Surfactant lavage for meconium aspiration syndrome: a pilot study

Causes of fetal death in the Flemish cattle herd in Brazil

Background and Aim

Flemish cattle in Brazil are on the brink of extinction and are found only in one herd in Lages, Santa Catarina State. This study aimed to uncover the reasons for the recurring abortions in the Flemish cattle herd.

Materials and Methods

Seventeen Flemish fetuses underwent postmortem examinations, with samples collected for histopathology and microbiology culture tests, polymerase chain reaction (PCR) test for Neospora caninum, and reverse transcription-PCR (RT-PCR) test for bovine viral diarrhea virus (BVDV) from 2015 to 2020.

Results

Of the 17 fetuses, N. caninum was the most common diagnosis and was found in 88% (15/17). One fetus (5.8%) had a coinfection with N. caninum and Citrobacter amalonaticus, leading to fibrinonecrotic pericarditis. All fetuses tested negative for BVDV by RT-PCR. Of the 107 dams tested by indirect immunofluorescence assay, 26 (25.2%) were anti-N. caninum seropositive, with 17 (65.4%) aborting and 5 (19.2%) having estrus repetition. Reverse transcription-PCR results showed that 9 (8.4%) of the serum samples collected from dams tested positive, which tested follow-up test 3 months later, indicating a BVDV transient infection. The factors that contributed to neosporosis included dogs' access to pastures and improper disposal of fetal remains, which made it easier for dogs to consume them.

Conclusion

This study warns the occurrence of N. caninum as a cause of reproductive disorders that can lead to abortion in the studied Flemish cattle herd.

Surfactant lavage for neonatal meconium aspiration syndrome-An updated meta-analysis

BACKGROUND

Surfactant lavage seems to have a good application prospect both in experimental models and patients with meconium aspiration syndrome (MAS). Data regarding the effect of surfactant lavage on pulmonary complications of MAS are conflicting. In view of these uncertainties, an updated meta-analysis including the latest literatures is performed.

METHODS

A search was conducted by two investigators involved in this research in PubMed, Embase, and Cochrane databases for studies in English and other languages, in Wanfang, VIP, and Cnki databases for Chinese studies (all last launched on December 18, 2018). Ultimately, we identified 11 original studies, including the surfactant lavage group (n = 189) and the control group (n = 204). Odds ratio and weighted mean difference were calculated using a random effects or fixed effects model, depending on the data type and heterogeneity of the included studies.

RESULTS

The comparison of effectiveness on MAS: (1) With respect to oxygen index at 48 hours stage and 72 hours stage, data showed significant difference between surfactant lavage/control groups (we/ighted mean difference [WMD] = -3.37, 95% confidence interval [CI], -5.68 ~ -1.06; p = 0.004 and 95% CI, -5.03 ~ -2.37; p < 0.00001). (2) With respect to days on mechanical ventilation, the analysis showed that there was significant difference between surfactant lavage group and control group (WMD = -1.12, 95% CI, -1.40 ~ -0.84; p < 0.00001). (3) Regarding the need for extracorporeal membrane oxygenation, days of oxygen therapy, and hospital stay, no significant differences were found. The comparison of possible complications of MAS: (1) Regarding pneumothorax, the analysis showed there was significant difference between surfactant lavage and control groups (odds ratio [OR] = 0.46, 95% CI, 0.24 ~ 0.85; p = 0.01). (2) With respect to mortality, persist pulmonary hypertension and pulmonary hemorrhage, the results showed no difference between the two groups.

CONCLUSION

With respect to oxygen index and days on mechanical ventilation, surfactant lavage is significantly effective compared with control group, though didn't eventually shorten days of oxygen therapy and hospital stay. In addition, our meta-analysis showed that surfactant lavage does not increase the risk of complications.

Surfactant therapy for meconium aspiration syndrome in neonates: a systematic overview of systematic reviews and recent clinical trials

Aim: To conduct a systematic overview of systematic reviews (SRs) and randomized clinical trials (RCTs) on surfactant therapy in neonatal meconium aspiration syndrome. Methods: We searched EMBASE, PROQUEST and PubMed to summarize the different effects of surfactant lung lavage and bolus surfactant therapies in neonates with meconium aspiration syndrome. Results: With a total of 1377 patients, three SRs and two RCTs were included in analysis. Surfactant effectiveness was concluded by low-quality SRs, with high risk of bias, which was contradicted by high-quality SRs, with low risk of bias. In SRs, the surfactant lung lavage reduced mortality, need for extracorporeal membrane oxygenation and hospitalization, while the bolus surfactant did not. In recent high-quality RCTs, however, the two modalities did not significantly differ. Conclusion: The evidence on surfactant effectiveness and its method of administration is sparse and inconsistent.

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.

Surfactant with and without bronchoalveolar lavage in an experimental model of meconium aspiration syndrome

OBJECTIVES

To assess the effect of surfactant administration, preceded or not by bronchoalveolar lavage (BAL) with dilute surfactant, on pulmonary function in experimental severe meconium aspiration syndrome.

METHODS

Twenty-one newborn pigs received 20% meconium in saline intratracheally and were randomly allocated to one of three groups: I, control; II, surfactant only (poractant alfa, 200 mg/kg); or III, dilute surfactant BAL followed by 125 mg/kg surfactant. Arterial blood gases (ABGs), lung compliance, and resistance were assessed.

RESULTS

Thirty minutes after treatment, mean PaO2 (mm Hg) increased to 72 in group I, to 106 in group II and to 172 in group III (P=0.01). After 3 h, mean PaO2 (mm Hg) was 70 in group I, 95 in group II and 198 in group III (P<0.01). After 6 h, it was 79 in group I, 110 in group II, and 217 in group III (P=0.01). From the 30-min point onward, there were significant differences among treatment groups in all other parameters and at every point of assessment, except for compliance and resistance 3 h after treatment.

CONCLUSIONS

BAL with dilute surfactant, followed by an additional dose of surfactant, produced significant improvements in ABGs and pulmonary mechanics as compared with a single dose of surfactant.

Surfactant for meconium aspiration syndrome in term and late preterm infants

BACKGROUND

Surfactant replacement therapy has been proven beneficial in the prevention and treatment of neonatal respiratory distress syndrome (RDS). The deficiency of surfactant or surfactant dysfunction may contribute to respiratory failure in a broader group of disorders, including meconium aspiration syndrome (MAS).

OBJECTIVES

To evaluate the effect of surfactant administration in the treatment of late preterm and term infants with meconium aspiration syndrome.

SEARCH METHODS

We searched The Cochrane Library (Issue 4, 2006), MEDLINE and EMBASE (1985 to December 2006), previous reviews including cross-references, abstracts, conference and symposia proceedings, expert informants, and journal handsearching, without language restrictions. We contacted study authors for additional data.We ran an updated search in November 2014 and searched the following sites for ongoing or recently completed trials: www.clinicaltrials.gov; www.controlled-trials.com; and www.who.int/ictrp.

SELECTION CRITERIA

Randomised controlled trials which evaluated the effect of surfactant administration in late preterm and term infants with meconium aspiration syndrome are included in the analyses.

DATA COLLECTION AND ANALYSIS

We extracted data on clinical outcomes including mortality, treatment with extracorporeal membrane oxygenation (ECMO), pneumothorax, duration of assisted ventilation, duration of supplemental oxygen, intraventricular haemorrhage (any grade and severe IVH), and chronic lung disease. We conducted data analyses in accordance with the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

Four randomised controlled trials met our inclusion criteria. The meta-analysis of four trials (326 infants) showed no statistically significant effect on mortality [typical risk ratio (RR) 0.98, 95% confidence interval (CI) 0.41 to 2.39; typical risk difference (RD) -0.00, 95% CI -0.05 to 0.05]. There was no heterogeneity for this outcome (I² = 0% for both RR and RD). The risk of requiring extracorporeal membrane oxygenation was significantly reduced in a meta-analysis of two trials (n = 208); [typical RR 0.64, 95% CI 0.46 to 0.91; typical RD -0.17, 95% CI -0.30 to -0.04; number needed to treat for an additional beneficial outcome (NNTB) 6, 95% CI 3 to 25]. There was no heterogeneity for RR (1² = 0%) but moderate heterogeneity for RD (I² = 50%). One trial (n = 40) reported a statistically significant reduction in the length of hospital stay (mean difference -8 days, 95% CI -14 to -3 days; test for heterogeneity not applicable). There were no statistically significant reductions in any other outcomes studied (duration of assisted ventilation, duration of supplemental oxygen, pneumothorax, pulmonary interstitial emphysema, air leaks, chronic lung disease, need for oxygen at discharge or intraventricular haemorrhage).

AUTHORS' CONCLUSIONS

In infants with MAS, surfactant administration may reduce the severity of respiratory illness and decrease the number of infants with progressive respiratory failure requiring support with ECMO. The relative efficacy of surfactant therapy compared to, or in conjunction with, other approaches to treatment including inhaled nitric oxide, liquid ventilation, surfactant lavage and high frequency ventilation remains to be tested.

Delivery and performance of surfactant replacement therapies to treat pulmonary disorders

Lung surfactant is crucial for optimal pulmonary function throughout life. An absence or deficiency of surfactant can affect the surfactant pool leading to respiratory distress. Even if the coupling between surfactant dysfunction and the underlying disease is not always well understood, using exogenous surfactants as replacement is usually a standard therapeutic option in respiratory distress. Exogenous surfactants have been extensively studied in animal models and clinical trials. The present article provides an update on the evolution of surfactant therapy, types of surfactant treatment, and development of newer-generation surfactants. The differences in the performance between various surfactants are highlighted and advanced research that has been conducted so far in developing the optimal delivery of surfactant is discussed.

Lung lavage for meconium aspiration syndrome in newborn infants

BACKGROUND

Meconium aspiration syndrome (MAS) can occur when a newborn infant inhales a mixture of meconium and amniotic fluid into the lungs around the time of delivery. Other than supportive measures, little effective therapy is available. Lung lavage may be a potentially effective treatment for MAS by virtue of removing meconium from the airspaces and altering the natural course of the disease.

OBJECTIVES

To evaluate the effects of lung lavage on morbidity and mortality in newborn infants with MAS.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library), MEDLINE, and EMBASE up to December 2012; previous reviews including cross-references, abstracts, and conference proceedings; and expert informants. We contacted authors directly to obtain additional data. We used the following subject headings and text words: meconium aspiration, pulmonary surfactants, fluorocarbons, bronchoalveolar lavage, lung lavage, pulmonary lavage.

SELECTION CRITERIA

Randomised controlled trials that evaluated the effects of lung lavage in infants with MAS, including those intubated for the purpose of lavage. Lung lavage was defined as any intervention in which fluid is instilled into the lung that is followed by an attempt to remove it by suctioning and/or postural drainage.

DATA COLLECTION AND ANALYSIS

The review authors extracted from the reports of the clinical trial, data regarding clinical outcomes, including mortality, requirement for extracorporeal membrane oxygenation (ECMO), pneumothorax, duration of mechanical ventilation and oxygen therapy, length of hospital stay, indices of pulmonary function, and adverse effects of lavage. Data analysis was done in accordance with the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

Only four small randomised controlled trials fulfilled the selection criteria. For one of these trials, no data are available for the control group. Two studies compared lavage using diluted surfactant with standard care. Meta-analysis of these two studies did not show a significant effect on mortality (typical relative risk 0.42, 95% confidence interval [CI] 0.12 to 1.46; typical risk difference -0.10, 95% CI -0.24 to 0.04) or the use of ECMO (typical relative risk 0.27, 95% CI 0.04 to 1.86; typical risk difference -0.15, 95% CI -0.35 to 0.04). For the composite outcome of death or use of ECMO, a significant effect favoured the lavage group (typical relative risk 0.33, 95% CI 0.11 to 0.96; typical risk difference -0.19, 95% CI -0.34 to -0.03; number needed to benefit [NNTB] 5). No other benefits were reported. The other published study compared surfactant lavage followed by a surfactant bolus with surfactant bolus therapy alone in MAS complicated by pulmonary hypertension. No significant improvements in mortality, pneumothorax, duration of mechanical ventilation. or duration of hospitalisation were observed.

AUTHORS' CONCLUSIONS

In infants with meconium aspiration syndrome, lung lavage with diluted surfactant may be beneficial, but additional controlled clinical trials of lavage therapy should be conducted to confirm the treatment effect, to refine the method of lavage treatment, and to compare lavage treatment with other approaches, including surfactant bolus therapy. Long-term outcomes should be evaluated in further clinical trials.

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.

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.

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.

Intratracheal catheter suction removes the same volume of meconium with less impact on desaturation compared with meconium aspirator in meconium aspiration syndrome

OBJECTIVE

To evaluate the impact of suction technique on the rate of meconium removal, oxygenation, and hemodynamics in an animal experimental model of meconium aspiration syndrome (MAS).

METHODS

MAS was induced in ventilated rabbits using 3.5 ml/kg of 20% human meconium. Tracheal suction with either catheter suction (CS) or meconium aspirator (MA) was performed after meconium instillation. Percentage of meconium collection rate, PaO(2) trends for 2h after tracheal suction, and acute-phase SpO(2) trends were compared between CS and the other three groups, the tube was withdrawn while meconium was aspirated with an MA, then the trachea was reintubated 5, 10 or 15s after suctioning of meconium.

RESULTS

Percentage of meconium collection rate and PaO(2) showed no significant differences between groups. The MA group taking 15s for reintubation after meconium suctioning, showed a significantly lower acute-phase SpO(2) than the CS group (P<0.05). The time for SpO(2) to return to >or=90% was also longer in the MA group taking 15s for reintubation than in the CS group (P<0.05).

CONCLUSION

Intratracheal CS removed the same volume of meconium with less impact on desaturation compared with meconium aspiration in an animal model of MAS. Intratracheal CS may be benefit to remove meconium in non-vigorous infants with meconium-stained amniotic fluid at birth.

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.

The role of surfactant treatment in preterm infants and term newborns with acute respiratory distress syndrome

Surfactant treatment in preterm infants and term newborns with (acute respiratory distress syndrome) ARDS-like severe respiratory failure has become part of an individualized treatment strategy in many intensive care units around the world. These babies constitute heterogeneous groups of gestational ages, lung maturity, as well as of the underlying disease processes and postnatal interventions. The pathophysiology of respiratory failure in preterm infants is characterized by a combination of primary surfactant deficiency and surfactant inactivation as a result of plasma proteins leaking into the airways from areas of epithelial disruption and injury. Various pre- and postnatal factors, such as exposure to chorioamnionitis, pneumonia, sepsis and asphyxia, induce an injurious inflammatory response in the lungs of preterm infants, which may subsequently affect surfactant function, synthesis and alveolar stability. Surfactant inactivation--and dysfunction--is also a hallmark in newborns with meconium aspiration syndrome (MAS), pneumonia and other disorders affecting the pulmonary function. Although for the majority of suggested indications no data from randomized controlled trials exist, a surfactant replacement that counterbalances surfactant inactivation seems to improve oxygenation and lung function in many babies with ARDS without any apparent negative side effects. Newborns with MAS will definitely benefit from a reduced need for extracorporeal membrane oxygenation (ECMO). Clinical experience seems to justify surfactant treatment in neonates with ARDS.

Pharmacotherapy for meconium aspiration

In this article we have attempted to review the current pharmacological treatment options for infants with meconium aspiration syndrome with or without persistent pulmonary hypertension. These treatments include ventilatory support, surfactant treatment and inhaled nitric oxide (INO), in addition to older and newer pharmacological treatments. These include sedatives, muscle relaxants, alkali infusion, antibiotics and the newer vasodilators. Many aspects of treatment, including ventilatory care, surfactant treatment and the use of INO, are reviewed in great detail in this issue. On the other hand, many newer pharmacological modalities of treatment described here have not been evaluated with randomized control trials. We have given an overview of these emerging therapies.

Treatment of MAS with PPHN using combined therapy: SLL, bolus surfactant and iNO

The objective of the study was to compare the effectiveness of surfactant treatment either by bolus or surfactant lung lavage followed by inhaled nitric oxide (iNO) therapy in infants with meconium aspiration syndrome (MAS) complicated by persistent pulmonary hypertension (PPHN). In this study, thirteen infants with diagnosis of MAS and PPHN were first treated with conventional respiratory support. Then between 2 and 22h of life they were randomized either to bolus surfactant treatment (n=6) or surfactant lung lavage (SLL, n=7) treatment. Then all infants were treated with iNO therapy. The groups were compared with regard to their clinical course: changes in PaO(2), FiO(2), MAP, OI, A-a oxygen gradient, duration of iNO therapy, length of ventilation and hospitalization. Complications and mortality were also compared. The results showed that infants treated with SLL had significant improvements in oxygenation, decreases in MAP and A-a gradients. But there were no significant differences in duration of ventilation, iNO treatment, length of hospitalization or complications. In conclusion these data show no advantage of SLL therapy over bolus surfactant treatment in infants with MAS complicated by PPHN.

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.

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.

Bronchoalveolar lavage plus surfactant in a piglet model of meconium aspiration syndrome

INTRODUCTION

Meconium aspiration produces airway obstruction and surfactant inhibition. Bronchoalveolar lavage (BAL) and surfactant replacement have been proposed as treatments for the syndrome.

OBJECTIVE

To evaluate the effect of BAL with normal saline followed by a supplementary dose of surfactant in a piglet model of meconium aspiration syndrome.

METHODS

15 newborn piglets were used in the study. The animals were ventilated with fixed settings. After inhalation of 4 ml/kg of diluted meconium, the piglets were randomized into three groups: group I (n = 5) - tracheal aspiration without BAL; group II (n = 5) - BAL with normal saline (15 ml/kg), and group III (n = 5) - BAL with normal saline (15 ml/kg) followed by a supplementary dose of surfactant (Curosurf(R) 100 mg/kg). Arterial blood gas samples were obtained 30 min and 6 h after the inhalation of meconium.

RESULTS

A significant increase of PaO(2 )values at 6 h after treatment was only observed in group III (from 51 +/- 13 to 189 +/- 115 mm Hg; p = 0.04). At this time, PaO(2) in group III was significantly higher compared to group II (189 +/- 115 and 37 +/- 11 mm Hg, respectively; p = 0.023) and showed a borderline significance when compared to group I (p = 0.066).

CONCLUSION

BAL with normal saline followed by a supplementary dose of surfactant may improve oxygenation in an experimental piglet model of meconium aspiration syndrome.

Meconium stained fluid: approach to the mother and the baby

Meconium aspiration syndrome (MAS) is a common problem that most pediatricians will encounter in the delivery room and normal newborn nursery. Approximately 13% of all live births are complicated by meconium stained amniotic fluid (MSAF). MAS is defined as respiratory distress in an infant born through MSAF whose symptoms cannot be otherwise explained. Optimal care for an infant born through MSAF involves cooperation between the obstetrician and pediatrician, each with separate but imperative roles.

Surfactant for meconium aspiration syndrome in full term/near term infants

BACKGROUND

Surfactant replacement therapy has been proven beneficial in the prevention and treatment of neonatal respiratory distress syndrome (RDS). The deficiency of surfactant or surfactant dysfunction may contribute to respiratory failure in a broader group of disorders, including meconium aspiration syndrome (MAS).

OBJECTIVES

To evaluate the effect of surfactant administration in the treatment of term/near-term infants with MAS.

SEARCH STRATEGY

Searches were made using The Cochrane Library (Issue 4, 2006), MEDLINE and EMBASE (1985 to December 2006), previous reviews including cross-references, abstracts, conference and symposia proceedings, expert informants, and journal hand searching. No language restrictions were applied. Authors were directly contacted to provide additional data.

SELECTION CRITERIA

Randomised controlled trials which evaluated the effect of surfactant administration in term infants with meconium aspiration syndrome are included in the analyses.

DATA COLLECTION AND ANALYSIS

Data regarding clinical outcomes including mortality, treatment with extracorporeal membrane oxygenation (ECMO), pneumothorax, duration of assisted ventilation, duration of supplemental oxygen, intraventricular haemorrhage (any grade and severe IVH), and chronic lung disease, and were excerpted from the reports of the clinical trails by the review authors. Data analyses were done in accordance with the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

Four randomised controlled trials met inclusion criteria. The meta-analysis of 4 trials enrolling 326 infants showed no statistically significant effect on mortality (typical relative risk 0.98 (95% CI 0.41, 2.39), typical risk difference 0.00 (95% CI -0.05, 0.05). The risk of requiring extracorporeal membrane oxygenation was significantly reduced in a meta-analysis of two trials (n = 208); (typical relative risk 0.64, 95% CI 0.46, 0.91; typical risk difference -0.17, 95% CI -0.30, -0.04); number needed to treat to benefit 6 (95% CI 3, 25). One trial (n = 40) reported a statistically significant reduction in the length of hospital stay [mean difference - 8 days (95% CI -14, -3 days)]. There were no statistically significant reductions in any other outcomes studied (duration of assisted ventilation, duration of supplemental oxygen, pneumothorax, pulmonary interstitial emphysema, air leaks, chronic lung disease, need for oxygen at discharge or intraventricular haemorrhage).

AUTHORS' CONCLUSIONS

In infants with MAS, surfactant administration may reduce the severity of respiratory illness and decrease the number of infants with progressive respiratory failure requiring support with ECMO. The relative efficacy of surfactant therapy compared to, or in conjunction with, other approaches to treatment including inhaled nitric oxide, liquid ventilation, surfactant lavage and high frequency ventilation remains to be tested.

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.

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.

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.

Hypoxic respiratory failure in the late preterm infant

Hypoxic respiratory failure in late preterm infants has received increased attention in the last decade, and while the incidence is low, it accounts for a significant number of admissions to neonatal ICUs because of the large number of late preterm births in the United States and worldwide. Causes of respiratory distress include transient tachypnea of the newborn, surfactant deficiency, pneumonia, and pulmonary hypertension. The physiologic mechanisms underlying delayed transition caused by surfactant deficiency and poor fetal lung fluid absorption have been reviewed recently elsewhere. This article focuses on the less-explored problem of severe hypoxic respiratory failure in the late preterm infant and discusses potential strategies for management.

Lung surfactants

PURPOSE

The pharmacology, clinical efficacy, and cost considerations of exogenous lung surfactants are reviewed.

SUMMARY

Exogenous pulmonary surfactants, along with advancements in ventilatory care, have significantly reduced the incidence of respiratory distress syndrome (RDS) and its related complications in infants. The following exogenous surfactants are approved for the prophylaxis and treatment (rescue) of neonatal RDS: beractant, a modified natural surfactant; calfactant and poractant, both natural surfactants; and colfosceril, a synthetic surfactant that is not currently available in the United States. Lucinactant, a synthetic surfactant, is under investigation and received approvable status from the Food and Drug Administration in February 2005. The surfactants are delivered directly to their site of action, and only small amounts reach the systemic circulation. Bioavailability to the distal airways and alveoli depends on the method of delivery, the stage and severity of pulmonary disease, and the properties of the particular surfactant. According to data from clinical trials, the use of exogenous surfactant therapy for rescue within the first two hours of life appears to be as efficacious as prophylaxis in most premature infants.

CONCLUSION

Comparative trials of surfactants have proven the efficacy of both synthetic and natural surfactants in the prevention and treatment of RDS. However, these trials have universally demonstrated greater reduction in the immediate need for ventilator support in infants who receive natural surfactants. Natural preparations cause less pneumothorax, bronchopulmonary dysplasia, and mortality compared with synthetic preparations. Synthetic agents offer the potential advantages of an unlimited supply with consistent pharmaceutical quality and no risk of transmitting infectious disease or causing immunologic sensitization.

Effects of therapeutic bronchoalveolar lavage and partial liquid ventilation on meconium-aspirated newborn piglets

OBJECTIVE

To investigate the therapeutic effects of bronchoalveolar lavage (BAL) with either diluted surfactant (SBAL) or perfluorochemical liquid (PBAL), followed by either conventional mechanical ventilation (CMV) or partial liquid ventilation (PLV), on lung injury and proinflammatory cytokine production induced by meconium aspiration in newborn piglets.

DESIGN

A prospective, randomized, experimental study.

SETTING

An animal research laboratory at a medical center.

SUBJECTS

Anesthetized and mechanically ventilated newborn piglets (n = 27).

INTERVENTIONS

The animals were instilled with 3-5 mL/kg 25% human meconium via an endotracheal tube to induce meconium aspiration syndrome (MAS). After stabilization, animals were randomly assigned to either CMV group (no BAL) or one of the treatment groups (SBAL-CMV, SBAL-PLV, PBAL-CMV, and PBAL-PLV).

MEASUREMENTS AND MAIN RESULTS

Cardiopulmonary variables were monitored, and interleukin-1beta and interleukin-6 content of the serum and lung tissue was measured. The animals without any treatment (CMV group) displayed the worst outcome; the animals in the PBAL-PLV group had the best gas exchange, lung compliance, and least pulmonary damage; and the SBAL-CMV, PBAL-CMV, and SBAL-PLV groups had intermediate effects. The serum interleukin-1beta concentration of the CMV group was significantly higher than all other groups over time (p < .05), and interleukin-6 concentration was significantly higher than the PBAL-PLV group (p < .05). The tissue interleukin-1beta and interleukin-6 contents were also highest in the CMV group and lowest in the PBAL-PLV group.

CONCLUSIONS

Initial therapeutic BAL and therapeutic BAL followed by PLV with the same perfluorochemical liquid provided significant therapeutic effects in treating an animal model with severe MAS and therefore warrant consideration in cases that are intractable to other therapies.

Novas opções terapêuticas na síndrome de aspiração de mecônio

OBJETIVOS: revisar a literatura sobre a síndrome de aspiração de mecônio (SAM), enfocando aspectos clínicos, fisiopatológicos e abordagem terapêutica, com destaque ao uso do surfactante e lavado broncoalveolar. MÉTODOS: revisão baseada em artigos publicados na MEDLINE, SCIELO e resumos de congressos internacionais de 1988 a 2004, incluindo ensaios randomizados ou quasi-randomizados, estudos caso-controle e metanálises. RESULTADOS: devido à comprovação da inibição do surfactante na SAM, houve modificações em sua abordagem terapêutica. O manejo atual consiste na aspiração das vias aéreas na sala de parto, seguida de suporte ventilatório necessário para manter a oxigenação arterial adequada, e tratamento das complicações. Tendo em vista a obstrução mecânica do mecônio e seu efeito inibitório sobre o surfactante, a reposição e lavado broncoalveolar com surfactante estão sendo estudados atualmente. CONCLUSÕES: estudos em animais e em recém-nascidos apresentam resultados controversos quanto aos benefícios do uso de surfactante e lavado broncoalveolar na SAM. Torna-se importante a realização de mais estudos para avaliar novas estratégias ventilatórias e se existem vantagens no uso do surfactante e lavado broncoalveolar com surfactante na SAM.

Treatment of severe meconium aspiration syndrome with porcine surfactant: a multicentre, randomized, controlled trial

AIM

A randomized, controlled clinical trial was performed in 19 Chinese neonatal intensive care units to evaluate the safety and efficacy of exogenous surfactant replacement therapy for severe meconium aspiration syndrome (MAS) in term and near-term neonates.

METHODS

Sixty-one term infants with severe MAS were randomly assigned to either a surfactant or a control group within 36 h after birth. The infants in the surfactant group (n=31) received an initial dose of porcine lung-derived surfactant (Curosurf) at 200 mg/kg, and repeated doses of 200, 100 and 100 mg/kg were given at 6-12 h intervals to a maximum of four doses if oxygenation index (OI) deteriorated by >2 from baseline. The primary outcomes were a reduction of OI to less than 10 and an increase of the pre-treatment a/A PO(2) ratio of 100% over baseline 24 h after surfactant treatment. The secondary outcomes were duration of mechanical ventilation, incidence of complications and survival to discharge from hospital.

RESULTS

The general demographic characteristics of the study subjects were similar. There was a trend for surfactant-treated infants to have an improvement in arterial oxygenation compared to the control group. In comparison with the control group at 24 h, the surfactant group had a lower mean OI (8.1 vs 10.9), more infants with a 100% increase of a/A PO(2) (83% vs 48%, p<0.01) over baseline, and a larger area under the curve for PaO(2)/FiO(2) over baseline (3762+/-1877 vs 2715+/-1644 mmHg(.)h, p<0.05). Repeated measures of these parameters were also in favour of the surfactant group during 24 h to 3 and 7 d compared to the baseline (p<0.05). No differences were found in mean duration of mechanical ventilation, incidence of major complications and number of survivors between the two groups.

CONCLUSION

Surfactant replacement therapy improved oxygenation in the study subjects, suggesting that surfactant may have a role in the treatment of severe MAS in term and near-term infants.

Airway lavage with exogenous surfactant in an animal model of meconium aspiration syndrome

BACKGROUND

Meconium aspiration syndrome (MAS) is a major cause of respiratory morbidity and mortality in term infants, and occasionally causes serious respiratory disturbance. Viscous meconium debris in the trachea interferes with ventilation, and chest physiotherapy (CPT) is effective for removing secretions from the trachea. The effects of conventional exogenous diluted surfactant lavage combined with CPT were evaluated in a MAS animal model in a randomized controlled study.

METHODS

Twenty-three MAS model adult Japanese rabbits were randomized into three groups and artificially ventilated for 3 h with the following treatments: group 1, suction only (n = 7); group 2, surfactant lavage (n = 7); group 3, surfactant lavage with CPT (n = 7). Surfactant lavage was performed by infusing 2 mL/kg of diluted Surfactant TA (Surfacten; 6 mg/mL) into the trachea over approximately 5 s, then performing gentle manual bagging six times, and aspirating the tracheal contents using a suction catheter. This procedure was performed four times in four different positions (total, 8 mL/kg). In group 3, CPT (squeezing) was performed during expiration of manual bagging in surfactant lavage.

RESULTS

In group 3, PaO(2) improved significantly (P < 0.05) at all time points compared with those in the other groups. Oxygenation index (OI) in group 3 improved significantly (P < 0.05) at all time points except after 0.5 h compared with that in group 1, and at 2, 2.5, and 3 h compared with that in group 2.

CONCLUSIONS

A combination of exogenous surfactant lavage and CPT (squeezing) improves respiratory disturbance in MAS.

Lavage administration of dilute surfactant in a piglet model of meconium aspiration

Maldistribution of exogenous surfactant may preclude any clinical response in acute lung injury associated with surfactant dysfunction. Our previous studies have shown the effectiveness of surfactant lavage after homogenous lung injury. The present study utilizes a histologically confirmed non-homogeneous lung injury model induced by saline lung-lavage followed by meconium injected into a mainstem bronchus. Piglets were then treated with Infasurf or Exosurf by lavage (I-LAVAGE, n = 7; E-LAVAGE, n = 5) or bolus (I-BOLUS, n = 8; E-BOLUS, n = 5), or went untreated (CONTROL, n = 4). Lavage administration utilized a dilute surfactant (35 ml/kg; 4 mg phospholipid/ml) instilled into the lung, followed by gravity drainage. The retained doses of the respective surfactant in the lavage and bolus groups were similar. Results showed that the surfactant distribution was more uniform in the lavage groups compared to the bolus groups. Significant and consistent increases in PaO2 were observed in the lavage groups compared to the bolus groups and the controls. PaO2 (mmHg) at 240 min posttreatment: I-LAVAGE = 297 +/- 54, E-LAVAGE = 280 +/- 57; I-BOLUS = 139 +/- 31; E-BOLUS = 152 +/- 29; C = 119 +/- 73 (mean +/- SEM). Other improved pulmonary function parameters favored lavage administration. We conclude that better surfactant distribution achieved by lavage administration can be more effective than bolus administration in this type of non-homogeneous lung injury.

EARLY MECHANICAL VENTILATION IS DELETERIOUS AFTER ASPIRATION-INDUCED LUNG INJURY IN RABBITS

We investigated whether mechanical ventilation after aspiration is deleterious when started before surfactant therapy. Gas exchange and lung mechanics were measured in rabbits after aspiration either mechanically ventilated before or after lavage with diluted surfactant or Ringer's solution. Lung injury was induced by intratracheal instillation of 2 mL/kg of a betain/HCl pepsin mixture. After 30 min of spontaneous breathing, ventilation was started in 12 rabbits, which were then treated by lavage with diluted surfactant (15 mL/kg body weight; 5.3 mg/mL, group MVpre S) or with Ringer's solution (1 mL/kg; group MVpre R). Another 12 rabbits were treated by lavage while spontaneously breathing and were then connected to the ventilator (MVpost S and MVpost R). Sham control rabbits were mechanically ventilated for 4 h. At the end of experiment, PaO2/FiO2 ratio in MVpost S was five times higher than in MVpre S (P=0.0043). Lung mechanics measurements showed significant difference between MVpre S and MVpost S (P=0.0072). There was histopathologic evidence of decreased lung injury in MVpost S. Immediate initiation of ventilation is harmful when lung injury is induced by aspiration. Further investigations are needed to clarify whether the timing of lavage with diluted surfactant has an impact on the treatment of patients with aspiration or comparable types of direct lung injury.

Surfactant Therapy for Meconium Aspiration Syndrome

Meconium aspiration syndrome (MAS) is an important cause of respiratory distress in the term infant. Therapy for the disease remains problematic, and newer treatments such as high-frequency ventilation and inhaled nitric oxide are being applied with increasing frequency. There is a significant disturbance of the pulmonary surfactant system in MAS, with a wealth of experimental data indicating that inhibition of surfactant function in the alveolar space is an important element of the pathophysiology of the disease. This inhibition may be mediated by meconium, plasma proteins, haemoglobin and oedema fluid, and, at least in vitro, can be overcome by increasing surfactant phospholipid concentration. These observations have served as the rationale for administration of exogenous surfactant preparations in MAS, initially as standard bolus therapy and, more recently, in association with therapeutic lung lavage. Bolus surfactant therapy in ventilated infants with MAS has been found to improve oxygenation in most studies, although there are a significant proportion of nonresponders and in many cases the effect is transient. Pooled data from randomised controlled trials of surfactant therapy suggest a benefit in terms of a reduction in the requirement for extracorporeal membrane oxygenation (relative risk 0.48 in surfactant-treated infants) but no diminution of air leak or ventilator days. Current evidence would support the use of bolus surfactant therapy on a case by case basis in nurseries with a relatively high mortality associated with MAS, or the lack of availability of other forms of respiratory support such as high-frequency ventilation or nitric oxide. If used, bolus surfactant should be administered as early as practicable to infants who exhibit significant parenchymal disease, at a phospholipid dose of at least 100 mg/kg, rapidly instilled into the trachea. Natural surfactant or a third-generation synthetic surfactant should be used and the dosage repeated every 6 hours until oxygenation has improved. Lung lavage with dilute surfactant has recently emerged as an alternative to bolus therapy in MAS, which has the advantage of removing surfactant inhibitors from the alveolar space in addition to augmenting surfactant phospholipid concentration. Combined animal and human data suggest that lung lavage can remove significant amounts of meconium and alveolar debris, and thereby improve oxygenation and pulmonary mechanics. Arterial oxygen saturation inevitably falls during lavage but has been noted to recover relatively rapidly, even in infants with severe disease. Several randomised controlled trials of surfactant lavage in MAS are underway, and until the results are known, lavage must be considered an unproven and experimental therapy.

Les déficits secondaires en surfactant

Preterm babies born before the 33rd week of gestation often exhibit primary surfactant deficiency responsible for the respiratory distress syndrome or hyaline membrane disease. In that situation, there is a limited and insufficient production of surfactant by type II alveolar cells of the lung due to immaturity. Secondary surfactant deficiencies occur in patients with prior normal surfactant synthesis and can be related to sepsis, hypoxia, ventilator induced lung injury or surfactant inhibition by a variety of substances reaching the alveolar spaces. They occur in full-term newborns with meconium aspiration syndrome, acute respiratory distress syndrome and congenital diaphragmatic hernia. In children and adults, acute respiratory distress syndrome and respiratory syncytial virus bronchiolitis can be responsible. In prematures they occur after the initial primary deficiency during pulmonary hemorrhage, pneumonia and bronchopulmonary dysplasia. Treatment with exogenous surfactant may be beneficial. There is a need for randomized controlled studies for evaluation of this treatment. Next generation of surfactants containing recombinant surfactant protein or synthetic peptides appear as promising agents in these situations of secondary surfactant deficiencies.

Controversies in the treatment of meconium aspiration syndrome

MAS remains an infrequent but challenging condition confronting neonatologists. Avoidance of postterm pregnancies, improved intrapartum monitoring,and amnioinfusion have been beneficial. Studies have not demonstrated conclusively that any form of ventilation is superior to others, but strategies that recruit alveoli are desirable. Surfactant lavage or replacement may be beneficial. When hypoxic respiratory failure progresses, iNO may improve oxygenation and avoid ECMO.

[Meconium aspiration syndrome requiring mechanical ventilation: incidence and respiratory management in France (2000-2001)]

OBJECTIVES

To precise the number of term neonates with a meconium aspiration syndrome requiring mechanical ventilation in 2000 and 2001 in continental France and the related mortality. To study the different respiratory management.

METHOD

A written questionnaire was sent to all intensive care units of continental France.

RESULTS

Thirty-nine units were contacted and 31 answered (80%). On 30 answering centers, 265 cases are reported in 2000 and 249 in 2001. Extrapolation to the 39 centers led to a number of 347 cases in 2000 and 324 in 2001. Mortality rate was 6.4% for 2 years. Causes of death were: neurological 61%, respiratory 18% and others 21%. Twenty-six on 29 units used exogenous surfactant and/or high frequency oscillatory ventilation (HFOV) and/or inhaled nitric oxide (iNO). The sequence of use and the indication criteria of these therapies were quite variable with a majority of units using HFOV in the first place.

CONCLUSIONS

Meconium aspiration syndrome is still a frequent neonatal condition despite a codified prevention strategy. Respiratory management in intensive care units remains very variable.

Meconium stained fluid: approach to the mother and the baby

Meconium aspiration syndrome is a common problem that most pediatricians will encounter in the delivery room and normal newborn nursery. Approximately 13% of all live births are complicated by meconium-stained amniotic fluid. Like many aspects of the perinatal period, optimal care of an infant born through meconium-stained amniotic fluid involves collaboration between obstetrician and pediatrician, each with separate but important roles. As always, effective communication and advanced preparation and anticipation of potential problems form the cornerstone of this partnership. Together the health of infants may be improved.

Surfactant use for neonatal lung injury: beyond respiratory distress syndrome

Surfactant has led to a significant reduction in neonatal mortality for premature infants with lung immaturity and respiratory distress. However, surfactant therapy has been shown to be effective in the treatment of a number of other neonatal respiratory disorders and the evidence for surfactant use in such circumstances is presented. Meconium aspiration is characterised by severe atelectasis, the influx of neutrophils, edema, and hyaline membranes, with decreased levels of SP-A and SP-B and the large aggregate fraction of lung surfactant, and altered surfactant surface morphology. Meconium contains cholesterol, free fatty acids and bilirubin all of which can interfere with surfactant function in a dose-dependent fashion. Providing larger amounts of surfactant can overcome some of this inhibition. Animal models of meconium aspiration treated with surfactant have improved histology, lung mechanics and gas exchange. Studies in human infants with meconium aspiration have found elevated concentrations of total protein, albumin, and membrane-derived phospholipid in lung lavage fluid, and haemorrhagic pulmonary edema. Clinical studies in such neonates have reported improved gas exchange and clinical outcomes following surfactant treatment. More recently surfactant lavage has been shown to be a potentially efficacious therapy for such infants. The inflammatory exudate containing plasma proteins and cytokines which accompanies neonatal pneumonia may inactivate surfactant. Surfactant treatment given to animals following the tracheal instillation of group B Streptococcal resulted in significantly less bacterial growth and improved lung function. Small clinical experiences have demonstrated the benefit of surfactant to infants with pneumonia/sepsis. Pulmonary haemorrhage, which some consider a complication of surfactant therapy, has also been effectively managed using surfactant instillation. The hemoglobin and red blood cell lipids may act to inhibit natural surfactant and treatment with surfactant has been shown to improve outcome for infants with pulmonary haemorrhage. Animal models of congenital diaphragmatic hernia (CDH) have hypoplastic lungs with evidence of decreased lamellar bodies in their type II pneumocytes and resultant surfactant deficiency, and respond to surfactant replacement with improved gas exchange and lung mechanics. The lungs of human infants with CDH contain less phospholipids and phosphatidylcholine per milligram of DNA than control infants. Case reports have reported a benefit of surfactant for infants with CDH. In the near-term infants with severe respiratory distress, surfactant is one of the therapies along with inhaled nitric oxide and high frequency ventilations, that have resulted in improved outcomes. Surfactant treatment may be of significant benefit in newborn infants with respiratory compromise secondary to a number of insults, and further prospective evidence of its efficacy in such disorders is needed.

Exogenous surfactant therapy: newer developments

There are numerous pulmonary conditions in which qualitative or quantitative anomalies of the surfactant system have been demonstrated. In premature newborns with immature lungs, a functional deficit in surfactant is the main physiopathologic mechanism of the neonatal respiratory distress syndrome (RDS). Since the landmark pilot study of Fujiwara, published more than 20 years ago, the efficacy of exogenous surfactant for the treatment of neonatal RDS has been established by numerous controlled studies and meta-analyses. Promising results have also been reported in infants suffering from other lung disorders in which endogenous surfactant function is compromised. Enlightened by a growing insight into both the structure and function of the different surfactant components, a new generation of synthetic surfactants has been developed. Various complementary approaches have confirmed the fundamental role of the two hydrophobic proteins, SP-B and SP-C, in the surfactant system, thus opening the way to the design of analogues, either by chemical synthesis or expression in a prokaryotic system. These peptide-containing synthetic surfactant preparations are presently undergoing clinical trials, and may eventually replace the animal-derived surfactants currently used for the treatment of RDS.

Therapeutic lung lavage in the piglet model of meconium aspiration syndrome

Therapeutic lung lavage is an emerging treatment for meconium aspiration syndrome. Our objective was to investigate the type of fluid and aliquot volume most appropriate for lung lavage in this condition. Meconium injury was induced in 2-week-old piglets, followed by a 30 ml/kg lavage in two aliquots 40 minutes later. Lavage with either dilute bovine surfactant (2.5 mg/ml) or a perfluorocarbon emulsion (20% wt/vol) improved oxygenation compared with a nonlavaged control group, but only with dilute surfactant was there a sustained improvement in oxygenation (alveolar-arterial oxygen difference at 5 hours: dilute surfactant 250 mm Hg; perfluorocarbon emulsion 460 mm Hg; controls 460 mm Hg; p = 0.0031). There was histologic and biochemical evidence of decreased lung injury in the dilute surfactant group. In a further study, 30 ml/kg dilute surfactant lavage was performed 40 minutes after meconium injury using either two aliquots of 15 ml/kg, or multiple 3-ml aliquots. Aliquot volume of 15 ml/kg was associated with increased meconium removal, better post-lavage lung function, and less lung injury. Dilute surfactant lavage using two 15-ml/kg aliquots is an effective therapy in the piglet model of meconium aspiration, and should be evaluated in human infants with this condition.