Bronchoalveolar oxyradical inflammatory elements herald bronchopulmonary dysplasia

Early Biomarkers of Bronchopulmonary Dysplasia: A Quick Look to the State of the Art

Bronchopulmonary dysplasia (BPD) is one of the most common pulmonary sequelae of extreme preterm birth, with long-lasting respiratory symptoms and reduced lung function. A reliable predictive tool of BPD development is urgent and its search remains one of the major challenges for neonatologists approaching the upcoming arrival of possible new preventive therapies. Biomarkers, identifying an ongoing pathogenetic pathway, could allow both the selection of preterm infants with an evolving disease and potentially the therapeutic targets of the indicted pathogenesis. The "omic" sciences represent well-known promising tools for this objective. In this review, we resume the current laboratoristic, metabolomic, proteomic, and microbiomic evidence in the prediction of BPD. KEY POINTS: · The early prediction of BPD development would allow the targeted implementation of new preventive therapies.. · BPD is a multifactorial disease consequently it is unlikely to find a single disease biomarker.. · "Omic" sciences offer a promising insight in BPD pathogenesis and its development's fingerprints..

Bronchopulmonary dysplasia

In the absence of effective interventions to prevent preterm births, improved survival of infants who are born at the biological limits of viability has relied on advances in perinatal care over the past 50 years. Except for extremely preterm infants with suboptimal perinatal care or major antenatal events that cause severe respiratory failure at birth, most extremely preterm infants now survive, but they often develop chronic lung dysfunction termed bronchopulmonary dysplasia (BPD; also known as chronic lung disease). Despite major efforts to minimize injurious but often life-saving postnatal interventions (such as oxygen, mechanical ventilation and corticosteroids), BPD remains the most frequent complication of extreme preterm birth. BPD is now recognized as the result of an aberrant reparative response to both antenatal injury and repetitive postnatal injury to the developing lungs. Consequently, lung development is markedly impaired, which leads to persistent airway and pulmonary vascular disease that can affect adult lung function. Greater insights into the pathobiology of BPD will provide a better understanding of disease mechanisms and lung repair and regeneration, which will enable the discovery of novel therapeutic targets. In parallel, clinical and translational studies that improve the classification of disease phenotypes and enable early identification of at-risk preterm infants should improve trial design and individualized care to enhance outcomes in preterm infants.

Oxidative Stress and Anti-Oxidant Markers in Premature Infants with Respiratory Distress Syndrome

BACKGROUND

Neonatal respiratory distress syndrome (RDS) caused by decreased surfactant and structural lung immaturity. The imbalance between oxidative status and antioxidant defence system was suggested to be an important trigger for lung affection with RDS.

AIM

The goal of the current research was to elucidate the significance of the oxidant/ antioxidant status in the pathogenesis of RDS in preterm infants.

PATIENTS AND METHODS

This controlled study included 31 preterm neonates with RDS and 36 healthy preterm neonates. Quantification level of oxidative stress biomarkers; malondialdehyde (MDA) & hydrogen peroxide (H₂O₂) along with antioxidant enzymes activity; catalase (CAT) & superoxide dismutase (SOD) in plasma of healthy premature neonates compared with those with RDS.

RESULTS

status of oxidative stress markers (MDA & H₂O₂) showed a significant increase with decreased levels of antioxidant enzymes activity (CAT & SOD) in neonates with RDS when compared to healthy prematures.

CONCLUSION

The results obtained in this study indicate that the increased oxidative stress accompanied by reduced antioxidant defences may play a significant role in the pathogenesis of respiratory distress in preterm newborns.

Antioxidant strategies in respiratory medicine

Pulmonary oxidant stress plays an important pathogenetic role in disease conditions including acute lung injury/adult respiratory distress syndrome (ALI/ARDS), hyperoxia, ischemia-reperfusion, sepsis, radiation injury, lung transplantation, COPD, and inflammation. Reactive oxygen species (ROS), released from activated macrophages and leukocytes or formed in the pulmonary epithelial and endothelial cells, damage the lungs and initiate cascades of pro-inflammatory reactions propagating pulmonary and systemic stress. Diverse molecules including small organic compounds (e.g. gluthatione, tocopherol (vitamin E), flavonoids) serve as natural antioxidants that reduce oxidized cellular components, decompose ROS and detoxify toxic oxidation products. Antioxidant enzymes can either facilitate these antioxidant reactions (e.g. peroxidases using glutathione as a reducing agent) or directly decompose ROS (e.g. superoxide dismutases [SOD] and catalase). Many antioxidant agents are being tested for treatment of pulmonary oxidant stress. The administration of small antioxidants via the oral, intratracheal and vascular routes for the treatment of short- and long-term oxidant stress showed rather modest protective effects in animal and human studies. Intratracheal and intravascular administration of antioxidant enzymes are being currently tested for the treatment of acute oxidant stress. For example, intratracheal administration of recombinant human SOD is protective in premature infants exposed to hyperoxia. However, animal and human studies show that more effective delivery of drugs to cells experiencing oxidant stress is needed to improve protection. Diverse delivery systems for antioxidants including liposomes, chemical modifications (e.g. attachment of masking pegylated [PEG]-groups) and coupling to affinity carriers (e.g. antibodies against cellular adhesion molecules) are being employed and currently tested, mostly in animal and, to a limited extent, in humans, for the treatment of oxidant stress. Further studies are needed, however, in order to develop and establish effective applications of pulmonary antioxidant interventions useful in clinical practice. Although beyond the scope of this review, antioxidant gene therapies may eventually provide a strategy for the management of subacute and chronic pulmonary oxidant stress.

Biomarkers, Early Diagnosis, and Clinical Predictors of Bronchopulmonary Dysplasia

The pathogenesis of bronchopulmonary dysplasia (BPD) is multifactorial, and the clinical phenotype of BPD is extremely variable. Several clinical and laboratory biomarkers have been proposed for the early identification of infants at higher risk of BPD and for determination of prognosis of infants with a diagnosis of BPD. The authors review available literature on prediction tools and biomarkers of BPD, using clinical variables and biomarkers based on imaging, lung function measures, and measurements of various analytes in different body fluids that have been determined to be associated with BPD either in a targeted manner or by unbiased omic profiling.

Early Inhaled Budesonide for the Prevention of Bronchopulmonary Dysplasia

BACKGROUND

Systemic glucocorticoids reduce the incidence of bronchopulmonary dysplasia among extremely preterm infants, but they may compromise brain development. The effects of inhaled glucocorticoids on outcomes in these infants are unclear.

METHODS

We randomly assigned 863 infants (gestational age, 23 weeks 0 days to 27 weeks 6 days) to early (within 24 hours after birth) inhaled budesonide or placebo until they no longer required oxygen and positive-pressure support or until they reached a postmenstrual age of 32 weeks 0 days. The primary outcome was death or bronchopulmonary dysplasia, confirmed by means of standardized oxygen-saturation monitoring, at a postmenstrual age of 36 weeks.

RESULTS

A total of 175 of 437 infants assigned to budesonide for whom adequate data were available (40.0%), as compared with 194 of 419 infants assigned to placebo for whom adequate data were available (46.3%), died or had bronchopulmonary dysplasia (relative risk, stratified according to gestational age, 0.86; 95% confidence interval [CI], 0.75 to 1.00; P=0.05). The incidence of bronchopulmonary dysplasia was 27.8% in the budesonide group versus 38.0% in the placebo group (relative risk, stratified according to gestational age, 0.74; 95% CI, 0.60 to 0.91; P=0.004); death occurred in 16.9% and 13.6% of the patients, respectively (relative risk, stratified according to gestational age, 1.24; 95% CI, 0.91 to 1.69; P=0.17). The proportion of infants who required surgical closure of a patent ductus arteriosus was lower in the budesonide group than in the placebo group (relative risk, stratified according to gestational age, 0.55; 95% CI, 0.36 to 0.83; P=0.004), as was the proportion of infants who required reintubation (relative risk, stratified according to gestational age, 0.58; 95% CI, 0.35 to 0.96; P=0.03). Rates of other neonatal illnesses and adverse events were similar in the two groups.

CONCLUSIONS

Among extremely preterm infants, the incidence of bronchopulmonary dysplasia was lower among those who received early inhaled budesonide than among those who received placebo, but the advantage may have been gained at the expense of increased mortality. (Funded by the European Union and Chiesi Farmaceutici; ClinicalTrials.gov number, NCT01035190.).

Total antioxidant capacity and total oxidant status after surfactant treatment in preterm infants with respiratory distress syndrome

BACKGROUND

Oxidative damage is important in the pathogenesis of respiratory distress syndrome (RDS). However, data on the effect of surfactant therapy on oxidative stress in vivo are limited. We aimed to evaluate the oxidant/antioxidant status in preterm infants with RDS via measurement of total antioxidant capacity (TAC) and total oxidant status (TOS), to determine the effect of surfactant on oxidant/antioxidant balance and to assess the association between TAC, TOS and clinical outcomes of the patients.

METHODS

Sixty-nine infants with RDS were included. Blood samples for determining TAC and TOS were collected before and 48 h after surfactant treatment. TAC and TOS levels were analysed in serum. Patients were followed up until discharge or death.

RESULTS

Post-surfactant TAC levels were significantly higher than pre-surfactant TAC levels (P = 0.029). TAC/TOS ratio significantly increased after surfactant treatment (P = 0.018). Infants <28 weeks of gestational age had lower levels of baseline TAC than those ≥28 weeks of gestational age (P = 0.020), whereas TOS levels were similar. Baseline TAC/TOS ratio was lower in infants who died in the study period than those who survived (P = 0.023). After controlling gestational age, baseline TAC levels were significantly and inversely correlated with the duration of total respiratory support (r = -0.343; P = 0.009) and hospitalization (r = -0.341; P = 0.009). TAC or TOS levels were not associated with the development of bronchopulmonary dysplasia or other complications as determined during the investigation period.

CONCLUSIONS

Oxidant-antioxidant balance shifts in favour of the antioxidant system after surfactant treatment. Lower TAC/TOS ratio in preterm infants may be associated with increased mortality.

Ureia como marcador de diluição em amostras de lavado traqueobrônquico de potros com rodococose

No estudo das infecções e dos mecanismos inflamatórios do trato respiratório posterior, a diluição desconhecida de amostras de lavados traqueobrônquicos leva a um grave problema na interpretação das concentrações de várias substâncias. Foi investigada a amplitude da diluição em uma situação clínica verdadeira, com o objetivo de determinar a validez do uso da dosagem da ureia em lavados traqueobrônquicos para correção da diluição. As amostras do estudo consistiram em lavados traqueobrônquicos obtidos de sete potros com infecção por Rhodococcus equi. Foi realizada a contagem celular total e diferencial e comprado com o quadro clínico e a recuperação bacteriana de todas as amostras. Os fatores de diluição dos lavados variaram entre 14,3 e 130 (média 59,7). O uso da ureia como marcador de diluição melhorou a exatidão na determinação da concentração total de células nos lavados. Estes resultados sugerem que a prática de mensurar substâncias em lavado traqueobrônquico sem correção da diluição possa induzir a falsas conclusões.

Pneumatoceles in preterm infants-incidence and outcome in the post-surfactant era

OBJECTIVE

Pneumatoceles are gas-filled cysts within the lung parenchyma resulting mostly from ventilator-induced lung injury and air-leak in premature infants with respiratory distress syndrome. The use of surfactant in the treatment of respiratory distress syndrome has resulted in a decrease in the incidence of air-leak disease. Our aim was to study the incidence and clinical course of pneumatoceles in the surfactant era.

STUDY DESIGN

A retrospective study of infants born at < or =30 weeks gestational age was admitted to the University of Connecticut Health Center NICU from 1998 to 2007. Pneumatoceles and other intrathoracic air-leaks were identified and comparisons were made with infants without these conditions.

RESULT

Pneumatoceles were identified in 19 preterm infants, born at gestational age < or =30 weeks, needing positive pressure ventilation for respiratory distress syndrome between the years 1998 to 2007. Pneumatoceles appeared early (median, 7th day of life; range, 1st to 28th day of life) and usually resolved with decrease in mean airway pressure (median, 4 days; range, 3 to 125 days). The majority of pneumatoceles were located in the right parahilar region (18/19). Associated intrathoracic air-leaks were pulmonary interstitial emphysema (5/19), pneumothorax (10/19), and pneumomediastinum (1/19). None of the infants required any invasive procedures to alleviate the pneumatoceles. In infants who survived, most pneumatoceles resolved with a decrease in mean airway pressure or extubation (14/15). One infant had a persistent pneumatocele for 125 days without any cardiopulmonary compromise and five infants died as a result air-leaks along with other complications of prematurity.

CONCLUSION

Pneumatoceles are a manifestation of intrathoracic air-leaks of prematurity. They are markers for ventilator-induced lung injury and are associated with significant mortality similar to other intrathoracic air-leaks. However, conservative management with reduction in mean airway pressure is effective in the resolution of this condition and interventional decompression of the pneumatocele is generally not necessary.

Gastrin-releasing peptide, immune responses, and lung disease

Gastrin-releasing peptide (GRP) is produced by pulmonary neuroendocrine cells (PNECs), with highest numbers of GRP-positive cells present in fetal lung. Normally GRP-positive PNECs are relatively infrequent after birth, but PNEC hyperplasia is frequently associated with chronic lung diseases. To address the hypothesis that GRP mediates chronic lung injury, we present the cumulative evidence implicating GRP in bronchopulmonary dysplasia (BPD), the chronic lung disease of premature infants who survive acute respiratory distress syndrome. The availability of well-characterized animal models of BPD was a critical tool for demonstrating that GRP plays a direct role in the early pathogenesis of this disease. Potential mechanisms by which GRP contributes to injury are analyzed, with the main focus on innate immunity. Autoreactive T cells may contribute to lung injury late in the course of disease. A working model is proposed with GRP triggering multiple cell types in both the innate and adaptive immune systems, promoting cascades culminating in chronic lung disease. These observations represent a paradigm shift in the understanding of the early pathogenesis of BPD, and suggest that GRP blockade could be a novel treatment to prevent this lung disease in premature infants.

The Respiratory System

One of the most critical events of birth is the conversion of the fluid-filled lung, unimportant to fetal intrauterine existence, into a hollow organ distended with air and capable of gaseous exchange sufficient to support life. Indeed, it has been argued that the major determinant of perinatal survival is respiratory function (Wigglesworth and Desai 1982).

The failure to make this conversion adequately may lead, directly or indirectly, to infant death, and the pathologist often needs to assess the contribution made by respiratory inadequacy to the sequence of events leading to death. In the preterm infant, problems are mainly related to pulmonary immaturity and associated therapy. In the mature infant, birth asphyxia primarily results in cerebral damage but can engender significant respiratory complications when associated with aspiration of meconium. Even in stillbirths, where primary pulmonary pathology is rarely a cause of death, lung pathology may provide clues to antecedent events. Poor lung growth and maturation may point to the presence of pathology elsewhere. Consequently, adequate pathological investigation of the fetal or infant respiratory system is critical in any perinatal autopsy.

Pulmonary antioxidant concentrations and oxidative damage in ventilated premature babies

OBJECTIVE

To determine the relation between lipid peroxidation and the antioxidants ascorbate, urate, and glutathione in epithelial lining fluid in ventilated premature babies, and to relate the biochemical findings to clinical outcome.

DESIGN

A cohort study conducted between January 1999 and June 2001.

SETTING

A NHS neonatal intensive care unit.

PATIENTS

An opportunity sample of 43 ventilated babies of less than 32 weeks gestation.

MAIN OUTCOME MEASURES

The duration of supplementary oxygen according to the definition of bronchopulmonary dysplasia (BPD; oxygen dependency at 36 weeks gestational age).

METHODS

Epithelial lining fluid was sampled by bronchoalveolar lavage. Ascorbate, urate, glutathione, and malondialdehyde (a marker of lipid peroxidation) were measured.

RESULTS

Babies who developed BPD had significantly lower initial glutathione concentrations (mean (SEM) 1.89 (0.62) v 10.76 (2.79) microM; p = 0.043) and higher malondialdehyde concentrations (mean (SEM) 1.3 (0.31) v 0.345 (0.09) microM; p < 0.05) in the epithelial lining fluid than those who were not oxygen dependent. These variables were poor predictors of the development of BPD. Gestational age, endotracheal infection, and septicaemia had good predictive power. The level of oxidative damage was associated with the presence of endotracheal infection/septicaemia rather than inspired oxygen concentration.

CONCLUSIONS

Endotracheal infection, septicaemia, and gestational age, rather than antioxidant concentrations, are the most powerful predictors of the development of BPD.

Nitric oxide metabolites in the urine of full-term and preterm infants

BACKGROUND

In newborn full-term and preterm infants the urine nitrites and nitrates (NOx) were measured, in order to investigate the effects of different pathological conditions (infection, hypoxia) on systemic nitric oxide production.

METHODS

Urine nitrites and nitrates were determined by means of the Griess reaction, after reduction of nitrates to nitrites with nitrate reductase.

RESULTS

The NOx level was higher in preterm (278 nmol/mL) than full-term (176 nmol/mL) infants. Low NOx (115 nmol/mL) levels accompanied generalized infections, while its high contents (650 nmol/mL) was found in cytomegalovirus and one case of Pneumocystis carinii infection. Moderate increase of NOx production was observed in infants with local pulmonary infections and encephalopathies.

CONCLUSIONS

The results indicate urinary NOx level is lowered in infants with life-threatening generalized infection. A possibility of a rapid test based on newborn urinary NOx level determination is considered.

Global effects of xanthine oxidase stress on alveolar type II cells

OBJECTIVE: To delineate biochemical details of graded xanthine oxidase stress toward cultured alveolar type II cells, particularly oxidant-mediated damage of type II cell nucleic acid, protein, and lipid, as an in vitro model of distant ischemia-reperfusion lung injury. DESIGN: In vitro injury model using native rat and immortalized mouse alveolar type II cells and exogenous xanthine oxidase. SETTING: Research laboratory. Measurement: Cultured type II cells were subjected to xanthine oxidase-derived reactive oxygen stress at variable concentrations and incubation times. Reduction of type II cell double-stranded DNA, inhibition of de novo phosphatidyl choline synthesis, enhancement of lipid peroxidation, and suppression of mitochondrial redox capacity were analyzed in relation to high-intensity (xanthine oxidase, 25 munits/mL) oxidant stress. Alterations in type II cell cellular glutathione-related antioxidant repertoire were assessed at both high-intensity and low-intensity (xanthine oxidase, 1 munits/mL) oxidant stress. MAIN RESULTS: High-intensity xanthine oxidase stress significantly increased type II cell DNA strand breakage, inhibited de novo phosphatidyl choline synthesis, diminished mitochondrial integrity, and enhanced lipid peroxidation in the absence of overt cytolysis. This injury was modulated with addition of exogenous glutathione peroxidase, or catalase/superoxide dismutase, but not glutathione or N-acetylcysteine. Although aspects of the glutathione antioxidant repertoire were similarly diminished with high-intensity xanthine oxidase stress, low-dose (long duration) xanthine oxidase stress augmented the activities of type II cell glutathione peroxidase and gamma-glutamyl transferase (the rate-limiting enzyme in glutathione synthesis). CONCLUSION: High-intensity xanthine oxidase stress (in vitro model of in vivo ischemia-reperfusion) may overwhelm type II cell antioxidant defenses and mediate oxidant injury to nucleic acid, protein, and lipid in the absence of cell lysis. Immortalized murine type II cells seem to appropriately model xanthine oxidase-mediated nucleic acid and protein injury of native rat type II cells. Exogenous glutathione peroxidase reduces oxidant injury in this in vitro model. Depending on magnitude (and possibly duration) of the xanthine oxidase stress, type II cell glutathione antioxidant elements may be diminished or enhanced.

Cardiac adverse effects of early dexamethasone treatment in preterm infants: a randomized clinical trial

This study evaluates the effects of early administration of dexamethasone on left ventricle dimensions and their clinical significance in preterm infants. Fifty preterm infants with birth weight < or = 1250 g and gestational age < or = 30 weeks were randomly assigned after 72 hours of life to the dexamethasone group (n = 25) or to the control group (n = 25). The treated infants received dexamethasone intravenously from the 4th day of life for 7 days (0.5 mg/kg/day for the first 3 days, 0.25 mg/kg/day for the next 3 days, and 0.125 mg/kg/day for the 7th day). Serial echocardiographic measurements of end systolic interventricular septum thickness, end diastolic interventricular septum thickness, end systolic left ventricle posterior wall thickness, end diastolic left ventricle posterior wall thickness, left ventricle end diastolic diameter, and left ventricle end systolic diameter were taken before starting dexamethasone, on days 3 and 7 of treatment, 7 days after the interruption of treatment, and at the 28th day of life. Five infants of each group were excluded by the final analysis because of the lack of a complete cardiac evaluation, leaving 20 treated and 20 control infants. Infants receiving dexamethasone had a significantly larger increase in mean septal and left posterior wall thickness during the treatment and 7 days after the dexamethasone weaning. The mean left ventricle diameter of treated infants was significantly lower than that of control infants from the 7th day of treatment to the 28th day of life. Four neonates (20%) in the dexamethasone group developed left ventricular myocardial hypertrophy without left ventricle outflow tract obstruction, showing signs of decreased cardiac output and ischemic changes on ECG. The daily fluid intake was increased to 200 ml/kg to ensure an adequate preload volume, and the complete resolution of left ventricle hypertrophy was obtained within the 2nd to 3rd week after dexamethasone weaning. Preterm infants receiving an early (< 96 hours of life) short course of dexamethasone develop a left ventricular myocardial hypertrophy that can be symptomatic and clinically significant. Preterm infants included in future studies with the goal to find the minimum dose and duration of dexamethasone treatment should be strictly monitored echocardiographically for this side effect.

Immunopathologic effects of tumor necrosis factor alpha in murine mycobacterial infection are dose dependent

In experimental mycobacterial infection, tumor necrosis factor alpha (TNF-alpha) is required for control of bacillary growth and the protective granulomatous response, but may cause immunopathology. To directly examine the positive and detrimental effects of this cytokine, a murine model was used in which different amounts of TNF-alpha were delivered to the site of infection. Mice with a disruption in the TNF-alpha gene (TNF-KO) or wild-type mice were infected with low or high doses of recombinant Mycobacterium bovis BCG that secreted murine TNF-alpha (BCG-TNF). Infection of TNF-KO mice with BCG containing the vector (BCG-vector) at a low dose led to increased bacillary load in all organs and an extensive granulomatous response in the lungs and spleen. The mice succumbed to the infection by approximately 40 days. However, when TNF-KO mice were infected with low doses of BCG-TNF, bacillary growth was controlled, granulomas were small and well differentiated, the spleen was not enlarged, and the mice survived. Infection with high inocula of BCG-TNF resulted in bacterial clearance, but was accompanied by severe inflammation in the lungs and spleen and earlier death compared to the results from the mice infected with high inocula of BCG-vector. Wild-type mice controlled infection with either recombinant strain, but showed decreased survival following high-dose BCG-TNF infection. The effects of TNF-alpha required signaling through an intact receptor, since the differential effects were not observed when TNF-alpha receptor-deficient mice were infected. The results suggest that the relative amount of TNF-alpha at the site of infection determines whether the cytokine is protective or destructive.

Meter-dosed, inhaled beclomethasone initiated at birth to prevent bronchopulmonary dysplasia

OBJECTIVE

To examine the hypothesis that meter-dosed, inhaled beclomethasone administered to premature infants, beginning at birth and continuing in a tapering dosage schedule over the first 12 days of life, decreases the occurrence of bronchopulmonary dysplasia (BPD), at 36 wks corrected gestational age.

DESIGN

Prospective, randomized, double-blind, placebo-controlled, small pilot clinical trial.

SETTING

Tertiary care, neonatal intensive care unit.

PATIENTS

Premature low birth weight neonates (<or=1300 g) followed from birth until 36 wks corrected gestational age.

INTERVENTIONS

Aerosolized beclomethasone dipropionate was administered in a tapering dosage schedule beginning at birth and extended for the first 12 days of life, utilizing an aerosol spacer chamber and manual hand ventilation. In a subset of the subjects, a cosyntropin stimulation test was conducted on day 13 to ascertain potential hypothalamic-pituitary-adrenal axis suppression. Need for mechanical ventilation/continuous positive airway pressure (CPAP) and/or oxygen was assessed at 30 days of life and 36 wks corrected gestational age in addition to a number of other variables clinically relevant to the development of BPD.

MEASUREMENTS AND MAIN RESULTS

In total, 19 placebo-treated and 20 beclomethasone-treated infants completed the study. Inhaled beclomethasone significantly reduced the need for supplemental oxygen at 30 days (p =.005) of life but not at 36 wks corrected gestational age (p =.243). A significantly greater proportion of infants receiving beclomethasone were extubated before 2 wks of age (p =.035), and infants receiving beclomethasone required significantly fewer days of mechanical ventilation (p =.004), but increased days of nasal CPAP as compared with the control group. Although fewer beclomethasone-treated than placebo-treated infants were administered intravenous steroids after 2 wks of age, this difference was not significant. No differences between groups were noted for the diagnoses of retinopathy of prematurity, nosocomial infection, or intraventricular hemorrhage. Similarly, no differences in the cosyntropin stimulation test were ascertained between treated and nontreated infants. No adverse effects were attributable to inhaled beclomethasone.

CONCLUSIONS

In this small series, inhaled beclomethasone initiated at birth did not reduce the occurrence of BPD as defined by the continued requirement for supplemental oxygen at 36 wks corrected gestational age. However, inhaled beclomethasone did reduce the need for supplemental oxygen at 30 days of life and appeared to facilitate the transition from intubation/mechanical ventilation to less invasive nasal CPAP, as demonstrated by more frequent extubation before 2 wks of age and decreased total duration of mechanical ventilation in the beclomethasone-treated group. No adverse effects, including adrenal suppression, were noted in infants treated with inhaled beclomethasone. On the basis of the safety and apparent effectiveness of early inhaled beclomethasone in reducing the need for invasive mechanical ventilation and supplemental oxygen during the first month of life in premature infants, a larger clinical trial with greater power is warranted to ascertain if early inhaled beclomethasone can attenuate the occurrence of BPD.

Modulation of hyperoxia-induced TNF-alpha expression in the newborn rat lung by thalidomide and dexamethasone

The effect of high oxygen concentrations on lungs of neonatal rats was studied. In addition, some oxygen-exposed animals were treated with either dexamethasone or thalidomide. No gross histologic changes were noted in the lungs following exposure to 95% oxygen nor were there changes in the total number or the phenotypic distribution of BAL cells obtained from these lungs compared to lungs from air exposed (control) neonatal rats. The majority of the BAL cells were CD45+ leukocytes (macrophages). However, when BAL cells were exposed to LPS in vitro, TNF-alpha production was higher in cells from rats exposed to 95% oxygen compared to cells from rats exposed to ambient air. In addition, lung TNF-alpha and IL-6 mRNA levels were increased after exposure to 95% oxygen. In the lungs of animals treated with either dexamethasone or thalidomide, TNF-alpha mRNA levels were reduced, while only dexamethasone treatment also reduced IL-6 mRNA levels.

Protein carbonyls and lipid peroxidation products as oxidation markers in preterm infant plasma: associations with chronic lung disease and retinopathy and effects of selenium supplementation

The purpose of this study was to determine whether protein carbonyls and the lipid peroxidation product malondialdehyde (MDA) are elevated in plasma from very low birth weight (<1500 g) infants, whether they are affected by selenium supplementation, and whether they are associated with poor respiratory outcome or retinopathy. The study group comprised 173 infants enrolled in a randomized controlled trial of selenium supplementation. Plasma samples, collected before randomization, at 7 and 28 d after birth, and at 36 wk postmenstrual age, were analyzed for protein carbonyls and total MDA. Respiratory outcome was assessed as oxygen requirement at 28 d of age or 36 wk postmenstrual age and as number of days on oxygen. Protein carbonyl concentrations in very low birth weight infants were significantly higher than for adults but lower than for cord blood from term infants. Median values decreased significantly by 28 d, and there was no relationship with birth weight. MDA concentrations in very low birth weight infants overlapped the ranges for healthy adults and cord blood from term infants. They correlated positively with birth weight at 28 d but not at other times. Supplementation almost doubled plasma selenium concentrations, but carbonyls and MDA did not differ between the supplemented and unsupplemented groups. There were no significant differences in oxidant marker levels in infants who did or did not develop chronic lung disease or retinopathy. Protein carbonyls and MDA measurements in plasma do not show evidence of systemic oxidative stress in <1500-g infants and are not affected by selenium supplementation. Oxidative injury at sites such as the lung may be important in prematurity, but markers from such sites must be measured to relate to outcome and antioxidant supplementation.

Preterm infants with high polyunsaturated fatty acid and plasmalogen content in tracheal aspirates develop bronchopulmonary dysplasia less often

OBJECTIVE

Oxygen toxicity causes chronic bronchopulmonary dysplasia (BPD) in extremely preterm infants. Polyunsaturated fatty acids (PUFA) and plasmalogens are the two main substrates for lipid peroxidation in the pulmonary surfactant. In the present study, we tested whether low concentrations of both were associated with development of BPD and whether both were further reduced during mechanical ventilation with oxygen.

DESIGN

Prospective, noninterventional, descriptive study.

SETTING

Level III neonatal intensive care unit in a university hospital.

PATIENTS

In 25 extremely low birth weight infants with respiratory distress syndrome, tracheal aspirates were collected immediately after birth and in the following 4 days. As control, tracheal and pharyngeal aspirates were collected from healthy infants immediately after birth. The amount of PUFA and dimethylacetals (DMA, representing plasmalogens) was determined gas-chromatographically.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The relative percentages of PUFA and DMA on all fatty acids in non-BPD infants (PUFA% 26+/-8.9, DMA% 3.5+/-1.2) were higher compared with infants who developed BPD (PUFA% 14.5+/-3.8, DMA% 1.8+/-0.9). In term healthy infants, DMA% and PUFA% were in the same range as in the BPD group. The higher levels found for non-BPD infants decreased after day 1 to values equal to the BPD group and remained low.

CONCLUSIONS

The results suggest that initially higher levels of PUFA and plasmalogens in the tracheal effluent are associated with a reduced risk of developing BPD and are reduced during the first day of ventilation.

Elevated protein carbonyls and lipid peroxidation products correlating with myeloperoxidase in tracheal aspirates from premature infants

The purpose of this study is to determine whether the oxidative injury markers, protein carbonyls and malondialdehyde (MDA), are elevated in tracheal aspirates from very low birth weight (< 1500 g) infants; to determine whether levels correlate with myeloperoxidase as a marker of neutrophil inflammation; and to assess whether high levels are associated with poor respiratory outcome. Tracheal aspirates (144 samples) were collected from 86 infants < 1500 g at times of routine suctioning. Aspirates (82 samples) from 54 infants > or = 1500 g who required intubation for a variety of diagnoses were analyzed for comparison. Analyses were performed for protein carbonyls by ELISA, total malondialdehyde by HPLC, and myeloperoxidase activity. Respiratory outcome was assessed as oxygen requirement at 28-d or 36-wk postmenstrual age, and as the number of days of oxygen requirement. Protein carbonyls were significantly higher in infants < 1500 g than larger infants, and were highest close to birth. MDA concentrations were also higher in the earlier samples. There was a strong positive correlation between protein carbonyls and myeloperoxidase, suggesting a link between protein oxidation and neutrophil activation. A similar but weaker correlation was seen for MDA. Carbonyls in samples taken after steroid administration were less than for controls with a similar age distribution. We did not see significant associations between oxidant marker levels and development of chronic lung disease. Our findings of higher amounts of protein and lipid oxidation products in tracheal aspirates with high myeloperoxidase activity, taken together with other studies showing a link between neutrophil accumulation and chronic lung disease, suggest a possible contribution by neutrophil-derived reactive oxygen species to the injury.

Pathogenesis and management of respiratory insufficiency following pulmonary resection

The underlying principle of the surgical treatment of non-small-cell lung cancer (NSCLC) is complete removal of the local/regional disease within the thorax. Pulmonary resection should be as conservative as possible without compromising the adequacy of tumor removal. A multitude of factors influence the incidence and severity of complications following pulmonary resection including the pre-operative physical and psychological status of the patient, the pathologic process requiring resection, the physiologic impact of the procedure, and the addition of pre-operative or postoperative adjuvant therapy. The insidious onset of interstitial changes on chest X-ray (CXR) 1 to 2 days after pulmonary resection forewarns of respiratory distress; however, the pathophysiology of adult respiratory distress syndrome (ARDS) with progression to respiratory failure requiring mechanical ventilation and advanced critical care often unfolds. Management of patients with severe respiratory failure remains primarily supportive. "Good critical care" is the mainstay of therapy: this includes gentle mechanical ventilation to avoid ventilator-induced barotrauma and over-extension of remaining functional alveoli, diuresis, infection identification and management, and nutritional support. New therapeutic strategies that may impact on outcomes in the adult population include pressure-limited ventilation (permissive hypercapnia), inverse ratio ventilation, high-frequency jet ventilation, high-frequency oscillatory ventilation, intratracheal pulmonary ventilation, and prone position ventilation. In addition, alternative therapies such as partial liquid ventilation, inhaled nitric oxide, and extracorporeal techniques including extracorporeal membrane oxygenation (ECMO), extracorporeal carbon dioxide removal (ECCO(2)R), intravascular oxygenation (IVOX), and arteriovenous carbon dioxide removal (AVCO(2)R), provide additional modalities. A component of some or all of these strategies is finding a role in clinical practice.

Validity of markers of dilution in small volume lung lavage

Definitive analysis of solute concentrations in lung lavage fluid involves the use of a marker of dilution to correct for variable recovery of epithelial lining fluid (ELF), but the question of the most appropriate dilutional marker remains unresolved. In lavage fluid collected from infants with lung disease and healthy control subjects, we examined ELF concentration of protein, albumin, sphingomyelin (SM), and IgA secretory component (SC), and critically appraised the relative validity of SC and urea as dilutional markers in the context of lung infection and lung injury. Protein, albumin, and SM were found not to be valid dilutional markers, as their ELF concentration varied significantly between the diseased, recovering, and normal lung. Differences in concentration were noted in both tracheal aspirate samples (TA, 4 x 0.5 ml) and nonbronchoscopic bronchoalveolar lavage fluid (NB-BAL, 3 x 1 ml/kg), but were not uniform (e.g., TA-disease versus control: albumin 2.8 versus 0.68 mg/ml, SM 45 versus 16 microgram/ml, both p < 0.05; NB-BAL-disease versus recovery: protein 8.1 versus 4.8 mg/ml, albumin 2.9 versus 1. 4 mg/ml, both p < 0.05). Overall, SC concentrations in ELF were not different between the diseased and normal lung, but in the NB-BAL samples, significantly higher SC concentration was noted in viral bronchiolitis and pneumonia than in noninfective lung diseases. No clear evidence of additional influx of urea into lavage fluid in association with epithelial disruption was found in the diseased lung. Comparative analysis of SC and urea revealed no difference in TA samples, but in NB-BAL specimens, urea best standardized the lavage concentration of surfactant indices to correspond to the degree of lung dysfunction as indicated by oxygenation index. We conclude that SC and urea, but not protein, albumin, or SM, are valid dilutional markers with which to estimate ELF recovery during small volume lung lavage. Urea appears a more appropriate choice in return fluid derived from the distal tracheobronchial tree, and SC should not be used in the context of lung infection.

Liposomal prostaglandin E1 (TLC C-53) in acute respiratory distress syndrome: a controlled, randomized, double-blind, multicenter clinical trial. TLC C-53 ARDS Study Group

OBJECTIVE

To evaluate the safety and efficacy of an intravenous liposomal dispersion of prostaglandin E1 as TLC C-53 in the treatment of patients with acute respiratory distress syndrome (ARDS).

DESIGN

Randomized, prospective, multicenter, double-blind, placebo-controlled, phase III clinical trial.

SETTING

Forty-seven community and university-affiliated hospitals in the United States.

PATIENTS

A total of 350 patients with ARDS were enrolled in this clinical trial.

INTERVENTION

Patients were prospectively randomized in a 1:1 ratio to receive either liposomal prostaglandin E1 or placebo. The study drug was infused intravenously for 60 mins every 6 hrs for 7 days starting with a dosage of 0.15 microg/kg/hr. The dose was increased every 12 hrs until the maximal dose (3.6 microg/kg/hr) was attained or intolerance to further increases developed. Patients received standard aggressive medical/surgical care during the infusion period.

OUTCOME MEASURES

The primary outcome measure was the time it took to wean the patient from the ventilator. Secondary end points included time to improvement of the PaO2/FIO2 ratio (defined as first PaO2/FIO2 > 300 mm Hg), day 28 mortality, ventilator dependence at day 8, changes in PaO2/FIO2, incidence of and time to development/resolution of organ failure other than ARDS.

RESULTS

A total of 348 patients could be evaluated for efficacy. The distribution of variables at baseline describing gender, lung injury scores, Acute Physiology and Chronic Health Evaluation II scores, PaO2/FIO2, pulmonary compliance, and time from onset of ARDS or from institution of mechanical ventilation to the first dose of study drug was similar among patients in the liposomal prostaglandin E1 (n = 177) and the placebo (n = 171) treatment arms. There was no significant difference in the number of days to the discontinuation of ventilation in the liposomal prostaglandin E1 group compared with the placebo group (median number of days to off mechanical ventilation, 16.9 in patients receiving liposomal prostaglandin E1 and 19.6 in those administered placebo; p = .94). Similarly, mortality at day 28 was not significantly different in the two groups (day 28 mortality, 57 of 176 (32%) in the liposomal prostaglandin E1 group and 50 of 170 (29%) in patients receiving placebo; p = .55). In contrast, treatment with liposomal prostaglandin E1 was associated with a significantly shorter time to reach a PaO2/FIO2 ratio of >300 mm Hg (median number of days to reaching a PaO2/FIO2 ratio >300 mm Hg: 9.8 days in the liposomal prostaglandin E1 group and 13.7 days in patients receiving the placebo; p = .02). Among the subgroups examined, time to off mechanical ventilation was significantly reduced in patients who received at least 85% of a full dose (i.e., > 45.9 microg/kg) of liposomal prostaglandin E1 (median number of days to discontinuation of ventilation, 10.3 in the liposomal prostaglandin E1 group and 16.3 days in patients receiving placebo; p = .05). The overall incidence of serious adverse events was not significantly different in the liposomal prostaglandin E1 (40%) or placebo-treated (37%) groups. Drug-related adverse events of all kinds were reported in 69% of the patients receiving liposomal prostaglandin E1 compared with 33% of the placebo group, with hypotension and hypoxia (occurring in 52% and 24% of the liposomal prostaglandin E1-treated patients, respectively, and 17% and 5% of the placebo-treated patients, respectively) being noted most frequently.

CONCLUSIONS

In the intent-to-treat population of patients with ARDS, treatment with liposomal prostaglandin E1 accelerated improvement in indexes of oxygenation but did not decrease the duration of mechanical ventilation and did not improve day 28 survival.

Intraerythrocyte nonprotein-bound iron and plasma malondialdehyde in the hypoxic newborn

Intraerythrocyte nonprotein-bound iron (INPBI), malondialdehyde (MDA), and hypoxanthine plasma levels (HxPL), were determined by high-pressure liquid chromatography in 138 randomly selected newborn infants with gestational ages ranging from 23 to 42 weeks at birth and on fourth day of life. MDA plasma levels were significantly higher in cord and fourth-day blood samples of preterm babies than term infants as well as babies born by emergency Caesarean section than babies born by vaginal delivery and in intubated than in nonintubated newborns. Highly significant correlations both in cord blood and fourth-day blood samples were observed between MDA plasma levels and gestational age, birth weight, Apgar score at 1 min and 5 min, HxPL, pH, base deficit, and INPBI content. Multiple regression analysis identified HxPL as the best single predictor of MDA plasma levels in cord blood, and INPBI content in fourth-day blood as the best single predictor of MDA plasma levels in fourth-day blood. The results indicate that red cells and plasma lipoproteins are a common target of free radical-induced oxidative stress during hypoxia.

Effect of complement inhibition with soluble complement receptor 1 on pig allotransplant lung function

BACKGROUND

Lung dysfunction after transplantation continues to be a significant clinical problem. Soluble complement receptor 1 (sCR1) is a potent inhibitor of complement activation. We evaluated the inhibitory effect of sCR1 on complement activation and reperfusion injury in pig lung allografts.

METHODS

In a randomized and blinded study, left lung transplantation was performed in 13 pigs. Donor lungs were flushed and then stored for 30 hr at 4 degrees C. Control pigs (n=7) received saline, and the treatment group (n=6) received 15 mg/kg sCR1 1 hr before reperfusion. One hour after reperfusion, the right pulmonary artery was clamped for 10 min to assess the function of the transplanted lung. Pulmonary function was assessed again on day 3.

RESULTS

Complement inhibition was 93% in the sCR1 group and returned to baseline (8% inhibition) after 3 days. There was a trend toward a higher partial pressure of oxygen at 1 hr in the sCR1 group compared with the control group (mean +/- SE: 408+/-42 mmHg vs. 288+/-69 mmHg, P = 0.19). Alveolar ventilation was better in the sCR1 group than in the control group (P = 0.01) at 1 hr. Mixed venous saturation was significantly lower in the control group at both 1 hr (P = 0.02) and 3 days (P = 0.001). The wet/dry weight of the lung tissue was lower in the sCR1 group compared with the control group on day 3 (P < 0.05). Chemiluminescence, an index of phagocyte priming, was lower in the sCR1 group when cells were stimulated with complement opsonized zymosan but not when stimulated with zymosan or phorbol myristate acetate.

CONCLUSION

sCR1 improves ventilation, reduces pulmonary edema, and may be beneficial in improving posttransplant lung oxygenation.

Upregulation of xanthine oxidase by lipopolysaccharide, interleukin-1, and hypoxia. Role in acute lung injury

LPS and selected cytokines upregulate xanthine dehydrogenase/xanthine oxidase (XDH/XO) in cellular systems. However, the effect of these factors on in vivo XDH/XO expression, and their contribution to lung injury, are poorly understood. Rats were exposed to normoxia or hypoxia for 24 h after treatment with LPS (1 mg/kg) and IL-1beta (100 microg/kg) or sterile saline. Lungs were then harvested for measurement of XDH/XO enzymatic activity and gene expression, and pulmonary edema was assessed by measurement of the wet/dry lung weight ratio (W/D). Although treatment with LPS + IL-1beta or hypoxia independently produced a 2-fold elevation (p < 0. 05 versus exposure to normoxia and treatment with saline) in lung XDH/XO activity and mRNA, the combination of LPS + IL-1beta and hypoxia caused a 4- and 3.5-fold increase in these values, respectively. XDH/XO protein expression was increased 2-fold by hypoxia alone and 1.3-fold by treatment with LPS + IL-1beta alone or combination treatment. Compared with normoxic lungs, W/D was significantly increased by exposure to hypoxia, LPS + IL-1beta, or combination treatment. This increase was prevented by treatment of the animals with tungsten, which abrogated lung XDH/XO activity. In conclusion, LPS, IL-1beta, and hypoxia significantly upregulate lung XDH/XO expression in vivo. The present data support a role for this enzyme in the pathogenesis of acute lung injury.

Outcome prediction in Greek neonatal intensive care units using a score for neonatal acute physiology (SNAP)

OBJECTIVES

This study was undertaken to evaluate the performance of the score for neonatal acute physiology (SNAP) in Greece, to examine the predictive power of SNAP calculated during the 12 hours after admission in comparison with customarily calculated SNAP during the first 24 hours, and to assess SNAP during the second 12 hours from admission as a measure of response to treatment.

METHODOLOGY

A total of 579 newborns admitted to three neonatal intensive care units (NICUs) from two cities in Greece were enrolled in the study; SNAP was determined during the first 12 hours, the second 12 hours, and the first 24 hours from admission to the NICU and calculated using an algorithm based on deviations from normal values of 26 physiologic parameters.

RESULTS

All three variants of SNAP were powerful predictors of vital status at discharge, as well as of duration of stay among survivors. A five-point increase in SNAP in the first 12 hours corresponds to a more than twofold ratio in the odds for death, whereas a five-unit difference in SNAP from the second 12 hours corresponds to a more than threefold ratio. The combined 24-hour score was similar to that for the first 12 hours. A considerable advantage of SNAP was its independence from more traditional predictors of neonatal death, notably gestational age, birth weight, and Apgar score. The combination of all of these predictors improved further the overall predictive potential.

CONCLUSIONS

SNAP is a useful tool in medical research and can be applied in different population groups. Its independence from birth weight underlines its added value to predict fatality ratios. Moreover, the results of the present study indicate that SNAP can be estimated without loss of predictive efficiency during the first 12 hours from admission to the NICU, whereas SNAP during the second 12 hours adequately reflects the effectiveness of early medical interventions.

The effect of early dexamethasone administration on bronchopulmonary dysplasia in preterm infants with respiratory distress syndrome

OBJECTIVES

This study was carried to evaluate the effect of early administration of dexamethasone on the incidence of bronchopulmonary dysplasia (BPD) and/or death in surfactant-treated preterm infants with respiratory distress syndrome (RDS).

STUDY DESIGN

In a multicenter, double-blind, placebo-controlled trial, 109 preterm infants with RDS and birth weights between 700 and 1600 gm, who were treated with mechanical ventilation and surfactant, were randomly assigned before 36 hours of life to receive dexamethasone (n = 55) or placebo (n = 54) for 12 days.

RESULTS

There were no differences in the incidence of BPD and/or death between groups. However, fewer patients in the dexamethasone group were oxygen-dependent at 36 weeks after conception (8% vs 33%, p < 0.05). The dexamethasone group had a lower incidence of necrotizing enterocolitis (0% vs 9%, p < 0.05). The incidence of arterial hypertension, hyperglycemia, and sepsis was not affected by the treatment. Basal and poststimulation serum cortisol levels did not differ between groups.

CONCLUSION

The administration of dexamethasone early in the course of RDS does not decrease the incidence of BPD and/or death in preterm infants. However, dexamethasone may reduce oxygen dependency at 36 weeks after conception.

Combined differential lung ventilation and inhaled nitric oxide therapy in the management of unilateral pulmonary contusion

Unilateral pulmonary contusion after blunt thoracic trauma can prove to be a devastating injury. Regional disturbances in blood flow and alveolar ventilation can significantly alter pulmonary function. We present a case report of unilateral pulmonary contusion that resulted in significant pulmonary dysfunction. This patient was successfully managed with multimodality therapy consisting of differential lung ventilation and inhaled nitric oxide. The effect of nitric oxide applied to the "normal" lung, the "injured" lung, and both lungs is described. The use of inhaled nitric oxide was associated with an increase in oxygenation when applied to the normal or both lungs. The use of nitric oxide in conjunction with differential lung ventilation appeared to offer benefit in this patient with severe unilateral pulmonary contusion.

Protection of porcine endothelial cells from complement-mediated cytotoxicity by the human complement regulators CD59, C1 inhibitor, and soluble complement receptor type 1. Analysis in a pig-to-human in vitro model relevant to hyperacute xenograft rejection

Inhibition of complement activation is considered a prerequisite to overcome hyperacute xenograft rejection. In the present study, we investigated the efficacy of C1 inhibitor (C1 inh) and recombinant soluble complement receptor type 1 (rsCR1) to protect xenogeneic cells against complement-mediated cytotoxicity in an in vitro xenotransplantation model. The addition of the soluble complement regulators to human serum led to a dose-dependent inhibition of complement-mediated destruction of aortic porcine endothelial cells (PEC). On a molar base, rsCR1 was more efficient than C1 inh. Transfection of PEC with cDNA of human CD59 resulted in several clones where protection against complement-mediated cell destruction correlated with the expression level of the inhibitor. Addition of low concentrations of C1 inh and rsCR1 to a CD59 (human)-positive PEC clone, expressing a suboptimal level of the membrane-bound regulator, resulted in a significant improvement of protection against complement-mediated cell destruction.