Surfactant Therapy for Meconium Aspiration Syndrome

Neonatal surfactant therapy beyond respiratory distress syndrome

Whilst exogenous surfactant therapy is central to the management of newborn infants with respiratory distress syndrome, its use in other neonatal lung diseases remains inconsistent and controversial. Here we discuss the evidence and experience in relation to surfactant therapy in newborns with other lung conditions in which surfactant may be deficient or dysfunctional, including meconium aspiration syndrome, pneumonia, congenital diaphragmatic hernia and pulmonary haemorrhage. We find that, for all of these diseases, administration of exogenous surfactant as bolus therapy is frequently associated with transient improvement in oxygenation, likely related to temporary mitigation of surfactant inhibition in the airspaces. However, for none of them is there a lasting clinical benefit of surfactant therapy. By virtue of interrupting disease pathogenesis, lavage therapy with dilute surfactant in MAS offers the greatest possibility of a more pronounced therapeutic effect, but this has yet to be definitively proven. Lavage therapy also involves a greater degree of procedural risk.

Meconium Aspiration Syndrome: A Narrative Review

Meconium aspiration syndrome is a clinical condition characterized by respiratory failure occurring in neonates born through meconium-stained amniotic fluid. Worldwide, the incidence has declined in developed countries thanks to improved obstetric practices and perinatal care while challenges persist in developing countries. Despite the improved survival rate over the last decades, long-term morbidity among survivors remains a major concern. Since the 1960s, relevant changes have occurred in the perinatal and postnatal management of such patients but the most appropriate approach is still a matter of debate. This review offers an updated overview of the epidemiology, etiopathogenesis, diagnosis, management and prognosis of infants with meconium aspiration syndrome.

Lung Lavage with Dilute Surfactant vs. Bolus Surfactant for Meconium Aspiration Syndrome

OBJECTIVE

To compare the effectiveness of lung lavage with surfactant vs. bolus surfactant treatment in meconium aspiration syndrome (MAS).

PATIENTS AND METHODS

This randomized controlled trial included newborns ventilated with MAS. In lavage group (n = 17) 30 ml/kg of diluted porcine surfactant was instilled into the lung. In bolus group (n = 16) porcine surfactant (100 mg/kg) was administered as bolus. Respiratory outcomes and mortality were compared between groups.

RESULTS

Duration of respiratory support was found to be similar between lavage and bolus groups (3 vs. 3.5 days, p = 0.36). Death or requirement for extracorporeal membrane oxygenation (ECMO) was 12% vs. 6%; respectively (RR: 2, 95% CI 0.16-24.48; p = 1.0). Duration of oxygen therapy, high-frequency ventilation or inhaled nitric oxide requirement did not differ among the groups.

CONCLUSION

Lung lavage did not show any advantage over bolus therapy on duration of respiratory support. The incidence of pneumothorax and surfactant re-administration decreased nonsignificantly in lavage group.

CLINICAL TRIAL REGISTRATION

We registered the trial to ClinicalTrials.gov (http://clinicaltrials.gov) under identifier NCT02041546.

REGISTRY NAME

Lung Lavage With Dilute Poractant Alfa for Meconium Aspiration Syndrome.

Morphologic Damage of Rat Alveolar Epithelial Type II Cells Induced by Bile Acids Could Be Ameliorated by Farnesoid X Receptor Inhibitor Z-Guggulsterone In Vitro

Objective. To determine whether bile acids (BAs) affect respiratory functions through the farnesoid X receptor (FXR) expressed in the lungs and to explore the possible mechanisms of BAs-induced respiratory disorder. Methods. Primary cultured alveolar epithelial type II cells (AECIIs) of rat were treated with different concentrations of chenodeoxycholic acid (CDCA) in the presence or absence of FXR inhibitor Z-guggulsterone (GS). Then, expression of FXR in nuclei of AECIIs was assessed by immunofluorescence microscopy. And ultrastructural changes of the cells were observed under transmission electron microscope and analyzed by Image-Pro Plus software. Results. Morphologic damage of AECIIs was exhibited in high BAs group in vitro, with high-level expression of FXR, while FXR inhibitor GS could attenuate the cytotoxicity of BAs to AECIIs. Conclusions. FXR expression was related to the morphologic damage of AECIIs induced by BAs, thus influencing respiratory functions.

Acute Neonatal Respiratory Failure

Acute respiratory failure requiring assisted ventilation is one of the most common reasons for admission to the neonatal intensive care unit. Respiratory failure is the inability to maintain either normal delivery of oxygen to the tissues or normal removal of carbon dioxide from the tissues. It occurs when there is an imbalance between the respiratory workload and ventilatory strength and endurance. Definitions are somewhat arbitrary but suggested laboratory criteria for respiratory failure include two or more of the following: PaCO₂ > 60 mmHg, PaO₂ < 50 mmHg or O₂ saturation <80 % with an FiO₂ of 1.0 and pH < 7.25 (Wen et al. 2004).

In vivo effect of pneumonia on surfactant disaturated-phosphatidylcholine kinetics in newborn infants

Background

Bacterial pneumonia in newborns often leads to surfactant deficiency or dysfunction, as surfactant is inactivated or its production/turnover impaired. No data are available in vivo in humans on the mechanism of surfactant depletion in neonatal pneumonia. We studied the kinetics of surfactant's major component, disaturated-phosphatidylcholine (DSPC), in neonatal pneumonia, and we compared our findings with those obtained from control newborn lungs.

Methods

We studied thirty-one term or near-term newborns (gestational age 39.7±1.7 weeks, birth weight 3185±529 g) requiring mechanical ventilation. Fifteen newborns had pneumonia, while 16 newborns were on mechanical ventilation but had no lung disease. Infants received an intratracheal dose of ¹³C labeled dipalmitoyl-phosphatidylcholine at the study start. We measured the amount and the isotopic enrichment of DSPC-palmitate from serial tracheal aspirates by gas chromatography and gas chromatography-mass spectrometry, respectively, and we calculated the DSPC half-life (HL) and pool size (PS) from the isotopic enrichment curves of surfactant DSPC-palmitate.

Results

The mean DSPC amount obtained from all tracheal aspirates did not differ between the two groups. DSPC HL was 12.7 (6.5–20.2) h and 25.6 (17.9–60.6) h in infants with pneumonia compared with control infants (p = 0.003). DSPC PS was 14.1 (6.6–30.9) mg/kg in infants with pneumonia and 34.1 (25.6–65.0) mg/kg in controls, p = 0.042. Myeloperoxidase (MPO) activity, as a marker of lung inflammation, was 1322 (531–2821) mU/ml of Epithelial Lining Fluid (ELF) and 371(174–1080) mU/ml ELF in infants with pneumonia and in controls, p = 0.047. In infants with pneumonia, DSPC PS and HL significantly and inversely correlated with mean Oxygenation Index (OI) during the study (DSPC PS vs. OI R = −0.710, p = 0.004 and HL vs. OI R = −0.525, p = 0.044, respectively).

Conclusions

We demonstrated for the first time in vivo in humans that DSPC HL and PS were markedly impaired in neonatal pneumonia and that they inversely correlated with the degree of respiratory failure.

Budesonide added to modified porcine surfactant Curosurf may additionally improve the lung functions in meconium aspiration syndrome

Severe meconium aspiration syndrome (MAS) in newborns is often treated by exogenous surfactant. Because its efficacy is reduced by meconium-induced inflammation, glucocorticoid budesonide was added into surfactant preparation Curosurf to enhance efficacy of the surfactant therapy in experimental model of MAS. Oxygen-ventilated rabbits were intratracheally given meconium (25 mg/ml, 4 ml/kg) to induce respiratory failure. Thirty minutes later, animals were treated by intratracheal budesonide (0.25 mg/kg) or surfactant lung lavage (10 ml/kg, 5 mg phospholipids/ml) repeated twice, followed by undiluted Curosurf (100 mg phospholipids/kg) or by the above mentioned surfactant treatment with the last surfactant dose fortified with budesonide (0.25 mg/kg) or were untreated. Animals were ventilated for additional 5 hours and respiratory parameters were measured regularly. After sacrificing animals, wet-dry lung weight ratio was evaluated and plasma levels of interleukins (IL)-1beta, -6, -8, and TNF-alpha were measured by ELISA method. Efficacy of the given therapies to enhance lung functions and to diminish lung edema formation and inflammation increased from budesonide-only and surfactant-only therapy to surfactant+budesonide therapy. Combined therapy improved gas exchange from 30 min of administration, and showed a longer-lasting effect than surfactant-only therapy. In conclusions, budesonide additionally improved the effects of exogenous surfactant in experimental MAS.

Effects of Natural versus Synthetic Surfactant with SP-B and SP-C Analogs in a Porcine Model of Meconium Aspiration Syndrome

BACKGROUND

Meconium displaces surfactant from the alveolar surface and inhibits its function. The development of active synthetic surfactants is complicated, especially to synthesize the hydrophobic surfactant proteins SP-B and SP-C. A synthetic surfactant, CHF5633 containing SP-B and SP-C analogs, has been designed to act similarly to the natural surfactant poractant alfa.

OBJECTIVE

To test the resistance to meconium inactivation of CHF5633 compared to poractant alfa. Secondary outcome measurements were respiratory and inflammatory parameters.

METHODS

Twenty-six newborn pigs, bodyweight 1.4-2.0 kg were randomized to receive either poractant alfa or CHF5633. After anesthesia, surgery and final stabilization, meconium was instilled endotracheally followed by surfactant. Bronchial lavage fluid was obtained before intervention and every second hour. Respiratory parameters were registered and blood samples drawn before intervention and every hour.

RESULTS

Surfactant was inactivated in both groups 6 h after meconium instillation, but CHF5633 was more resistant than poractant alfa in terms of lipid peroxidation. Respiratory parameters were similar in both groups. Inflammatory and hemostatic parameters differed between groups, suggesting that the surfactants may play different roles in the meconium-induced inflammatory process. Due to the differential effects and complex pattern observed, the data do not indicate that one of the surfactants was superior with respect to inflammatory and hemostatic responses.

CONCLUSION

This study indicates that CHF5633 is as efficient as poractant alfa in experimental meconium aspiration syndrome.

Use of therapeutic surfactant lavage in a preterm infant with massive pulmonary hemorrhage

We report a case of a premature infant presenting with recurrent pulmonary hemorrhage in which we performed a therapeutic lavage with diluted surfactant after an acute episode of bleeding with severe intractable hypoxemia. Repeated small aliquots of diluted surfactant (10×2 mL) allowed rapid improvement in oxygenation and reduction of required mean airway pressures during high frequency oscillatory ventilation. This observation may suggest that surfactant lavage could be beneficial in massive pulmonary hemorrhage in infants. A randomized controlled trial might be needed to clarify the potential benefit of this therapeutic intervention on outcome of infants suffering from this life-threatening complication.

Comparative effects of bronchoalveolar lavage with saline, surfactant, or perfluorocarbon in experimental meconium aspiration syndrome

OBJECTIVE

Today, in meconium aspiration syndrome, treatment focuses on bronchoalveolar lavage, because it removes meconium and proinflammatory factors from airways. This technique might be more effective if different solutions were used such as saline solution, a protein-free surfactant, or a perfluorocarbon, because these would be less inhibited by meconium proteins.

SETTING

Pulmonary physiology research unit, Cruces Hospital.

DESIGN

Prospective, randomized study.

SUBJECTS

We studied 24 lambs (<6 days) on mechanical ventilation for 180 mins. Catheters were placed and femoral and pulmonary arteries pressures registered (systemic and pulmonary arterial pressures).

INTERVENTIONS

Lambs were instilled with 20% meconium (3-5 mL/Kg) and were randomly assigned to one of the following groups (n = 6): control: only continuous mechanical ventilation; saline bronchoalveolar lavage: bronchoalveolar lavage with 30 mL/kg of saline solution; dilute surfactant bronchoalveolar lavage: bronchoalveolar lavage with 32 mL/kg of diluted surfactant (lucinactant, 10 mg/mL); or perfluorocarbon bronchoalveolar lavage: bronchoalveolar lavage with 30 mL/kg of perfluorocarbon.

MEASUREMENTS AND MAIN RESULTS

Blood gases, cardiovascular parameters, and pulmonary mechanics were assessed. Meconium instillation produced severe hypoxia, hypercapnia, acidosis, and pulmonary hypertension with impairment of pulmonary mechanics (p < .05). Lung lavage with dilute surfactant resulted in the resolution of pulmonary hypertension as well as better gas exchange and pulmonary mechanics than the control group (p < .05). Bronchoalveolar lavage with perfluorocarbon produced a transient improvement in gas exchange and ventilatory indices in comparison with control and saline bronchoalveolar lavage groups.

CONCLUSIONS

In lambs with meconium aspiration syndrome, bronchoalveolar lavage with diluted lucinactant is an effective therapy producing significant improvements in gas exchange, pulmonary hypertension, and pulmonary mechanics. In addition, bronchoalveolar lavage with perfluorocarbon appears to confer some advantages over lavage with equal volumes of saline or no lavage.

Respiratory support in meconium aspiration syndrome: a practical guide

Meconium aspiration syndrome (MAS) is a complex respiratory disease of the term and near-term neonate. Inhalation of meconium causes airway obstruction, atelectasis, epithelial injury, surfactant inhibition, and pulmonary hypertension, the chief clinical manifestations of which are hypoxaemia and poor lung compliance. Supplemental oxygen is the mainstay of therapy for MAS, with around one-third of infants requiring intubation and mechanical ventilation. For those ventilated, high ventilator pressures, as well as a relatively long inspiratory time and slow ventilator rate, may be necessary to achieve adequate oxygenation. High-frequency ventilation may offer a benefit in infants with refractory hypoxaemia and/or gas trapping. Inhaled nitric oxide is effective in those with pulmonary hypertension, and other adjunctive therapies, including surfactant administration and lung lavage, should be considered in selected cases. With judicious use of available modes of ventilation and adjunctive therapies, infants with even the most severe MAS can usually be supported through the disease, with an acceptably low risk of short- and long-term morbidities.

Surfactant for bacterial pneumonia in late preterm and term infants

BACKGROUND

Pulmonary surfactant is an important part of the host defence against respiratory infections. Bacterial pneumonia in late preterm or term newborn infants often leads to surfactant deficiency or dysfunction, as surfactant is either inactivated or peroxidated. Studies of animal models of pneumonia and clinical case reports suggest that exogenous surfactant might be beneficial to infants with bacterial pneumonia.

OBJECTIVES

To assess the effect of exogenous surfactant treatment on mortality and pulmonary complications in infants with bacterial pneumonia.

SEARCH METHODS

We used standard Cochrane Collaboration methodology to conduct our search of databases. We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 6); MEDLINE (accessed via Ovid SP June 2011); EMBASE (via Ovid SP 1980 to June 2011); and CINAHL Plus (accessed via EBSCOHost June 2011).

SELECTION CRITERIA

We limited our search to randomised and quasi-randomised trials of surfactant replacement therapy in infants > 35 weeks gestation with bacterial pneumonia in the first 28 days of life. The primary outcome measures were death, time to resolution of pneumonia, incidence of chronic lung disease, pneumothoraces and pulmonary haemorrhage.

DATA COLLECTION AND ANALYSIS

We assessed all studies with predefined criteria as to whether they were eligible for inclusion. We extracted data using RevMan 5 (RevMan 2011). We used the standard Cochrane Collaboration methodology for data collection and analysis to assess risk of bias, heterogeneity, treatment effect, missing data and reporting bias where appropriate.

MAIN RESULTS

We did not identify any studies that met our inclusion criteria.

AUTHORS' CONCLUSIONS

There is no evidence from randomised controlled trials (RCTs) to support or refute the efficacy of surfactant in near-term and term infants with proven or suspected bacterial pneumonia. RCTs are still required to answer this question.

Surfactant lavage therapy for meconium aspiration syndrome: a systematic review and meta-analysis

BACKGROUND

Lung lavage with diluted surfactant has emerged as an innovative treatment for meconium aspiration syndrome (MAS). However, the treatment effect has not yet been fully established.

OBJECTIVE

To investigate the effects of surfactant lavage therapy for MAS by a systematic meta-analysis.

METHODS

Relevant studies were identified by database searches in MEDLINE (from 1950), EMBASE (from 1980), and CENTRAL, up to June 2010, and by additional hand searches. Meta-analyses were separately conducted for randomized controlled trials (RCTs) and non-randomized controlled studies (NRSs). Risk of bias was assessed and clinical as well as statistical heterogeneities were also investigated in explaining the potential bias.

RESULTS

Two RCTs (87 patients) and eight NRSs (178 patients) were identified. From the results of the meta-analysis of RCTs, surfactant lavage significantly decreased death or the need for extracorporeal membrane oxygenation (RR 0.34, 95% CI 0.11, 0.99). An interventional benefit was indicated for other outcomes, although it was not statistically significant based only on the two RCTs. Results from the analysis of outcomes from NRSs are consistent with those from RCTs and demonstrated a beneficial effect, which could be considered as supporting evidence.

CONCLUSIONS

Lung lavage with diluted surfactant appeared to improve the clinical outcome in infants with MAS. Given that less than 100 infants were included in the two RCTs, the findings of this study may still be regarded as insufficient evidence. Further research will be needed to confirm the benefit as well as to refine the lavage technique.

Comparative study of clinical pulmonary surfactants using atomic force microscopy

Clinical pulmonary surfactant is routinely used to treat premature newborns with respiratory distress syndrome, and has shown great potential in alleviating a number of neonatal and adult respiratory diseases. Despite extensive study of chemical composition, surface activity, and clinical performance of various surfactant preparations, a direct comparison of surfactant films is still lacking. In this study, we use atomic force microscopy to characterize and compare four animal-derived clinical surfactants currently used throughout the world, i.e., Survanta, Curosurf, Infasurf and BLES. These modified-natural surfactants are further compared to dipalmitoyl phosphatidylcholine (DPPC), a synthetic model surfactant of DPPC:palmitoyl-oleoyl phosphatidylglycerol (POPG) (7:3), and endogenous bovine natural surfactant. Atomic force microscopy reveals significant differences in the lateral structure and molecular organization of these surfactant preparations. These differences are discussed in terms of DPPC and cholesterol contents. We conclude that all animal-derived clinical surfactants assume a similar structure of multilayers of fluid phospholipids closely attached to an interfacial monolayer enriched in DPPC, at physiologically relevant surface pressures. This study provides the first comprehensive survey of the lateral structure of clinical surfactants at various surface pressures. It may have clinical implications on future application and development of surfactant preparations.

Randomized controlled trial of lung lavage with dilute surfactant for meconium aspiration syndrome

OBJECTIVE

To evaluate whether lung lavage with surfactant changes the duration of mechanical respiratory support or other outcomes in meconium aspiration syndrome (MAS).

STUDY DESIGN

We conducted a randomized controlled trial that enrolled ventilated infants with MAS. Infants randomized to lavage received two 15-mL/kg aliquots of dilute bovine surfactant instilled into, and recovered from, the lung. Control subjects received standard care, which in both groups included high frequency ventilation, nitric oxide, and, where available, extracorporeal membrane oxygenation (ECMO).

RESULTS

Sixty-six infants were randomized, with one ineligible infant excluded from analysis. Median duration of respiratory support was similar in infants who underwent lavage and control subjects (5.5 versus 6.0 days, P = .77). Requirement for high frequency ventilation and nitric oxide did not differ between the groups. Fewer infants who underwent lavage died or required ECMO: 10% (3/30) compared with 31% (11/35) in the control group (odds ratio, 0.24; 95% confidence interval, 0.060-0.97). Lavage transiently reduced oxygen saturation without substantial heart rate or blood pressure alterations. Mean airway pressure was more rapidly weaned in the lavage group after randomization.

CONCLUSION

Lung lavage with dilute surfactant does not alter duration of respiratory support, but may reduce mortality, especially in units not offering ECMO.

Influence of serum protein and albumin addition on the structure and activity of an exogenous pulmonary surfactant

The comparative analysis of the deleterious action of albumin and total serum proteins (SP) might help to understand the nature of the interaction surfactant--SP. This study evaluated the effects of serum proteins and albumin on bulk shear viscosity, surface tension, surface area reduction, and the ratio between the light and heavy subtypes of surfactant suspensions. Our results showed a correlation between the bulk viscosity and aggregation degree of surfactant suspensions. The addition of albumin or SP induced the transformation from the heavy to the light subtype, reducing the viscosity. SP caused disaggregation and inactivation, whereas albumin caused only disaggregation without loss of surface activity. When SP were removed, the heavy fraction obtained recovered its surface activity. We conclude that the disaggregation may not be the primary cause for the loss of surface activity. Surfactant inactivation by a serum component, different from albumin, would be probably due to a physical interaction, a phenomenon that is reversed when SP are removed.

Effective lavage volume of diluted surfactant improves the outcome of meconium aspiration syndrome in newborn piglets

Meconium aspiration syndrome (MAS) is one of the top causes of severe respiratory failure in neonates. This study was designed to investigate the effective volume of therapeutic bronchoalveolar lavage (BAL) with diluted surfactant in the treatment of MAS in newborn piglets. Human meconium was instilled in 24 piglets to induce MAS, and the piglets were randomly divided into four groups: 1) control, no lavage; 2) lavage-10, BAL with diluted surfactant (5 mg/mL, Survanta) 10 mL/kg in two aliquots; 3) lavage-20, 20 mL/kg in two aliquots; 4) lavage-30, 30 mL/kg in two aliquots. Cardiopulmonary parameters were monitored, and the lung tissue was histologically examined after experiments. The changes in oxygenation and lung compliance of lavage-20 and lavage-30 groups were significantly better than control and lavage-10 groups (p < 0.05), but there was no significant difference between lavage-20 and lavage-30 groups. The lung injury scores were significantly lower in the dependent site of lavage-20 and lavage-30 groups than the other two groups. In conclusion, using 20 mL/kg diluted surfactant in two aliquots to perform therapeutic BAL was as effective as 30 mL/kg in improving the pathophysiological outcomes in MAS and may warrant consideration clinically in treating MAS.

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.

Albumin lavage does not improve the outcome of meconium aspiration syndrome

OBJECTIVE

Meconium aspiration syndrome is still a serious condition with high mortality and morbidity. No specific treatment is yet available, although surfactant is known to reduce the need for extracorporeal membrane oxygenation and surfactant lavage has shown promising results in animal studies. Our group has previously shown reduced oxygenation index in an experimental model of meconium aspiration syndrome in newborn pigs when mixing albumin with meconium before endotracheal instillation. Lung compliance increased when albumin was instilled after meconium as a rescue. The aim of this study was to combine the effect of albumin and lavage.

METHODS

Sixteen newborn pigs (six in the meconium-albumin group, six in the meconium group, and four control animals) were anesthetized and tracheotomized. Meconium 4 mL/kg was instilled endotracheally. After five minutes, albumin 15 mL/kg was instilled in the meconium-albumin group followed by endotracheal suctioning. The observation time was six hours. Respiratory and hemodynamic parameters were measured. The terminal complement complex and proinflammatory cytokines were analyzed in plasma.

RESULTS

Oxygenation index, ventilatory index, and the terminal complement complex (sC5b-9) increased significantly in both groups, but significantly more in the meconium-albumin group. Compliance decreased, but significantly more in the meconium-albumin group. The terminal sC5b-9 complex increased in both groups, but significantly more in the meconium-albumin group. Tumor necrosis factor-alpha, interleukin (IL)- 1beta, and IL-6 increased significantly in both groups.

CONCLUSION

Albumin-lavage did not improve the outcome of experimental meconium aspiration syndrome.

Bronchoalveolar lavage with pulmonary surfactant/dextran mixture improves meconium clearance and lung functions in experimental meconium aspiration syndrome

Surfactant lung lavage is a promising approach in the treatment of meconium aspiration syndrome (MAS). We hypothesise that the enrichment of modified natural surfactant with dextran will enhance meconium clearance from the airspaces during lung lavage and improve lung function in experimental MAS. Human meconium (30 mg/ml; 4 ml/kg) was instilled into the tracheal cannula of anaesthetised and paralysed adult rabbits to induce respiratory failure. The animals were then lavaged with saline (Sal), surfactant without (Surf) and with dextran (Surf+dex). Lung lavage (10 ml/kg in three portions) was performed with diluted surfactant (Curosurf, 10 mg/ml, 100 mg/kg) without or with dextran (3 mg/mg of surfactant phospholipids) or saline and the animals were conventionally ventilated with 100% O(2) for an additional hour. Lung functions were measured prior to and after meconium instillation, and 10, 30 and 60 min after lavage. The recovery of meconium in bronchoalveolar lavage (BAL) fluid was quantified. More meconium solids was recovered in the surfactant-lavaged than in the saline-lavaged groups (Surf: 12.4 +/- 3.9% and Surf+dex: 17.5 +/- 3.5% vs. Sal: 4.8 +/- 1.0%; both P < 0.01). Moreover, more meconium solids was obtained by Curosurf/dextran than by Curosurf-only lavage (P < 0.05). In the Surf group, the values for PaO(2)/FiO(2) were significantly higher than in the controls (at 60 min: 24.5 +/- 4.2 kPa vs.9.1 +/- 2.2 kPa, P < 0.01). An additional increase in oxygenation was seen in the Surf+dex group (at 60 min: 34.2 +/- 8.1 kPa, P vs. Surf group <0.01). The lung-thorax compliance was higher in the Surf+dex group in comparison with the Sal and Surf groups (at 60 min: 9.6 +/- 0.9 vs.7.6 +/- 1.2, P < 0.01 and 8.0 +/- 0.7 ml/kPa/kg, P < 0.05). The enrichment of Curosurf with dextran improves meconium clearance and lung functions in surfactant-lavaged rabbits with meconium aspiration.

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.

Therapeutic lung lavage with diluted surfactant in neonates with severe meconium aspiration syndrome

Meconium aspiration syndrome (MAS) may result in considerable morbidity and mortality in newborn infants. The current standard treatment is still in need of improvement for the most severe patients. We report 3 cases with devastating MAS that was successfully treated with therapeutic lung lavage. These cases were all delivered in local obstetrics clinics or hospitals with meconium-stained amniotic fluid and non-vigorous appearance at birth. However, no endotracheal suction was performed when they were born. All of them suffered from severe hypoxia and unstable vital signs despite there being high ventilatory settings when they were transferred to the tertiary medical center. Therapeutic lung lavage with diluted surfactant (Survanta, 5 mg/mL, 30 mL/kg in 2 aliquots) was performed within 24 hours of age. Bloody fluid (about 40-50% of total lavage amount) was recovered in all 3 cases. Although brief desaturation and bradycardia were observed during the procedures, 2 of them tolerated the procedures well and improved soon after lavage. The other patient received lung lavage in a relatively unstable condition and needed chest tapping to relieve bilateral pleural effusion. Their respiratory condition improved after the procedures, and they were all discharged within 1 month without major respiratory complications. These successful experiences are compatible with previous animal studies and other case reports with different lavage protocols. We conclude that therapeutic lung lavage may improve the outcome in newborn infants with severe MAS, and there were no significant adverse side effects observed. Before performing lung lavage, stabilization and optimal support may prevent unexpected results during and after lavage.

What's new in surfactant? A clinical view on recent developments in neonatology and paediatrics

Surfactant therapy has significantly changed clinical practice in neonatology over the last 25 years. Recent trials in infants with respiratory distress syndrome (RDS) have not shown superiority of any natural surfactant over another. Advancements in the development of synthetic surfactants are promising, yet to date none has been shown to be superior to natural preparations. Ideally, surfactant would be administered without requiring mechanical ventilation. An increasing number of studies investigate the roles of alternative modes of administration and the use of nasal continuous positive airway pressure to minimise the need for mechanical ventilation. Whether children with other lung diseases benefit from surfactant therapy is less clear. Evidence suggests that infants with meconium aspiration syndrome and children with acute lung injury/acute respiratory distress syndrome may benefit, while no positive effect of surfactant is seen in infants with congenital diaphragmatic hernia. However, more research is needed to establish potential beneficial effects of surfactant administration in children with lung diseases other than RDS. Furthermore, genetic disorders of surfactant metabolism have recently been linked to respiratory diseases of formerly unknown origin. It is important to consider these disorders in the differential diagnosis of unexplained respiratory distress although no established treatment is yet available besides lung transplantation for the most severe cases.

CONCLUSION

Research around surfactant is evolving and recent developments include further evolution of synthetic surfactants, evaluation of surfactant as a therapeutic option in lung diseases other than RDS and the discovery of genetic disorders of surfactant metabolism. Ongoing research is essential to continue to improve therapeutic prospects for children with serious respiratory disease involving disturbances in surfactant.

Therapeutic lung lavage in meconium aspiration syndrome: a preliminary report

AIM

To explore the effects of a large volume lung lavage procedure in ventilated infants with meconium aspiration syndrome.

METHODS

Infants with severe meconium aspiration requiring high-frequency ventilation underwent lung lavage using dilute bovine surfactant at a phospholipid concentration of 5 mg/mL. Lavage aliquot volumes were increased through the case series, aiming to deliver two aliquots of 15 mL/kg in rapid sequence. Physiological effects of lavage were documented, and comparison was made with a group of infants with meconium aspiration requiring high-frequency ventilation, in whom lavage was not performed.

RESULTS

Nine episodes of lavage were performed in eight infants at a median age of 23 h (range 8-83 h). Three infants underwent a lavage that was defined as potentially therapeutic (total lavage volume of at least 25 mL/kg administered before 24 h of age). Lavage was not associated with bradycardia or hypotension. Recovery of arterial oxygen saturation to above 80% was achieved within 12 min in all but one infant in whom oxygen saturation was below 80% at the outset. Mean airway pressure was significantly lower in the Therapeutic lavage group compared with non-lavaged infants in the first 48 h, with a trend towards improved oxygenation.

CONCLUSION

Dilute surfactant lavage with aliquots of up to 15 mL/kg appears to be feasible in haemodynamically stable ventilated infants with meconium aspiration syndrome, and its efficacy deserves further investigation in a randomised controlled trial.

Expanded use of surfactant therapy in newborns

Although there is no doubt that administration of exogenous surfactant to very preterm babies who have respiratory distress syndrome is safe and efficacious, surfactant inactivation or deficiency plays a role in the pathophysiology of other pulmonary disorders affecting newborn infants. Preliminary data suggest that there may be a role for surfactant administration to babies who have meconium aspiration syndrome, pneumonia, and possibly bronchopulmonary dysplasia. Further investigation is necessary but seems warranted.

Prise en charge précoce des enfants nés avec un liquide méconial: enquête dans les maternités françaises

The meconium aspiration syndrome is the first cause of respiratory distress in full term newborns. At birth, management includes systematical oropharyngeal suctioning, before and after shoulders delivery, followed by tracheal suction. During last 10 years, many trials were published which discuss again the value of this strategy.

AIM

To assess practices of the current management of births with a meconial amniotic liquid in the French maternities.

METHODS

Observational survey by written questionnaires sent to the 617 French maternities.

RESULTS

The rate of answers was of 54.3%. The incidence of the births presenting a meconial amniotic fluid was of 8.2%, complicated of meconium aspiration syndrome in 4.7%. In case of birth with presence of a meconial amniotic liquid, half of the maternities resorted systematically to oropharyngeal suctioning before shoulders delivery. A glottis exposition under laryngoscopy was practiced of principle for half of the newborn. Tracheal suctioning was achieved systematically in a quarter of the establishments. These techniques, with the exception of suctioning before clearing of the shoulders, were especially been achieved in a systematic way in the maternities of I and II A levels.

CONCLUSION

This survey shows the necessity of harmonization of the practices in France for the management of the births with a meconial amniotic liquid.