Vasantha H.S. Kumar

Early Use of Inhaled Nitric Oxide in Preterm Infants: Is there a Rationale for Selective Approach?

Background Inhaled nitric oxide (iNO) is being increasingly used in preterm infants < 34 weeks with hypoxemic respiratory failure (HRF) and/or pulmonary hypertension (PH). Objective To evaluate the risk factors, survival characteristics, and lung histopathology in preterm infants with PH/HRF. Methods Retrospective chart review was conducted to determine characteristics of 93 preterm infants treated with iNO in the first 28 days and compared with 930 matched controls. Factors associated with survival with preterm HRF and smooth muscle actin from nine autopsies were evaluated. Results Preterm neonates treated with iNO had a higher incidence of preterm prolonged rupture of membrane (pPROM ≥ 18 hours), oligohydramnios and delivered by C‐section. In infants treated with iNO, antenatal steroids (odds ratio [OR],3.7; confidence interval [CI], 1.2‐11.3; p = 0.02), pPROM (OR, 1.001; CI, 1.0‐1.004; p = 0.3), and oxygenation response to iNO (OR, 3.7; CI, 1.08‐13.1; p = 0.037) were associated with survival. Thirteen infants with all three characteristics had 100% (13/13) survival without severe intraventricular hemorrhage (IVH)/periventricular leukomalacia (PVL) compared with 48% survival (12/25, p = 0.004) and 16% severe IVH/PVL without any of these factors. Severity of HRF correlated with increased smooth muscle in pulmonary vasculature. Conclusion Preterm infants with HRF exposed to antenatal steroids and pPROM had improved oxygenation with iNO and survival without severe IVH/PVL. Precisely targeting this subset may be beneficial in future trials of iNO.

Long-Term Effects of Neonatal Hyperoxia in Adult Mice: NEONATAL HYPEROXIA & LONG-TERM EFFECTS IN MICE

The outcomes of premature infants have improved greatly; however, the health risks in adulthood are still relatively unclear. Bronchopulmonary dysplasia (BPD) in premature infants is a major risk factor for alteration in lung function and predisposition to respiratory morbidity, and is associated with hyperoxia. The study explores the effect of neonatal hyperoxia on organ systems in adult mice. Newborn mouse litters were randomized to 85%O2 or room air (RA) on P3 for 12 days; mice were sacrificed at P3, P7, P15, 3 months and 9 months. Lungs were assessed by histopathology, radial alveolar count, mean linear intercept, and α‐Smooth muscle actin immunohistochemistry. Aortic assessment included histology, wall thickness, elastin, and collagen content. Glomerular histology and nephron number were assessed in the kidneys. Hyperoxia‐exposed mice had progressive alveolar simplification and poor weight gain over time. Greater thickness of pulmonary arterioles by 3 months and a higher Fulton index by 9 months suggest worsening pulmonary hypertension. Aortic wall thickness to lumen ratio was greater with a lower aortic elastin‐to‐collagen ratio suggesting long‐term effects of neonatal hyperoxia. Hyperoxia‐exposed mice at 9 months had smaller glomeruli as indicated by glomerular diameter and volume. Prolonged neonatal hyperoxia during the critical period of development induces irreversible lung damage, pulmonary hypertension and structural changes in the kidneys and aorta in adult mice. This could have implications for chronic adult diseases following exposure to high levels of oxygen in the newborn period. Anat Rec, 301:717–726, 2018.

Adaptive immune responses are altered in adult mice following neonatal hyperoxia

Premature infants with bronchopulmonary dysplasia (BPD), are at risk for frequent respiratory infections and reduced pulmonary function. We studied whether neonatal hyperoxia disrupts adaptive immune responses in adult mice, contributing to higher respiratory‐related morbidities seen in these infants. Newborn mice litters were randomized at 3 days to 85% O2 or room air (RA) for 12 days. Whole lung mRNA was isolated in both the groups at 2 weeks and 3 months. Gene expression for T‐cell and B‐cell adaptive immune response was performed by real‐time PCR and qRT‐PCR; protein expression (p21, IL4, IL10, IL27, cd4) was performed by enzyme immunoassay along with p21 immunohistochemistry. Hyperoxia increased expression of p21 and decreased expression of 19 genes representing T/B‐cell activation by ≥ fourfold; three of them significantly (Rag1, Cd1d1, Cd28) compared to the RA group at 2 weeks. Despite RA recovery, the expression of IFNγ, IL27, and CD40 was significantly reduced at 3 months in the hyperoxia group. Expression of p21 was significantly higher and IL27 protein lower at 2 weeks following hyperoxia. Adult mice exposed to neonatal hyperoxia had lower IL4 and IL10 in the lung at 3 months. Adaptive immune responses are developmentally regulated and neonatal hyperoxia suppresses expression of genes involved in T‐/B‐cell activation with continued alterations in gene expression at 3 months. Dysfunction of adaptive immune responses increases the risk for susceptibility to infection in premature infants.

Response to pulmonary vasodilators in infants with congenital diaphragmatic hernia

BackgroundCongenital diaphragmatic hernia (CDH) is associated with lung hypoplasia, cardiac dysfunction and pulmonary hypertension. Inhaled nitric oxide (iNO) and milrinone are commonly used pulmonary vasodilators in CDH. We studied the hemodynamic effects of iNO and milrinone in infants with CDH.MethodsA retrospective chart review was performed of all CDH infants admitted to two regional perinatal centers and infants classified into three groups: No-iNO group; iNO-responders and iNO-nonresponders. Oxygenation and hemodynamic effects of iNO and milrinone were assessed by blood gases and echocardiography.ResultsFifty-four percent (39/72) of infants with CDH received iNO and 31% of these infants (12/39) had complete oxygenation response to iNO. Oxygenation response to iNO was not associated with a decrease in right ventricular pressures (RVP) or ECMO use. Four infants (33%) in the iNO-responder group and eight infants (30%) in the iNO-nonresponder group received milrinone. Milrinone lowered RVP and improved ejection fraction (EF). Response to iNO was associated with improved oxygenation to milrinone and increased survival following ECMO (67 vs. 20% among nonresponders).ConclusionsResponse to inhaled nitric oxide in combination with milrinone may be associated with improved oxygenation and better survival after ECMO in infants with CDH.

Current and Emerging Therapies in the Management of Hypoxic Ischemic Encephalopathy in Neonates

Neonatal hypoxic ischemic encephalopathy (HIE) presents a significant clinical burden with its high mortality and morbidity rates globally. Therapeutic hypothermia (TH) is now standard of care for infants with moderate to severe HIE, but has not definitively changed outcomes in severe HIE. In this review, we discuss newer promising markers that may help the clinician identify severity of HIE. Therapies that are beneficial and agents that hold promise for neuroprotection are described, both for use either alone or as adjuncts to TH. These include endogenous pathway modifiers such as erythropoietin and analogues, melatonin, and remote ischemic post conditioning. Stem cells have therapeutic potential in this condition, as in many other neonatal conditions. Of the agents listed, only erythropoietin and analogues are currently being evaluated in large randomized controlled trials (RCTs). Exogenous therapies such as argon and xenon, allopurinol, monosialogangliosides, and magnesium sulfate continue to be investigated. The recognition of tertiary mechanisms of brain damage has opened up new research into therapies not only to attenuate brain damage but also to promote cell repair and regeneration in a developmentally disorganized brain long after the perinatal insult. These alternative modalities may be especially important in mild HIE and in areas of the world where there is limited access to expensive hypothermia equipment and services.

Liver Failure and Conjugated Hyperbilirubinemia in a Preterm Neonate: Role of Early IVIG and Exchange Transfusion

Neonatal liver failure (NLF) is a rare diagnosis but carries with it significant risks of mortality and morbidity. Common etiologies for NLF include metabolic causes, gestational alloimmune liver disease (GALD or neonatal hemochromatosis), and viral infections. We report a case of liver failure in a premature infant with abnormal iron profile within 48 hours of birth. Lack of accepted guidelines for the initial management of severe jaundice with a high direct component in the first week after birth made treatment challenging. The infant underwent intensive phototherapy along with four exchange transfusions (ET) and two courses of intravenous immunoglobulins (IVIG). The clinical goals were to keep total bilirubin values ≤ 20 mg/dL in this premature neonate and to minimize the risk of bilirubin-induced neurologic dysfunction and decompensated liver failure. Abnormal iron studies and later magnetic resonance imaging were suggestive of GALD. Liver functions improved over time with normal neurodevelopmental assessment at 3 years of age. To conclude, in infants with NLF soon after birth, earlier consideration of IVIG/ET in the first few days may be beneficial. Larger multicenter data analyses are required to formulate treatment guidelines and indications for phototherapy, ET, and IVIG in sick neonates with NLF.

Nfib hemizygous mice are protected from hyperoxic lung injury and death

Nuclear Factor I (Nfi) genes encode transcription factors essential for the development of organ systems including the lung. Nfib null mice die at birth with immature lungs. Nfib hemizygous mice have reduced lung maturation with decreased survival. We therefore hypothesized that these mice would be more sensitive to lung injury and would have lower survival to hyperoxia. Adult Nfib hemizygous mice and their wild‐type (Wt) littermates were exposed to 100% O2 for 89, 80, 72 and 66 h for survival studies with lung outcome measurements at 66 h. Nfib hemizygous and Wt controls were also studied in RA at 66 h. Cell counts and cytokines were measured in bronchoalveolar lavage (BAL); lung sections examined by histopathology; lung angiogenic and oxidative stress gene expression assessed by real‐time PCR. Unexpectedly, Nfib hemizygous mice (0/14–0%) had significantly lower mortality compared to Wt mice (10/22–45%) at 80 h of hyperoxia (P < 0.003). LD50 was 80 h in the Wt group versus 89 h in the hemizygous group. There were no differences in BAL cell counts between the groups. Among the cytokines studied, MIP‐2 was significantly lower in hemizygous mice exposed to hyperoxia. New vessel formation, edema, congestion, and alveolar hemorrhage were noted on histopathology at 72 and 80 h in wild‐type mice. Nfib hemizygous lungs had significant downregulation of genes involved in redox signaling and inflammatory pathways. Adult Nfib hemizygous mice are relatively resistant to hyperoxia compared to wild‐type littermates. Mechanisms contributing to this resistance are not clear; however, transcription factors such as Nfib may regulate cell survival and play a role in modulating postnatal lung development.

Impact of bradycardia or asystole on neonatal cardiopulmonary resuscitation at birth

Fetal hypoxia from intrapartum events can lead to absent heart rate (HR) or bradycardia at birth requiring aggressive neonatal resuscitation. Neonatal resuscitation guidelines do not differentiate bradycardia (HR <100 beats/min) from absent HR at birth. Given that HR is the primary determinant of resuscitation, we hypothesize that infants with no HR at 1 min would require more extensive resuscitation with worse clinical outcome than infants with bradycardia at 1 min.

Natriuretic peptide C receptor in the developing sheep lung: role in perinatal transition

BackgroundAt birth, the release of surfactant from alveolar type II cells (ATIIs) is stimulated by increased activity of the beta-adrenergic/adenylyl cyclase/cyclic 3′-5′ adenosine monophosphate-signaling cascade. Atrial natriuretic peptide (ANP) stimulates surfactant secretion through natriuretic peptide receptor A (NPR-A). ANP inhibits adenylyl cyclase activity through its binding to NPR-C. We wished to further understand the role of the NPR-C in perinatal transition.MethodsWe studied ATII expression of NPR-C in fetal and newborn sheep using immunohistochemistry, and surfactant secretion in isolated ATIIs by measuring 3[H] choline release into the media.ResultsANP induced surfactant secretion, and, at higher doses, it inhibits the stimulatory effect of the secretagogue terbutaline. ATII NPR-C expression decreased significantly after birth. Premature delivery also markedly decreased ANP and NPR-C in ATIIs. Co-incubation of terbutaline (10−4 M) with ANP (10−6 M) significantly decreased 3[H] choline release from isolated newborn ATII cells when compared with terbutaline alone; this inhibitory effect was mimicked by the specific NPR-C agonist, C-ANP (10−10 M).ConclusionANP may act as an important epithelial-derived inhibitor of surfactant release in the fetal lung, and downregulation of ANP and NPR-C following birth may sensitize ATII cells to the effects of circulating catecholamines, thus facilitating surfactant secretion.

598 Effects of Catalytic Antioxidant Mntbap on Pulmonary Angiogenic and Oxidative Gene Expression to Hyperoxia in Newborn Mice

Background Development of lung injury during prolonged O2 exposure is a complex process, associated with changes in expression of a number of genes important in the adaptive response to hyperoxia. MnTBAP is a compound with strong antioxidant properties. Objective To study the effects of MnTBAP on angiogenic and oxidative gene expression in C57BL6 neonatal mice following hyperoxia. Design and methods: Newborn mice litters were randomized on postnatal day 4 to hyperoxia (> 95% O2)(OX) or room air (RA) for 72 hrs during which they received MnTBAP (MN) 10mg/kg or saline (SL) daily by IP injection for 3 days and then were sacrificed. Whole lung angiogenic and oxidative gene expression profiling (84 related genes for each) was done by real-time, reverse transcription, quantitative PCR (n=4). Data was processed and analyzed using SA Biosciences PCR array data analysis web portal. Results Hyperoxia significantly upregulated peroxiredoxin 6 expression compared to room air exposed newborn mice. Treatment with MnTBAP downregulated the expression of myeloperoxidase and Prdx6-rs1. Hyperoxia downregulated the expression of angiogenic genes such as angiopoietin 1 & 2, TGF 1, TGF 3 and HGF; MnTBAP treatment during the hyperoxia exposure reversed this effect and these genes were upregulated. Conclusions The catalytic antioxidant MnTBAP reversed the effects of hyperoxia on angiogenic gene expression in newborn mice. The protective effects of antioxidants in newborn hyperoxia models need to be studied further to provide additional understanding of the management of bronchopulmonary dysplasia.