Resuscitation with room air instead of 100% oxygen prevents oxidative stress in moderately asphyxiated term neonates

Oxygen in the neonatal ICU: a complicated history and where are we now?

Despite major advances in neonatal care, oxygen remains the most commonly used medication in the neonatal intensive care unit (NICU). Supplemental oxygen can be life-saving for term and preterm neonates in the resuscitation period and beyond, however use of oxygen in the neonatal period must be judicious as there can be toxic effects. Newborns experience substantial hemodynamic changes at birth, rapid energy consumption, and decreased antioxidant capacity, which requires a delicate balance of sufficient oxygen while mitigating reactive oxygen species causing oxidative stress. In this review, we will discuss the physiology of neonates in relation to hypoxia and hyperoxic injury, the history of supplemental oxygen in the delivery room and beyond, supporting clinical research guiding trends for oxygen therapy in neonatal care, current practices, and future directions.

Perinatal Outcome following the Suspension of Intrapartum Oxygen Treatment

OBJECTIVE

 This study aimed to evaluate whether the suspension of intrapartum maternal oxygen supplementation for nonreassuring fetal heart rate is associated with adverse perinatal outcomes.

STUDY DESIGN

 A retrospective cohort study, including all individuals that underwent labor in a single tertiary medical center. On April 16, 2020, the routine use of intrapartum oxygen for category II and III fetal heart rate tracings was suspended. The study group included individuals with singleton pregnancies that underwent labor during the 7 months between April 16, 2020, and November 14, 2020. The control group included individuals that underwent labor during the 7 months before April 16, 2020. Exclusion criteria included elective cesarean section, multifetal pregnancy, fetal death, and maternal oxygen saturation <95% during delivery. The primary outcome was defined as the rate of composite neonatal outcome, consisting of arterial cord pH <7.1, mechanical ventilation, respiratory distress syndrome, necrotizing enterocolitis, intraventricular hemorrhage grade 3/4, and neonatal death. The secondary outcome was the rate of cesarean and operative delivery.

RESULTS

 The study group included 4,932 individuals, compared with 4,906 individuals in the control group. The suspension of intrapartum oxygen treatment was associated with a significant increase in the rate of composite neonatal outcome (187 [3.8%] vs. 120 [2.4%], p < 0.001), including the rate of abnormal cord arterial pH <7.1 (119 [2.4%] vs. 56 [1.1%], p < 0.01). A higher rate of cesarean section due to nonreassuring fetal heart rate was noted in the study group (320 [6.5%] vs. 268 [5.5%], p = 0.03).A logistic regression analysis revealed that the suspension of intrapartum oxygen treatment was independently associated with the composite neonatal outcome (adjusted odds ratio = 1.55 [95% confidence interval, 1.23-1.96]) while adjusting for suspected chorioamnionitis, intrauterine growth restriction, and recent coronavirus disease 2019 exposure.

CONCLUSION

 Suspension of intrapartum oxygen treatment for nonreassuring fetal heart rate was associated with higher rates of adverse neonatal outcomes and urgent cesarean section due to fetal heart rate.

KEY POINTS

· The available data on intrapartum maternal oxygen supplementation are equivocal.. · Suspension of maternal oxygen for nonreassuring fetal heart rate during labor was associated with adverse neonatal outcomes.. · Oxygen treatment might still be important and relevant during labor..

Effect of maternal hyperoxygenation on neonatal outcomes among women in labour with pathological cardiotocography: an open-label randomized controlled trial

BACKGROUND

Hyperoxygenation has shown promise in improving suspicious fetal heart patterns in women in labor. However, the effect of hyperoxygenation on neonatal outcomes in women in labor with pathologic fetal heart rate tracing has not been studied.

OBJECTIVE

This study aimed to evaluate the effect of fractional inspiration of oxygen of 80% compared with fractional inspiration of oxygen of 40% on neonatal outcomes in women with pathologic fetal heart rate tracing.

STUDY DESIGN

This randomized, open-label, parallel arm, outcome assessor-blinded clinical trial was conducted in a large tertiary care university hospital. Singleton parturients aged ≥18 years at term gestation in active labor (cervical dilatation of ≥6 cm) with pathologic fetal heart rate tracing were recruited in the study. Pathologic fetal heart rate tracing was defined according to the International Federation of Gynecology and Obstetrics 2015 guidelines. The International Federation of Gynecology and Obstetrics classifies fetal heart rate tracings into 3 categories (normal, suspicious, and pathologic) based on rate, variability, and deceleration. Women in the intervention arm received oxygen at 10 L/min via a nonrebreathing mask, and those in the usual care arm received oxygen at 6 L/min with a simple face mask. Oxygen supplementation was continued until cord clamping. The primary outcome measure was a 5-minute Apgar score. The secondary outcome measures were the proportion of neonatal intensive care unit admission, umbilical cord blood gas variables, level of methyl malondialdehyde in the cord blood, and mode of delivery.

RESULTS

Overall, 148 women (74 women in the high fractional inspiration of oxygen arm and 74 in the low fractional inspiration of oxygen arm) with pathologic fetal heart rate tracing were analyzed. The demographic data, obstetrical profiles, and comorbidities were comparable. The median 5-minute Apgar scores were 9 (interquartile range, 8-10) in the hyperoxygenation arm and 9 (interquartile range, 8-10) in the usual care arm (P=.12). Furthermore, the rate of neonatal intensive care unit admission (9.5% vs 12.2%; P=.6) and the requirement of positive pressure ventilation (6.8% vs 8.1%; P=.75) were comparable. Concerning cord blood gas parameters, the hyperoxygenation arm had a significantly higher base deficit in the umbilical vein and lactate level in the umbilical artery. The cesarean delivery rate was significantly lower in women who received hyperoxygenation (4.1% [3/74]) than in women who received normal oxygen supplementation (25.7% [19/74]) (P=.00). In addition, umbilical vein malondialdehyde level in the umbilical vein was lower in the hyperoxygenation group (8.28±4.65 μmol/L) than in the normal oxygen supplementation group (13.44±8.34 μmol/L) (P=.00).

CONCLUSION

Hyperoxygenation did not improve the neonatal Apgar score in women with pathologic fetal heart rate tracing. In addition, neonatal intensive care unit admission rate and blood gas parameters remained comparable. Therefore, the results of this trial suggest that a high fractional inspiration of oxygen supplementation confers no benefit on neonatal outcomes in women with pathologic fetal heart rate tracings and normal oxygen saturation.

Monitoring SpO2: The Basics of Retinopathy of Prematurity (Back to Basics) and Targeting Oxygen Saturation

Oxygen (O2) is a drug frequently used in newborn care. Adverse effects of hypoxia are well known but the damaging effects of excess oxygen administration and oxidative stress have only been studied in the last 2 decades. Many negative effects have been described, including retinopathy of prematurity . Noninvasive pulse oximetry (SpO2) is useful to detect hypoxemia but requires careful evaluation and understanding of the frequently changing relationship between O2 and hemoglobin to prevent hyperoxemia. Intention to treat SpO2 ranges should be individualized for every newborn receiving supplemental O2, according to gestational age, post-natal age, and clinical condition.

Comparison of the efficacy of two natural surfactants (BERAKSURF and BLES) in the treatment of respiratory distress syndrome among preterm neonates

BACKGROUND

The benefit of surfactant replacement therapy for respiratory distress syndrome (RDS) has been demonstrated. However, some surfactants are expensive and usually inaccessible. Consequently, the Iranian Survanta was produced, but its effect on complications and mortality of RDS is unknown. This study aimed to compare the therapeutic outcomes of Iranian surfactant (beraksurf) and BLES (bovine lipid extract surfactant) on RDS treatment among preterm neonates.

METHODS

This triple blinded randomized controlled trial study was performed on 128 eligible neonates diagnosed with RDS in Afzalipour hospital in Kerman, Iran. Diagnosis of RDS, gestational age of 28-34 weeks and weight ≥ 1 kg were considered as inclusion criteria. Congenital anomalies such as congenital cyanotic heart diseases, digestive system anomalies and chromosome abnormalities were the exclusion criteria Neonates were randomly assigned into two equal groups: (1) those treated with BLES (n = 64) and (2) those treated with beraksurf (n = 64). Complications including patent ductus arteriosus (PDA), sepsis, intraventricular hemorrhage (IVH), pneumothorax, pulmonary hemorrhage, mortality, and also, the number of days required for invasive mechanical ventilation (using ventilator) and non-invasive continuous positive airway pressure (CPAP) were evaluated for all neonates. The risk ratio (RR) was calculated at 95% of confidence intervals (CI).

RESULTS

Compared with BLES group, the RR estimate among neonates in beraksurf group was 0.89 (0.66-1.20) for PDA, 0.71 (0.23-2.13) for IVH, 0.44 (0.14-1.36) for sepsis, 0.35 (0.13-0.93) for pneumothorax, 0.33 (0.12-0.86) for pulmonary hemorrhage, and 0.55 (0.28-1.05) for mortality.

CONCLUSIONS

Despite advances in the use of exogenous surfactants for the treatment of neonatal respiratory distress syndrome; There are still some controversial topics in this field. The results obtained in the present study showed that the two types of surfactant (BERAKSURF and BLES) have similar efficacy for the treatment and short-term outcomes in preterm infants with respiratory distress syndrome. Therefore, due to the cost-effectiveness of BRAKSURF compared to BLES, We recommend choosing BERAKSURF in terms of treatment.

Meconium aspiration syndrome: a comprehensive review

Meconium aspiration syndrome (MAS) is a complex respiratory disease that continues to be associated with significant morbidities and mortality. The pathophysiological mechanisms of MAS include airway obstruction, local and systemic inflammation, surfactant inactivation and persistent pulmonary hypertension of the newborn (PPHN). Supplemental oxygen and non-invasive respiratory support are the main therapies for many patients. The management of the patients requiring invasive mechanical ventilation could be challenging because of the combination of atelectasis and air trapping. While studies have explored various ventilatory modalities, evidence to date does not clearly support any singular modality as superior. Patient's pathophysiology, symptom severity, and clinician/unit expertise should guide the respiratory management. Early identification and concomitant management of PPHN is critically important as it contributes significantly to mortality and morbidities.

The role of oxygen in the development and treatment of bronchopulmonary dysplasia

Oxygen (O2) is crucial for both the development and treatment of one of the most important consequences of prematurity: bronchopulmonary dysplasia (BPD). In fetal life, the hypoxic environment is important for alveolar development and maturation. After birth, O2 becomes a double-edged sword. While O2 is needed to prevent hypoxia, it also causes oxidative stress leading to a plethora of morbidities, including retinopathy and BPD. The advent of continuous O2 monitoring with pulse oximeters has allowed clinicians to recognize the narrow therapeutic margins of oxygenation for the preterm infant, but more knowledge is needed to understand what these ranges are at different stages of the preterm infant's life, including at birth, in the neonatal intensive care unit and after hospital discharge. Future research, especially in innovative technologies such as automated O2 control and remote oximetry, will improve the understanding and treatment of the O2 needs of infants with BPD.

Maternal Oxygen Administration during Labor: A Controversial Practice

Oxygen administration to the mother is commonly performed during labor, especially in the case of a non-reassuring fetal heart rate, aiming to increase oxygen diffusion through the placenta to fetal tissues. The benefits and potential risks are controversial, especially when the mother is not hypoxemic. Its impact on placental gas exchange and the fetal acid-base equilibrium is not fully understood and it probably affects the sensible placental oxygen equilibrium causing a time-dependent vasoconstriction of umbilical and placental vessels. Hyperoxia might also cause the generation of radical oxygen species, raising concerns for the developing fetal cells. Moreover, this practice affects the maternal cardiovascular system, causing alterations of the cardiac index, heart rate and vascular resistance, and unclear effects on uterine blood flow. In conclusion, there is no evidence that maternal oxygen administration can provide any benefit in the case of a non-reassuring fetal heart rate pattern, while possible collateral effects warn of its utilization. Oxygen administration during labor should be reserved for cases of maternal hypoxia.

Comparison of Bevacizumab and Aflibercept for Suppression of Angiogenesis in Human Retinal Microvascular Endothelial Cells

Bevacizumab (Avastin) is a vascular endothelial growth factor (VEGF) inhibitor that is widely used for aggressive posterior retinopathy of prematurity (APROP). Its use is associated with multiple adverse effects. Aflibercept (Eylea) is a VEGFR-1 analogue that is approved for ocular use, but its efficacy for APROP is less studied. We tested the hypothesis that Eylea is as effective as Avastin for suppression of intermittent hypoxia (IH)-induced angiogenesis. Human retinal microvascular endothelial cells (HRECs) were treated with Avastin and low- or high-dose Eylea and exposed to normoxia, hyperoxia (50% O₂), or neonatal IH for 24, 48, or 72 h. Cells were assessed for migration and tube formation capacities, as well as biomarkers of angiogenesis and oxidative stress. Both doses of Eylea suppressed migration and tube formation in all oxygen environments, although the effect was not as robust as Avastin. Furthermore, the lower dose of Eylea appeared to be more effective than the higher dose. Eylea induced soluble VEGFR-1 (sVEGFR-1) coincident with high IGF-I levels and decreased Notch/Jagged-1, demonstrating a functional association. Given the role of VEGFR-1 and Notch as guidance cues for vascular sprouting, these data suggest that Eylea may promote normal vascular patterning in a dose-dependent manner.

Sevoflurane Exposure in Neonates Perturbs the Expression Patterns of Specific Genes That May Underly the Observed Learning and Memory Deficits

Exposure to commonly used anesthetics leads to neurotoxic effects in animal models-ranging from cell death to learning and memory deficits. These neurotoxic effects invoke a variety of molecular pathways, exerting either immediate or long-term effects at the cellular and behavioural levels. However, little is known about the gene expression changes following early neonatal exposure to these anesthetic agents. We report here on the effects of sevoflurane, a commonly used inhalational anesthetic, on learning and memory and identify a key set of genes that may likely be involved in the observed behavioural deficits. Specifically, we demonstrate that sevoflurane exposure in postnatal day 7 (P7) rat pups results in subtle, but distinct, memory deficits in the adult animals that have not been reported previously. Interestingly, when given intraperitoneally, pre-treatment with dexmedetomidine (DEX) could only prevent sevoflurane-induced anxiety in open field testing. To identify genes that may have been altered in the neonatal rats after sevoflurane and DEX exposure, specifically those impacting cellular viability, learning, and memory, we conducted an extensive Nanostring study examining over 770 genes. We found differential changes in the gene expression levels after exposure to both agents. A number of the perturbed genes found in this study have previously been implicated in synaptic transmission, plasticity, neurogenesis, apoptosis, myelination, and learning and memory. Our data thus demonstrate that subtle, albeit long-term, changes observed in an adult animal's learning and memory after neonatal anesthetic exposure may likely involve perturbation of specific gene expression patterns.

PROspective Meta-analysis Of Trials of Initial Oxygen in preterm Newborns (PROMOTION): Protocol for a systematic review and prospective meta-analysis with individual participant data on initial oxygen concentration for resuscitation of preterm infants

BACKGROUND

Clinicians favour low oxygen concentrations when resuscitating preterm infants immediately after birth despite inconclusive evidence to support this practice. Prospective meta-analysis (PMA) is a novel approach where studies are identified as eligible for inclusion in the meta-analysis before their results are known.

AIMS

To explore whether high (60%) or low (30%) oxygen is associated with greater efficacy and safety for the initial resuscitation (immediately after birth) of preterm infants born at <29 weeks' gestation.

METHODS

We will conduct a prospective meta-analysis (PMA) with individual participant data (IPD). We will perform a systematic search to identify ongoing RCTs including infants <29 weeks' gestation randomised to high (60%) or low (30%) oxygen for initial resuscitation after birth. IPD will be sought for all infants randomised for the purpose of meta-analysis. We will employ a one-stage random-effects approach to IPD meta-analysis. Potential heterogeneity and the differential effect of high or low oxygen will be explored through subgroup and interaction analyses. The primary outcome of this study is all-cause mortality prior to hospital discharge. There will be a follow-up analysis of neurodevelopmental outcomes once available.

RESULTS/CONCLUSION

The results of neonatal outcomes at hospital discharge are expected by 2025, and neurodevelopmental outcomes by 2027.

Future of clinical trials in the delivery room: time for pragmatism

Despite increased amounts of research, most of the evidence that supports treatment of newborns in the delivery room is rated 'low' rather than 'high' quality. This assessment stems largely from a lack of evidence from clinical trials. When trials have been performed, the evidence has often been downgraded due to enrolment of small or poorly representative samples, and for lack of blinding of caregivers and outcome assessors. Delivery room trials present particular challenges when obtaining consent, enrolling participants, taking measures to limit bias and identifying appropriate outcome measures. We hope our suggestions as to how future delivery room trials could be more pragmatic will inform the design of large studies that are necessary to allow clinical practice to evolve.

Closed-loop automated oxygen control in ventilated infants born at or near term: A crossover trial

AIM

To determine if the use of closed-loop automated oxygen control (CLAC) reduced the incidence and duration of hypoxemic episodes (SpO₂  < 92%) in ventilated infants born at or above 34 weeks of gestation.

METHODS

Infants were studied on two consecutive days for 6 h each day. They were randomised to receive standard care (manual oxygen control) or standard care with a CLAC system (automated oxygen control) first.

RESULTS

Sixteen infants with a median (IQR) gestational age of 37.4 (36.6-38.8) weeks were studied at a median (IQR) postmenstrual age of 38.8 (37.4-39.8) weeks. During the automated oxygen control period, infants spent less time in hypoxemia (SpO₂  < 92%) (p = 0.033), episodes of desaturation were shorter (p = 0.001), the time spent within target SpO₂ range (92%-96%) was increased (p = 0.001), and the FiO₂ delivery was lower (p = 0.018). The time spent in hyperoxemia (SpO₂  > 96%) was reduced during automated oxygen control (p = 0.011), the episodes of hyperoxemia were of shorter duration (p = 0.008) and fewer manual adjustments were made to the FiO₂ (p = 0.005).

CONCLUSIONS

Closed-loop automated oxygen control in ventilated infants born at or near term was associated with a reduction in the incidence and duration of hypoxemic episodes with more time spent in the target oxygen range.

Initial Use of 100% but Not 60% or 30% Oxygen Achieved a Target Heart Rate of 100 bpm and Preductal Saturations of 80% Faster in a Bradycardic Preterm Model

Background: Currently, 21−30% supplemental oxygen is recommended during resuscitation of preterm neonates. Recent studies have shown that 58% of infants < 32 week gestation age are born with a heart rate (HR) < 100 bpm. Prolonged bradycardia with the inability to achieve a preductal saturation (SpO2) of 80% by 5 min is associated with mortality and morbidity in preterm infants. The optimal oxygen concentration that enables the achievement of a HR ≥ 100 bpm and SpO2 of ≥80% by 5 min in preterm lambs is not known. Methods: Preterm ovine model (125−127 d, gestation equivalent to human neonates < 28 weeks) was instrumented, and asphyxia was induced by umbilical cord occlusion until bradycardia. Ventilation was initiated with 30% (OX30), 60% (OX60), and 100% (OX100) for the first 2 min and titrated proportionately to the difference from the recommended preductal SpO2. Our primary outcome was the incidence of the composite of HR ≥ 100 bpm and SpO2 ≥ 80%, by 5 min. Secondary outcomes were to evaluate the time taken to achieve the primary outcome, gas exchange, pulmonary/systemic hemodynamics, and the oxidative injury. Results: Eighteen lambs (OX30-6, OX60-5. OX100-7) had an average HR < 91 bpm with a pH of <6.92 before resuscitation. Sixty seven percent achieved the primary outcome in OX100, 40% in OX60, and none in OX30. The time taken to achieve the primary outcome was significantly shorter with OX100 (6 ± 2 min) than with OX30 (10 ± 3 min) (* p = 0.04). The preductal SpO2 was highest with OX100, while the peak pulmonary blood flow was lowest with OX30, with no difference in O2 delivery to the brain or oxidative injury by 10 min. Conclusions: The use of 30%, 60%, and 100% supplemental O2 in a bradycardic preterm ovine model did not demonstrate a significant difference in the composite primary outcome. The current recommendation to use 30% oxygen did not achieve a preductal SpO2 of 80% by 5 min in any preterm lambs. Clinical studies to optimize supplemental O2 in depressed preterm neonates not requiring chest compressions are warranted.

The quest for optimum oxygenation during newborn delivery room resuscitation: Is it the baby or is it us?

Achieving "normal oxygenation" in sick newborn infants requiring resuscitation is one of the most difficult and incompletely informed practices in neonatal care. Suboptimal oxygenation, whether too little or too much, has profound repercussions, including death. In the last two decades, clinicians have lost equipoise for the use of higher oxygen strategies due to concerns of hyperoxia but emerging evidence suggests that lower oxygen strategies may also be as detrimental, especially in infants with pulmonary pathologies such as those born at the cusp of viability. Practice at the coalface using rapidly evolving recommendations has also uncovered continuing complexities in the quest to achieve optimum oxygenation during the first critical minutes of life. There are adjustable factors, such as the practical impediments to acquiring knowledge, equipment and expertise as well as unadjustable factors, such as inherent infant pathology, that necessitates agile clinical manipulation to "first do no harm". This review will address the deficiencies in knowledge that currently impede our quest to determine the best and safest means to deliver oxygen to sick infants during the first critical minutes of life and suggest practical solutions for current practice while awaiting definitive evidence from large scale, well defined, randomized controlled studies.

A Dose-Limited Dexamethasone and Bubble Continuous Positive Airway Pressure in Ventilation-Dependent Extremely Premature Infants

OBJECTIVE

 Dexamethasone has been associated with early extubation and shorter duration of mechanical ventilation in preterm infants. High doses or prolonged courses of dexamethasone may be associated with poor neurodevelopmental outcomes.

STUDY DESIGN

 This is an observational cohort study assessing the efficacy of a low-dose short dexamethasone course combined with postextubation bubble continuous positive airway pressure (bCPAP) strategy on rates of successful extubation and reduction of the duration of invasive mechanical ventilation in extremely preterm infants. We compared the short-term outcomes of implementing such strategy on a group of infants with birth weight <750 g to a historical cohort.

RESULTS

 Among infants intubated for at least 10 days, median time to extubation from starting the dexamethasone course was 2 days (interquartile range: 1-3). Total duration of intubation was significantly shorter in infants who received dexamethasone compared with the control groups (21 ± 6 vs. 30 ± 10 days, p = 0.03), and although statistically nonsignificant, duration to wean to 21% bCPAP was shorter compared with the control group (48 ± 13 vs. 74 ± 29 days, p = 0.06).

CONCLUSION

 A low-dose short dexamethasone course combined with postextubation bCPAP intervention may be associated with successful early extubation and shorter duration of mechanical ventilation.

KEY POINTS

· Noninvasive strategies may not succeed in infants < 750 g birth weight.. · Bubble CPAP has been shown to be associated with reduced complications including chronic lung disease.. · Postnatal dexamethasone therapy may succeed in conjunction with bubble CPAP to reduce reintubation..

Direct Derivatization in Dried Blood Spots for Oxidized and Reduced Glutathione Quantification in Newborns

The glutathione (GSH)-to-glutathione disulfide (GSSG) ratio is an essential node contributing to intracellular redox status. GSH/GSSG determination in whole blood can be accomplished by liquid chromatography–mass spectrometry (LC-MS) after the derivatization of GSH with N-ethylmaleimide (NEM). While this is feasible in a laboratory environment, its application in the clinical scenario is cumbersome and therefore ranges reported in similar populations differ noticeably. In this work, an LC-MS procedure for the determination of GSH and GSSG in dried blood spot (DBS) samples based on direct in situ GSH derivatization with NEM of only 10 µL of blood was developed. This novel method was applied to 73 cord blood samples and 88 residual blood volumes from routine newborn screening performed at discharge from healthy term infants. Two clinical scenarios simulating conditions of sampling and storage relevant for routine clinical analysis and clinical trials were assessed. Levels of GSH-NEM and GSSG measured in DBS samples were comparable to those obtained by liquid blood samples. GSH-NEM and GSSG median values for cord blood samples were significantly lower than those for samples at discharge. However, the GSH-NEM-to-GSSG ratios were not statistically different between both groups. With DBS testing, the immediate manipulation of samples by clinical staff is reduced. We therefore expect that this method will pave the way in providing an accurate and more robust determination of the GSH/GSSG values and trends reported in clinical trials.

Oxygen for the delivery room respiratory support of moderate-to-late preterm infants. An international survey of clinical practice from 21 countries

AIM

The aim of this study was to determine clinician opinion regarding oxygen management in moderate-late preterm resuscitation.

METHODS

An anonymous online questionnaire was distributed through email/social messaging platforms to neonatologists in 21 countries (October 2020-March 2021) via REDCap.

RESULTS

Of the 695 respondents, 69% had access to oxygen blenders and 90% had pulse oximeters. Respondents from high-income countries were more likely to have oxygen blenders than those from middle-income countries (72% vs. 66%). Most initiated respiratory support with FiO₂ 0.21 (43%) or 0.3 (36%) but only 45% titrated FiO₂ to target SpO₂ . Most (89%) considered heart rate as a more important indicator of response than SpO₂ . Almost all (96%) supported the need for well-designed trials to examine oxygenation in moderate-late preterm resuscitation.

CONCLUSION

Most clinicians resuscitated moderate-late preterm infants with lower initial FiO₂ but some cannot/will not target SpO₂ or titrate FiO₂ . Most consider heart rate as a more important indicator of infant response than SpO₂ .Large and robust clinical trials examining oxygen use for moderate-late preterm resuscitation, including long-term neurodevelopmental outcomes, are supported amongst clinicians.

Supplemental Oxygen in the Newborn: Historical Perspective and Current Trends

Oxygen is the final electron acceptor in aerobic respiration, and a lack of oxygen can result in bioenergetic failure and cell death. Thus, administration of supplemental concentrations of oxygen to overcome barriers to tissue oxygen delivery (e.g., heart failure, lung disease, ischemia), can rescue dying cells where cellular oxygen content is low. However, the balance of oxygen delivery and oxygen consumption relies on tightly controlled oxygen gradients and compartmentalized redox potential. While therapeutic oxygen delivery can be life-saving, it can disrupt growth and development, impair bioenergetic function, and induce inflammation. Newborns, and premature newborns especially, have features that confer particular susceptibility to hyperoxic injury due to oxidative stress. In this review, we will describe the unique features of newborn redox physiology and antioxidant defenses, the history of therapeutic oxygen use in this population and its role in disease, and clinical trends in the use of therapeutic oxygen and mitigation of neonatal oxidative injury.

Metabolomics to Diagnose Oxidative Stress in Perinatal Asphyxia: Towards a Non-Invasive Approach

There is a need for feasible and non-invasive diagnostics in perinatal asphyxia. Metabolomics is the study of small molecular weight products of cellular metabolism that may, directly and indirectly, reflect the level of oxidative stress. Saliva analysis is a novel approach that has a yet unexplored potential in metabolomics in perinatal asphyxia. The aim of this review was to give an overview of metabolomics studies of oxidative stress in perinatal asphyxia, particularly searching for studies analyzing non-invasively collected biofluids including saliva. We searched the databases PubMed/Medline and included 11 original human and 4 animal studies. In perinatal asphyxia, whole blood, plasma, and urine are the most frequently used biofluids used for metabolomics analyses. Although changes in oxidative stress-related salivary metabolites have been reported in adults, the utility of this approach in perinatal asphyxia has not yet been explored. Human and animal studies indicate that, in addition to antioxidant enzymes, succinate and hypoxanthine, as well acylcarnitines may have discriminatory diagnostic and prognostic properties in perinatal asphyxia. Researchers may utilize the accumulating evidence of discriminatory metabolic patterns in perinatal asphyxia to develop bedside methods to measure oxidative stress metabolites in perinatal asphyxia. Although only supported by indirect evidence, saliva might be a candidate biofluid for such point-of-care diagnostics.

Interventions for Intrapartum Fetal Heart Rate Abnormalities

Intrapartum fetal heart rate (FHR) decelerations may represent interrupted oxygen transfer to the fetus. In many cases, these interruptions are transient and do not result in progressive fetal acidemia with risk for asphyxia and neurological compromise. When significant FHR decelerations are present, reversible causes of reduced fetal oxygen delivery should be considered and corrective measures should be undertaken to optimize oxygenation. In this review, we describe potential intrapartum causes of reduced fetal oxygen delivery and the efficacy of common interventions for an abnormal FHR tracing.

Differential Alveolar and Systemic Oxygenation during Preterm Resuscitation with 100% Oxygen during Delayed Cord Clamping

OBJECTIVE

 Delayed cord clamping (DCC) and 21 to 30% O₂ resuscitation is recommended for preterm infants but is commonly associated with low pulmonary blood flow (Qp) and hypoxia. 100% O₂ supplementation during DCC for 60 seconds followed by 30% O₂ may increase Qp and oxygen saturation (SpO₂).

STUDY DESIGN

 Preterm lambs (125-127 days of gestation) were resuscitated with 100% O₂ with immediate cord clamping (ICC, n = 7) or ICC + 30% O₂, and titrated to target SpO₂ (n = 7) or DCC + 100% O₂ for 60 seconds, which followed by cord clamping and 30% O₂ titration (n = 7). Seven preterm (23-27 weeks of gestation) human infants received continuous positive airway pressure (CPAP) + 100% O₂ for 60 seconds during DCC, cord clamping, and 30% O₂ supplementation after cord clamping.

RESULTS

 Preterm lambs in the ICC + 100% O₂ group resulted in PaO₂ (77 ± 25 mmHg), SpO₂ (77 ± 11%), and Qp (27 ± 9 mL/kg/min) at 60 seconds. ICC + 30% O₂ led to low Qp (14 ± 3 mL/kg/min), low SpO₂ (43 ± 26%), and PaO₂ (19 ± 7 mmHg). DCC + 100% O₂ led to similar Qp (28 ± 6 mL/kg/min) as ICC + 100% O₂ with lower PaO₂. In human infants, DCC + CPAP with 100% O₂ for 60 seconds, which followed by weaning to 30% resulted in SpO₂ of 92 ± 11% with all infants >80% at 5 minutes with 100% survival without severe intraventricular hemorrhage.

CONCLUSION

 DCC + 100% O₂ for 60 seconds increased Qp probably due to transient alveolar hyperoxia with systemic normoxia due to "dilution" by umbilical venous return. Larger translational and clinical studies are warranted to confirm these findings.

KEY POINTS

· Transient alveolar hyperoxia during delayed cord clamping can enhance pulmonary vasodilation.. · Placental transfusion buffers systemic oxygen tension and limits hyperoxia.. · Use of 100% oxygen for 60 seconds during DCC was associated with SpO2 ≥80% by 5 minutes..

Congenital diaphragmatic hernia: a narrative review of controversies in neonatal management

The consequences of most hernias can be immediately corrected by surgical repair. However, this isn't always the case for children born with a congenital diaphragmatic hernia. The derangements in physiology encountered immediately after birth result from pulmonary hypoplasia and hypertension caused by herniation of abdominal contents into the chest early in lung development. This degree of physiologic compromise can vary from mild to severe. Postnatal management of these children remains controversial. Although heavily studied, multi-institutional randomized controlled trials are lacking to help determine what constitutes best practice. Additionally, the results of the many studies currently within the literature that have investigated differing aspect of care (i.e., inhaled nitric oxide, ventilator type, timing of repair, role of extracorporeal membrane oxygenation, etc.) are difficult to interpret due to the small numbers investigated, the varying degree of physiologic compromise, and the contrasting care that exists between institutions. The aim of this paper is to review areas of controversy in the care of these complex kids, mainly: the use of fraction of inspired oxygen, surfactant therapy, gentle ventilation, mode of ventilation, medical management of pulmonary hypertension (inhaled nitric oxide, sildenafil, milrinone, bosentan, prostaglandins), the utilization of extracorporeal membrane oxygenation, and the timing of surgical repair.

The effect of intrapartum oxygen supplementation on category II fetal monitoring

BACKGROUND

Maternal oxygen administration is a widely used intrauterine resuscitation technique for fetuses with category II electronic fetal monitoring patterns, despite a paucity of evidence on its ability to improve electronic fetal monitoring patterns.

OBJECTIVE

This study investigated the effect of intrapartum oxygen administration on Category II electronic fetal monitoring patterns.

STUDY DESIGN

This is a secondary analysis of a randomized trial conducted in 2016-2017, in which patients with fetuses at ≥37 weeks' gestation in active labor with category II electronic fetal monitoring patterns were assigned to 10 L/min of oxygen by face mask or room air until delivery. Trained obstetrical research nurses blinded to allocation extracted electronic fetal monitoring data. The primary outcome was a composite of high-risk category II features including recurrent variable decelerations, recurrent late decelerations, prolonged decelerations, tachycardia, or minimal variability 60 minutes after randomization to room air or oxygen. Secondary outcomes included individual components of the composite high-risk category II features, resolution of recurrent decelerations within 60 minutes of randomization, and total deceleration area. The outcomes between the room air and oxygen groups were compared using univariable statistics. Time-to-event analysis was used to compare time to resolution of recurrent decelerations between the groups. Paired analysis was used to compare the pre- and postrandomization outcomes within each group.

RESULTS

All 114 randomized patients (57 room air and 57 oxygen) were included in this analysis. There was no difference in resolution of recurrent decelerations within 60 minutes between the oxygen and room air groups (75.4% vs 86.0%; P=.15). The room air and oxygen groups had similar rates of composite high-risk category II features including recurrent variable decelerations, recurrent late decelerations, prolonged decelerations, tachycardia, and minimal variability 60 minutes after randomization. Time to resolution of recurrent decelerations and total deceleration area were similar between the room air and oxygen groups. Among patients who received oxygen, there was no difference in the electronic fetal monitoring patterns pre- and postrandomization. Similar findings were observed in the electronic fetal monitoring patterns pre- and postrandomization in room air patients.

CONCLUSION

Intrapartum maternal oxygen administration for category II electronic fetal monitoring patterns did not resolve high-risk category II features or hasten the resolution of recurrent decelerations. These results suggest that oxygen administration has no impact on improving category II electronic fetal monitoring patterns.

Effects of Klotho supplementation on hyperoxia-induced renal injury in a rodent model of postnatal nephrogenesis

BACKGROUND

Hyperoxia (HO) causes kidney injury in preterm infants; however, whether these effects are modifiable is unknown. We hypothesized that administration of exogenous soluble Klotho, a kidney-derived antioxidant, would attenuate HO-induced kidney injury during postnatal nephrogenesis in rats.

METHODS

Sprague Dawley neonatal rats assigned to normoxia (21% O₂) or HO (85% O₂) groups from postnatal day (P) 1 to 21 were randomly assigned to receive alternate day intraperitoneal injections of recombinant Klotho or placebo for 3 weeks. They were recovered in normoxia for an additional 3 weeks and sacrificed at 6 weeks. Renal artery resistance and pulsatility indices, tubular injury scores, glomerular area, and renal antioxidant capacity were assessed.

RESULTS

Rodents exposed to HO during postnatal nephrogenesis had reduced kidney Klotho expression, glomerulomegaly, and higher tubular injury scores. Exogenous Klotho administration improved renal perfusion as indicated by decreases in both resistance and pulsatility indices and increased antioxidant enzyme expression.

CONCLUSIONS

HO exposure during postnatal nephrogenesis in rodents results in a decline in kidney Klotho expression, decreased renal perfusion, enlarged glomerular size, and tubular injury. The exogenous administration of Klotho attenuated HO-induced kidney injury and augmented antioxidant capacity.

Oxygen Therapy for Neonatal Resuscitation in the Delivery Room

Oxygen is commonly used in the delivery room during neonatal resuscitation. The transition from intrauterine to extrauterine life is a challenge to newborns, and exposure to too much oxygen can cause an increase in oxidative stress. The goal of resuscitation is to achieve normal oxygen levels as quickly as possible while avoiding excessive oxygen exposure and preventing inadequate oxygen supplementation. Although it has been shown that room air resuscitation is as effective as using 100% oxygen, often preterm infants need some degree of oxygen supplementation. The ideal concentration of oxygen with which to initiate resuscitation is yet to be determined. Current delivery room resuscitation guidelines recommend the use of room air for term newborns and preterm newborns of greater than or equal to 35 weeks' gestation and the use of a fraction of inspired oxygen of 0.21 to 0.3 for preterm infants of less than 35 weeks' gestation. Further recommendations include titrating oxygen supplementation as needed to obtain goal saturations. However, there is no current consensus on an intermediate oxygen concentration to start resuscitation or goal range saturations for preterm and asphyxiated term infants.

Optimizing oxygen therapy for preterm infants at birth: Are we there yet?

Premature infants undergo a complex postnatal adaptation at birth. For last two centuries, oxygen has been integral to respiratory support of preterm infants at birth. Excess oxygen can cause oxidative stress and tissue injury. Preterm infants due to lung immaturity may need oxygen for successful transition at birth. Although, considerable progress has been made in the last 3 decades, optimum oxygen therapy for preterm delivery room resuscitation remains unknown. In this review, we discuss the history and physiology behind oxygen therapy in the delivery room, evaluate current literature, provide practice points and point out knowledge gaps of oxygen therapy in preterm infant at birth.

Oxygen in the neonatal period: Oxidative stress, oxygen load and epigenetic changes

Preterm infants frequently require positive pressure ventilation and oxygen supplementation in the first minutes after birth. It has been shown that the amount of oxygen provided during stabilization, the oxygen load, if excessive may cause hyperoxia, and oxidative damage to DNA. Epidemiologic studies have associated supplementation with pure oxygen in the first minutes after birth with childhood cancer. Recent studies have shown that the amount of oxygen supplemented to preterm infants after birth modifies the epigenome. Of note, the degree of DNA hyper-or hypomethylation correlates with the oxygen load provided upon stabilization. If these epigenetic modifications would persist, oxygen supplied in the first minutes after birth could have long term consequences. Further studies with a robust power calculation and long-term follow up are needed to bear out the long-term consequences of oxygen supplementation during postnatal stabilization of preterm infants.

Free radicals and neonatal encephalopathy: mechanisms of injury, biomarkers, and antioxidant treatment perspectives

Neonatal encephalopathy (NE), most commonly a result of the disruption of cerebral oxygen delivery, is the leading cause of neurologic disability in term neonates. Given the key role of free radicals in brain injury development following hypoxia-ischemia-reperfusion, several oxidative biomarkers have been explored in preclinical and clinical models of NE. Among these, antioxidant enzyme activity, uric acid excretion, nitric oxide, malondialdehyde, and non-protein-bound iron have shown promising results as possible predictors of NE severity and outcome. Owing to high costs and technical complexity, however, their routine use in clinical practice is still limited. Several strategies aimed at reducing free radical production or upregulating physiological scavengers have been proposed for NE. Room-air resuscitation has proved to reduce oxidative stress following perinatal asphyxia and is now universally adopted. A number of medications endowed with antioxidant properties, such as melatonin, erythropoietin, allopurinol, or N-acetylcysteine, have also shown potential neuroprotective effects in perinatal asphyxia; nevertheless, further evidence is needed before these antioxidant approaches could be implemented as standard care.

Oxygen for respiratory support of moderate and late preterm and term infants at birth: Is air best?

Oxygen has been used for newborn infant resuscitation for more than two centuries. In the last two decades, concerns about oxidative stress and injury have changed this practice. Air (FiO₂ 0.21) is now preferred as the starting point for respiratory support of infants 34 weeks gestation and above. These recommendations are derived from studies that were conducted on asphyxiated, term infants, recruited more than 10 years ago using strategies that are not commonly used today. The applicability of these recommendations to current practice, is uncertain. In addition, whether initiating respiratory support with air for infants with pulmonary disorders provides sufficient oxygenation is also unclear. This review will address these concerns and provide suggestions for future steps to address knowledge and practice gaps.

Oxygen therapy in preterm infants with pulmonary hypertension

Premature neonates <34 weeks gestation can present with early-onset, late-onset and bronchopulmonary dysplasia (BPD) associated pulmonary hypertension (PHT), with clinical, echocardiographic, and histological features similar to term infants with PHT. Changes in pulmonary vascular resistance (PVR) in response to oxygen are diminished in preterm infants compared to term. Studies from preterm lambs and human infants with BPD have shown that PaO₂ > 30-55 mm Hg promotes pulmonary vasodilation. Targeting saturations of 80-85% by 5 min, 85-95% by 10 min during resuscitation and 90-95% during the postnatal course are appropriate targets for routine management of preterm infants. Among preterm infants with PHT, avoiding hypoxia/hyperoxia by titrating supplemental oxygen to maintain saturations in low to mid 90s with alarm limits at 90 and 97% seems to be a reasonable approach pending further studies. Further high-quality evidence generated from randomized trials is required to guide oxygen therapy in preterm PHT.

Oxygen metabolism and oxygenation of the newborn

The premature infant is to some extent protected from hypoxia, however defense against hyperoxia is poorly developed. The optimal assessment of oxygenation is to measure oxygen delivery and extraction. At the bedside PaO₂ and SpO₂ are approximations of oxygenation at the tissue level. After birth asphyxia it is crucial to know whether or not to give oxygen supplementation, when, how much, and for how long. Oxygen saturation targets in the delivery room have been studied, but the optimal targets might still be unknown because factors like gender and delayed cord clamping influence saturation levels. However, SpO₂ > 80% at 5 min of age is associated with favorable long term outcome in preterm babies. Immature infants most often need oxygen supplementation beyond the delivery room. Predefined saturation levels, and narrow alarm limits together with the total oxygen exposure may impact on development of oxygen related diseases like ROP and BPD. Hyperoxia is a strong trigger for genetic and epigenetic changes, contributing to the development of these conditions and perhaps lifelong changes.

Small molecule biomarkers for neonatal hypoxic ischemic encephalopathy

Hypoxic Ischemic Encephalopathy (HIE) is one of the most deleterious conditions in the perinatal period and the access to small molecule biomarkers aiding accurate diagnosis and disease staging, progress monitoring, and early outcome prognosis could provide relevant advances towards the development of personalized therapies. The emergence of metabolomics, the "omics" technology enabling the holistic study of small molecules, for biomarker discovery employing different analytical platforms, animal models and study populations has drastically increased the number and diversity of small molecules proposed as candidate biomarkers. However, the use of very few compounds has been implemented in clinical guidelines and authorized medical devices. In this work we review different approaches employed for discovering HIE-related small molecule biomarkers. Their role in associated biochemical disease mechanisms as well as the way towards their translation into the clinical practice are discussed.

Cathelicidin attenuates hyperoxia-induced kidney injury in newborn rats

Aim: Supplemental oxygen is often used to treat neonates with respiratory disorders. Human and animal studies have demonstrated that neonatal hyperoxia increases oxidative stress and induces damage and collagen deposition in kidney during the perinatal period. Cathelicidin LL-37 is one important group of human antimicrobial peptides which exhibits antioxidant activity and its overexpression resists hyperoxia-induced oxidative stress. This study was designed to evaluate the protective effects of cathelicidin in hyperoxia-induced kidney injury in newborn rats.

Methods: Sprague-Dawley rat pups were reared in either room air (RA) or hyperoxia (85% O₂) and were randomly treated with low-dose (4 mg/kg) and high-dose (8 mg/kg) cathelicidin in normal saline (NS) administered intraperitoneally on postnatal days 1–6. The following six groups were obtained: RA + NS, RA + low-dose cathelicidin, RA + high-dose cathelicidin, O₂ + NS, O₂ + low-dose cathelicidin, and O₂ + high-dose cathelicidin. Kidneys were taken for Western blot and histological analyses on postnatal day 7.

Results: The hyperoxia-reared rats exhibited significantly lower body weights and anti-inflammatory M2 macrophages, but the kidney injury scores, oxidative stress marker 8-hydroxy-2'-deoxyguanosine (8-OHdG)-positive cells, pro-inflammatory M1 macrophages, collagen deposition, and NF-κB expression were higher than did the RA-reared rats.

Conclusions: Cathelicidin treatment attenuated kidney injury as evidenced by lower kidney injury scores, 8-OHdG-positive cells, collagen deposition, and reversion of hyperoxia-induced M1/M2 macrophage polarization. The role of Cathelicidin in ameliorates kidney injury of the hyperoxia newborn rats was accompanied by decreased NF-κB expression, which probably through the modulating NF-κB activity in the kidney.

[Hypoxic-ischemic brain damage in premature newborns]

One of the main causes of cerebral dysfunction in premature newborns is hypoxia. High mortality and lifelong morbidity in these children is a frequent result of neonatal hypoxic brain damage. The article presents some data on the prevalence of neurological diseases that have arisen in the perinatal period, and highlights the key etiological factors leading to hypoxia in both the intranatal and early postnatal periods. The pathogenesis of hypoxic-ischemic brain lesions in premature infants is described in detail. At the same time, more careful consideration is given to the glutathione system, which protects against lipid peroxidation, the glutamate-calcium cascade, and the excitotoxicity mediated by it, as well as the processes of necrosis and apoptosis of nerve cells. The advantages and disadvantages of modern methods for diagnosing cerebral lesions are noted, and the principles of treatment of these disorders are analyzed.

Resuscitation outcomes of infants that do not achieve a 5 min target SpO2 saturation

OBJECTIVE

To determine differences in the duration and level of resuscitation between infants that achieve a peripheral oxygen saturation (SpO₂) of 80% by 5 min compared with those who remain below 80% saturation.

STUDY DESIGN

Infants < 32 weeks GA were analyzed. Pulse rate, SpO₂, airway pressure, and fraction of inspired oxygen were collected during the first 10 min of life.

RESULTS

Two hundred and eighty-four infants were analyzed of which 100 had SpO₂ < 80% at 5 min of life. Composite outcome of death and any IVH was greater in the <80% at 5 min group. These infants had lower heart rates and lower SpO₂ despite increased mean airway pressure and higher FiO₂ (p < 0.001).

CONCLUSION

Infants <32 weeks GA that do not achieve a peripheral arterial saturation of 80% by 5 min of life experience more death or severe IVH. This association is amongst the strongest seen of any predictor of morbidity in the delivery room.

Novel interventions to reduce oxidative-stress related brain injury in neonatal asphyxia

Perinatal asphyxia-induced brain injury may present as hypoxic-ischemic encephalopathy in the neonatal period, and disability including cerebral palsy in the long term. The brain injury is secondary to both the hypoxic-ischemic event and the reoxygenation-reperfusion following resuscitation. Early events in the cascade of brain injury can be classified as either inflammation or oxidative stress through the generation of free radicals. The objective of this paper is to present efforts that have been made to limit the oxidative stress associated with hypoxic-ischemic encephalopathy. In the acute phase of ischemia/hypoxia and reperfusion/reoxygenation, the outcomes of asphyxiated infants can be improved by optimizing the initial delivery room stabilization. Interventions include limiting oxygen exposure, and shortening the time to return of spontaneous circulation through improved methods for supporting hemodynamics and ventilation. Allopurinol, melatonin, noble gases such as xenon and argon, and magnesium administration also target the acute injury phase. Therapeutic hypothermia, N-acetylcysteine2-iminobiotin, remote ischemic postconditioning, cannabinoids and doxycycline target the subacute phase. Erythropoietin, mesenchymal stem cells, topiramate and memantine could potentially limit injury in the repair phase after asphyxia. To limit the injurious biochemical processes during the different stages of brain injury, determination of the stage of injury in any particular infant remains essential. Currently, therapeutic hypothermia is the only established treatment in the subacute phase of asphyxia-induced brain injury. The effects and side effects of oxidative stress reducing/limiting medications may however be difficult to predict in infants during therapeutic hypothermia. Future neuroprotection in asphyxiated infants may indeed include a combination of therapies. Challenges include timing, dosing and administration route for each neuroprotectant.

Antioxidants & bronchopulmonary dysplasia: Beating the system or beating a dead horse?

Preterm birth is a primary cause of worldwide childhood mortality. Bronchopulmonary dysplasia, characterized by impaired alveolar and lung vascular development, affects 25-50% of extremely low birth weight (BW; <1 kg) infants. Abnormalities in lung function persist into childhood in affected infants and are second only to asthma in terms of childhood respiratory disease healthcare costs. While advances in the medical care of preterm infants have reduced mortality, the incidence of BPD has not decreased in the past 10 years. Reactive oxygen intermediates play a key role in the development of lung disease but, despite promising preclinical therapies, antioxidants have failed to translate into meaningful clinical interventions to decrease the incidence of lung disease in premature infants. In this review we will summarize the state of the art research developments in regards to antioxidants and premature lung disease and discuss the limitations of antioxidant therapies in order to more fully comprehend the reasons why therapeutic antioxidant administration failed to prevent BPD. Finally we will review promising therapeutic strategies and targets.

Is There a "Right" Amount of Oxygen for Preterm Infant Stabilization at Birth?

The amount of oxygen given to preterm infants within the first few minutes of birth is one of the most contentious issues in modern neonatology. Just two decades ago, pure oxygen (FiO2 1.0) was standard of care and oximetry monitoring was not routine. Due to concerns about oxidative stress and injury, clinicians rapidly adopted the practice of using less oxygen for the respiratory support of all infants, regardless of gestational maturity and pulmonary function. There is now evidence that initial starting fractional inspired oxygen may not be the only factor involved in providing optimum oxygenation and that the amount of oxygen given to babies within the first 10 min of life is a crucial factor in determining outcomes, including death and neurodevelopmental injury. In addition, evolving practice, such as non-invasive respiratory support and delayed cord clamping, need to be taken into consideration when considering oxygen delivery to preterm infants. This review will discuss evidence to date and address the major knowledge gaps that need to be answered in this pivotal aspect of neonatal practice.

Targeting Oxygen in Term and Preterm Infants Starting at Birth

Transition into the extrauterine world is characterized by a substantial increase in oxygen availability to tissue. Exact oxygen provision may be needed to avoid negative consequences of hypoxia or hyperoxia. For term and near-term infants, it is recommended to start with air and titrate the oxygen supplement to the saturation nomogram. However, oxygen supplementation in infants less than 32 weeks' gestation is an unsolved conundrum. At present, the inspired fraction of oxygen is set according to gestational age and blended to achieve targeted saturations and heart rates. Studies are still needed to overcome uncertainties about oxygen supplementation during preterm stabilization.

Rodent models of respiratory control and respiratory system development-Clinical significance

The newborn infant's respiratory system must rapidly adapt to extra-uterine life. Neonatal rat and mouse models have been used to investigate early development of respiratory control and reactivity in both health and disease. This review highlights several rodent models of control of breathing and respiratory system development (including pulmonary function), discusses their translational strengths and limitations, and underscores the importance of creating clinically relevant models applicable to the human infant.

Cellular senescence in the lung across the age spectrum

Cellular senescence results in cell cycle arrest with secretion of cytokines, chemokines, growth factors, and remodeling proteins (senescence-associated secretory phenotype; SASP) that have autocrine and paracrine effects on the tissue microenvironment. SASP can promote remodeling, inflammation, infectious susceptibility, angiogenesis, and proliferation, while hindering tissue repair and regeneration. While the role of senescence and the contributions of senescent cells are increasingly recognized in the context of aging and a variety of disease states, relatively less is known regarding the portfolio and influences of senescent cells in normal lung growth and aging per se or in the induction or progression of lung diseases across the age spectrum such as bronchopulmonary dysplasia, asthma, chronic obstructive pulmonary disease, or pulmonary fibrosis. In this review, we introduce concepts of cellular senescence, the mechanisms involved in the induction of senescence, and the SASP portfolio that are relevant to lung cells, presenting the potential contribution of senescent cells and SASP to inflammation, hypercontractility, and remodeling/fibrosis: aspects critical to a range of lung diseases. The potential to blunt lung disease by targeting senescent cells using a novel class of drugs (senolytics) is discussed. Potential areas for future research on cellular senescence in the lung are identified.

Oxygen therapy of the newborn from molecular understanding to clinical practice

Oxygen is one of the most critical components of life. Nature has taken billions of years to develop optimal atmospheric oxygen concentrations for human life, evolving from very low, peaking at 30% before reaching 20.95%. There is now increased understanding of the potential toxicity of both too much and too little oxygen, especially for preterm and asphyxiated infants and of the potential and lifelong impact of oxygen exposure, even for a few minutes after birth. In this review, we discuss the contribution of knowledge gleaned from basic science studies and their implication in the care and outcomes of the human infant within the first few minutes of life and afterwards. We emphasize current knowledge gaps and research that is needed to answer a problem that has taken Nature a considerably longer time to resolve.

Oxidative Stress in the Newborn Period: Useful Biomarkers in the Clinical Setting

Aerobic metabolism is highly efficient in providing energy for multicellular organisms. However, even under physiological conditions, an incomplete reduction of oxygen produces reactive oxygen species and, subsequently, oxidative stress. Some of these chemical species are highly reactive free radicals capable of causing functional and structural damage to cell components (protein, lipids, or nucleotides). Oxygen is the most used drug in ill-adapted patients during the newborn period. The use of oxygen may cause oxidative stress-related diseases that increase mortality and cause morbidity with adverse long-term outcomes. Conditions such as prematurity or birth asphyxia are frequently treated with oxygen supplementation. Both pathophysiological situations of hypoxia⁻reoxygenation in asphyxia and hyperoxia in premature infants cause a burst of reactive oxygen species and oxidative stress. Recently developed analytical assays using mass spectrometry have allowed us to determine highly specific biomarkers with minimal samples. The detection of these metabolites will help improve the diagnosis, evolution, and response to therapy in oxidative stress-related conditions during the newborn period.

Effect of various inspired oxygen concentrations on pulmonary and systemic hemodynamics and oxygenation during resuscitation in a transitioning preterm model

BACKGROUND

The Neonatal Resuscitation Program recommends initial resuscitation of preterm infants with low oxygen (O₂) followed by titration to target preductal saturations (SpO₂). We studied the effect of resuscitation with titrated O₂ on gas exchange, pulmonary, and systemic hemodynamics.

METHODOLOGY

Twenty-nine preterm lambs (127 d gestation) were randomized to resuscitation with 21% O₂ (n = 7), 100% O₂ (n = 6), or initiation at 21% and titrated to target SpO₂ (n = 16). Seven healthy term control lambs were ventilated with 21% O₂.

RESULTS

Preductal SpO₂ achieved by titrating O₂ was within the desired range similar to term lambs in 21% O₂. Resuscitation of preterm lambs with 21% and 100% O₂ resulted in SpO₂ below and above the target, respectively. Ventilation of preterm lambs with 100% O₂ and term lambs with 21% O₂ effectively decreased pulmonary vascular resistance (PVR). In contrast, preterm lambs with 21% O₂ and titrated O₂ demonstrated significantly higher PVR than term lambs on 21% O₂.

CONCLUSION(S)

Initial resuscitation with 21% O₂ followed by titration of O₂ led to suboptimal pulmonary vascular transition at birth in preterm lambs. Ventilation with 100% O₂ in preterm lambs caused hyperoxia but reduced PVR similar to term lambs on 21% O₂. Studies evaluating the initiation of resuscitation at a higher O₂ concentration followed by titration based on SpO₂ in preterm neonates are needed.

Effect of Oxygen vs Room Air on Intrauterine Fetal Resuscitation: A Randomized Noninferiority Clinical Trial

IMPORTANCE

Two-thirds of women in labor receive supplemental oxygen to reverse perceived fetal hypoxemia and prevent acidemia. Oxygen is routinely administered for category II fetal heart tracings, a class of fetal tracing used to designate intermediate risk for acidemia. This liberal use of oxygen may not be beneficial, particularly because neonatal hyperoxygenation is harmful.

OBJECTIVE

To test the hypothesis that room air is noninferior to oxygen in improving fetal metabolic status among patients with category II fetal heart tracings.

DESIGN, SETTING, AND PARTICIPANTS

This was a randomized, unblinded noninferiority clinical trial conducted between June 2016 and July 2017 in the labor and delivery ward of a single tertiary care center. Women with singleton pregnancies at 37 weeks' gestational age or more who were admitted for delivery were eligible. Of those who met inclusion criteria, the patients who developed category II tracings in labor that necessitated intrauterine resuscitation were randomized in a 1:1 ratio to room air or oxygen. Analyses were intention-to-treat.

INTERVENTIONS

The oxygen group received 10 L of oxygen per minute by nonrebreather facemask until delivery. The room air group was exposed to room air only without a facemask.

MAIN OUTCOMES AND MEASURES

The primary outcome was umbilical artery lactate, a marker of metabolic acidosis and neonatal morbidity. Noninferiority was defined as a mean difference between groups of less than 9.0 mg/dL (1.0 mmol/L). Secondary outcomes were other umbilical artery gases, cesarean delivery for nonreassuring fetal status, and operative vaginal delivery.

RESULTS

Of the 705 patients who met inclusion criteria, 277 (39.3%) were enrolled on admission. During labor, 114 patients (41.2% of the enrolled patients) developed category II tracings and were randomized to room air (57 patients; 50.0% of the randomized patients) or oxygen (57 patients; 50.0% of the randomized patients). A total of 99 patients (86.8% of the randomized patients) with paired cord gases were included in the modified intention-to-treat analysis. The 99 patients included 76 African American women (77%); mean (SD) age was 27.3 (6.3) years in the oxygen group and 27.8 (5.3) years in the room air group. There was no difference in umbilical artery lactate between the group on oxygen and the group on room air (mean, 30.6 mg/dL [95% CI, 27.0 to 34.2 mg/dL] vs 31.5 mg/dL [95% CI, 27.9 to 36.0 mg/dL]); P = .69). The mean difference in lactate was 0.9 mg/dL (95% CI, -4.5 to 6.3 mg/dL), which was within the noninferiority margin. There was no difference in other umbilical artery gas components or mode of delivery between groups.

CONCLUSIONS AND RELEVANCE

Among patients with category II fetal heart tracings, intrauterine resuscitation with room air is noninferior to oxygen in improving umbilical artery lactate. The results of this trial challenge the efficacy of a ubiquitous obstetric practice and suggest that room air may be an acceptable alternative.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02741284.

Oxygen Therapy in the Delivery Room: What Is the Right Dose?

Oxygen is the most commonly used medicine used during neonatal resuscitation in the delivery room. Oxygen therapy in delivery room should be used judiciously to avoid oxygen toxicity while delivering sufficient oxygen to prevent hypoxia. Measurement of appropriate oxygenation relies on pulse oximetry, but adequate ventilation and perfusion are equally important for oxygen delivery. In this article, we review oxygenation while transitioning from fetal to neonatal life, the importance of appropriate oxygen therapy, its measurement in the delivery room, and current recommendations for oxygen therapy and its limitations.

Lower versus higher oxygen concentrations titrated to target oxygen saturations during resuscitation of preterm infants at birth

BACKGROUND

Initial resuscitation with air is well tolerated by most infants born at term. However, the optimal fractional inspired oxygen concentration (FiO₂ - proportion of the breathed air that is oxygen) targeted to oxygen saturation (SpO₂ - an estimate of the amount of oxygen in the blood) for infants born preterm is unclear.

OBJECTIVES

To determine whether lower or higher initial oxygen concentrations, when titrated according to oxygen saturation targets during the resuscitation of preterm infants at birth, lead to improved short- and long-term mortality and morbidity.

SEARCH METHODS

We conducted electronic searches of the Cochrane Central Register of Controlled Trials (13 October 2017), Ovid MEDLINE (1946 to 13 October 2017), Embase (1974 to 13 October 2017) and CINAHL (1982 to 13 October 2017); we also searched previous reviews (including cross-references), contacted expert informants, and handsearched journals.

SELECTION CRITERIA

We included randomised controlled trials (including cluster- and quasi-randomised trials) which enrolled preterm infants requiring resuscitation following birth and allocated them to receive either lower (FiO₂ < 0.4) or higher (FiO₂ ≥ 0.4) initial oxygen concentrations titrated to target oxygen saturation.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the eligibility of studies for inclusion, extracted data and assessed methodological quality. Primary outcomes included mortality near term or at discharge (latest reported) and neurodevelopmental disability. We conducted meta-analysis using a fixed-effect model. We assessed the quality of the evidence using GRADE.

MAIN RESULTS

The search identified 10 eligible trials. Meta-analysis of the 10 included studies (914 infants) showed no difference in mortality to discharge between lower (FiO₂ < 0.4) and higher (FiO₂ ≥ 0.4) initial oxygen concentrations targeted to oxygen saturation (risk ratio (RR) 1.05, 95% confidence interval (CI) 0.68 to 1.63). We identified no heterogeneity in this analysis. We graded the quality of the evidence as low due to risk of bias and imprecision. There were no significant subgroup effects according to inspired oxygen concentration strata (FiO₂ 0.21 versus ≥ 0.4 to < 0.6; FiO₂ 0.21 versus ≥ 0.6 to 1.0; and FiO₂ ≥ 0.3 to < 0.4 versus ≥ 0.6 to 1.0). Subgroup analysis identified a single trial that reported increased mortality from use of lower (FiO₂ 0.21) versus higher (FiO₂ 1.0) initial oxygen concentration targeted to a lowest SpO₂ of less than 85%, whereas meta-analysis of nine trials targeting a lowest SpO₂ of 85% to 90% found no difference in mortality.Meta-analysis of two trials (208 infants) showed no difference in neurodevelopmental disability at 24 months between infants receiving lower (FiO₂ < 0.4) versus higher (FiO₂ > 0.4) initial oxygen concentrations targeted to oxygen saturation. Other outcomes were incompletely reported by studies. Overall, we found no difference in use of intermittent positive pressure ventilation or intubation in the delivery room; retinopathy (damage to the retina of the eyes, measured as any retinopathy and severe retinopathy); intraventricular haemorrhage (any and severe); periventricular leukomalacia (a type of white-matter brain injury); necrotising enterocolitis (a condition where a portion of the bowel dies); chronic lung disease at 36 weeks' gestation; mortality to follow up; postnatal growth failure; and patent ductus arteriosus. We graded the quality of the evidence for these outcomes as low or very low.

AUTHORS' CONCLUSIONS

There is uncertainty as to whether initiating post birth resuscitation in preterm infants using lower (FiO₂ < 0.4) or higher (FiO₂ ≥ 0.4) oxygen concentrations, targeted to oxygen saturations in the first 10 minutes, has an important effect on mortality or major morbidity, intubation during post birth resuscitation, other resuscitation outcomes, and long-term outcomes including neurodevelopmental disability. We assessed the quality of the evidence for all outcomes as low to very low. Further large, well designed trials are needed to assess the effect of using different initial oxygen concentrations and the effect of targeting different oxygen saturations.