Use of Inhaled Nitric Oxide in Preterm Infants: Is There Sufficient Evidence?

Clinical Analysis of Inhaled Nitric Oxide Therapy in Preterm Infants at Different Gestational Ages: A National Retrospective Multicenter Study

This study aimed to investigate clinical features of inhaled nitric oxide (iNO) in preterm infants with a gestational age (GA) < 34 weeks in China.The clinical data of 434 preterm infants with GA < 34 weeks, treated with iNO in the neonatology departments of eight Class A tertiary hospitals in China over a 10-year period from January 2013 to December 2022, were included in this retrospective multicenter investigation. The infants were divided into three groups based on GA: 24 to 27 weeks (extremely preterm infants), 28 to 31 weeks (very preterm infants), and 32 to 33 weeks (moderate preterm infants). The use of iNO, perinatal data, incidence and mortality of indication for iNO treatment, therapeutic effects of iNO, incidence of short-term complications for iNO treatment, and mortality were compared among these three groups.Over the past 10 years, the proportion of iNO use was highest in extremely preterm infants each year. The lower the GA, the higher the iNO use rate: 4.20% for GA 24 to 27 weeks, 1.54% for GA 28 to 31 weeks, and 0.85% for GA 32 to 33 weeks. There was no significant difference in the therapeutic effect of iNO among the three groups. The incidence of neonatal pulmonary hemorrhage, neonatal shock, late-onset diseases, retinopathy of prematurity requiring intervention, intracranial hemorrhage (grade 3 or 4), periventricular leukomalacia, neonatal necrotizing enterocolitis (≥stage II), and moderate to severe bronchopulmonary dysplasia was highest in extremely preterm infants and increased with decreasing GA. Mortality was negatively correlated with GA and birth weight. The highest rate of iNO treatment in 24 to 27 weeks' preterm infants was due to hypoxic respiratory failure (HRF), whereas the highest rate of iNO treatment in 32 to 33 weeks' preterm infants was due to documented persistent pulmonary hypertension of the newborn (PPHN). The rates of iNO treatment due to HRF and documented PPHN were 54.3 and 60.6%, respectively, in extremely preterm infants, significantly higher than in very preterm and moderate preterm infants (all p < 0.05). Within the same GA group, the proportion of preterm infants treated with iNO for HRF was lower than that for documented PPHN (all p < 0.05), but there was no statistically significant difference in mortality between HRF and documented PPHN treated with iNO (all p > 0.05).Among preterm infants with GA < 34 weeks, the rate of iNO usage was highest in extremely preterm infants. However, iNO failed to improve the clinical outcome of extremely preterm infants with refractory hypoxemia, and there was no significant difference in the therapeutic effect of iNO among preterm infants with different GAs.

The effect of inhaled nitric oxide treatment on biomarkers of oxidative/nitrosative damage to proteins and DNA/RNA

Inhaled nitric oxide (iNO) is a selective pulmonary vasodilator that is used as a treatment for persistent pulmonary hypertension in neonates (PPHN) with hypoxic respiratory failure. The generation of reactive oxygen and nitrogen species might induce oxidative/nitrosative damage to multiple organs. There is an increasing scientific and clinical interest in the determination of specific biomarkers to measure the degree of oxidative/nitrosative stress in non-invasively collected biofluids. A method for the simultaneous detection of a panel of oxidative and nitrosative stress-related biomarkers for quantifying damage to proteins and DNA/RNA in 20 μL of infant urine samples based on reversed-phase ultra-performance liquid chromatography coupled to tandem mass spectrometry operating in positive electrospray ionization mode (ESI+) was optimized and validated. Infant urine samples from two different studies were analyzed: (i) term and preterm infants from a nutrition study (Nutrishield, N = 50) and (ii) infants with respiratory insufficiency, including infants with PPHN (N = 16) that required iNO treatment and a control group without treatment (N = 14). Eleven of 14 metabolites were detected in >50 % of infant urine samples, with ranges between 0.008 and 1400 μmol/g creatinine. When comparing across groups, differences in samples collected after iNO treatment in comparison to the rest of the groups were found for m-tyrosine (m-Tyr and m-Tyr/Phe) and ortho-tyrosine (o-Tyr and o-Tyr/Phe) (p-values <0.001, Wilcoxon rank-sum test). Positive linear relationships were found with NO exposure corrected by infant weight for m-Tyr, m-Tyr/Phe, o-Tyr, o-Tyr/Phe and 3-nitrotyrosine. Future studies will focus on the evaluation of the impact of iNO treatment on health and oxidative/nitrosative stress-related morbidities associated with prematurity.

The vascular phenotype of BPD: new basic science insights-new precision medicine approaches

Bronchopulmonary dysplasia (BPD) is the most common complication of preterm birth. Up to 1/3 of children with BPD develop pulmonary hypertension (PH). PH increases mortality, the risk of adverse neurodevelopmental outcome and lacks effective treatment. Current vasodilator therapies address symptoms, but not the underlying arrested vascular development. Recent insights into placental biology and novel technological advances enabling the study of normal and impaired lung development at the single cell level support the concept of a vascular phenotype of BPD. Dysregulation of growth factor pathways results in depletion and dysfunction of putative distal pulmonary endothelial progenitor cells including Cap1, Cap2, and endothelial colony-forming cells (ECFCs), a subset of vascular progenitor cells with self-renewal and de novo angiogenic capacity. Preclinical data demonstrate effectiveness of ECFCs and ECFC-derived particles including extracellular vesicles (EVs) in promoting lung vascular growth and reversing PH, but the mechanism is unknown. The lack of engraftment suggests a paracrine mode of action mediated by EVs that contain miRNA. Aberrant miRNA signaling contributes to arrested pulmonary vascular development, hence using EV- and miRNA-based therapies is a promising strategy to prevent the development of BPD-PH. More needs to be learned about disrupted pathways, timing of intervention, and mode of delivery. IMPACT: Single-cell RNA sequencing studies provide new in-depth view of developmental endothelial depletion underlying BPD-PH. Aberrant miRNA expression is a major cause of arrested pulmonary development. EV- and miRNA-based therapies are very promising therapeutic strategies to improve prognosis in BPD-PH.

Morbidity and mortality in neonates with Down Syndrome based on gestational age

BACKGROUND

Greater than 50% of neonates with Down Syndrome (DS) have perinatal complications that require admission to the neonatal intensive care unit (NICU) at birth. Previous studies have shown increased morbidity and mortality rates in neonates without DS delivered prior to 39 weeks of completed gestation.

OBJECTIVE

To determine if an association exists between gestational age at delivery and adverse outcomes in neonates with DS.

STUDY DESIGN

Neonates with DS admitted to a large, tertiary care center NICU from 2010 to 2020 were evaluated. Gestational age (GA) was stratified into 4 groups: <34 (preterm), 34-36 (late-preterm), 37-38 (early-term) and ≥39 (term + post-term) completed weeks. Fisher's exact tests were used to evaluate morbidity and mortality rates between groups.

RESULT

Of the 314 neonates with DS, 10% (N = 31) were <34 weeks, 22% (N = 68) 34-36 weeks, 40% (N = 127) 37-38 weeks, and 28% (N = 88) ≥39 completed weeks at birth. Baseline characteristics were similar between groups. GA at birth <34 weeks was associated with a higher in-hospital mortality rate when compared to those born 37-38 (19% vs. 0%, P < 0.001) and ≥39 (19% vs. 3%, P = 0.01). Neonates with DS born <34 weeks had a higher likelihood of oxygen requirement at time of discharge compared to 34-36, 37-38, and ≥39 groups (P = 0.01; P < 0.001; P < 0.001 respectively). Neonates with DS < 34 weeks were more likely to develop necrotizing enterocolitis (P = 0.02) and require nitric oxide (P = 0.014) compared to neonates with DS ≥ 39. We observed no differences in the need for surgical interventions between groups aside from the rate of gastrostomy/jejunostomy tube placement between 34-36 weeks and 37-38 weeks GA.

CONCLUSION

Neonates with DS born preterm (<34 weeks) represent a highly vulnerable subgroup. Multidisciplinary strategies are needed to address their higher rates of morbidity and mortality.