Oxygen radical disease in the newborn, revisited: Oxidative stress and disease in the newborn period

Maternal Diabetes Mellitus and Persistent Pulmonary Hypertension of the Newborn: Accumulated Evidence From Observational Studies

OBJECTIVES

Maternal diabetes mellitus (including pre-existing and gestational diabetes mellitus) is linked with adverse infant outcomes. However, the question of whether maternal diabetes increases the risk of persistent pulmonary hypertension of the newborn (PPHN) is unclear. Herein, we conducted a systematic review and meta-analysis to summarize clinical evidence to determine the association between maternal diabetes mellitus and PPHN.

METHODS

In this systematic review and meta-analysis, we systematically searched PubMed, Embase, Cochrane Library, Web of Science and Google Scholar to identify relevant studies according to predefined criteria. Data from selected studies were extracted, and meta-analysis was performed using fixed effects modelling.

RESULTS

In all, we included 7 unique studies with aggregated data on 2 million individuals and >5,000 cases of PPHN. Maternal diabetes was significantly associated with a higher risk of PPHN (risk ratio [RR], 1.37; 95% confidence interval [CI], 1.23 to 1.51). Both case-control and cohort studies exhibited that the presence of maternal diabetes increased the risk of PPHN (case-control: RR, 1.91; 95% CI, 1.02 to 2.79; cohort: RR, 1.36; 95% CI, 1.22 to 1.50). By omitting 1 study at a time, sensitivity analysis made sure that no individual study was entirely responsible for the combined results.

CONCLUSIONS

Maternal diabetes was associated with increased risk of PPHN. For babies with refractory hypoxemia, with mothers with diabetes, PPHN should be taken into consideration in clinical practice.

Melatonin long-lasting beneficial effects on pulmonary vascular reactivity and redox balance in chronic hypoxic ovine neonates

Pulmonary arterial hypertension of the neonate (PAHN) is a pathophysiological condition characterized by maladaptive pulmonary vascular remodeling and abnormal contractile reactivity. This is a multifactorial syndrome with chronic hypoxia and oxidative stress as main etiological drivers, and with limited effectiveness in therapeutic approaches. Melatonin is a neurohormone with antioxidant and vasodilator properties at the pulmonary level. Therefore, this study aims to test whether a postnatal treatment with melatonin during the neonatal period improves in a long-lasting manner the clinical condition of PAHN. Ten newborn lambs gestated and born at 3600 m were used in this study, five received vehicle and five received melatonin in daily doses of 1 mg kg^-1 for the first 3 weeks of life. After 1 week of treatment completion, lung tissue and small pulmonary arteries (SPA) were collected for wire myography, molecular biology, and morphostructural analyses. Melatonin decreased pulmonary arterial pressure the first 4 days of treatment. At 1 month old, melatonin decreased the contractile response to the vasoconstrictors K⁺ , TX₂ , and ET-1. Further, melatonin increased the endothelium-dependent and muscle-dependent vasodilation of SPA. Finally, the treatment decreased pulmonary oxidative stress by inducing antioxidant enzymes and diminishing pro-oxidant sources. In conclusion, melatonin improved vascular reactivity and oxidative stress at the pulmonary level in PAHN lambs gestated and born in chronic hypoxia.

Adjunctive therapy to treat neonatal sepsis

Introduction: Neonatal sepsis (NS) is a very severe condition that causes significant morbidity and mortality.Areas covered: To overcome the limits of antibiotic therapy and improve NS outcomes, measures chosen among those theoretically able to improve host defenses or positively interfere with deleterious immune responses could be suggested. This paper discusses the mechanisms of action of these measures, whether their efficacy in prophylaxis justifies use in NS therapy and their impact.Expert opinion: NS remains a relevant problem despite the availability of antibiotics effective against the most common agents and the introduction of effective preventive measures such as group B Streptococcus prenatal screening and intrapartum antibiotic prophylaxis. This explains why attempts to introduce new prophylactic and therapeutic measures have been made. Unfortunately, none of the measures suggested and tested to date can be considered a definitive advance. It is highly likely that in the future, new measures will be proposed according to the increase in the knowledge of the characteristics of immune system function in preterm infants and the methods to modulate unproper immune responses.

Recent advances in our understanding of the mechanisms of lung alveolarization and bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the most common cause of morbidity and mortality in preterm infants. A key histopathological feature of BPD is stunted late lung development, where the process of alveolarization-the generation of alveolar gas exchange units-is impeded, through mechanisms that remain largely unclear. As such, there is interest in the clarification both of the pathomechanisms at play in affected lungs, and the mechanisms of de novo alveoli generation in healthy, developing lungs. A better understanding of normal and pathological alveolarization might reveal opportunities for improved medical management of affected infants. Furthermore, disturbances to the alveolar architecture are a key histopathological feature of several adult chronic lung diseases, including emphysema and fibrosis, and it is envisaged that knowledge about the mechanisms of alveologenesis might facilitate regeneration of healthy lung parenchyma in affected patients. To this end, recent efforts have interrogated clinical data, developed new-and refined existing-in vivo and in vitro models of BPD, have applied new microscopic and radiographic approaches, and have developed advanced cell-culture approaches, including organoid generation. Advances have also been made in the development of other methodologies, including single-cell analysis, metabolomics, lipidomics, and proteomics, as well as the generation and use of complex mouse genetics tools. The objective of this review is to present advances made in our understanding of the mechanisms of lung alveolarization and BPD over the period 1 January 2017-30 June 2019, a period that spans the 50th anniversary of the original clinical description of BPD in preterm infants.

Increasing Respiratory Effort With 100% Oxygen During Resuscitation of Preterm Rabbits at Birth

Background: Spontaneous breathing is essential for successful non-invasive respiratory support delivered by a facemask at birth. As hypoxia is a potent inhibitor of spontaneous breathing, initiating respiratory support with a high fraction of inspired O₂ may reduce the risk of hypoxia and increase respiratory effort at birth. Methods: Preterm rabbit kittens (29 days gestation, term ~32 days) were delivered and randomized to receive continuous positive airway pressure with either 21% (n = 12) or 100% O₂ (n = 8) via a facemask. If apnea occurred, intermittent positive pressure ventilation (iPPV) was applied with either 21% or 100% O₂ in kittens who started in 21% O₂, and remained at 100% O₂ for kittens who started the experiment in 100% O₂. Respiratory rate (breaths per minute, bpm) and variability in inter-breath interval (%) were measured from esophageal pressure recordings and functional residual capacity (FRC) was measured from synchrotron phase-contrast X-ray images. Results: Initially, kittens receiving 21% O₂ had a significantly lower respiratory rate and higher variability in inter-breath interval, indicating a less stable breathing pattern than kittens starting in 100% O₂ [median (IQR) respiratory rate: 16 (4-28) vs. 38 (29-46) bpm, p = 0.001; variability in inter-breath interval: 33.3% (17.2-50.1%) vs. 27.5% (18.6-36.3%), p = 0.009]. Apnea that required iPPV, was more frequently observed in kittens in whom resuscitation was started with 21% compared to 100% O₂ (11/12 vs. 1/8, p = 0.001). After recovering from apnea, respiratory rate was significantly lower and variability in inter-breath interval was significantly higher in kittens who received iPPV with 21% compared to 100% O₂. FRC was not different between study groups at both timepoints. Conclusion: Initiating resuscitation with 100% O₂ resulted in increased respiratory activity and stability, thereby reducing the risk of apnea and need for iPPV after birth. Further studies in human preterm infants are mandatory to confirm the benefit of this approach in terms of oxygenation. In addition, the ability to avoid hyperoxia after initiation of resuscitation with 100% oxygen, using a titration protocol based on oxygen saturation, needs to be clarified.