New approaches for persistent pulmonary hypertension of newborn

Correlation of ABO blood groups with treatment response and efficacy in infants with persistent pulmonary hypertension of the newborn treated with inhaled nitric oxide

OBJECTIVE

Not all infants with persistent pulmonary hypertension of the newborn (PPHN) respond to inhaled nitric oxide (iNO) therapy, as it is known to improve oxygenation in only 50% to 60% of cases. In this study, we investigated whether ABO blood groups were a relevant factor affecting the improvement of oxygenation by nitric oxide (NO) therapy in infants with PPHN.

METHODS

This study was a retrospective, multicenter, and cohort-controlled trial that involved 37 medical units. Infants with PPHN who met the inclusion criteria and were treated with NO (a vasodilator) alone from July 1, 2015, to June 30, 2020, were selected and assigned into three groups: blood type A, blood type B, and blood type O (there were only 7 cases of blood type AB, with a small number of cases, and therefore, blood type AB was excluded for further analysis). The response to iNO therapy was defined as an increase in the ratio of the partial pressure of arterial oxygen (PaO2)/fraction of inspired oxygen (FiO2) > 20% from the basal value after treatment. Oxygenation was assessed mainly based on the two values, oxygenation index (OI) and PaO2/FiO2. The correlation of ABO blood groups with responses to iNO therapy and their influence on the efficacy of iNO therapy was analyzed based on the collected data.

RESULTS

The highest proportion of infants with PPHN who eventually responded to iNO therapy was infants with blood type O. Infants with blood type O more readily responded to iNO therapy than infants with blood type B. Oxygenation after iNO treatment group was optimal in the blood type O group and was the worst in the blood type A group among the three groups. Infants with blood type O showed better efficacy than those with blood types A and B.

CONCLUSION

ABO blood groups are correlated with responses to iNO therapy in infants with PPHN, and different blood groups also affect the efficacy of NO therapy in infants with PPHN. Specifically, infants with blood type O have a better response and experience the best efficacy to iNO therapy.

Pulmonary hypertension in congenital diaphragmatic hernia: ANTENATAL PREDICTION AND IMPACT ON NEONATAL MORTALITY

OBJECTIVE

To determine the prevalence of pulmonary hypertension(PAH) in left-sided congenital diaphragmatic hernia(CDH); how we could predict it; and how PAH contributed to the model for mortality prediction.

STUDY DESIGN

Retrospective analysis in three European centers. The primary outcome was the presence of PAH on postnatal day(d)1,7, and at discharge. Studied predictors of PAH were: observed/expected-lung/head-ratio(o/e LHR), liver-herniation, FETO, and gestational age(GA) at delivery. The combined effect of pre-and postnatal variables on mortality was modeled by Cox regression.

RESULTS

Of the 197 neonates, 56(28.4%) died. At d1, 67.5%(133/197) had PAH and 61.9% (101/163) by d7. Overall, 6.4% (9/141) had PAH at discharge.At d1, o/eLHR(OR 0.96) and FETO(OR 2.99) independently correlated to PAH(AUC:0.74). At d7, PAH significantly correlated only with the use of FETO (OR 3.9;AUC:0.65). None were significant for PAH at discharge.Combining the occurrence of PAH with antenatal biomarkers improved mortality prediction(p=0.02), in a model including o/eLHR(HR:0.94), FETO(HR:0.35), liver herniation(HR:16.78), and PAH(HR:15.95).

CONCLUSIONS

Antenatal prediction of PAH was only moderate. The postnatal occurrence of PAH further increases the risk of death. Whereas this may be used to counsel parents in the postnatal period, our study demonstrates there is a need to find more accurate antenatal predictors for PAH. This article is protected by copyright. All rights reserved.

A Meta-Analysis of the Risk Factors of Persistent Pulmonary Hypertension in Newborns

Objective: To determine the risk factors of persistent pulmonary hypertension of the newborn using a meta-analysis method and provide a reference for its clinical prevention and treatment. Methods: A meta-analysis was performed by searching the PubMed, Embase, Cochrane Library, China Biology Medicine Disc, Wanfang, and Chinese VIP journal databases, as well as the China National Knowledge Infrastructure. Results: A total of 22 references were included in the meta-analysis; the cumulative medical records comprised 7,937 cases, and 2,613,072 control cases were included. A total of 12 related risk factors were included (7 were associated with pregnant women and 5 were associated with newborns). Conclusion: Among the 12 associated risk factors included, the three most important and their combined odds ratio values and 95% CI were as follows: (1) pregnant women smoking, 4.85 (1.98-11.9) during pregnancy; (2) gestational weeks <37, 4.34 (1.64-11.5); (3) perinatal asphyxia, 3.9 (2.87-5.31).

Intrapulmonary artery Doppler to predict mortality and morbidity in fetuses with mild or moderate left-sided congenital diaphragmatic hernia

OBJECTIVES

In fetuses with isolated left-sided congenital diaphragmatic hernia (LCDH), prenatal detection of severe pulmonary hypoplasia is important, as fetal therapy can improve survival. Cases with mild or moderate lung hypoplasia still carry a considerable risk of mortality and morbidity, but there has been less interest in the accurate prediction of outcome in these cases. In this study of fetuses with mild or moderate isolated LCDH, we aimed to investigate: (1) the association between intrapulmonary artery (IPA) Doppler findings and mortality at discharge; (2) whether adding IPA Doppler findings improves the prediction of mortality based on lung size and liver herniation; and (3) the association between IPA Doppler findings and early neonatal morbidity.

METHODS

This was a retrospective study of all consecutive fetuses assessed at the BCNatal and UZ Leuven hospitals between 2008 and 2020 with a prenatal diagnosis of isolated, non-severe LCDH, defined as observed-to-expected lung-to-head ratio (o/e-LHR) > 25%, that were managed expectantly during pregnancy followed by standardized neonatal management. An additional inclusion criterion was the availability of IPA Doppler measurements. The primary outcome was the association between IPA Doppler findings and mortality at discharge. Other predictors included o/e-LHR, liver herniation and gestational age at birth. Secondary outcomes were the association between IPA Doppler findings and the presence of pulmonary hypertension (PHT), need for supplemental oxygen at discharge and need for extracorporeal membrane oxygenation. IPA pulsatility index (PI) values were converted into Z-scores. Logistic regression analysis was performed to investigate the associations between predictor variables and outcome, and the best model was chosen based on the Nagelkerke R² .

RESULTS

Observations for 70 non-severe LCDH cases were available. Fifty-four (77%) fetuses survived until discharge. On logistic regression analysis, higher IPA-PI was associated with an increased risk of mortality (odds ratio (OR), 3.96 (95% CI, 1.62-9.70)), independently of o/e-LHR (OR, 0.87 (95% CI, 0.79-0.97)). An IPA-PI Z-score cut-off of 1.8 predicted mortality with a detection rate of 69% and specificity of 93%. Adding IPA-PI to o/e-LHR improved significantly the model's performance (Nagelkerke R² , 46% for o/e-LHR + IPA-PI vs 28% for o/e-LHR (P < 0.002)), with a detection rate of 81% at a 10% false-positive rate. IPA-PI was associated with PHT (OR, 2.20 (95% CI, 1.01-4.59)) and need for oxygen supplementation at discharge (OR, 1.90 (95% CI, 1.10-3.40)), independently of lung size.

CONCLUSIONS

In fetuses with mild or moderate LCDH, IPA-PI was associated with mortality and morbidity, independently of lung size. A model combining o/e-LHR with IPA-PI identified up to four in five cases that eventually died, despite being considered to have non-severe pulmonary hypoplasia. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Sildenafil for pulmonary hypertension in neonates: An updated systematic review and meta-analysis

OBJECTIVES

To provide an updated review and meta-analysis on the efficacy and safety of sildenafil for treating persistent pulmonary hypertension in neonates (PPHN).

METHODS

PubMed/Medline, SCOPUS, Cochrane Central Register of Controlled Trials, and Web of Science were searched from the inception of publication to January 2021. The principal outcomes include oxygenation parameters, hemodynamic metrics and echocardiographic measurements, as well as adverse outcomes.

RESULTS

A total of eight studies were included with 216 term and premature neonates with PPHN. Compelling evidence showed the use of sildenafil could improve the prognosis of PPHN neonates, compared with baseline or placebo in neonates with PPHN, and a time-dependent pattern of the improvements can be observed. After 24 h of treatment, the Oxygenation index suggested a steady decrease (SD: -1.80, 95% confidence interval [CI]: -2.92, -0.67) and sildenafil exerted peak effects after 72 h of treatment (SD: -4.02, 95% CI: -5.45, -2.59). No clinically significant side effects were identified. Egger's test and funnel plots of the major outcomes were performed, and the publication bias was not significant.

CONCLUSION

Improvements were shown in oxygenation index, pulmonary arterial pressure, and adverse outcomes after using sildenafil for PPHN in neonates. However, future research with robust longitudinal or randomized controlled design is still needed.

Pediatric Pulmonary Hypertension: Definitions, Mechanisms, Diagnosis, and Treatment

Pediatric pulmonary hypertension (PPH) is a multifactorial disease with diverse etiologies and presenting features. Pulmonary hypertension (PH), defined as elevated pulmonary artery pressure, is the presenting feature for several pulmonary vascular diseases. It is often a hidden component of other lung diseases, such as cystic fibrosis and bronchopulmonary dysplasia. Alterations in lung development and genetic conditions are an important contributor to pediatric pulmonary hypertensive disease, which is a distinct entity from adult PH. Many of the causes of pediatric PH have prenatal onset with altered lung development due to maternal and fetal conditions. Since lung growth is altered in several conditions that lead to PPH, therapy for PPH includes both pulmonary vasodilators and strategies to restore lung growth. These strategies include optimal alveolar recruitment, maintaining physiologic blood gas tension, nutritional support, and addressing contributing factors, such as airway disease and gastroesophageal reflux. The outcome for infants and children with PH is highly variable and largely dependent on the underlying cause. The best outcomes are for neonates with persistent pulmonary hypertension (PPHN) and reversible lung diseases, while some genetic conditions such as alveolar capillary dysplasia are lethal. © 2021 American Physiological Society. Compr Physiol 11:2135-2190, 2021.

Persistent pulmonary hypertension of the newborn

Persistent pulmonary hypertension of the newborn (PPHN) is a significant clinical problem characterized by refractory and severe hypoxemia secondary to elevated pulmonary vascular resistance resulting in right-to-left extrapulmonary shunting of deoxygenated blood. PPHN is associated with diverse cardiopulmonary disorders and a high early mortality rate for infants with severe PPHN. Surviving infants with PPHN have an increased risk of long-term morbidities. PPHN physiology can be categorized by (1) maladaptation: pulmonary vessels have normal structure and number but have abnormal vasoreactivity; (2) excessive muscularization: increased smooth muscle cell thickness and increased distal extension of muscle to vessels that are usually not muscularized; and (3) underdevelopment: lung hypoplasia associated with decreased pulmonary artery number. Treatment involves adequate lung recruitment, optimization of cardiac output and left ventricular function, and pulmonary vasodilators such as inhaled nitric oxide. Infants who fail to respond to conventional therapy should be evaluated for lethal lung disorders including alveolar-capillary dysplasia, T-box transcription factor 4 gene, thyroid transcription factor-1, ATP-binding cassette A3 gene, and surfactant protein diseases.

Fetal endoscopic tracheal occlusion reverses the natural history of right-sided congenital diaphragmatic hernia: European multicenter experience

OBJECTIVE

To evaluate the neonatal outcome of fetuses with isolated right-sided congenital diaphragmatic hernia (iRCDH) based on prenatal severity indicators and antenatal management.

METHODS

This was a retrospective review of prospectively collected data on consecutive cases diagnosed with iRCDH before 30 weeks' gestation in four fetal therapy centers, between January 2008 and December 2018. Data on prenatal severity assessment, antenatal management and perinatal outcome were retrieved. Univariate and multivariate logistic regression analysis were used to identify predictors of survival at discharge and early neonatal morbidity.

RESULTS

Of 265 patients assessed during the study period, we excluded 40 (15%) who underwent termination of pregnancy, two cases of unexplained fetal death, two that were lost to follow-up, one for which antenatal assessment of lung hypoplasia was not available and six cases which were found to have major associated anomalies or syndromes after birth. Of the 214 fetuses with iRCDH included in the neonatal outcome analysis, 86 were managed expectantly during pregnancy and 128 underwent fetal endoscopic tracheal occlusion (FETO) with a balloon. In the expectant-management group, lung size measured by ultrasound or by magnetic resonance imaging was the only independent predictor of survival (observed-to-expected lung-to-head ratio (o/e-LHR) odds ratio (OR), 1.06 (95% CI, 1.02-1.11); P = 0.003). Until now, stratification for severe lung hypoplasia has been based on an o/e-LHR cut-off of 45%. In cases managed expectantly, the survival rate was 15% (4/27) in those with o/e-LHR ≤ 45% and 61% (36/59) for o/e-LHR > 45% (P = 0.001). However, the best o/e-LHR cut-off for the prediction of survival at discharge was 50%, with a sensitivity of 78% and specificity of 72%. In the expectantly managed group, survivors with severe pulmonary hypoplasia stayed longer in the neonatal intensive care unit than did those with mildly hypoplastic lungs. In fetuses with an o/e-LHR ≤ 45% treated with FETO, survival rate was higher than in those with similar lung size managed expectantly (49/120 (41%) vs 4/27 (15%); P = 0.014), despite higher prematurity rates (gestational age at birth: 34.4 ± 2.7 weeks vs 36.8 ± 3.0 weeks; P < 0.0001). In fetuses treated with FETO, gestational age at birth was the only predictor of survival (OR, 1.25 (95% CI, 1.04-1.50); P = 0.02).

CONCLUSIONS

Antenatal measurement of lung size can predict survival in iRCDH. In fetuses with severe lung hypoplasia, FETO was associated with a significant increase in survival without an associated increase in neonatal morbidity. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Optimal oxygenation and role of free radicals in PPHN

Effective ventilation of the lungs is essential in mediating pulmonary vasodilation at birth to allow effective gas exchange and an increase in systemic oxygenation. Unsuccessful transition prevents the increase in pulmonary blood flow after birth resulting in hypoxemia and persistent pulmonary hypertension of the newborn (PPHN). Management of neonates with PPHN includes ventilation of the lungs with supplemental oxygen to correct hypoxemia. Optimal oxygenation should meet oxygen demand to the tissues and avoid hypoxic pulmonary vasoconstriction (HPV) while preventing oxidative stress. The optimal target for oxygenation in PPHN is not known. Animal models have demonstrated that PaO₂<45 mmHg exacerbates HPV. However, there are no practical methods of assessing oxygen levels associated with oxidant stress. Oxidant stress can be due to free radical generation from underlying lung disease or from free radicals generated by supplemental oxygen. Free radicals act on the nitric oxide pathway reducing cGMP and promoting pulmonary vasoconstriction. Antioxidant therapy improves systemic oxygenation in an animal model of PPHN but there are no clinical trials to support such therapy. Targeting preductal SpO₂ between 90 and 97% and PaO₂ at 50-80 mmHg appears prudent in PPHN but clinical trials to support this practice are lacking. Preterm infants with PPHN present unique challenges due to lack of antioxidant defenses and functional and structural immaturity of the lungs. This review highlights the need for additional studies to mitigate the impact of oxidative stress in the lung and pulmonary vasculature in PPHN.

Persistent Pulmonary Hypertension in the Newborn

Persistent pulmonary hypertension of the newborn (PPHN) is a syndrome of failed circulatory adaptation at birth due to delay or impairment in the normal fall in pulmonary vascular resistance (PVR) that occurs following birth. The fetus is in a state of physiological pulmonary hypertension. In utero, the fetus receives oxygenated blood from the placenta through the umbilical vein. At birth, following initiation of respiration, there is a sudden precipitous fall in the PVR and an increase of systemic vascular resistance (SVR) due to the removal of the placenta from circulation. There is dramatic increase in pulmonary blood flow with a decrease in, and later reversal of shunts at the foramen ovale and ductus arteriosus. The failure of this normal physiological pulmonary transition leads to the syndrome of PPHN. PPHN presents with varying degrees of hypoxemic respiratory failure. Survival of infants with PPHN has significantly improved with the use of gentle ventilation, surfactant and inhaled nitric oxide (iNO). PPHN is associated with significant mortality and morbidity among survivors. Newer agents that target different enzymatic pathways in the vascular smooth muscle are in different stages of development and testing. Further research using these agents is likely to further reduce morbidity and mortality associated with PPHN.

Prediction of Neonatal Respiratory Function and Pulmonary Hypertension in Fetuses with Isolated Congenital Diaphragmatic Hernia in the Fetal Endoscopic Tracleal Occlusion Era: A Single-Center Study

Objective: To correlate prenatal indicators of pulmonary hypoplasia with neonatal lung function and pulmonary hypertension (PHT) in isolated congenital diaphragmatic hernia (iCDH). Materials and Methods: Prospective single-center study on 40 fetuses with iCDH either expectantly managed (n = 13) or undergoing tracheal occlusion (n = 27). Prenatal predictors included observed/expected lung-head ratio (O/E LHR), observed/expected total fetal lung volume, fetal pulmonary reactivity to maternal O2 administration (Δpulsatility index, ΔPI) and liver-to-thorax ratio (LiTR) as measured in the second and third trimesters. Postnatal outcome measures included survival until discharge, best oxygenation index (OI) and alveolar-arterial oxygen gradient [D(A-a)O2] in the first 24 h of life and the occurrence of PHT in the first 28 days of life. Results: Median gestational age (GA) at evaluations was 27.2 and 34.3 weeks. GA at delivery was 36.0 weeks, and overall survival was 55%. In the second trimester, measurement of lung size, LiTR and pulmonary reactivity were significantly related to survival and the best OI and D(A-a)O2.The occurrence of PHT was better predicted by ΔPI and LiTR. Conclusions: O/E LHR, LiTR and vascular reactivity correlate with ventilatory parameters in the first 24 h of life. Occurrence of PHT at ≥28 days was best predicted by LiTR and ΔPI, but not by lung size.

Predictors of mortality and major morbidities in extremely low birth weight neonates

OBJECTIVE

To determine predictors of mortality and morbidity in extremely low birth weight neonates (ELBW) from a developing country.

STUDY DESIGN

Prospective observational study.

SETTING

Level III neonatal unit in Northern India.

SUBJECTS

Neonates <1000 g born and admitted to intensive care during study period were enrolled. They were analyzed based on survival and development of major morbidity. Multivariable logistic regression model was used to determine independent risk factors.

OUTCOME

Mortality and major morbidity (one or more of the following: Bronchopulmonary dysplasia (BPD), Retinopathy of Prematurity (ROP) requiring laser, grade III or IV intraventricular hemorrhage (IVH), periventricular leukomalacia (PVL) and necrotizing enterocolitis (NEC) stage III) during hospital stay.

RESULTS

Of 255 ELBW neonates born, 149 received optimal care, of which 78 (52%) survived and 57 (39%) developed morbidities. Mean birth weight and gestational age were 29.1±2.6 weeks and 843±108 g. Major causes of mortality were sepsis (46%), birth asphyxia (20%) and pulmonary hemorrhage (19%). Birth weight <800 g [OR (95% CI)-3.51 (1.39-8.89), P=0.008], mechanical ventilation [4.10 (1.64-10.28), P=0.003] and hypotensive shock [10.75 (4.00-28.89), P<0.001] predicted mortality while birth weight <800 g [3.75 (1.47-9.50), P=0.006], lack of antenatal steroids [2.62 (1.00-6.69), P=0.048), asphyxia [4.11 (1.45-11.69), P=0.008], ventilation [4.38 (1.29-14.79), P=0.017] and duration of oxygen therapy [0.004 (1.001-1.006), P=0.002] were the predictors of major morbidities.

CONCLUSIONS

Low birth weight, mechanical ventilation and hypotensive shock predicted mortality in ELBW neonates while low birth weight, lack of antenatal steroids, birth asphyxia, ventilation and duration of oxygen therapy were predictors for major morbidity.

The pulmonary circulation in neonatal respiratory failure

The pulmonary circulation rapidly adapts at birth to establish lungs as the site of gas exchange. Abnormal transition at birth and/or parenchymal lung disease can result in neonatal hypoxemic respiratory failure. This article reviews the functional changes in pulmonary hemodynamics and structural changes in pulmonary vasculature secondary to (1) normal and abnormal transition at birth, and (2) diseases associated with neonatal hypoxemic respiratory failure. Various management strategies to correct respiratory failure are also discussed.

A randomized, double-blind, placebo-controlled, prospective study of bosentan for the treatment of persistent pulmonary hypertension of the newborn

OBJECTIVE

To assess the efficacy and safety of bosentan as an adjuvant therapy of persistent pulmonary hypertension of the newborn (PPHN).

STUDY DESIGN

Forty-seven neonates with PPHN were randomly assigned to receive either bosentan (n=24) or placebo (n=23). Efficacy was evaluated with a favorable outcome defined as fulfilling all the following criteria (for example, oxygenation index <15, normal pulmonary artery pressure (<20 mm Hg) and no premature discontinuation of the drug because of drug-related toxicity or lack of efficacy). Evaluation of safety was done by monitoring drug-related adverse events.

RESULT

Bosentan treatment was superior to placebo with a favorable response in 87.5% of patients treated with bosentan as compared with 20% of those who received placebo (P<0.0001). None of patients in the bosentan group had drug-related clinical or laboratory adverse events.

CONCLUSION

Bosentan may be a useful adjuvant therapy of PPHN.

Hypoxia and nitric oxide exposure promote apoptotic signaling in contractile pulmonary arterial smooth muscle but not in pulmonary epithelium

RATIONALE

Neonatal pulmonary hypertension is characterized by hypoxia, abnormal vascular remodeling, and impaired alveolarization. Nitric oxide (NO) regulates cell replication and activation of apoptosis. Our objective was to examine cell phenotype-specific effects of hypoxia and NO exposure on cumulative apoptotic signal in neonatal pulmonary epithelial cells and arterial smooth muscle.

DESIGN/METHODS

Primary cultured newborn porcine pulmonary arterial myocytes and epithelial cells were grown in normoxic (21% O2) or hypoxic conditions (10% O2). Myocyte phenotype was predetermined by serum-supplementation or -deprivation. Cells were exposed to sodium nitroprusside (10(-7) -10(-4)  M) or diluent for 3 days. Cell survival was estimated by MTT assay; BAX, Bcl-2, and cleaved caspase-3 by Western blot; cell cycle entry by laser scanning cytometry.

RESULTS

Hypoxic epithelial cells exhibited a small increase in anti-apoptotic Bcl2, and decrease in BAX. Cell survival and active caspase-3 were unchanged. Exposure to NO had no impact on epithelial apoptosis, but initiated necrosis. In contractile myocytes, pro-apoptotic BAX abundance and caspase-3 activation were increased by hypoxia, augmented by NO exposure promoting apoptosis. Hypoxia decreased BAX/Bcl-2 ratio and promoted survival of synthetic myocytes; NO increased apoptosis of normoxic synthetic myocytes, but decreased apoptosis of hypoxic synthetic myocytes.

CONCLUSION

The effect of NO on pulmonary apoptosis is phenotype-dependent. A cumulative apoptotic effect of hypoxia and NO in vitro exerted on contractile myocytes may lead to contraction of this subpopulation, while synthetic myocyte survival and proliferation is enhanced by hypoxia and NO. Epithelial survival is unaffected. We speculate that alveolar rarefaction reported after neonatal hypoxia may arise from growth arrest in the vascular rather than the epithelial compartment.

Advances in the management of meconium aspiration syndrome

Meconium aspiration syndrome (MAS) is a common cause of severe respiratory distress in term infants, with an associated highly variable morbidity and mortality. MAS results from aspiration of meconium during intrauterine gasping or during the first few breaths. The pathophysiology of MAS is multifactorial and includes acute airway obstruction, surfactant dysfunction or inactivation, chemical pneumonitis with release of vasoconstrictive and inflammatory mediators, and persistent pulmonary hypertension of newborn (PPHN). This disorder can be life threatening, often complicated by respiratory failure, pulmonary air leaks, and PPHN. Approaches to the prevention of MAS have changed over time with collaboration between obstetricians and pediatricians forming the foundations for care. The use of surfactant and inhaled nitric oxide (iNO) has led to the decreased mortality and the need for extracorporeal membrane oxygenation (ECMO) use. In this paper, we review the current understanding of the pathophysiology and management of MAS.

Inhaled nitric oxide improves systemic microcirculation in infants with hypoxemic respiratory failure

OBJECTIVES

To investigate the effect of inhaled nitric oxide on the systemic microcirculation. We hypothesized that inhaled nitric oxide improves the systemic microcirculation. Inhaled nitric oxide improves outcome in infants with persistent pulmonary hypertension of the newborn diagnosed by improving pulmonary blood flow and oxygenation. It reduces pulmonary vascular resistance without decline in systemic blood pressure. Inhaled nitric oxide is also utilized in the treatment of acute hypoxemic respiratory failure in children and adults. It is thought to improve regional ventilation perfusion by regional selective pulmonary vasodilation.

DESIGN

Pilot study.

SETTING

Intensive care unit of a level III university children's hospital.

PATIENTS

Consecutive ventilated patients who were treated with inhaled nitric oxide (20 ppm) were enrolled in this study. Eight patients (five boys, three girls) were included; five had congenital diaphragmatic hernia diagnosed, one had persistent pulmonary hypertension of the newborn diagnosed, one had acute respiratory distress syndrome diagnosed, and one had bronchiolitis diagnosed. The median age was 0 months (range, 0-38 months).

INTERVENTIONS

Inhaled nitric oxide administration.

MEASUREMENTS AND MAIN RESULTS

The microcirculation was assessed in the buccal mucosa within 1 hr before and within 1 hr after the start of inhaled nitric oxide using orthogonal polarization spectral imaging. The median functional capillary density before the inhaled nitric oxide was started was 4.0 cm/cm (range, 1.8-5.6 cm/cm) and improved to 4.9 cm/cm (range, 2.8-6.6 cm/cm; p = .017) after the start of inhaled nitric oxide.

CONCLUSIONS

Inhaled nitric oxide improves the systemic microcirculation in children with hypoxemic respiratory failure.

Therapeutic approaches using nitric oxide in infants and children

Pulmonary hypertension contributes significantly to the morbidity and mortality associated with many pediatric pulmonary and cardiac diseases. Nitric oxide, a gas molecule, is a unique pharmaceutical agent that can be inhaled and thus delivered directly to the lung. Inhaled nitric oxide was approved by the FDA in 1999 as a therapy for infants with persistent pulmonary hypertension. Since then, the use of inhaled nitric oxide has expanded to other neonatal and pediatric conditions, and our knowledge of its properties and mechanisms of action has increased tremendously. This review discusses the physiology of nitric oxide signaling, the most common indications for its clinical use, and promising new investigations that may enhance endogenous production of nitric oxide and/or improve vascular response to it.

Phosphodiesterases: emerging therapeutic targets for neonatal pulmonary hypertension

Pulmonary hypertension in the neonate is associated with multiple underlying problems such as respiratory distress syndrome, meconium aspiration syndrome, congenital diaphragmatic hernia, bronchopulmonary dysplasia, sepsis, or congenital heart disease. Because of the heterogeneous group of disorders, the therapeutic approach and response often depends on the underlying disease. In many of these conditions, there is evidence that cyclic nucleotide signaling and specifically phosphodiesterases (PDEs) are disrupted. PDE inhibitors represent an emerging class of pulmonary vasodilators in adults. Studies are now under way to evaluate the utility, efficacy, and safety of such therapies in infants with pulmonary hypertension.

Randomized controlled trial of early compared with delayed use of inhaled nitric oxide in newborns with a moderate respiratory failure and pulmonary hypertension

OBJECTIVE

To evaluate whether early treatment with inhaled nitric oxide (iNO) will prevent newborns with moderate respiratory failure from developing severe hypoxemic respiratory failure (oxygenation index (OI)>or=40).

STUDY DESIGN

A total of 56 newborns with moderate respiratory failure (OI between 10 and 30) were randomized before 48 h after birth to early treatment with 20 p.p.m. of iNO (Early iNO group, n=28) or conventional mechanical ventilation with FiO(2) 1.0 (Control group, n=28). Infants received iNO and/or high-frequency oscillatory ventilation (HFOV) if they developed an OI>40.

RESULT

7 of 28 early iNO patients (25%) compared to 17 of 28 control patients (61%) developed an OI>40 (P<0.05). In the Early iNO group mean OI significantly decreased from 22 (baseline) to 19 at 4 h (P<0.05) and remained lower over time: 19 (12 h), 18 (24 h) and 16 at 48 h. In contrast, OI increased in the Control group and remained significantly higher than the Early iNO group during the first 48 h of study: 22 (baseline), 29, 35, 32 and 23 at 4, 12, 24 and 48 h, respectively (P<0.01). Of 17, 6 control patients who developed an OI>40 were successfully treated with iNO. Nine of the remaining eleven control patients and six of seven Early iNO patients who had an OI>40 despite use of iNO responded with the addition of HFOV. One patient of the Early iNO group and two of the Control group died. Median (range) duration of oxygen therapy was significantly shorter in the Early iNO group: 11.5 (5 to 90) days compared to 18 (6 to 142) days of the Control group (P<0.03).

CONCLUSION

Early use of iNO in newborns with moderate respiratory failure improves oxygenation and decreases the probability of developing severe hypoxemic respiratory failure.

Evaluation of a pumpless lung assist device in hypoxia-induced pulmonary hypertension in juvenile piglets

Persistent pulmonary hypertension is an important cause of mortality and morbidity in term infants. The lung assist device (LAD) is a novel, pumpless, low-resistance extracorporeal oxygenator to supplement mechanical ventilation. The LAD may be associated with fewer complications compared with conventional extracorporeal membrane oxygenation. The objective was to test the feasibility and efficacy of the LAD in juvenile piglets with hypoxia-induced pulmonary hypertension. Pulmonary hypertension was acutely induced by hypoxia in six 3- to 4-wk-old acutely instrumented and intubated piglets. The LAD was attached between a carotid artery and jugular vein. Gas exchange and hemodynamic variables, including pulmonary arterial pressure (PAP) and cardiac output (CO), were measured. Successful LAD cannulation was achieved without complications in all animals. Extracorporeal shunt flow through the device averaged 18% of CO. The LAD achieved oxygen delivery of 20% of total oxygen consumption. PAP was reduced by 35% from 28 +/- 5 to 18 +/- 4 mm Hg (p < 0.05) and systemic Pao2 increased by 33% from 27 +/- 2 to 36 +/- 4 mm Hg (p < 0.05). Other hemodynamic variables remained stable. The novel LAD shows feasibility and efficacy in improving gas exchange and reducing PAPs in a juvenile animal model of hypoxia-induced pulmonary hypertension.

Neonatal pulmonary hypertension treated with inhaled nitric oxide and high-frequency ventilation

Term and near-term infants with pulmonary hypertension are frequently treated with inhaled nitric oxide. This therapy can be delivered with high-frequency ventilation, but there has been limited study of the relative effectiveness of high-frequency jet ventilation and high-frequency oscillatory ventilation.

OBJECTIVE

To compare short-term clinical outcomes of neonates with pulmonary hypertension treated with inhaled nitric oxide plus either high-frequency jet ventilation or high-frequency oscillatory ventilation.

STUDY DESIGN

Study infants met the following criteria: >or=35 weeks gestation, respiratory failure with pulmonary hypertension, no congenital malformations and treatment in the first week of life with inhaled nitric oxide plus either high-frequency jet ventilation (n=22) or high-frequency oscillatory ventilation (n=43). Data were collected from medical records.

RESULT

The jet ventilation and oscillatory ventilation groups were similar in terms of gestational age, but the jet ventilation group had less severe respiratory illness (that is, lower oxygenation index) just prior to initiation of the combination of nitric oxide and high-frequency ventilation. The jet ventilation group spent more hours on inhaled nitric oxide (71.4 versus 40.8; P=0.004) but was less likely to require extracorporeal membrane oxygenation (2(9%) versus 19(44%); P=0.004). No difference was found in the ages at which oxygen and high-frequency ventilation were discontinued.

CONCLUSION

Term and near-term neonates with pulmonary hypertension who require nitric oxide have similar short-term outcomes regardless of whether nitric oxide is delivered by high-frequency jet ventilation or high-frequency oscillatory ventilation.

Bleeding after circumcision in a newborn receiving sildenafil

This report describes a case of bleeding as a complication of circumcision in a 2-week-old infant being treated with sildenafil for persistent pulmonary hypertension of the newborn. The vasodilatory effects of sildenafil on the penile vasculature may have contributed to the postoperative bleeding in this patient.

Criteria supporting the study of drugs in the newborn

BACKGROUND

Profound changes in the development and the maturation of neonates' organs and organ systems over variable periods of time potentially place neonates at increased risk and/or at different risks compared with adults or older children on exposure to pharmaceutical agents. Most studies of drugs in neonates focus on pharmacokinetic and pharmacodynamic end points and include insufficient numbers of patients to permit evaluation of safety. Only one fourth to one third of approved drugs have received adequate pediatric study to permit labeling for treatment of all appropriate pediatric populations.

OBJECTIVE

The initial goal of the Newborn Drug Prioritization Group was to develop a reproducible, objective process for evaluating drugs most in need of study in the neonatal population based on a universally acceptable priority ranking. The criteria would be applicable across therapeutic classes and would identify those drugs for which immediate study was most needed.

METHODS

Because the therapeutic requirements of the neonate are unique in comparison to older infants and children, the National Institute of Child Health and Human Development and the US Food and Drug Administration (FDA) developed the Newborn Drug Development Initiative to address the limited study of off-patent drugs in newborns. In March 2003, they convened a meeting of pediatric pharmacologists and pediatric specialists from the FDA, the American Academy of Pediatrics, the National Institutes of Health, and academic institutions to discuss how to increase the study of drugs for the newborn. One of the working groups was charged to develop generic criteria for overall prioritization of drugs for study in newborns. Because resources are limited, and not all drugs identified by the 4 clinically focused working groups can receive study at the same time, a process for priority ranking is necessary.

RESULTS

The panel identified 4 general categories containing different numbers of criteria as important for ranking drugs for priority investigation: (1) the disease and indication, including elements such as the potential for adverse outcomes, frequency in newborns, and level of evidence for treatment of newborns; (2) drug characteristics, including elements such as duration of dosing, lack of age-appropriate formulation, clinically relevant drug-drug and drug-disease interactions, and drug disposition in newborns; (3) feasibility and methodology for newborn studies, including both analytical considerations and clinical end points; and (4) the ethical basis for study, including elements to address benefit or harm due to exposure to the study drug, study methodology, and benefit of the new treatment relative to established standard therapy. Based on these categories, a list of criteria to warrant study of a drug in newborns was developed.

CONCLUSION

A process for judicious use of limited resources to rectify these deficiencies remains an urgent public health need.

Persistent pulmonary hypertension of the newborn

In utero, fetal pulmonary vascular resistance (PVR) is high, but rapidly falls after birth. Expansion of the lungs, increase in oxygenation, release of vasoactive mediators, growth factors and remodeling of the vascular wall, all contribute to the reduction in PVR. Persistent pulmonary hypertension of the newborn (PPHN) is defined as a failure of the pulmonary vasculature to relax at birth, resulting in hypoxemia. PPHN is in fact a variety of disorders that have a common presentation. Some of the pathophysiological mechanisms and the therapeutic approaches are discussed below.

Newborns and drug studies: the NICHD/FDA newborn drug development initiative

BACKGROUND

Progress has been made in research on the effects of drug therapy on pediatric patients, but neonates are still an understudied population. Those most likely to receive drug therapy (eg, preterm infants) are least likely to be studied.

OBJECTIVES

The purposes of this article are to summarize an initiative developed jointly by the National Institute of Child Health and Human Development (NICHD) and the US Food and Drug Administration (FDA) and to introduce a series of articles developed as a result of this initiative.

METHODS

Information for this article was gathered from the proceedings of a workshop cosponsored by the NICHD and the FDA that took place March 29 and 30, 2004, in Rockville, Maryland.

RESULTS

: Dosing based on use in adults and older children has resulted in adverse events among newborn infants, and may have long-term effects. Moreover, formulations appropriate for use in neonates are often unavailable, and compensatory efforts such as mixing crushed tablets into formula may interfere with accurate dose delivery. Under the Best Pharmaceuticals for Children Act of 2002, government agencies work with experts in pediatrics and pediatric research to develop and prioritize a list of off-patent drugs for which pediatric studies are urgently needed. Four such listings were published in the Federal Register from January 2003 through January 2005. The NICHD and FDA have also initiated the Newborn Drug Development Initiative (NDDI), a multiphase program to determine gaps in knowledge concerning neonatal pharmacology and clinical trial design and to explore novel study designs for use in newborns, with the ultimate goal of increasing our knowledge about the safety and efficacy of drugs used to treat newborns.

CONCLUSIONS

Most drugs used to treat newborns still lack appropriate dosing, efficacy, and safety studies in this vulnerable population. The NICHD and FDA developed the NDDI as an ongoing process to identify and suggest strategies for addressing obstacles to conducting drug trials in the newborn.