Pulmonary surfactant therapy

Laparoscopic versus open repair of recto-bladderneck and recto-prostatic anorectal malformations: a systematic review and meta-analysis

OBJECTIVE

The laparoscopically-assisted anorectal pull-through (LAARP) for recto-bladderneck and recto-prostatic anorectal malformations (RB/RP-ARMs) is believed to improve patient outcomes. We performed a systematic review of the effect of LAARP on postoperative mucosal prolapse and defecation dysfunction.

METHODS

A comprehensive search of MEDLINE, EMBASE, CENTRAL, and grey literature was performed (2000-2014). Full-text screening, data abstraction and quality appraisal were conducted in duplicate. Included studies reported a primary diagnosis of RB/RP-ARM and compared LAARP versus open repair (OPEN).

RESULTS

From 3681 retrieved articles, 7 studies enrolling 187 patients were analyzed. One was a randomized control trial, 6 were retrospective observational studies, and all were single-centre. The majority were of poor-moderate quality (MINORS scores: mean 16.42 (SD 2.225) out of 24). Mucosal prolapse was not significantly different after LAARP versus OPEN (p = 0.18). Defecation outcomes were inconsistently reported but were no different between LAARP and OPEN for either children >3 years old (p = 0.84), or all ages combined (p = 0.11).

CONCLUSION

We found no significant difference in rates of mucosal prolapse or defecation scores for LAARP compared to OPEN for children with RB/RP-ARMs. However, studies are small and of poor-moderate quality and results are heterogeneous. Comprehensive, standardized, reliable reporting is necessary to guide practice and inform postoperative guidelines.

LEVEL OF EVIDENCE

1c.

High-performing dry powder inhalers of paclitaxel DPPC/DPPG lung surfactant-mimic multifunctional particles in lung cancer: physicochemical characterization, in vitro aerosol dispersion, and cellular studies

Inhalable lung surfactant-based carriers composed of synthetic phospholipids, dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG), along with paclitaxel (PTX), were designed and optimized as respirable dry powders using organic solution co-spray-drying particle engineering design. These materials can be used to deliver and treat a wide variety of pulmonary diseases with this current work focusing on lung cancer. In particular, this is the first time dry powder lung surfactant-based particles have been developed and characterized for this purpose. Comprehensive physicochemical characterization was carried out to analyze the particle morphology, surface structure, solid-state transitions, amorphous character, residual water content, and phospholipid bilayer structure. The particle chemical composition was confirmed using attenuated total reflectance-Fourier-transform infrared (ATR-FTIR) spectroscopy. PTX loading was high, as quantified using UV-VIS spectroscopy, and sustained PTX release was measured over weeks. In vitro cellular characterization on lung cancer cells demonstrated the enhanced chemotherapeutic cytotoxic activity of paclitaxel from co-spray-dried DPPC/DPPG (co-SD DPPC/DPPG) lung surfactant-based carrier particles and the cytotoxicity of the particles via pulmonary cell viability analysis, fluorescent microscopy imaging, and transepithelial electrical resistance (TEER) testing at air-interface conditions. In vitro aerosol performance using a Next Generation Impactor™ (NGI™) showed measurable powder deposition on all stages of the NGI and was relatively high on the lower stages (nanometer aerodynamic size). Aerosol dispersion analysis of these high-performing DPIs showed mass median diameters (MMADs) that ranged from 1.9 to 2.3 μm with excellent aerosol dispersion performance as exemplified by high values of emitted dose, fine particle fractions, and respirable fractions.

Essential childbirth and postnatal interventions for improved maternal and neonatal health

Childbirth and the postnatal period, spanning from right after birth to the following several weeks, presents a time in which the number of deaths reported still remain alarmingly high. Worldwide, about 800 women die from pregnancy- or childbirth-related complications daily while almost 75% of neonatal deaths occur within the first seven days of delivery and a vast majority of these occur in the first 24 hours. Unfortunately, this alarming trend of mortality persists, as 287,000 women lost their lives to pregnancy and childbirth related causes in 2010. Almost all of these deaths were preventable and occurred in low-resource settings, pointing towards dearth of adequate facilities in these parts of the world. The main objective of this paper is to review the evidence based childbirth and post natal interventions which have a beneficial impact on maternal and newborn outcomes. It is a compilation of existing, new and updated interventions designed to help physicians and policy makers and enable them to reduce the burden of maternal and neonatal morbidities and mortalities. Interventions during the post natal period that were found to be associated with a decrease in maternal and neonatal morbidity and mortality included: advice and support of family planning, support and promotion of early initiation and continued breastfeeding; thermal care or kangaroo mother care for preterm and/or low birth weight babies; hygienic care of umbilical cord and skin following delivery, training health personnel in basic neonatal resuscitation; and postnatal visits. Adequate delivery of these interventions is likely to bring an unprecedented decrease in the number of deaths reported during childbirth.

Early prophylactic versus late selective use of surfactant for respiratory distress syndrome in very preterm infants: a collaborative study of 53 multi-center trials in Korea

Pulmonary surfactant (PS) therapy was proven to be highly successful for the treatment of respiratory distress syndrome in premature infants. As a results, early prophylactic (EP) PS therapy has been introduced recently in Europe, the US and Korea. However, no multi-center study was compared EP and late selective (LS) PS therapies in Korea. We performed a retrospective multi-center study to compare the outcomes of EP and LS PS therapies in very preterm infants. We analyzed clinical morbidity and mortality for 1,291 infants in 2010 (LS group) and 1,249 infants in 2011 (EP group); the infants were born <30 weeks of gestation and had birth weight ≤1,250 g, and were chosen from 53 neonatal intensive care units in Korea. Compared to the LS group (22.5%), the overall mortality was better in the EP group (19.9%) and there was no increased need for retreatment.There were additional benefits in the EP group such as fewer associated complications. To the best of knowledge, our study is the first nationwide Korean study to compare the outcomes of EP and LS therapies, and it provides evidences that EP PS therapy is important in very preterm infants to improve for survival and reduce morbidities.

Minimally invasive surfactant therapy with a gastric tube is as effective as the intubation, surfactant, and extubation technique in preterm babies

AIM

Preterm infants requiring surfactant replacement have been treated using the INSURE technique, which requires sedation and comprises tracheal intubation, surfactant instillation and extubation. However, minimally invasive surfactant therapy (MIST) does not require sedation, minimises airway injury and avoids placing positive pressure ventilation on an immature lung. This study compared the feasibility of the two techniques and the outcomes in preterm babies with respiratory distress syndrome (RDS).

METHODS

Preterm infants with RDS prospectively received surfactant via a gastric tube placed in the trachea by direct laryngoscopy with no sedation. Technique-related complications and respiratory outcomes were analysed.

RESULTS

We compared 44 patients who received MIST with a historic cohort of 31 patients who received INSURE. This showed no differences in the rate of intubation and mechanical ventilation in the first 72 h, or secondary respiratory outcomes and relevant morbidities, between the babies who received INSURE and those who received MIST. More babies in the MIST group (35%) needed a second dose of surfactant than the INSURE group (6.5%) (p < 0.0001).

CONCLUSION

Surfactant administration using MIST, with no sedation, is feasible in preterm infants with RDS. No significant differences in secondary respiratory outcomes were found between the MIST and INSURE techniques.

Nanoparticle-mediated pulmonary drug delivery: a review

Colloidal drug delivery systems have been extensively investigated as drug carriers for the application of different drugs via different routes of administration. Systems, such as solid lipid nanoparticles, polymeric nanoparticles and liposomes, have been investigated for a long time for the treatment of various lung diseases. The pulmonary route, owing to a noninvasive method of drug administration, for both local and systemic delivery of an active pharmaceutical ingredient (API) forms an ideal environment for APIs acting on pulmonary diseases and disorders. Additionally, this route offers many advantages, such as a high surface area with rapid absorption due to high vascularization and circumvention of the first pass effect. Aerosolization or inhalation of colloidal systems is currently being extensively studied and has huge potential for targeted drug delivery in the treatment of various diseases. Furthermore, the surfactant-associated proteins present at the interface enhance the effect of these formulations by decreasing the surface tension and allowing the maximum effect. The most challenging part of developing a colloidal system for nebulization is to maintain the critical physicochemical parameters for successful inhalation. The following review focuses on the current status of different colloidal systems available for the treatment of various lung disorders along with their characterization. Additionally, different in vitro, ex vivo and in vivo cell models developed for the testing of these systems with studies involving cell culture analysis are also discussed.

Mothers of babies enrolled in a randomized trial immediately after birth report a positive experience

OBJECTIVE

Randomized trials are essential for improving outcomes, but researchers can be hesitant about undertaking clinical trials in newborn babies because of perceived vulnerability of the baby and risk of increasing parental anxiety. There is a paucity of evidence about the parental experience. We investigated mothers' experiences of having their newborn baby participate in a randomized double-blind placebo-controlled trial soon after birth.

STUDY DESIGN

Eligible mothers had consented to their baby's participation in the Sugar Babies Study. Mothers of potentially eligible babies were invited to join the study antenatally, but others were approached postnatally. Babies were enrolled in the study soon after birth and remained in the study for 48 h. After 2 weeks the birth mothers were interviewed by phone about their experience.

RESULT

Four hundred and eighty-one mothers were enrolled, of whom 310 (64%) gave consent antenatally. All mothers were contacted and 477 (99%) were interviewed. The majority of mothers (458, 96%) reported they would consent to participating again, if they had another eligible baby, and 460 mothers (96%) reported they would recommend participation to family and friends. Nineteen mothers (4%) reported they did not like the heel lance blood tests, which were part of routine clinical care and not part of the trial protocol.

CONCLUSION

Most mothers reported the experience of having their newborn baby participate in a clinical trial as positive. Most negative responses were related to aspects of routine care rather than the trial protocol.

Immunomodulatory properties of surfactant preparations

Surfactant replacement significantly decreased acute pulmonary morbidity and mortality among preterm neonates with respiratory distress syndrome. Besides improving lung function and oxygenation, surfactant is also a key modulator of pulmonary innate and acquired immunity regulating lung inflammatory processes. In this review, we describe the immunomodulatory features of surfactant preparations. Various surfactant preparations decrease the proinflammatory cytokine and chemokine release, the oxidative burst activity, and the nitric oxide production in lung inflammatory cells such as alveolar neutrophils, monocytes and macrophages; they also affect lymphocyte proliferative response and immunoglobulin production, as well as natural killer and lymphokine-activated killer cell activity. In addition, surfactant preparations are involved in airway remodeling, as they decrease lung fibroblast proliferation capacity and the release of mediators involved in remodeling. Moreover, they increase cell transepithelial resistance and VEGF synthesis in lung epithelial cells. A number of different signaling pathways and molecules are involved in these processes. Because the inhibition of local immune response may decrease lung injury, surfactant therapeutic efficacy may be related not only to its biophysical characteristics but, at least in part, to its anti-inflammatory features and its effects on remodeling processes. However, further studies are required to identify which surfactant preparation ensures the highest anti-inflammatory activity, thereby potentially decreasing the inflammatory process underlying respiratory distress syndrome. In perspective, detailed characterization of these anti-inflammatory effects could help to improve the next generation of surfactant preparations.

Neonatal cardiac care, a perspective

Every year in the United States approximately 40,000 infants are born with congenital heart disease. Several of these infants require corrective or palliative surgery in the neonatal period. Mortality rates after cardiac surgery are highest amongst neonates, particularly those born prematurely. There are several reasons for the increased surgical mortality risk in neonates. This review outlines these risks, with particular emphasis on the relative immaturity of the organ systems in the term and preterm neonate.

Pediatric calfactant in acute respiratory distress syndrome trial

RATIONALE

Our previous studies in children with acute lung injury/acute respiratory distress syndrome demonstrated improved outcomes with exogenous surfactant (calfactant) administration. Sample sizes in those studies were small, however, and the subject populations heterogeneous, thus making recommendations tenuous.

OBJECTIVE

To investigate the efficacy of surfactant administration in a larger, more homogenous population of children with lung injury/acute respiratory distress syndrome due to direct lung injury.

DESIGN AND SETTING

Masked, randomized, placebo-controlled trial in 24 children's hospitals in six different countries.

PATIENTS AND METHODS

Children 37 weeks postconception to 18 years old with lung injury/acute respiratory distress syndrome due to direct lung injury were randomized to receive up to three doses of 30 mg/cm height of surfactant (calfactant) versus placebo (air) within 48 hours of intubation and initiation of mechanical ventilation. The primary outcome was mortality at 90 days. Ventilator-free days, changes in oxygenation, and adverse events were also assessed.

RESULTS

The study was stopped at the sponsor's request after the second interim analysis for presumed futility. A total of 110 subjects were enrolled, with consent withdrawn from one whose data are unavailable. There were no significant differences between groups except in hospital-free days (10.4 ± 7.8 placebo vs 6.4 ± 7.8 surfactant; p = 0.01). Overall 90-day mortality was 11% (seven surfactant, five placebo). No immediate improvement in oxygenation was associated with surfactant administration.

CONCLUSIONS

Surfactant did not improve outcomes relative to placebo in this trial of children with direct lung injury/acute respiratory distress syndrome. Differences in concentration of the surfactant, failure to recruit the lung during surfactant administration, or using two rather than four position changes during administration are possible explanations for the difference from previous studies. Exogenous surfactant cannot be recommended at this time for children with direct lung injury/acute respiratory distress syndrome.

Advances in monitoring and management of pediatric acute lung injury

This article focuses on the respiratory management and monitoring of pediatric acute lung injury (ALI) as a specific cause for respiratory failure. Definitive, randomized, controlled trials in pediatrics to guide optimal ventilatory management are few. The only adjunct therapy that has been proved to improve clinical outcome is low tidal volume ventilation, but only in adult patients. Careful monitoring of the patient's respiratory status with airway graphic analysis and capnography can be helpful. Definitive data are needed in the pediatric population to assist in the care of infants, children, and adolescents with ALI to improve survival and functional outcome.

Pulmonary GLP-1 receptor increases at birth and exogenous GLP-1 receptor agonists augmented surfactant-protein levels in litters from normal and nitrofen-treated pregnant rats

The glucagon-like peptide-1 receptor (GLP-1R) is found in a variety of tissues outside of the pancreas. For example, GLP-1R is expressed in the lung, where it has been implicated in the regulation of the lipid fraction of surfactants, suggesting it fulfills an important role in lung function. Here, we show that GLP-1R expression is strongly up-regulated immediately after birth in neonatal rats, particular in male offspring. Moreover, administering long half-life GLP-1R agonists to the mother from gestational day 14 to birth (exendin-4 or liraglutide) increased surfactant protein (SP)-A and SP-B mRNA expression and the amount of SPs in the amniotic fluid at the end of pregnancy. These effects were similar or more potent to those induced by the glucocorticoid dexamethasone, which also increased GLP-1R expression in fetuses just before delivery. Lir increased fetal SP-A and GLP-1R expression in control rats and in a nitrofen-induced model of lung hypoplasia. Moreover, lung size increased in controls after Lir administration, which also prevented the decrease in lung weight and the poor neonatal survival of the offspring from nitrofen-treated dams, effects that were not produced by dexamethasone. Taken together, our results demonstrate the importance of the GLP-1 system in regulating SP production and lung development.

Surfactant therapy for bronchiolitis in critically ill infants

BACKGROUND

Bronchiolitis is one of the most frequent causes of respiratory failure in infants; some infants will require intensive care and mechanical ventilation. There is lack of evidence regarding effective treatment for bronchiolitis other than supportive care. Abnormalities of surfactant quantity or quality (or both) have been observed in severe cases of bronchiolitis. Exogenous surfactant administration appears to favourably change the haemodynamics of the lungs and may be a potentially promising therapy for severe bronchiolitis. 

OBJECTIVES

To evaluate the efficacy of exogenous surfactant administration (i.e. intratracheal administration of surfactant of any type (whether animal-derived or synthetic), at any dose and at any time after start of ventilation) compared to placebo, no intervention or standard care in reducing mortality and the duration of ventilation in infants and children with bronchiolitis requiring mechanical ventilation.

SEARCH METHODS

We searched CENTRAL 2012, Issue 4 which contains the Cochrane Acute Respiratory Infections Group's Specialised Register, MEDLINE (1948 to May week 1, 2012), EMBASE (1974 to May 2012), CINAHL (1982 to May 2012), LILACS (1985 to May 2012) and Web of Science (1985 to May 2012).

SELECTION CRITERIA

We considered prospective, randomised controlled trials (RCTs) and quasi-RCTs evaluating the effect of exogenous surfactant in infants and children with bronchiolitis requiring mechanical ventilation.

DATA COLLECTION AND ANALYSIS

Two review authors selected studies independently. We extracted the data using a predefined proforma, independently analysed the data and performed meta-analyses.

MAIN RESULTS

We included three small RCTs enrolling 79 participants. Two trials did not use a placebo in the control arms and the third trial used air placebo. Two included studies did not describe mortality. We judged some of the included studies to have an unclear risk of bias but none of the included studies had a high risk of bias. Our pooled analysis of the three trials revealed that duration of mechanical ventilation was not different between the groups (mean difference (MD) -63.04, 95% confidence interval (CI) -130.43 to 4.35 hours) but duration of intensive care unit (ICU) stay was less in the surfactant group compared to the control group: MD -3.31 (95% CI -6.38 to -0.25 days). After excluding one trial which produced significant heterogeneity, the duration of mechanical ventilation and duration of ICU stay were significantly lower in the surfactant group compared to the control group: MD -28.99 (95% CI -40.10 to -17.87 hours) and MD -1.81 (95% CI -2.42 to -1.19 days), respectively. Use of surfactant had favourable effects on oxygenation and CO(2) elimination. No adverse effects and no complications were observed in any of the three included studies.

AUTHORS' CONCLUSIONS

The available evidence is insufficient to establish the effectiveness of surfactant therapy for bronchiolitis in critically ill infants who require mechanical ventilation. There is a need for larger trials with adequate power and a cost-effectiveness analysis to evaluate the effectiveness of exogenous surfactant therapy for infants with bronchiolitis who require intensive care management.

Brain injury in chronically ventilated preterm neonates: collateral damage related to ventilation strategy

Brain injury is a frequent comorbidity in chronically ventilated preterm infants. However, the molecular basis of the brain injury remains incompletely understood. This article discusses the subtle (diffuse) form of brain injury that has white matter and gray matter lesions without germinal matrix hemorrhage-intraventricular hemorrhage, posthemorrhagic hydrocephalus, or cystic periventricular leukomalacia. This article synthesizes data that suggest that diffuse lesions to white matter and gray matter are collateral damage related to ventilator strategy. Evidence is introduced from the 2 large-animal, physiologic models of evolving neonatal chronic lung disease that suggest that an epigenetic mechanism may underlie the collateral damage.

Prophylactic versus selective use of surfactant in preventing morbidity and mortality in preterm infants

BACKGROUND

Surfactant therapy is effective in improving the outcome of very preterm infants. Trials have studied a wide variety of surfactant preparations used either to prevent or treat respiratory distress syndrome (RDS). In animal models, prophylactic surfactant leads to more homogeneous distribution and less evidence of lung damage. However, administration requires intubation and treatment of infants who will not go on to develop RDS. This is of particular concern with the advent of improved approaches to providing continuous distending pressure, particularly in the form of nasal continuous positive airway pressure (CPAP).

OBJECTIVES

To compare the effect of prophylactic surfactant administration to surfactant treatment of established RDS in very preterm infants at risk of RDS.

SEARCH METHODS

We updated the search of the Cochrane Central Register of Controlled Trials (The Cochrane Library), MEDLINE, EMBASE, CINAHL, and clinical trials.gov register in December 13, 2011.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials that compared the effects of prophylactic surfactant administration to surfactant treatment of established RDS in preterm infants at risk of RDS.

DATA COLLECTION AND ANALYSIS

Data regarding clinical outcomes were extracted from the reports of the clinical trials by the reviewers. Data analysis was done in accordance with the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

Eleven studies were identified that met inclusion criteria [nine without routine application of continuous positive air way pressure (CPAP) in the selective treatment group; two with routine application of CPAP in the selective treatment group]The meta-analysis of studies conducted prior to the routine application of CPAP demonstrated a decrease in the risk of air leak and neonatal mortality associated with prophylactic administration of surfactant. However, the analyses of studies that allowed for routine stabilization on CPAP demonstrated a decrease in the risk of chronic lung disease or death in infants stabilized on CPAP. When all studies were evaluated together, the benefits of prophylactic surfactant could no longer be demonstrated.

AUTHORS' CONCLUSIONS

Although the early trials of prophylactic surfactant administration to infants judged to be at risk of developing RDS compared to selective use of surfactant in infants with established RDS demonstrated a decreased risk of air leak and mortality, recent large trials that reflect current practice (including greater utilization of maternal steroids and routine post delivery stabilization on CPAP) do not support these differences and demonstrate less risk of chronic lung disease or death when using early stabilization on CPAP with selective surfactant administration to infants requiring intubation.

An asymptotic model of particle deposition at an airway bifurcation

Particle transport and deposition associated with flow over a wedge is investigated as a model for particle transport and flow at the carina of an airway bifurcation during inspiration. Using matched asymptotics, a uniformly valid solution is obtained to represent the high Reynolds number flow over a wedge that considers the viscous boundary layer near the wedge and the outer inviscid region and is then used to solve the particle transport equations. Sometimes particle impaction on the wedge is prevented due to the boundary layer. We call this boundary layer shielding (BLS). This effect can be broken down into different types: rejection, trapping and deflection that are described by what happens to the particle's initial negative velocity normal to the wall either changing sign, reaching zero, or remaining negative in the boundary layer region. The deposition efficiency depends on the critical Stokes number but exhibits a weak dependence on Reynolds number. Deposition efficiency for S(c) in the range 0 < S(c) < 0.4 yields the following relationship De ≈ (1.867S(c)¹·⁷⁸-0.016) sin(βπ/2) at large Reynolds numbers, where βπ is the wedge angle. For a specific deposition efficiency, S(c) decreases as βπ increases. The distribution of impacted particles was also computed and revealed that particles primarily impact within one airway diameter of the carina, consistent with computational fluid dynamics approaches. This work provides a new insight that the BLS inherent to the wedge component of the structure is the dominant reason for the particle distribution. This finding is important in linking aerosol deposition to the location of airway disease as well as target sites for therapeutic deposition.

Current technology in the diagnosis of developmentally related lung disorders

Respiratory disorders that present in the newborn period may result from structural, functional, or acquired mechanisms that limit gas exchange between the airspace and vascular bed. Exciting new imaging, gene sequencing, mass spectrometry, and molecular and cell-based techniques are enhancing our understanding of mechanisms of disease; highlighting the complexity of interactions between genes, development, and environment in the manifestation of health and disease; and becoming part of the clinical armamentarium for the care of patients. Some of these technologies and their clinical potential are briefly reviewed in this paper.

A comprehensive approach to the prevention of bronchopulmonary dysplasia

The current bronchopulmonary dysplasia (BPD) is seen in infants born extremely premature, with less severe respiratory distress syndrome (RDS) and who received prenatal steroids-"new BPD". The pathophysiology of BPD is based on an impairment of lung maturation with prenatal and postnatal multi-hit insults and genetic susceptibility. This multifactorial pathophysiology of BPD suggests that no single "magic bullet" will prevent it. Thus, to avoid BPD we need to implement a complex and comprehensive strategy. This strategy is based on ventilatory and non-ventilatory measures. The ventilatory route allows an individualized endotracheal intubation approach. Early lung recruitment with nasal respiratory support (nasal continuous positive airway pressure [NCPAP] or nasal intermittent positive pressure ventilation [NIPPV] / synchronized NIPPV [SNIPPV]) and the INSURE (intubation, surfactant and early extubation) approach are discussed. Initial treatment with NCPAP did not reduce the rate of BPD compared to endotracheal ventilation and surfactant administration. While NIPPV/SNIPPV may have short-term advantages over NCPAP, the effect on BPD needs to be further studied. During hospitalization the respiratory goals should aim for adequate oxygenation, permissive hypercapnia, and gentle ventilation. However, these goals were found to have short-term benefits but did not reduce significantly the rate of BPD. Selective use of a short course of low dose corticosteroids can be considered after the first or second week of life in infants who are unable to be weaned from the ventilator and are at high risk for BPD. Non-ventilatory measures include early nutritional support with fluid restriction, caffeine and consideration of vitamin A. Hemodynamic significant patent ductus arteriosus (PDA) may be associated with BPD, but medical or surgical treatment of PDA were not shown to decrease BPD. Each component and the strategy as a whole needs to be further studied in large randomized prospective studies or by meta-analyses, especially in the target population of extremely premature infants who are the most prone to BPD.

Synthesis and activity of a novel diether phosphonoglycerol in phospholipase-resistant synthetic lipid:peptide lung surfactants()

This paper reports the chemical synthesis and purification of a novel phospholipase-resistant C16:0, C16:1 diether phosphonoglycerol with structural analogy to ester-linked anionic phosphatidylglycerol (PG) in endogenous pulmonary surfactant. This diether phosphonoglycerol (PG 1) is studied for phospholipase A(2) (PLA(2)) resistance and for surface activity in synthetic exogenous surfactants combined with Super Mini-B (S-MB) peptide and DEPN-8, a previously-reported diether phosphonolipid analog of dipalmitoyl phosphatidylcholine (DPPC, the major zwitterionic phospholipid in native lung surfactant). Activity experiments measured both adsorption and dynamic surface tension lowering due to the known importance of these surface behaviors in lung surfactant function in vivo. Synthetic surfactants containing 9 : 1 DEPN-8:PG 1 + 3% S-MB were resistant to degradation by PLA(2) in chromatographic studies, while calf lung surfactant extract (CLSE, the substance of the bovine clinical surfactant Infasurf®) was significantly degraded by PLA(2). The 9 : 1 DEPN-8:PG 1 + 3% S-MB mixture also had small but consistent increases in both adsorption and dynamic surface tension lowering ability compared to DEPN-8 + 3% S-MB. Consistent with these surface activity increases, molecular dynamics simulations using Protein Modeller, GROMACS force-field, and PyMOL showed that bilayers containing DPPC and palmitoyl-oleoyl-PC (POPC) as surrogates of DEPN-8 and PG 1 were penetrated to a greater extent by S-MB peptide than bilayers of DPPC alone. These results suggest that PG 1 or related anionic phosphono-PG analogs may have functional utility in phospholipase-resistant synthetic surfactants targeting forms of acute pulmonary injury where endogenous surfactant becomes dysfunctional due to phospholipase activity in the innate inflammatory response.

Randomized trial comparing 3 approaches to the initial respiratory management of preterm neonates

OBJECTIVE

We designed a multicenter randomized trial to compare 3 approaches to the initial respiratory management of preterm neonates: prophylactic surfactant followed by a period of mechanical ventilation (prophylactic surfactant [PS]); prophylactic surfactant with rapid extubation to bubble nasal continuous positive airway pressure (intubate-surfactant-extubate [ISX]) or initial management with bubble continuous positive airway pressure and selective surfactant treatment (nCPAP).

DESIGN/METHODS

Neonates born at 26 0/7 to 29 6/7 weeks' gestation were enrolled at participating Vermont Oxford Network centers and randomly assigned to PS, ISX, or nCPAP groups before delivery. Primary outcome was the incidence of death or bronchopulmonary dysplasia (BPD) at 36 weeks' postmenstrual age.

RESULTS

648 infants enrolled at 27 centers. The study was halted before the desired sample size was reached because of declining enrollment. When compared with the PS group, the relative risk of BPD or death was 0.78 (95% confidence interval: 0.59-1.03) for the ISX group and 0.83 (95% confidence interval: 0.64-1.09) for the nCPAP group. There were no statistically significant differences in mortality or other complications of prematurity. In the nCPAP group, 48% were managed without intubation and ventilation, and 54% without surfactant treatment.

CONCLUSIONS

Preterm neonates were initially managed with either nCPAP or PS with rapid extubation to nCPAP had similar clinical outcomes to those treated with PS followed by a period of mechanical ventilation. An approach that uses early nCPAP leads to a reduction in the number of infants who are intubated and given surfactant.

Short-term outcome of very low-birth-weight infants in a tertiary care hospital in Saudi Arabia

BACKGROUND AND OBJECTIVE

Published data on short-term outcomes of very low birth weight infants from Saudi Arabia are limited. In the present study, our objective was to describe and analyze the outcomes of very low birth weight infants admitted to our neonatal intensive care unit and to compare the results with data published by the National Institute of Child Health and Development.

DESIGN AND SETTING

This study was a retrospective analysis of prospectively collected data from a single tertiary care center over a three years period.

PATIENTS AND METHODS

Biodemographic data and data regarding multiple outcome measures were analyzed for infants with birth weight of 1500 g or less. Data were obtained from our neonatal intensive care unit database.

RESULTS

Our results included a total of 186 infants with birth weights of 1500 g or less. Of these infants, 154 (82.8%) survived to discharge. Seventy-six (40.9%) were male, and mean (SD) gestational age (GA) was 29 (2.9) weeks with a range of 21 weeks, 6 days to 36 weeks, 2 days. Mean (SD) birth weight was 1062 (302) g with a range of 420 to 1495 g. Fifty-seven (30.6%) infants were characterized as small for gestational age. Antenatal steroids were given to 74.2% of mothers. Eighty-five percent of infants were born by cesarean section. The rate of bronchopulmonary dysplasia was 17.7%, patent ductus arteriosus 31.2%, intraventricular hemorrhage 12.9%, periventricular leukomalacia 3.8%, necrotizing enterocolitis 7.5%, retinopathy of prematurity 28.3%, and late-onset sepsis was 21.9%.

CONCLUSION

In this population of very low birth weight infants, survival rates and complications of prematurity were comparable to international data.

Intra-amniotic infection increases amniotic lamellar body count before 34 weeks of gestation

OBJECTIVE

To examine the lamellar body count (LBC) value in intra-amniotic infection cases and evaluate its association with the incidence of respiratory distress syndrome (RDS).

METHODS

Three hundred sixty-five amniotic fluid (AF) samples were obtained at caesarean section from 27 to 38 weeks of gestation. LBC and glucose concentrations in AF were measured with no centrifugation. We defined AF glucose concentrations<0.8 mmol/L and positive C-reactive protein (CRP) of the neonates as intra-amniotic infection.

RESULTS

An LBC cutoff value of 29,500/μL resulted in 94.0% sensitivity, 82.4% specificity, and 99.1% negative predictive value (NPV) for RDS. Neonates with glucose concentrations<0.8 mmol/L in AF and positive CRP had no RDS and significantly higher LBC values than controls before 34 weeks of gestation (17.0 vs. 4.3, p<0.05 and 25.5 vs. 5.0, p<0.05, respectively), but there were no significant differences after 34 weeks of gestation.

CONCLUSIONS

LBC is an accurate predictor of foetal lung maturity and our LBC cutoff value had a high NPV for predicting RDS. We showed that intra-amniotic infection was associated with significantly higher LBC values than the value in controls before 34 weeks of gestation, which correlated with a low incidence of RDS.

Evidence-based delivery room care of the very low birth weight infant

The first hour of a newborn's life is fraught with difficulty. Recommendations regarding the fundamental issues of resuscitation of these infants are developed and disseminated by the International Liaison Committee on Resuscitation and other organizations. However, these recommendations frequently do not address the needs of the very low birth weight infant and do not address some of the nuances that might lead to improved outcome. Improved organization and teamwork as well as improved monitoring and respiratory support can potentially improve the outcome of these infants.

Laryngeal mask airway for surfactant administration in a newborn animal model

Premature infants are subjected to adverse effects of intubation to benefit from surfactant. We hypothesized that administration of surfactant through a laryngeal mask airway (LMA) is as effective as administration through an endotracheal tube (ETT) and that time and physiologic changes during instrumentation will be less in the LMA group. This study is a randomized, controlled trial using newborn pigs. Lung injury was induced via surfactant washout. Animals were randomized into groups: 1) LMA placed, no surfactant administered (control; n = 8); 2) surfactant via an LMA (LMA group; n = 8); and 3) surfactant via an ETT (ETT group; n = 8). We demonstrated that partial pressure of oxygen in arterial blood (Pao2) levels of the LMA and ETT groups were not statistically different. Time for successful placement of LMA was 19 ± 1 s versus ETT 123 ± 35 s (mean ± SEM); number of attempts for successful LMA placement was 1.1 (1-2) versus ETT 1.9 (1-7) [mean (range)]. Administration of surfactant via an LMA compared with an ETT resulted in similar improvements in oxygenation. Placement of the device required less time and fewer attempts. These data suggest that further study in human neonates is justified. If proven effective, some infants with respiratory distress may be able to receive surfactant while avoiding intubation.

Dynamics of liquid plugs of buffer and surfactant solutions in a micro-engineered pulmonary airway model

We describe a bioinspired microfluidic system that resembles pulmonary airways and enables on-chip generation of airway occluding liquid plugs from a stratified air-liquid two-phase flow. User-defined changes in the air stream pressure facilitated by mechanical components and tuning the wettability of the microchannels enable generation of well-defined liquid plugs. Significant differences are observed in liquid plug generation and propagation when surfactant is added to the buffer. The plug flow patterns suggest a protective role of surfactant for airway epithelial cells against pathological flow-induced mechanical stresses. We discuss the implications of the findings for clinical settings. This approach and the described platform will enable systematic investigation of the effect of different degrees of fluid mechanical stresses on lung injury at the cellular level and administration of exogenous therapeutic surfactants.

Effect of exogenous surfactant therapy on levels of pulmonary surfactant proteins A and D in preterm infants with respiratory distress syndrome

OBJECTIVES

To examine whether exogenous pulmonary surfactants (exPS) substitute for or merely supplement endogenous pulmonary surfactants (enPS) by looking at sequential changes in the surfactant proteins (SP) SP-A and SP-D in alveolar pools.

METHODS

Fourteen preterm infants with RDS treated with an artificial surfactant were compared to five normal-term infants without RDS who were treated with artificial ventilation at birth.

RESULTS

Immediately after birth, SP-A and SP-D were essentially absent in the alveolar pools of the RDS group, but were present at normal levels in the controls. Treatment with exPS apparently stimulated enPS production.

CONCLUSIONS

In infants who responded well to exPS therapy, the SP concentration reached essentially normal levels within 48-72 h after birth.

Prophylactic protein free synthetic surfactant for preventing morbidity and mortality in preterm infants

BACKGROUND

Respiratory distress syndrome (RDS) is caused by a deficiency or dysfunction of pulmonary surfactant. A variety of surfactant products including protein free synthetic surfactant have been developed and tested in the prevention and treatment of RDS.

OBJECTIVES

To assess the effect of prophylactic administration of protein free synthetic surfactant (SS) on mortality, chronic lung disease and other morbidities associated with prematurity in preterm newborns at risk for developing RDS. Subgroup analysis were planned according to the degree of prematurity, surfactant product and dosage schedule.

SEARCH STRATEGY

Searches were made of the The Cochrane Library, MEDLINE, OVID, EMBASE, CINAHL from 1966 to 2009. In addition, previous reviews including cross references and abstracts from the Society for Pediatric Research were searched. No language restrictions were applied.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials that compared the effect of protein free SS administered to high risk preterm newborns at or shortly after birth in order to prevent RDS, mortality and complications of prematurity.

DATA COLLECTION AND ANALYSIS

Data regarding clinical outcomes was excerpted from the clinical trials by the reviewers. Data were analyzed according to the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

Studies of prophylactic administration of protein free SS note a variable improvement in the respiratory status and a decrease in respiratory distress syndrome in infants who receive prophylactic protein free SS. The meta-analysis supports a decrease in the risk of pneumothorax (typical relative risk 0.67, 95% CI 0.50, 0.90), pulmonary interstitial emphysema (typical relative risk 0.68, 95% CI 0.50, 0.93), and neonatal mortality (typical relative risk 0.70, 95% CI 0.58, 0.85). No differences were seen in the risk of intraventricular hemorrhage, necrotizing enterocolitis, bronchopulmonary dysplasia, retinopathy of prematurity and cerebral palsy. The meta-analysis supports an increase in the risk of patent ductus arteriosus associated with prophylactic SS administration (typical relative risk 1.11, 95% CI 1.00, 1.22), and an increase in the risk of pulmonary hemorrhage (typical relative risk 3.28, 95% CI 1.50, 7.16).

AUTHORS' CONCLUSIONS

Prophylactic intratracheal administration of protein free synthetic surfactant to infants at risk of developing respiratory distress syndrome has been demonstrated to improve clinical outcome. Infants who receive prophylactic protein free SS have a decreased risk of pneumothorax, a decreased risk of pulmonary interstitial emphysema, and a decreased risk of neonatal mortality. Infants who receive prophylactic protein free SS have an increased risk of developing patent ductus arteriosus and pulmonary hemorrhage.

WITHDRAWN. Surfactant therapy for bronchiolitis in critically ill infants

BACKGROUND

Viral bronchiolitis is a common cause of respiratory failure in infants and children, and accounts for a significant portion of intensive care unit (ICU) admissions during seasonal epidemics. Currently there is no evidence to support the use of anything but supportive care for this disease. Surfactant is a potentially promising therapy; alterations in its composition have been described in bronchiolitis, and it may play a role in the host immunity for this disease.

OBJECTIVES

To assess the efficacy of exogenous surfactant for the treatment of bronchiolitis in mechanically ventilated infants and children.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, 2006, issue 1) which contains the Acute Respiratory Infections Group's Specialized Register; MEDLINE (1966 to Week 1, February 2006); and EMBASE (1990 to September 2005).

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing surfactant with placebo or surfactant with no surfactant in mechanically ventilated infants and children with viral bronchiolitis.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed trial quality. Unpublished data were requested from trial authors when necessary.

MAIN RESULTS

Three trials containing a total of 79 patients met the inclusion criteria. No mortality or adverse effects associated with surfactant administration were reported in any of these trials. In the three trials, use of surfactant was associated with a decrease in duration of mechanical ventilation by 2.6 days (95% confidence interval (CI) -5.34 to 0.18 days; P value 0.07) and a decrease in ICU length of stay by 3.3 days (95% CI -6.38 to -0.23 days; P value 0.04). In two studies with 59 patients, in which duration of mechanical ventilation in the control groups was more comparable, surfactant was associated with a decrease in ventilator days by 1.21 days (95% CI 0.75 to 1.67 days) and a decrease in ICU stay by 1.81 days (95% CI 1.19 days to 2.42 days). Individually the studies reported some short term benefit of surfactant on pulmonary mechanics and gas exchange.

AUTHORS' CONCLUSIONS

Available data on surfactant were not sufficient to provide reliable estimates of its effects in mechanically ventilated infants and children with bronchiolitis. Future studies should be adequately powered and will need to address unresolved questions regarding which surfactant preparation may be best suited for the treatment of bronchiolitis, the appropriate dose and administration interval, and how the choice of ventilator strategy may modify its effects.

The relationship between systemic hemodynamic perturbations and periventricular-intraventricular hemorrhage--a historical perspective

Periventricular-intraventricular hemorrhage (PV-IVH) remains the major cause of injury to the developing brain. Predisposing factors include a germinal matrix with an immature vasculature, a pressure passive cerebral circulation, and hemodynamic perturbations in sick premature infants. Intact cerebral autoregulation has been documented in stable premature infants; however, it functions within a limited blood pressure range and is likely to be absent in the sick hypotensive infant, which increases the risk for PV-IVH with perturbations in blood pressure. The risk for PV-IVH is markedly increased in the absence of antenatal glucocorticoid exposure in the intubated low birthweight infant <1000 g with respiratory distress syndrome; +/- other complications. Although surfactant administration reduces the severity of respiratory distress syndrome, it has not led to a reduction in PV-IVH. Early postnatal administration of indomethacin has been associated with a reduction in PV-IVH, although this has not translated into long-term neurocognitive benefits.

Surfactant therapy for neonatal respiratory distress syndrome: a review of Korean experiences over 17 years

We undertook a multi-hospital collective study to evaluate outcomes of neonatal respiratory distress syndrome (RDS) patients treated with pulmonary surfactant (PS) over 17 yr in Korea (Group I; 1990/91, Group II; 1996, Group III; 2002, and Group IV; 2007). There were 60 neonates in Group I (16 hospitals), 1,179 in Group II (64), 1,595 in Group III (62), and 1,921 in Group IV (57). We adopted Bomsel's classification to evaluate initial chest radiographic findings, categorized RDS severities, and classified response types to PS therapy. Almost all cases were treated using a single dose in Groups I and II, but 19.5% received multiple-dose therapy in Group IV. In Group IV, Bomsel's stages III and IV composed 62.9% and initial severities of mild, moderate, and severe RDS were 23.0%, 42.0%, and 35.0%. More infants showed good response in Groups II, III, and IV than in Group I (71.7%, 66.8%, and 69.2% vs. 58.3%). Complications and mortality rate were lower in Group IV than in Groups I, II, and III (mortality rate: 14.3% vs. 40.0%, 30.0%, and 18.7%). We conclude that PS therapy in neonates with RDS had a remarkable impact on improving clinical course and outcomes over 17 yr in Korea.

Fighting tuberculosis: old drugs, new formulations

This review reports the state of the art on innovative drug delivery strategies designed for antitubercular chemotherapeutics. The introduction contains the fundamental biological background concerning tuberculosis and a review of the current antitubercular therapy, and is followed by a critical report of the micrometric and nanometric particulate systems designed and investigated to improve tuberculosis chemotherapy.

Protein-containing synthetic surfactant versus protein-free synthetic surfactant for the prevention and treatment of respiratory distress syndrome

BACKGROUND

Respiratory distress syndrome (RDS) is a significant cause of morbidity and mortality in preterm infants. RDS is caused by a deficiency, dysfunction, or inactivation of pulmonary surfactant. Numerous surfactants of either animal extract or synthetic design have been shown to improve outcomes. New surfactant preparations that include peptides or whole proteins that mimic endogenous surfactant protein have recently been developed and tested.

OBJECTIVES

To assess the effect of administration of synthetic surfactant containing surfactant protein mimics compared to protein free synthetic surfactant on the risk of mortality, chronic lung disease, and other morbidities associated with prematurity in preterm infants at risk for or having RDS.

SEARCH STRATEGY

Standard search methods of the Cochrane Neonatal Review Group were used. The search included MEDLINE (1966 - March 2009) and the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library) in all languages.

SELECTION CRITERIA

Randomized and quasi-randomized controlled clinical trials were considered for this review. Studies that enrolled preterm infants or low birth weight infants at risk for or having RDS who were treated with either a synthetic surfactant containing surfactant protein mimics or a protein free synthetic surfactant were included for this review. Studies of treatment or prevention of respiratory distress syndrome were included.

DATA COLLECTION AND ANALYSIS

Data regarding mortality, chronic lung disease and multiple secondary outcome measures were abstracted by the review authors. Statistical analysis was performed using Review Manager software. Categorical data were analyzed using relative risk, risk difference, and number needed to treat. 95% confidence intervals reported. A fixed effects model was used for the meta-analysis. Heterogeneity was assessed using the I(2) statistic.

MAIN RESULTS

One study was identified that compared protein containing synthetic surfactants (PCSS) to protein free synthetic surfactants. Infants who received protein containing synthetic surfactant compared to protein free synthetic surfactant did not demonstrate significantly different risks of prespecified primary outcomes: mortality at 36 weeks postmenstrual age (PMA) [RR 0.89 (95% CI 0.71, 1.11)], chronic lung disease at 36 weeks PMA [RR 0.89 (95% CI 0.78, 1.03)], or the combined outcome of mortality or chronic lung disease at 36 weeks PMA [RR 0.88 (95% CI 0.77, 1.01)]. Among the secondary outcomes, a decrease in the incidence of respiratory distress syndrome at 24 hours of age was demonstrated in the group that received PCSS [RR 0.83 (95% CI 0.72, 0.95).

AUTHORS' CONCLUSIONS

In the one trial comparing protein containing synthetic surfactants compared to protein free synthetic surfactant for the prevention of RDS, no statistically different clinical differences in death and chronic lung disease were noted. Clinical outcomes between the two groups were generally similar although the group receiving protein containing synthetic surfactants did have decreased incidence of respiratory distress syndrome. Further well designed studies comparing protein containing synthetic surfactant to the more widely used animal derived surfactant extracts are indicated.

Penetration depth of surfactant peptide KL4 into membranes is determined by fatty acid saturation

KL(4) is a 21-residue functional peptide mimic of lung surfactant protein B, an essential protein for lowering surface tension in the alveoli. Its ability to modify lipid properties and restore lung compliance was investigated with circular dichroism, differential scanning calorimetry, and solid-state NMR spectroscopy. KL(4) binds fluid lamellar phase PC/PG lipid membranes and forms an amphipathic helix that alters lipid organization and acyl chain dynamics. The binding and helicity of KL(4) is dependent on the level of monounsaturation in the fatty acid chains. At physiologic temperatures, KL(4) is more peripheral and dynamic in fluid phase POPC/POPG MLVs but is deeply inserted into fluid phase DPPC/POPG vesicles, resulting in immobilization of the peptide. Substantial increases in the acyl chain order are observed in DPPC/POPG lipid vesicles with increasing levels of KL(4), and POPC/POPG lipid vesicles show small decreases in the acyl chain order parameters on addition of KL(4). Additionally, a clear effect of KL(4) on the orientation of the fluid phase PG headgroups is observed, with similar changes in both lipid environments. Near the phase transition temperature of the DPPC/POPG lipid mixtures, which is just below the physiologic temperature of lung surfactant, KL(4) causes phase separation with the DPPC remaining in a gel phase and the POPG partitioned between gel and fluid phases. The ability of KL(4) to differentially partition into lipid lamellae containing varying levels of monounsaturation and subsequent changes in curvature strain suggest a mechanism for peptide-mediated lipid organization and trafficking within the dynamic lung environment.

Randomized clinical trial comparing two natural surfactant preparations to treat respiratory distress syndrome

OBJECTIVES

Natural surfactant preparations have been shown to reduce the severity and mortality of respiratory distress syndrome (RDS) in preterm infants. The objective of this study was to compare the efficacy of two natural surfactants, namely SF-RI 1 (Alveofact) and barectant (Survanta), on the incidence of chronic lung disease (CLD) and other associated complications of RDS in preterm infants.

METHODS

Preterm infants with RDS requiring artificial ventilation were randomly selected to receive an initial dose of either Alveofact or Survanta. The two treatment groups were tested for variation in gas exchange, ventilatory settings and neonatal complications such as CLD and mortality.

RESULTS

After 5 days the Survanta-treated infants had a lower fraction of inspired oxygen (FiO2) compared with the Alveofact-treated infants. There were no differences in the ventilatory settings. More infants in the Survanta group were extubated at 3 days and fewer required the use of postnatal steroids. Less CLD and duration of oxygenation were experienced by the Survanta-treated group.

CONCLUSIONS

Improved oxygenation and reduced ventilatory requirements were greater with Survanta compared to Alveofact, which in turn was associated with a trend towards a lower incidence of serious pulmonary complications.

An overview of pulmonary surfactant in the neonate: genetics, metabolism, and the role of surfactant in health and disease

Pulmonary surfactant is a complex mixture of phospholipids (PL) and proteins (SP) that reduce surface tension at the air-liquid interface of the alveolus. It is made up of about 70-80% PL, mainly dipalmitoylphosphatidylcholine (DPPC), 10% SP-A, B, C and D, and 10% neutral lipids, mainly cholesterol. Surfactant is synthesized, assembled, transported and secreted into the alveolus where it is degraded and then recycled. Metabolism of surfactant is slower in newborns, especially preterm, than in adults. Defective pulmonary surfactant metabolism results in respiratory distress with attendant morbidity and mortality. This occurs due to accelerated breakdown by oxidation, proteolytic degradation, inhibition or inherited defects of surfactant metabolism. Prenatal corticosteroids, surfactant replacement, whole lung lavage and lung transplantation have yielded results in managing some of these defects. Gene therapy could prove valuable in treating inherited defects of surfactant metabolism.

Metabolic precursors of surfactant disaturated-phosphatidylcholine in preterms with respiratory distress

Our objective was to study the metabolic precursors of surfactant disaturated-phosphatidylcholine (DSPC) in preterm infants with respiratory distress syndrome (RDS) on mechanical ventilation. We performed 46 DSPC kinetic studies in 23 preterms on fat-free parenteral nutrition and mechanical ventilation (birth weight = 1167 +/- 451 g, gestational age = 28.5 +/- 2.0 weeks). Eight infants received a simultaneous intravenous infusion of U(13)C-glucose and [16,16,16](2)H-palmitate, eight infants received U(13)C-glucose and (2)H(2)O, and seven received U(13)C-palmitate and (2)H(2)O. Surfactant DSPC kinetics were calculated from the isotopic enrichments of DSPC-palmitate from sequential tracheal aspirates and its metabolic precursors in plasma or urine. DSPC fractional synthesis rate (FSR) was 17 +/- 11, 21 +/- 16, and 15 +/- 6%/day from glucose, palmitate, and body water, respectively (P = 0.36). DSPC-FSR from U(13)C-glucose and (2)H(2)O were significantly correlated and yielded similar estimates (difference of -0.1 +/- 3%) (P = 0.91). The difference in the 15 infants receiving palmitate versus (2)H(2)O or palmitate versus glucose was +6.0 +/- 12%/day (P = 0.21). There was a significant correlation between DSPC-FSRs from plasma glucose and plasma FFA. The contribution of glucose versus palmitate to DSPC-FSR was 49 +/- 20% versus 51 +/- 20%, respectively. Plasma glucose and FFA showed similar contributions to DSPC-FSR in infants with RDS and fat-free parenteral nutrition. FSRs from (2)H(2)O or glucose were highly correlated.