Surfactant phosphatidylcholine pool size in human neonates with congenital diaphragmatic hernia requiring ECMO

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.

Neonatal Respiratory Diseases in the Newborn Infant: Novel Insights from Stable Isotope Tracer Studies

Respiratory distress syndrome is a common problem in preterm infants and the etiology is multifactorial. Lung underdevelopment, lung hypoplasia, abnormal lung water metabolism, inflammation, and pulmonary surfactant deficiency or disfunction play a variable role in the pathogenesis of respiratory distress syndrome. High-quality exogenous surfactant replacement studies and studies on surfactant metabolism are available; however, the contribution of surfactant deficiency, alteration or dysfunction in selected neonatal lung conditions is not fully understood. In this article, we describe a series of studies made by applying stable isotope tracers to the study of surfactant metabolism and lung water. In a first set of studies, which we call 'endogenous studies', using stable isotope-labelled intravenous surfactant precursors, we showed the feasibility of measuring surfactant synthesis and kinetics in infants using several metabolic precursors including plasma glucose, plasma fatty acids and body water. In a second set of studies, named 'exogenous studies', using stable isotope-labelled phosphatidylcholine tracer given endotracheally, we could estimate surfactant disaturated phosphatidylcholine pool size and half-life. Very recent studies are focusing on lung water and on the endogenous biosynthesis of the surfactant-specific proteins. Information obtained from these studies in infants will help to better tailor exogenous surfactant treatment in neonatal lung diseases.

Decreased surfactant phosphatidylcholine synthesis in neonates with congenital diaphragmatic hernia during extracorporeal membrane oxygenation

PURPOSE

Congenital diaphragmatic hernia (CDH) may result in severe respiratory insufficiency with a high morbidity. The role of a disturbed surfactant metabolism in the pathogenesis of CDH is unclear. We therefore studied endogenous surfactant metabolism in the most severe CDH patients who required extracorporeal membrane oxygenation (ECMO).

METHODS

Eleven neonates with CDH who required ECMO and ten ventilated neonates without significant lung disease received a 24-h infusion of the stable isotope [U-(13)C] glucose. The (13)C-incorporation into palmitic acid in surfactant phosphatidylcholine (PC) isolated from serial tracheal aspirates was measured. Mean PC concentration in epithelial lining fluid (ELF) was measured during the first 4 days of the study.

RESULTS

Fractional surfactant PC synthesis was decreased in CDH-ECMO patients compared to controls (2.4 +/- 0.33 vs. 8.0 +/- 2.4%/day, p = 0.04). The control group had a higher maximal enrichment (0.18 +/- 0.03 vs. 0.09 +/- 0.02 APE, p = 0.04) and reached this maximal enrichment earlier (46.7 +/- 3.0 vs. 69.4 +/- 6.6 h, p = 0.004) compared to the CDH-ECMO group, which reflects higher and faster precursor incorporation in the control group. Surfactant PC concentration in ELF was similar in both groups.

CONCLUSION

These results show that CDH patients who require ECMO have a decreased surfactant PC synthesis, which may be part of the pathogenesis of severe pulmonary insufficiency and has a negative impact on weaning from ECMO.

Can we improve outcome of congenital diaphragmatic hernia?

This review gives an overview of the disease spectrum of congenital diaphragmatic hernia (CDH). Etiological factors, prenatal predictors of survival, new treatment strategies and long-term morbidity are described. Early recognition of problems and improvement of treatment strategies in CDH patients may increase survival and prevent secondary morbidity. Multidisciplinary healthcare is necessary to improve healthcare for CDH patients. Absence of international therapy guidelines, lack of evidence of many therapeutic modalities and the relative low number of CDH patients calls for cooperation between centers with an expertise in the treatment of CDH patients. The international CDH Euro-Consortium is an example of such a collaborative network, which enhances exchange of knowledge, future research and development of treatment protocols.

Pulmonary surfactant kinetics of the newborn infant: novel insights from studies with stable isotopes

Deficiency or dysfunction of the pulmonary surfactant plays a critical role in the pathogenesis of respiratory diseases of the newborn. After a short review of the pulmonary surfactant, including its role in selected neonatal respiratory conditions, we describe a series of studies conducted by applying two recently developed methods to measure surfactant kinetics. In the first set of studies, namely 'endogenous studies', which used stable isotope-labeled intravenous surfactant precursors, we have shown the feasibility of measuring surfactant synthesis and kinetics in infants using several metabolic precursors, including plasma glucose, plasma fatty acids and body water. In the second set of studies, namely 'exogenous studies', which used a stable isotope-labeled phosphatidylcholine (PC) tracer given endotracheally, we estimated the surfactant disaturated phosphatidylcholine (DSPC) pool size and half-life. The major findings of our studies are presented here and can be summarized as follows: (a) the de novo synthesis and turnover rates of the surfactant (DSPC) in preterm infants with respiratory distress syndrome (RDS) are very low with either precursor; (b) in preterm infants with RDS, pool size is very small and half-life much longer than what has been reported in animal studies; (c) patients recovering from RDS who required higher continuous positive airway pressure pressure after extubation or reintubation have a lower level of intrapulmonary surfactant than those who did well after extubation; (d) term newborn infants with pneumonia have greatly accelerated surfactant catabolism; and (e) infants with uncomplicated congenital diaphragmatic hernia (CDH) and on conventional mechanical ventilation have normal surfactant synthesis, but those requiring extracorporeal membrane oxygenated (ECMO) do not. Information obtained from these studies in infants will help to better tailor exogenous surfactant treatment in neonatal lung diseases.

CC10 reduces inflammation in meconium aspiration syndrome in newborn piglets

Complications from meconium aspiration syndrome (MAS) remain significant despite a variety of therapeutic interventions. Clara cell protein (CC10) is a novel anti-inflammatory agent that can also inhibit phospholipase A2 (PLA2) (an important component of meconium). The present study examined whether administration of recombinant human CC10 (rhCC10) would reduce inflammation and improve lung function in a piglet model of MAS. Following meconium instillation, piglets exhibited significant physiologic dysfunction that improved significantly after surfactant administration. Analysis of tracheal aspirates revealed significant increases in both tumor necrosis factor (TNF) alpha and interleukin (IL)-8 after meconium instillation. rhCC10-treated animals had significantly lower TNF-alpha levels at 24 h (561 +/- 321 versus 1357 +/- 675 pg/mL, p < 0.05) compared with saline controls. There were no differences between rhCC10-treated and untreated groups with respect to other measured physiologic variables or inflammatory markers, including secretory PLA2 activity. Histologic analyses revealed marked inflammatory infiltrates and thickened alveolar walls, but no significant differences among rhCC10 and control animals. Newborn piglets with MAS have significant physiologic dysfunction, marked inflammatory changes and histologic abnormalities, which was partially counteracted by a single dose of exogenous surfactant and rhCC10.

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.

Surfactant disaturated-phosphatidylcholine kinetics in acute respiratory distress syndrome by stable isotopes and a two compartment model

BACKGROUND

In patients with acute respiratory distress syndrome (ARDS), it is well known that only part of the lungs is aerated and surfactant function is impaired, but the extent of lung damage and changes in surfactant turnover remain unclear. The objective of the study was to evaluate surfactant disaturated-phosphatidylcholine turnover in patients with ARDS using stable isotopes.

METHODS

We studied 12 patients with ARDS and 7 subjects with normal lungs. After the tracheal instillation of a trace dose of 13C-dipalmitoyl-phosphatidylcholine, we measured the 13C enrichment over time of palmitate residues of disaturated-phosphatidylcholine isolated from tracheal aspirates. Data were interpreted using a model with two compartments, alveoli and lung tissue, and kinetic parameters were derived assuming that, in controls, alveolar macrophages may degrade between 5 and 50% of disaturated-phosphatidylcholine, the rest being lost from tissue. In ARDS we assumed that 5-100% of disaturated-phosphatidylcholine is degraded in the alveolar space, due to release of hydrolytic enzymes. Some of the kinetic parameters were uniquely determined, while others were identified as lower and upper bounds.

RESULTS

In ARDS, the alveolar pool of disaturated-phosphatidylcholine was significantly lower than in controls (0.16 +/- 0.04 vs. 1.31 +/- 0.40 mg/kg, p < 0.05). Fluxes between tissue and alveoli and de novo synthesis of disaturated-phosphatidylcholine were also significantly lower, while mean resident time in lung tissue was significantly higher in ARDS than in controls. Recycling was 16.2 +/- 3.5 in ARDS and 31.9 +/- 7.3 in controls (p = 0.08).

CONCLUSION

In ARDS the alveolar pool of surfactant is reduced and disaturated-phosphatidylcholine turnover is altered.

Spatial and temporal expression of glucocorticoid, retinoid, and thyroid hormone receptors is not altered in lungs of congenital diaphragmatic hernia

The degree of associated pulmonary hypoplasia and persistent pulmonary hypertension are major determination factors for survival in congenital diaphragmatic hernia (CDH) patients. Glucocorticoids, thyroid hormone, and vitamin A have been shown to be involved in human lung development. To determine their therapeutic potential in hypoplastic lungs of CDH patients, the temporal and spatial expression of glucocorticoid receptor, thyroid hormone receptors, retinoic acid receptors, and retinoid X receptors were evaluated in lungs of CDH patients, hypoplastic lungs from other causes, and normal lungs. As a series of supportive experiments, the expressions of these receptors were analyzed in lungs of nitrofen-induced CDH rats. Immunohistochemistry (human and rat) and in situ hybridization (rat) demonstrated no overt difference between CDH, hypoplastic, and control lungs, either in the localization nor the timing of the first expression of all analyzed receptors. The mRNA expression of each receptor was detected in all human CDH lungs by quantitative PCR. Our results suggest that, as far as receptors are concerned, hypoplastic lungs of fetuses and newborns with CDH are potentially as responsive to glucocorticoids, thyroid hormone, and retinoic acid as the lungs of normal children.

Surfactant phosphatidylcholine metabolism in neonates with meconium aspiration syndrome

OBJECTIVE

Because meconium directly inhibits surfactant function, we sought to determine the effect of meconium on endogenous surfactant synthesis and clearance.

STUDY DESIGN

We studied surfactant phosphatidylcholine kinetics with the use of stable isotopes in 11 newborn infants with meconium aspiration syndrome (MAS) who required extracorporeal membrane oxygenation (ECMO). For comparison we studied 6 neonates with persistent pulmonary hypertension (PPHN) on ECMO and 10 term neonates ventilated for non-pulmonary indications and not on ECMO. All patients received a 24-hour [U- 13C]glucose infusion as precursor for the palmitic acid in surfactant phosphatidylcholine.

RESULTS

In the meconium group, the maximal 13C-incorporation in phosphatidylcholine (PC) was half of that in controls (0.09 +/- 0.01 vs 0.18 +/- 0.03 atom percent excess [APE], P = .027). There was a trend toward lower surfactant synthesis in the MAS group (3.3 +/- 0.7%/day) and PPHN group (2.6 +/- 0.3%/day) compared with controls 8.0 +/- 2.4%/day, P = .058). Significantly lower PC concentrations in tracheal aspirates were found in the MAS group (4.4 +/- 2.6 mg/mL) and PPHN group (3.6 +/- 2.0 mg/mL) compared with controls (12.8 +/- 2.6 mg/mL, P = .01). Endogenously synthesized surfactant had a similar half-life in all groups, ranging from 63 to 98 hours.

CONCLUSION

We conclude that surfactant synthesis is disturbed and that surfactant PC concentrations are low in infants with MAS on ECMO.

Corticosteroids for fetuses with congenital diaphragmatic hernia: can we show benefit?

BACKGROUND AND PURPOSE

Prenatal corticosteroids have been used in fetuses with congenital diaphragmatic hernia (CDH). We tested the utility of steroids by 2 methods.

METHODS

Mothers carrying fetuses with CDH were randomized to 3 weekly doses of betamethasone or placebo starting at 34 weeks. Patients were followed until death or discharge. In a separate cohort study, the CDH Registry was used to compare infants who received prenatal steroids to those who had not.

RESULTS

Thirty-four patients were enrolled at 7 centers, with 32 completing the trial. There were 15 placebo and 17 steroid patients. There was no difference in survival, length of stay, duration of ventilation, or oxygen use at 30 days. For the cohort study, we looked at infants older than 34 weeks who were born after October 2000 when data on prenatal steroids were collected. There were 1093 patients; 390 were evaluable, with 56 receiving steroids. There was no difference in survival, length of stay, ventilator days, or oxygen use at 30 days.

CONCLUSION

Neither the trial nor the CDH Registry suggest that late prenatal corticosteroids benefit fetuses with CDH. More than 1700 mothers and fetuses would need to be enrolled in a trial to show a 10% improvement in survival. It is unlikely that late steroids offer benefit to most fetuses with CDH.

Surfactant metabolism in the neonate

With the use of stable isotope-labeled intravenous precursors for surfactant phosphatidylcholine (PC) synthesis, it has been shown that the de novo synthesis rates in preterm infants with respiratory distress syndrome (RDS) are very low as are turnover rates. This is consistent with animal data. Surfactant therapy does not inhibit endogenous surfactant synthesis, and prenatal corticosteroids stimulate it. With the use of stable isotope-labeled PC given endotracheally, surfactant pool size was estimated. It turned out to be low in RDS, as expected. Similar studies were performed in term neonates with severe lung diseases. In general, patients with lung injury show a lower surfactant synthesis. The controversy around surfactant in congenital diaphragmatic hernia (CDH) persists: studies on CDH with and without extracorporeal membrane oxygenation yielded different results. In severe meconium aspiration syndrome surfactant synthesis was found to be decreased but surfactant pool size was maintained. It is possible and safe to study surfactant metabolism in human neonates with the use of stable isotopes. This can help in answering clinical questions and has the potential to bring new in vitro and animal findings about surfactant metabolism to the patient.

Surfactant protein expression is increased in the ipsilateral but not contralateral lungs of fetal sheep with left-sided diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) impairs fetal lung growth and increases the density of alveolar epithelial type 2 (AE2) cells. There is controversy whether surfactant protein (SP) expression is altered in CDH. The primary aim of this study was to assess SP expression (mRNA and protein) in the left and right lungs of fetal sheep with and without a diaphragmatic hernia (DH). Left-sided DH was created in four fetal sheep at 65 days of gestational age (g.a.). Sham-operated animals were used as controls. At 138 days g.a., lungs were harvested and the following parameters were measured: SP-A, -B, and -C mRNA expression (Northern blot), SP-A and -B expression (Western blot), and AE2 cell density (immunohistochemistry). The lung weight-to-body weight ratio was reduced by 42% in DH animals. The left-to-right lung weight ratio was lower in DH animals (0.47 +/- 0.03 vs. 0.69 +/- 0.03), indicative of asymmetric lung growth. SP-A, -B, and -C mRNA expression were increased by 61.7%, 32.9%, and 75.5%, respectively, in the left lungs of DH animals. SP-A and SP-B were also increased in DH. In the right lung, SP expression (mRNA and protein) was not different between groups. AE2 cell density was higher (by 67%) in the left but not right lungs of DH animals. Although DH in fetal sheep results in significant lung hypoplasia, SP expression is not reduced. On the contrary, SP expression was increased in the ipsilateral lung of fetuses with left-sided DH. Furthermore, AE2 cell density is increased in DH, suggesting that the increase in SP mRNA and protein levels is due to increases AE2 cell number. Our data further support the premise that fetal lung hypoplasia favors an AE2 phenotype.

Fetal lung and diaphragm development in congenital diaphragmatic hernia

Congenital Diaphragmatic Hernia (CDH) is a congenital disorder with an incidence of 1 in 2500 live births. Respiratory distress of newborns with CDH is the result of pulmonary hypoplasia and pulmonary hypertension. Hypoplastic lungs are characterized by a decreased number of airways with smaller airspaces, whereas the combination of a decreased number of vascular branches and an increased adventitia and medial thickness of the pulmonary arterial walls result in pulmonary hypertension. The appearance of the CDH lungs suggests that its complete formation is stalled during development. Understanding the basic mechanisms of lung development is mandatory to unravel the origin of CDH. Although the histological abnormalities in CDH lungs have been well described, less is known about the underlying molecular mechanisms. In this review we will discuss the current molecular and genetic background of lung formation, as well as a reflection of this knowledge towards CDH.

Metabolic kinetics of pulmonary surfactant in newborn infants using endogenous stable isotope techniques

We compared kinetic indices of pulmonary surfactant metabolism in premature infants (n = 41) with respect to i) tracer ([1-(13)C1]acetate, [U-(13)C6]glucose, and [1,2,3,4-(13)C4] palmitate), ii) phospholipid (PL) pool (total PLs or disaturated PLs), or iii) instrumentation [gas chromatography/mass spectrometry (GC/MS) or GC-combustion-isotope ratio mass spectometry (GC-C-IRMS)]. Tracer incorporation was measured in PLs extracted from serial tracheal aspirates after a 24 h tracer infusion. The fractional catabolic rate (FCR), representing the total fractional turnover from all sources of surfactant production, was independent of tracer. The fractional synthesis rate of surfactant PL from plasma palmitate was significantly higher than that from palmitate synthesized de novo from acetate, and these two sources of palmitate together accounted for only half of the total surfactant production in preterm infants. [U-(13)C6]glucose showed significant recycling of the (13)C label in intermediary metabolism, distinguishable by GC-MS but not by GC-C-IRMS, resulting in a slower apparent FCR when GC-C-IRMS was used. The extracted PL pool did not affect the surfactant metabolic indices. We suggest that FCR should be used as a primary measure of surfactant turnover kinetics and that tracers labeling both de novo synthesis (acetate and glucose) and preformed pathways (plasma palmitate) can be used to partition the fractional contribution of each pathway to total production.

Surfactant replacement therapy on ECMO does not improve outcome in neonates with congenital diaphragmatic hernia

BACKGROUND PURPOSE

Respiratory failure in neonates with congenital diaphragmatic hernia (CDH) may in part be caused by a primary or secondary surfactant deficiency. Knowledge of the optimal approach to surfactant replacement in neonates with CDH and respiratory failure is limited. The aim of this study was to determine if surfactant replacement on extracorporeal membrane oxygenation (ECMO) results in improved outcomes in neonates > or =35 weeks' gestation with unrepaired CDH.

METHODS

Using the CDH Study Group Registry, the authors identified 448 neonates with CDH who were > or =35 weeks' gestation, had no major anomalies, were treated with ECMO within the first 7 days of life, and underwent repair on or after ECMO therapy. Patients in 2 groups were compared: group 1 (- Surf, n = 334) consisted of patients who received no surfactant and group 2 (+ Surf, n = 114) consisted of patients who received at least 1 dose of surfactant while on ECMO. An analysis of all patients in both groups was performed. Additionally, subgroup analyses stratified by gestational age were performed for patients 351/7 to 366/7 weeks' gestation and for patients > or =37 weeks' gestation. Primary end-points for the study were survival and length of ECMO run. Secondary end-points were length of intubation, need for supplemental oxygen at 30 days of life, and at discharge to home. Demographic, clinical, and outcome variables were examined using Fisher's Exact tests for categorical variables and using unpaired t tests for continuous variables. Odds ratios were calculated for categorical end-point variables.

RESULTS

Demographic and clinical variables were similar between groups. Analyses of aggregate data showed no significant differences between groups in length of ECMO run, survival, number of days intubated, and percent of patients requiring supplemental oxygen at 30 days or discharge. Subgroup stratification by gestational age did not show significant differences between groups in any of the outcome variables.

CONCLUSIONS

The data from this study suggest that surfactant replacement on ECMO for neonates with congenital diaphragmatic hernia does not provide significant benefit in the infant's clinical course with respect to survival, length of ECMO course, length of intubation, or subsequent need for supplemental oxygen.

Is surfactant therapy beneficial in the treatment of the term newborn infant with congenital diaphragmatic hernia?

OBJECTIVES

To determine the impact of surfactant replacement on survival, need for extracorporeal membrane oxygenation (ECMO), and chronic lung disease in term infants with prenatally diagnosed congenital diaphragmatic hernia (CDH).

STUDY DESIGN

Prenatally diagnosed infants born at > or =37 weeks' gestation with immediate distress at delivery and no other major congenital anomalies, who were enrolled in the CDH Registry, were analyzed. For univariate analysis, chi 2 tests were used for categoric variables and unpaired t tests for nominal variables. Multiple logistic regression was used to calculate adjusted odds ratios.

RESULTS

Eligible infants (n = 522) were identified. Demographic variables were similar between the surfactant-treated (n = 192) and nonsurfactant-treated (n = 330) groups, with the exception of race (white, 88.0% vs 71.2%; P =.0007). The use of ECMO and incidence of chronic lung disease were higher (59.8 vs 50.6, P =.04; 59.9 vs 47.6, P =.0066) and survival lower in the surfactant-treated cohort (57.3 vs 70.0, P =.0033). Adjusted logistic regression for use of ECMO, survival, and chronic lung disease resulted in odds ratios inconsistent with an improved outcome associated with surfactant use.

CONCLUSIONS

This analysis shows no benefit associated with surfactant therapy for term infants with a prenatal diagnosis of isolated CDH.

A dual stable isotope tracer method for the measurement of surfactant disaturated-phosphatidylcholine net synthesis in infants with congenital diaphragmatic hernia

The aim of the study was to measure for the first time in humans surfactant disaturated-phosphatidylcholine (DSPC) net synthesis and kinetics by using a novel, dual stable isotope tracer approach. Ten infants with congenital diaphragmatic hernia [CDH; birth weight, 3.4 +/- 0.2; gestational age, 39.8 +/- 0.4 wk] and 6 age-matched control subjects with no lung disease (birth weight, 3.2 +/- 0.3 kg; gestational age, 39.1 +/- 1.1 wk), all of whom were admitted to the neonatal intensive care unit (Padua, Italy), were studied. All infants received simultaneously an intratracheal (carbon-13 di-palmitoyl-phosphatidylcholine) and an i.v. (deuterated palmitic acid) stable isotope tracer. Isotopic enrichment curves of DSPC from sequential tracheal aspirates were analyzed by mass spectrometry. DSPC kinetic data were expressed as mean +/- SEM and compared by the Mann-Whitney test. DSPC net synthesis from plasma palmitate was nearly identical in infants with CDH and control subjects (8.6 +/- 2.2 and 8.1 +/- 1.5 mg. kg(-1). d(-1); P = 0.7). DSPC apparent pool size was 36.7 +/- 7.5 and 58.5 +/- 9.1 mg/kg (P = 0.07) and half-life was 26.7 +/- 4.5 and 50.3 +/- 9.7 h (P = 0.03) in infants with CDH and control subjects, respectively. Both DSPC turnover and percentage of catabolism/recycling significantly correlated with duration of mechanical ventilation. In conclusion, the measurements of net DSPC synthesis and catabolism/recycling were reported for the first time in humans. Mean net DSPC synthesis was approximately 8 mg. kg(-1). d(-1). No significant differences were found between control subjects and infants with CDH. DSPC turnover was faster in infants with CDH, presumably reflecting an increased DSPC catabolism/recycling. Whether this may ultimately lead to a secondary surfactant deficiency in infants with CDH is still to be ascertained.

Surfactant does not improve survival rate in preterm infants with congenital diaphragmatic hernia

BACKGROUND

Use of exogenous surfactant in congenital diaphragmatic hernia (CDH) patients is routine in many centers. The authors sought to determine the impact of surfactant use in the premature infant with CDH.

METHODS

Data on liveborn infants with CDH from participating institutions were collected prospectively. Surfactant use and timing and outcome data were analyzed retrospectively. The authors evaluated the prenatal diagnosis patients as well. The outcome variable was survival to discharge. Odds ratios with confidence intervals were calculated.

RESULTS

Five hundred ten infants less than 37 weeks' gestation were entered in the CDH registry. Infants with severe anomalies (n = 80) were excluded. Information on surfactant use was available for 424 patients. Infants receiving surfactant (n = 209) had a greater odds of death than infants not receiving surfactant (n = 215, odds ratio, 2.17, 95% CI: 1.5 to 3.2; P <.01). In prenatally diagnosed infants with immediate distress, there was a trend toward worse survival rates among those receiving surfactant at 1 hour (52 patients) versus those that did not (93 patients; odds ratio, 1.93, 95% CI: 0.96 to 3.9; P <.07).

CONCLUSIONS

Surfactant, as currently used, is associated with a lower survival rate in preterm infants with CDH. The use of surfactant replacement in premature infants with CDH can be recommended only within the context of a randomized clinical trial.

Pulmonary surfactant protein A, B, and C mRNA and protein expression in the nitrofen-induced congenital diaphragmatic hernia rat model

Neonates with congenital diaphragmatic hernia (CDH) suffer from a diaphragmatic defect, lung hypoplasia, and pulmonary hypertension, with poor lung function forming the major clinical challenge. Despite prenatal diagnosis and advanced postnatal treatment strategies, the mortality rate of CDH is still high. CDH has been subject of extensive research over the past decades, but its etiology remains unknown. A major problem with CDH is the failure to predict the individual response to treatment modalities like high-frequency ventilation, inhaled nitric oxide, and extracorporeal membrane oxygenation. In this study, we tested the possibility that CDH lungs are surfactant protein deficient, which could explain the respiratory failure and difficulties in treating CDH infants. We investigated this hypothesis in the nitrofen-induced CDH rat model and assessed the cellular concentrations of surfactant protein (SP)-A, -B, and -C mRNA with a quantitative radioactive in situ hybridization technique. No differences were observed between control and CDH lungs for SP mRNA expression patterns. The cellular concentration (mean OD) of SP-A and SP-B mRNA was similar at all stages whereas the mean OD of SP-C mRNA and the volume fraction of cells (% Area) expressing SP mRNA was higher in CDH lungs at term. Immunohistochemical analysis revealed no differences between control and CDH lungs for SP protein expression. No differences in the mean OD or % Area for the SP mRNAs were found between the ipsi- and contralateral side of CDH lungs. We conclude that there is no primary deficiency of surfactant proteins in the nitrofen-induced CDH rat model.

Pulmonary surfactant disaturated-phosphatidylcholine (DSPC) turnover and pool size in newborn infants with congenital diaphragmatic hernia (CDH)

In animal CDH models, surfactant deficiency contributes to the pathophysiology of the condition but information on human disease is very limited. The aim of our study was to investigate surfactant kinetics in CDH newborns. We studied surfactant disaturated-phosphatidylcholine (DSPC) half-life, turnover and apparent pool size by stable isotope methodology in CDH newborns with no ExtraCorporeal Membrane Oxygenation (ECMO) support (n = 13, birth weight (BW) 3.2 +/- 2.2 kg, gestational age (GA) 39 +/- 0.4 wks, postnatal age 43 +/- 11 h) and in 8 term infants with no lung disease (CONTROLS, BW 2.7 +/- 0 kg, GA 38 +/- 0.8 wks, postnatal age 96 +/- 26 h). We administered a trace dose of 13C-palmitic acid dipalmitoyl-phosphatidylcholine (DPPC) through the endotracheal (ET) tube and we measured DSPC kinetics by gas chromatography-mass spectrometry from DSPC13C-enrichment decay curves obtained from sequential tracheal aspirates. DSPC amount from tracheal aspirates (TA-DSPC) was measured by gas chromatography. In CDH infants DSPC half-life was shorter (24 +/- 4 and 53 +/- 11 h, p = 0.01), turnover faster (0.6 +/- 0.1 and 1.5 +/- 0.3 d-1 p = 0.01), apparent pool size smaller (34 +/- 6 and 57 +/- 7 mg/kg body weight, p = 0.02) and tracheal aspirates DSPC amount lower (2.4 +/- 0.4 and 4.6 +/- 0.5 mg/mL Epithelial Lining Fluid (ELF), p = 0.007) than in CONTROLS. In conclusion surfactant kinetics is grossly abnormal in mechanically ventilated CDH. Whether alterations of DSPC kinetics in CDH infants are caused by a primary surfactant deficiency or are secondary to oxygen therapy and ventilator support has still to be determined.