strategies aimed at decreasing CPAP failure, starting with delivery room interventions and followed through to system-based efforts in the neonatal intensive care unit. Despite best efforts, some very premature neonates fail CPAP. Also reviewed are predictors of CPAP failure in this vulnerable population.

Rapid test for lung maturity, based on spectroscopy of gastric aspirate, predicted respiratory distress syndrome with high sensitivity

AIM

Respiratory distress syndrome (RDS) is a major cause of mortality and morbidity in premature infants. By the time symptoms appear, it may already be too late to prevent a severe course, with bronchopulmonary dysplasia or mortality. We aimed to develop a rapid test of lung maturity for targeting surfactant supplementation.

METHODS

Concentrations of the most surface-active lung phospholipid dipalmitoylphosphatidylcholine and sphingomyelin in gastric aspirates from premature infants were measured by mass spectrometry and expressed as the lecithin/sphingomyelin ratio (L/S). The same aspirates were analysed with mid-infrared spectroscopy. Subsequently, L/S was measured in gastric aspirates and oropharyngeal secretions from another group of premature infants using spectroscopy and the results were compared with RDS development. The 10-minute analysis required 10 μL of aspirate.

RESULTS

An L/S algorithm was developed based on 89 aspirates. Subsequently, gastric aspirates were sampled in 136 infants of 24-31 weeks of gestation and 61 (45%) developed RDS. The cut-off value of L/S was 2.2, sensitivity was 92%, and specificity was 73%. In 59 cases, the oropharyngeal secretions had less valid L/S than gastric aspirate results.

CONCLUSION

Our rapid test for lung maturity, based on spectroscopy of gastric aspirate, predicted RDS with high sensitivity.

A Noninvasive Surfactant Adsorption Test Predicting the Need for Surfactant Therapy in Preterm Infants Treated with Continuous Positive Airway Pressure

OBJECTIVE

To determine the diagnostic accuracy of the surfactant adsorption test (SAT) as a predictor for the need for surfactant replacement therapy in neonates with respiratory distress syndrome (RDS).

STUDY DESIGN

Amniotic fluid samples were collected from 41 preterm neonates with RDS treated with continuous positive airway pressure (CPAP) and 15 healthy control term neonates. Purified porcine surfactant served as a further control. Lamellar bodies and lung ultrasound score were also measured in a subset of the neonates treated with CPAP. Surfactant was administered according to the European guidelines, and clinical data were collected prospectively. Surfactant activity was measured as adsorption at the air/liquid interface and given in relative fluorescent units (RFU).

RESULTS

Surfactant activity differed among native porcine surfactant (median, 4863 RFU; IQR, 4405-5081 RFU), healthy term neonates (median, 2680 RFU; IQR, 2069-3050 RFU), and preterm neonates with RDS (median, 442 RFU; IQR, 92-920 RFU; P <.0001). The neonates who failed CPAP had lower surfactant activity compared with those who did not fail CPAP (median, 92 RFU; IQR, 0-315 RFU vs 749 RFU; IQR, 360-974 RFU; P = .0002). Differences between groups were more evident beyond 20-30 minutes of fluorescence; the 30-minute time point showed the highest area under the curve (0.84; P <.001) and the best cutoff level (170 RFU; specificity, 72%; sensitivity, 96%) for the prediction of CPAP failure. Surfactant activity at 30 minutes was significantly correlated with lamellar bodies (r = 0.51, P = .006) and lung ultrasound score (r = -0.39, P = .013).

CONCLUSION

This technique has the potential to be developed into a fast, simple-to-interpret clinical test. The SAT can reliably identify preterm infants with subsequent CPAP failure and shows promise as a screening test for surfactant replacement in preterm neonates.

Surfactant and noninvasive ventilation

There is mounting evidence that early continuous positive airway pressure (CPAP) from birth is feasible and safe even in very preterm infants. However, many infants will develop respiratory distress syndrome (RDS) and require surfactant treatment. Combining a noninvasive ventilation approach with a strategy for surfactant administration is important to ensure optimal outcome, but questions remain about the optimal timing, mode of delivery and value of predictive tests for surfactant deficiency. Key findings in this review include the following: (1) a noninvasive ventilation strategy with CPAP from birth has a similar outcome to routine intubation in the delivery room; (2) prophylactic surfactant treatment has no advantage over early CPAP with selective surfactant administration; (3) surfactant during CPAP can be safely administered by rapid intubation-extubation (the INSURE method or via tracheal placement of a thin catheter), and (4) predictive tests for surfactant deficiency are being developed and might in future aid in directing surfactant treatment to infants at risk of developing severe RDS. A strategy for surfactant administration should be part of a noninvasive ventilation approach for preterm infants at risk of developing significant RDS. The different methods for surfactant administration during CPAP are reviewed here.

Surface tension of airway aspirates withdrawn during neonatal resuscitation reflects lung maturity

The indications for treatment of neonates with exogenous pulmonary surfactant are still discussed controversially. Some premature neonates are sufficiently treated by CPAP, others need conventional ventilation and/or surfactant. The available lung maturity tests have limitations. The captive bubble surfactometer (CBS) provides measurement of surface activity from rather small amounts of surfactant. This study aimed to determine surface activity from small volume aspirates of the upper airways of neonates by means of the CBS and to correlate the results with clinical data. Small upper airway aspirates from 159 neonates (gestational age 25-42 weeks) were withdrawn and concentrated 16.7-fold by ultracentrifugation and resuspension in saline. Surface activities after 5 min of adsorption were determined in the CBS and correlated to the perinatal data (e.g., gestational age, birth weight, gender), airway interventions (like CPAP, conventional ventilation) and surfactant treatment. Additionally, 27 samples were analyzed for surfactant specific phosphatidylcholine concentrations by using electrospray ionization tandem mass-spectroscopy. Surface activities show a significant correlation to gestational age, birth weight, and the need for airway interventions. Comparing the need for airway interventions versus surface activity, a receiver operating characteristic calculated a sensitivity of 0.77 and a specificity of 0.72 at a "cut off" of 44 mN/m. Surface activity correlates significantly with the phosphatidylcholine concentrations and the latter one correlates with the gestational age. Determination of surface activity from upper airway aspirates is feasible. Further clinical studies are needed to prove the predictive value of the method.

Morbidity and mortality in preterm neonates with patent ductus arteriosus on day 3

OBJECTIVE

To assess the association between a patent ductus arteriosus (PDA) on day 3 of life and severe morbidity and mortality.

DESIGN

Cohort study.

SETTING

Neonatal Intensive Care Unit, Aarhus University Hospital, Denmark.

PATIENTS

All neonates with a gestational age less than 32 weeks admitted from 2010 to 2012.

INTERVENTIONS

All neonates (n=183) were routinely screened with echocardiography for PDA on day 3 of life. Information on baseline characteristics and outcome was collected by structured coding sheets and medical records.

MAIN OUTCOME MEASURES

The association among PDA diameter and pulmonary haemorrhage, intraventricular haemorrhage (IVH), necrotising enterocolitis, bronchopulmonary dysplasia (BPD), death, and the composite outcome of death or severe morbidity was assessed.

RESULTS

In neonates, born prior to 28 gestational weeks, a PDA on day 3 of life was associated with a threefold increase in odds of death or severe morbidity compared with neonates without PDA (OR=3.4; CI 1.1 to 11). The odds were highest in neonates with a large PDA (diameter ≥1.5 mm). Neonates with a large PDA were also found to have increased odds of IVH (OR 4.2; CI 1.3 to 14) and BPD (OR 3.7; CI 1.0 to 14) compared with neonates with no PDA.

CONCLUSIONS

In neonates born with a gestational age below 28 weeks the presence of a PDA on day 3 of life was associated with adverse outcome; this association was even more pronounced with a large PDA. Thus, early echocardiography may facilitate the identification of neonates suitable for a targeted approach to intervention in future randomised controlled trials.

Early surfactant guided by lamellar body counts on gastric aspirate in very preterm infants

BACKGROUND

We have developed a rapid method, based on lamellar body counts (LBC) on gastric aspirate, for identifying newborns who will develop respiratory distress syndrome with a need for surfactant supplementation.

OBJECTIVE

We set out to test whether it was possible to improve the outcome when used in a clinical trial.

METHODS

We randomly assigned 380 infants born at 24-29 weeks' gestation and supported with nasal continuous positive airway pressure (nCPAP) to receive surfactant guided either by LBC (intervention group) or increasing need for oxygen (control group). The primary outcome was mechanical ventilation or death within 5 days. Secondary outcomes included need for oxygen expressed by arterial to alveolar oxygen tension ratio (a/APO2) at the age of 6 h and need for oxygen at day 28.

RESULTS

The primary outcomes were equal (25%) in the two groups. The intervention group had higher a/APO2 than the control group at 6 h, median 0.64 versus 0.52 (p < 0.01), and the subgroup with gestational age 26-29 weeks needed fewer days of oxygen supplementation than the controls, median 2 vs. 9 days (p = 0.01), and fewer infants needed oxygen at day 28 (p = 0.04). Furthermore, there was a tendency in the intervention group towards a shorter duration of nCPAP. Too little or viscose aspirate in 23% of the cases was a limitation of the method.

CONCLUSION

Using LBC test as indicator of lung maturity and early surfactant therapy in very preterm newborns, it is possible to reduce the need for oxygen supplementation.

Initial respiratory support of preterm infants: the role of CPAP, the INSURE method, and noninvasive ventilation

This article explores the potential benefits and risks for the various approaches to the initial respiratory management of preterm infants. The authors focus on the evidence for the increasingly used strategies of initial respiratory support of preterm infants with continuous positive airway pressure (CPAP) beginning in the delivery room or very early in the hospital course and blended strategies involving the early administration of surfactant replacement followed by immediate extubation and stabilization on CPAP. Where possible, the evidence referenced in this review comes from individual randomized controlled trials or meta-analyses of those trials.

RDS--CPAP or surfactant or both

There is mounting evidence that early continuous positive airway pressure (CPAP) from birth is feasible and safe even in very preterm infants. However, many infants will develop respiratory distress syndrome (RDS) and require surfactant treatment. Combining a non-invasive ventilation approach with a strategy for surfactant administration is important, but questions remain about the optimal timing, mode of delivery and the value of predictive tests for surfactant deficiency.

CONCLUSION

Early CPAP in very preterm infants is as safe as routine intubation in the delivery room. However, a strategy for surfactant administration should be part of a non-invasive ventilation approach for those infants at risk of developing significant RDS.