Oxygen Targeting in Extremely Low Birth Weight Infants

Assessment of Autoregulation of the Cerebral Circulation during Acute Lung Injury in a Neonatal Porcine Model

In neonates with acute lung injury (ALI), targeting lower oxygenation saturations is suggested to limit oxygen toxicity while maintaining vital organ function. Although thresholds for cerebral autoregulation are studied for the management of premature infants, the impact of hypoxia on hemodynamics, tissue oxygen consumption and extraction is not well understood in term infants with ALI. We examined hemodynamics, cerebral autoregulation and fractional oxygen extraction, as measured by near-infrared spectroscopy (NIRS) and blood gases, in a neonatal porcine oleic acid injury model of moderate ALI. We hypothesized that in ALI animals, cerebral oxygen extraction would be increased to a greater degree than kidney or gut oxygen extraction as indicative of the brain's adaptive efforts to increase cerebral oxygen extraction at the expense of splanchnic end organs. Fifteen anesthetized, ventilated 5-day-old neonatal piglets were divided into moderate lung injury by treatment with oleic acid or control (sham injection). The degree of lung injury was quantified at baseline and after establishment of ALI by blood gases, ventilation parameters and calculated oxygenation deficit, hemodynamic indices by echocardiography and lung injury score by ultrasound. PaCO2 was maintained constant during ventilation. Cerebral, renal and gut oxygenation was determined by NIRS during stepwise decreases in inspired oxygen from 50% to 21%, correlated with PaO2 and PvO2; changes in fractional oxygen extraction (ΔFOE) were calculated from NIRS and from regional blood gas samples. The proportion of cerebral autoregulation impairment attributable to blood pressure, and to hypoxemia, was calculated from autoregulation nomograms. ALI manifested as hypoxemia with increasing intrapulmonary shunt fraction, decreased lung compliance and increased resistance, and marked increase in lung ultrasound score. Brain, gut and renal NIRS, obtained from probes placed over the anterior skull, central abdomen and flank, respectively, correlated with concurrent SVC (brain) or IVC (gut, renal) PvO2 and SvO2. Cerebral autoregulation was impaired after ALI as a function of blood pressure at all FiO2 steps, but predominantly by hypoxemia at FiO2 < 40%. Cerebral ΔFOE was higher in ALI animals at all FiO2 steps. We conclude that in an animal model of neonatal ALI, cerebrovascular blood flow regulation is primarily dependent on oxygenation. There is not a defined oxygenation threshold below which cerebral autoregulation is impaired in ALI. Cerebral oxygen extraction is enhanced in ALI, reflecting compensation for exhausted cerebral autoregulation due to the degree of hypoxemia and/or hypotension, thereby protecting against tissue hypoxia.

A Bayesian Reanalysis of the Overall and Sex-Disaggregated Results of the Neonatal Oxygenation Prospective Meta-Analysis (NeOProM)

Data from the Neonatal Oxygenation Prospective Meta-analysis (NeOProM) indicate that targeting a higher (91-95%) versus lower (85-89%) pulse oximeter saturation (SpO2) range may reduce mortality and necrotizing enterocolitis (NEC) and increase retinopathy of prematurity (ROP). Aiming to re-evaluate the strength of this evidence, we conducted a Bayesian reanalysis of the NeOProM data. We used Bayes factors (BFs) to evaluate the likelihood of the data under the combination of models assuming the presence vs. absence of effect, heterogeneity, and moderation by sex. The Bayesian reanalysis showed moderate evidence in favor of no differences between SpO2 targets (BF10 = 0.30) in death or major disability, but moderate evidence (BF10 = 3.60) in favor of a lower mortality in the higher SpO2 group. Evidence in favor of differences was observed for bronchopulmonary dysplasia (BPD) (BF10 = 14.44, lower rate with lower SpO2), severe NEC (BF10 = 9.94), and treated ROP (BF10 = 3.36). The only outcome with moderate evidence in favor of sex differences was BPD. This reanalysis of the NeOProM trials confirmed that exposure to a lower versus higher SpO2 range is associated with a higher mortality and risk of NEC, but a lower risk of ROP and BPD. The Bayesian approach can help in assessing the strength of evidence supporting clinical decisions.

Critical period of oxygen supplementation and invasive ventilation: implications for severe retinopathy of prematurity

BACKGROUND

Several studies have identified graded oxygen saturation targets to prevent retinopathy of prematurity (ROP), a serious complication in preterm infants. We aimed to analyze the critical period of oxygen supplementation and/or invasive ventilation associated with severe ROP.

METHODS

This retrospective case-control study included neonates with a gestational age (GA) < 29 weeks. Participants were divided into two groups: treated retinopathy and untreated/no retinopathy. Time-weighted average FiO2 (TWAFiO2) and weekly invasive ventilation were compared between groups by postnatal age (PNA) and postmenstrual age (PMA). The association of treated retinopathy with TWAFiO2 and invasive ventilation was analyzed.

RESULTS

Data from 287 neonates were analyzed; 98 were treated for ROP and had lower GAs (25.5 vs. 27.4 weeks, p < 0.01) and lower birthweights (747.6 vs. 1014 g, p < 0.001) than those with untreated/no ROP. TWAFiO2 was higher from PMA 26-34 weeks, except for PMA 31 weeks in treated ROP, and higher in the first nine weeks of life in treated ROP. On multiple logistic regression, TWAFiO2 and invasive ventilation were associated with ROP treatment during the first seven weeks PNA. Invasive ventilation was associated with ROP treatment from PMA 26-31 weeks; no association was found for TWAFiO2 and PMA.

CONCLUSIONS

Amount of oxygen supplementation and/or invasive ventilation during the first 7 weeks of life or up to 31 weeks PMA was associated with development of severe ROP. This period might be candidate timing for strict oxygen supplementation strategies in preterm infants, while concerns of mortality with low oxygen supplementation should be further explored.

Maturation of cardioventilatory physiological trajectories in extremely preterm infants

BACKGROUND

In extremely preterm infants, persistence of cardioventilatory events is associated with long-term morbidity. Therefore, the objective was to characterize physiologic growth curves of apnea, periodic breathing, intermittent hypoxemia, and bradycardia in extremely preterm infants during the first few months of life.

METHODS

The Prematurity-Related Ventilatory Control study included 717 preterm infants <29 weeks gestation. Waveforms were downloaded from bedside monitors with a novel sharing analytics strategy utilized to run software locally, with summary data sent to the Data Coordinating Center for compilation.

RESULTS

Apnea, periodic breathing, and intermittent hypoxemia events rose from day 3 of life then fell to near-resolution by 8-12 weeks of age. Apnea/intermittent hypoxemia were inversely correlated with gestational age, peaking at 3-4 weeks of age. Periodic breathing was positively correlated with gestational age peaking at 31-33 weeks postmenstrual age. Females had more periodic breathing but less intermittent hypoxemia/bradycardia. White infants had more apnea/periodic breathing/intermittent hypoxemia. Infants never receiving mechanical ventilation followed similar postnatal trajectories but with less apnea and intermittent hypoxemia, and more periodic breathing.

CONCLUSIONS

Cardioventilatory events peak during the first month of life but the actual postnatal trajectory is dependent on the type of event, race, sex and use of mechanical ventilation.

IMPACT

Physiologic curves of cardiorespiratory events in extremely preterm-born infants offer (1) objective measures to assess individual patient courses and (2) guides for research into control of ventilation, biomarkers and outcomes. Presented are updated maturational trajectories of apnea, periodic breathing, intermittent hypoxemia, and bradycardia in 717 infants born <29 weeks gestation from the multi-site NHLBI-funded Pre-Vent study. Cardioventilatory events peak during the first month of life but the actual postnatal trajectory is dependent on the type of event, race, sex and use of mechanical ventilation. Different time courses for apnea and periodic breathing suggest different maturational mechanisms.

Determining an Optimal Oxygen Saturation Target Range Based on Neonatal Maturity: Demonstration of a Decision Tree Analytic

The utility of decision tree machine learning in exploring the interactions among the SpO2 target range, neonatal maturity, and oxemic-risk is demonstrated.

METHODS

This observational study used 3 years of paired age-SpO2-PaO2 data from a neonatal ICU. The CHAID decision tree method was used to explore the interaction of postmenstrual age (PMA) on the risk of extreme arterial oxygen levels at six different potential SpO2 target ranges (88-92%, 89-93%, 90-94%, 91-95%, 92-96% and 93-97%). Risk was calculated using a severity-weighted average of arterial oxygen outside the normal range for neonates (50-80 mmHg).

RESULTS

In total, 7500 paired data points within the potential target range envelope were analyzed. The two lowest target ranges were associated with the highest risk, and the ranges of 91-95% and 92-96% were associated with the lowest risk. There were shifts in the risk associated with PMA. All the target ranges showed the lowest risk at ≥42 weeks PMA. The lowest risk for preterm infants was within a target range of 92-96% with a PMA of ≤34 weeks.

CONCLUSIONS

This study demonstrates the utility of decision tree analytics. These results suggest that SpO2 target ranges that are different from typical range might reduce morbidity and mortality. Further research, including prospective randomized trials, is warranted.

Oxygen saturation levels and retinopathy of prematurity in extremely preterm infants - a case control study

PURPOSE

To investigate the association of risk factors, including oxygen exposure, for developing retinopathy of prematurity (ROP) in preterm infants at increased risk of ROP.

METHODS

A case-control study was conducted where each infant born at < 28 weeks gestation with ROP was matched with another without ROP over five years (July 2015 - June 2020). Clinical information about the infants was collected from electronic medical records, including method of oxygen delivery, oxygen saturation (SpO2), fraction of inspired oxygen (FiO2) and mean airway pressure (MAP) measurements. MATLAB was used for a time-averaged analysis. Stata/SE 16.0 was used for statistical analysis.

RESULTS

123 ROP/non-ROP pairs were included in this study. The time-averaged SpO2 analysis showed non-ROP group spent more time in hyperoxia than the ROP group (p < 0.001). The non-ROP group had lower respiratory severity scores and analysis when FiO2 > 21% showed that were was no difference in SpO2 between the two groups when the infants were receiving oxygen support. Conditional logistic regressions showed neonatal surgery significantly increased the risk of ROP (OR = 1.4347, p = 0.010), while the influence of birthweight (odds ratio of 0.9965, p = 0.001) and oxygen exposure (OR = 0.9983, p = 0.012) on ROP outcome was found to be negligible as their odds ratios indicated no influence.

CONCLUSIONS

At times when infants were receiving respiratory support (FiO2 > 21%) the SpO2 data indicated no difference in SpO2 between the ROP and non-ROP groups. Analysis of clinical variables found that neonatal surgery increased the odds of developing ROP.

Routine use of automated FiO2 control in Poland: prospective registry and survey

Objective

The performance of automated control of inspired oxygen (A-FiO2) has been confirmed in dozens of studies but reports of routine use are limited. Broadly adopted in Poland, our aim is to share that experience.

Methods

We used a prospectively planned observational study of the performance, general use patterns, unit practices, and problems with A-FiO2, based on a web registry of case reports, complemented by surveys of subjective impressions.

Results

In 2019, a total of 92 A-FiO2 systems were in routine use in 38 centers. Of the 38 centers, 20 had agreed in 2013 to participate in the project. In these centers, A-FiO2 was applied in infants of all weights, but some centers restricted its use to weaning from oxygen and unstable infants. A cohort had reported their experience with each use (5/20 centers, 593 cases). A quarter of those infants were managed with a lower target range and three-quarters with alarms looser than European guidelines for manual SpO2 control. The perceived primary advantages of A-FiO2 were as follows: keeping the readings in the target range, reducing exposure to SpO2 extremes, reducing risk from nurse distraction, reducing workload, and reducing alarm fatigue. Practices did evolve with experience, including implementing changes in the alarm strategy, indications for use, and target range. The potential for over-reliance on automation was cited as a risk. There were a few reports of limited effectiveness (moderate 12/593 and poor 2/593).

Conclusions

Automated oxygen control is broadly perceived by users as an improvement in controlling SpO2 with infrequent problems.

Variable Association of Physiologic Changes With Electrographic Seizure-Like Events in Infants Born Preterm

OBJECTIVES

To determine the incidence of seizure-like events in a cohort of infants born preterm as well as the prevalence of associated vital sign changes (heart rate [HR], respiratory rate, and pulse oximetry [SpO2]).

STUDY DESIGN

We performed prospective conventional video electroencephalogram monitoring on infants born at 23-30 weeks of gestational age during the first 4 postnatal days. For detected seizure-like events, simultaneously captured vital sign data were analyzed during the pre-event baseline and during the event. Significant vital sign changes were defined as HR or respiratory rate >±2 SD from the infant's own baseline physiologic mean, derived from a 10-minute interval before the seizure-like event. Significant change in SpO2 was defined as oxygen desaturation during the event with a mean SpO2 <88%.

RESULTS

Our sample included 48 infants with median gestational age of 28 weeks (IQR 26-29) and birth weight of 1125 g (IQR 963-1265). Twelve (25%) infants had seizure-like discharges with a total of 201 events; 83% (10/12) of infants had vital sign changes during these events, and 50% (6/12) had significant vital sign changes during the majority of the seizure-like events. Concurrent HR changes occurred the most frequently.

CONCLUSIONS

Individual infant variability was observed in the prevalence of concurrent vital sign changes with electroencephalographic seizure-like events. Physiologic changes associated with preterm electrographic seizure-like events should be investigated further as a potential biomarker to assess the clinical significance of such events in the preterm population.

Modifiable Risk Factors and Preventative Strategies for Severe Retinopathy of Prematurity

Severe ROP is characterized by the development of retinal fibrovascular proliferation that may progress to retinal detachment. The purpose of this report is to review five of the most common and well-studied perinatal and neonatal modifiable risk factors for the development of severe ROP. Hyperoxemia, hypoxia, and associated prolonged respiratory support are linked to the development of severe ROP. While there is a well-established association between clinical maternal chorioamnionitis and severe ROP, there is greater variability between histologic chorioamnionitis and severe ROP. Neonatal sepsis, including both bacterial and fungal subtypes, are independent predictors of severe ROP in preterm infants. Although there is limited evidence related to platelet transfusions, the risk of severe ROP increases with the number and volume of red blood cell transfusions. Poor postnatal weight gain within the first six weeks of life is also strongly tied to the development of severe ROP. We also discuss preventative strategies that may reduce the risk of severe ROP. Limited evidence-based studies exist regarding the protective effects of caffeine, human milk, and vitamins A and E.

Retinopathy of prematurity: A review of pathophysiology and signaling pathways

Retinopathy of prematurity (ROP) is a vasoproliferative disorder of the retina and a leading cause of visual impairment and childhood blindness worldwide. The disease is characterized by an early stage of retinal microvascular degeneration, followed by neovascularization that can lead to subsequent retinal detachment and permanent visual loss. Several factors play a key role during the different pathological stages of the disease. Oxidative and nitrosative stress and inflammatory processes are important contributors to the early stage of ROP. Nitric oxide synthase and arginase play important roles in ischemia/reperfusion-induced neurovascular degeneration. Destructive neovascularization is driven by mediators of the hypoxia-inducible factor pathway, such as vascular endothelial growth factor and metabolic factors (succinate). The extracellular matrix is involved in hypoxia-induced retinal neovascularization. Vasorepulsive molecules (semaphorin 3A) intervene preventing the revascularization of the avascular zone. This review focuses on current concepts about signaling pathways and their mediators, involved in the pathogenesis of ROP, highlighting new potentially preventive and therapeutic modalities. A better understanding of the intricate molecular mechanisms underlying the pathogenesis of ROP should allow the development of more effective and targeted therapeutic agents to reduce aberrant vasoproliferation and facilitate physiological retinal vascular development.

Frequent hypoxemia found in infants with bronchopulmonary dysplasia after weaning home oxygen

OBJECTIVE

Parental reports and brief clinical examinations are the primary information used to assist clinicians in weaning home supplemental oxygen in infants with bronchopulmonary dysplasia (BPD). Recorded nocturnal oximetry provides an objective assessment of hypoxemia; however, it is unknown if it identifies clinically undetected hypoxemia in the home setting. Our objective was to determine if nocturnal oximetry can identify unreported hypoxemia in infants with BPD who appear ready to wean from supplemental oxygen.

STUDY DESIGN

We conducted a retrospective chart review of infants born <32 weeks gestation with BPD who were discharged to home receiving supplemental oxygen and completed recorded nocturnal oximetry in room air during an 18-month period. Abnormal oximetry was defined as >5 min with SpO₂  < 90% and/or an oxyhemoglobin desaturation index (ODI4) >5. Comparative analysis of patients with normal and abnormal overnight oximetry was performed using Fisher Exact and Wilcoxon signed-rank test.

RESULTS

Thirty-five former premature infants completed nocturnal oximetry at 5.8 (3.4-8.3) months corrected age. Nocturnal oximetry was abnormal as defined in 67% of the cohort (n = 21). Five percent of patients were hypoxemic, 52% had frequent desaturation events, and 43% had both. No significant differences existed in neonatal characteristics between patients with normal and abnormal studies.

CONCLUSIONS

Nocturnal oximetry was abnormal in the majority of infants with BPD who were otherwise clinically ready to wean from oxygen support, suggesting that recorded home oximetry could be a feasible and useful tool to evaluate for otherwise clinically unapparent nocturnal hypoxemia in patients with BPD.

Daily Oxygen Supplementation and Risk of Retinopathy of Prematurity

PURPOSE

Excessive oxygen supplementation increases risk of retinopathy of prematurity (ROP). While numerous oxygen parameters could be considered when predicting ROP (saturation targets, actual saturation, fraction of inspired oxygen, etc.), complicated measures are impractical as screening criteria. We sought to develop a simple, clinically useful measure of daily oxygen supplementation during ages 0-28 days to improve prediction of ROP.

METHODS

Secondary analysis of two Postnatal Growth and ROP (G-ROP) Study cohorts (G-ROP-1 and G-ROP-2) at 45 hospitals. Infants with a known ROP outcome and complete oxygen data were included. Associations between severe ROP and days on supplemental oxygen (FiO2 > 21%), during ages 0-28 days (DSO28) were assessed, controlling for birth weight (BW) and gestational age (GA). New screening criteria incorporating DSO were developed and compared to current guidelines.

RESULTS

Among 8,949 studied infants, 459 (5.1%) developed type 1 ROP. DSO28 was associated with severe ROP (adjusted-OR 1.05 per day supplemental oxygen, 95%CI 1.03-1.07, p < .0001). The following criteria had 100% sensitivity for type 1 ROP and higher specificity than current guidelines: new BW/GA criteria with DSO (BW<901 g, GA<26 weeks, or DSO >3), 23.4% fewer infants examined; modified G-ROP criteria including DSO, 29.0% fewer infants; original G-ROP criteria, 31.8% fewer infants.

CONCLUSION

In high-level neonatal-care settings, incorporating DSO (a simple measure of oxygen supplementation) into screening criteria improves sensitivity and specificity for type 1 ROP over current BW-GA criteria, but does not perform as well as the validated G-ROP criteria.

Oxygenation Factors Associated with Retinopathy of Prematurity in Infants of Extremely Low Birth Weight

OBJECTIVE

To study characteristics of oxygenation during the first 2 postnatal months and correlation with the occurrence and severity of retinopathy of prematurity (ROP) among infants of extremely low birth weight.

STUDY DESIGN

This retrospective study analyzed the incidence and severity of hyperoxemia and hypoxemia while on respiratory support with or without supplemental oxygen among infants of extremely low birth weight (birth weight <1000 g) admitted to the neonatal intensive care unit during 2016-2020. The findings were correlated with the occurrence and severity of ROP after adjusting for baseline covariates.

RESULTS

After adjusting for differences in baseline demographic and clinical features, the group with severe ROP was exposed to greater fraction of inspired oxygen (FiO₂) (P = .001) and experienced more frequent FiO₂ titration adjustments (P = .001) compared with the group without ROP. Ambient air hyperoxemia occurred more frequently in the group without ROP (P = .003), and iatrogenic hyperoxemia occurred more frequently in the group with severe ROP (P = .046). There were no differences in the severity of ambient and iatrogenic hyperoxemia in the study population. The group with severe ROP demonstrated more hypoxemic episodes (P = .01) and longer time spent in the severe hypoxemic range (P = .005) compared with the group without ROP.

CONCLUSIONS

Severe ROP is associated with greater FiO₂ exposure, increased iatrogenic hyperoxemia, decreased ambient air hyperoxemia, and increased hypoxemia in infants of extremely low birth weight despite a greater frequency of FiO₂ titration. This study illustrates the need for automated closed loop FiO₂ delivery systems to further optimize oxygen saturation targeting in this high-risk population.

Supplemental oxygen strategies in infants with bronchopulmonary dysplasia after the neonatal intensive care unit period: study protocol for a randomised controlled trial (SOS BPD study)

INTRODUCTION

Supplemental oxygen is the most important treatment for preterm born infants with established bronchopulmonary dysplasia (BPD). However, it is unknown what oxygen saturation levels are optimal to improve outcomes in infants with established BPD from 36 weeks postmenstrual age (PMA) onwards. The aim of this study is to compare the use of a higher oxygen saturation limit (≥95%) to a lower oxygen saturation limit (≥90%) after 36 weeks PMA in infants diagnosed with moderate or severe BPD.

METHODS AND ANALYSIS

This non-blinded, multicentre, randomised controlled trial will recruit 198 preterm born infants with moderate or severe BPD between 36 and 38 weeks PMA. Infants will be randomised to either a lower oxygen saturation limit of 95% or to a lower limit of 90%; supplemental oxygen and/or respiratory support will be weaned based on the assigned lower oxygen saturation limit. Adherence to the oxygen saturation limit will be assessed by extracting oxygen saturation profiles from pulse oximeters regularly, until respiratory support is stopped. The primary outcome is the weight SD score at 6 months of corrected age. Secondary outcomes include anthropometrics collected at 6 and 12 months of corrected age, rehospitalisations, respiratory complaints, infant stress, parental quality of life and cost-effectiveness.

ETHICS AND DISSEMINATION

Ethical approval for the trial was obtained from the Medical Ethics Review Committee of the Erasmus University Medical Centre, Rotterdam, the Netherlands (MEC-2018-1515). Local approval for conducting the trial in the participating hospitals has been or will be obtained from the local institutional review boards. Informed consent will be obtained from the parents or legal guardians of all study participants.

TRIAL REGISTRATION NUMBER

NL7149/NTR7347.

Neurosensory Alterations in Retinopathy of Prematurity: A Window to Neurological Impairments Associated to Preterm Birth

Retinopathy of prematurity (ROP) is one of the main blinding diseases affecting preterm newborns and is classically considered a vascular disorder. The premature exposure to the extrauterine environment, which is hyperoxic in respect to the intrauterine environment, triggers a cascade of events leading to retinal ischemia which, in turn, makes the retina hypoxic thus setting off angiogenic processes. However, many children with a history of ROP show persistent vision impairment, and there is evidence of an association between ROP and neurosensory disabilities. This is not surprising given the strict relationship between neuronal function and an adequate blood supply. In the present work, we revised literature data evidencing to what extent ROP can be considered a neurodegenerative disease, also taking advantage from data obtained in preclinical models of ROP. The involvement of different retinal cell populations in triggering the neuronal damage in ROP was described along with the neurological outcomes associated to ROP. The situation of ROP in Italy was assessed as well.

Interventions to Prevent Bronchopulmonary Dysplasia in Preterm Neonates: An Umbrella Review of Systematic Reviews and Meta-analyses

IMPORTANCE

Bronchopulmonary dysplasia (BPD) has multifactorial etiology and long-term adverse consequences. An umbrella review enables the evaluation of multiple proposed interventions for the prevention of BPD.

OBJECTIVE

To summarize and assess the certainty of evidence of interventions proposed to decrease the risk of BPD from published systematic reviews.

DATA SOURCES

MEDLINE, Cochrane Central Register of Controlled Trials, EMBASE, and Web of Science were searched from inception until November 9, 2020.

STUDY SELECTION

Meta-analyses of randomized clinical trials comparing interventions in preterm neonates that included BPD as an outcome.

DATA EXTRACTION AND SYNTHESIS

Data extraction was performed in duplicate. Quality of systematic reviews was evaluated using Assessment of Multiple Systematic Reviews version 2, and certainty of evidence was assessed using Grading of Recommendation, Assessment, Development, and Evaluation.

MAIN OUTCOMES AND MEASURES

(1) BPD or mortality at 36 weeks' postmenstrual age (PMA) and (2) BPD at 36 weeks' PMA.

RESULTS

A total of 154 systematic reviews evaluating 251 comparisons were included, of which 110 (71.4%) were high-quality systematic reviews. High certainty of evidence from high-quality systematic reviews indicated that delivery room continuous positive airway pressure compared with intubation with or without routine surfactant (relative risk [RR], 0.80 [95% CI, 0.68-0.94]), early selective surfactant compared with delayed selective surfactant (RR, 0.83 [95% CI, 0.75-0.91]), early inhaled corticosteroids (RR, 0.86 [95% CI, 0.75-0.99]), early systemic hydrocortisone (RR, 0.90 [95% CI, 0.82-0.99]), avoiding endotracheal tube placement with delivery room continuous positive airway pressure and use of less invasive surfactant administration (RR, 0.90 [95% CI, 0.82-0.99]), and volume-targeted compared with pressure-limited ventilation (RR, 0.73 [95% CI, 0.59-0.89]) were associated with decreased risk of BPD or mortality at 36 weeks' PMA. Moderate to high certainty of evidence showed that inhaled nitric oxide, lower saturation targets (85%-89%), and vitamin A supplementation are associated with decreased risk of BPD at 36 weeks' PMA but not the competing outcome of BPD or mortality, indicating they may be associated with increased mortality.

CONCLUSIONS AND RELEVANCE

A multipronged approach of delivery room continuous positive airway pressure, early selective surfactant administration with less invasive surfactant administration, early hydrocortisone prophylaxis in high-risk neonates, inhaled corticosteroids, and volume-targeted ventilation for preterm neonates requiring invasive ventilation may decrease the combined risk of BPD or mortality at 36 weeks' PMA.

Changes in institutional oxygen saturation targets are associated with an increased rate of severe retinopathy of prematurity

PURPOSE

To evaluate the effect of changes in institutional peripheral oxygen saturation (SpO₂) targets, made in response to recent randomized trials, on risk of developing severe retinopathy of prematurity (ROP).

METHODS

This study was a secondary analysis of data from 21 North American hospitals during the periods 2006-2012 and 2015-2017. Hospitals were categorized based on whether or not SpO₂ targets were increased between the two study periods. Severe ROP (type 1, type 2, or zone III stage 3+) rates were compared within and between groups. Generalized mixed effect models with random intercepts were used to account for within-center clustering and to calculate odds ratios (aOR) adjusted by birth weight (BW) and gestational age (GA), using patient-level data.

RESULTS

A total of 8,142 infants underwent ROP examinations at 21 hospitals during the two study periods: 5,716 in 2006-2012 (mean BW, 1109 ± 369 g; GA, 28.0 ± 2.6; 11.6% severe ROP); 2,426 in 2015-2017 (mean BW, 1086 ± 347 g; GA, 28.0 ± 2.8; 12.8% severe ROP). Fourteen hospitals increased SpO₂ targets, and 7 hospitals did not. Hospitals that increased targets had a 3% increase in severe ROP (from 12% to 15%; aOR = 1.25; 95% CI, 1.01-1.55; P = 0.044); hospitals without SpO₂ changes had a 2% decrease (from 11% to 9%; aOR = 0.72; 95% CI, 0.52-1.00; P = 0.049). The difference in change of severe ROP between groups of hospitals was significant (P = 0.005).

CONCLUSIONS

Increases in institutional SpO₂ targets in response to recent randomized trials were associated with increased severe ROP. Hospitals considering increasing their SpO₂ targets should anticipate increases in rates of severe ROP and manage screening and treatment resources accordingly.

Decoupling Oxygen Tension From Retinal Vascularization as a New Perspective for Management of Retinopathy of Prematurity. New Opportunities From β-adrenoceptors

Retinopathy of prematurity (ROP) is an evolutive and potentially blinding eye disease that affects preterm newborns. Unfortunately, until now no conservative therapy of active ROP with proven efficacy is available. Although ROP is a multifactorial disease, premature exposition to oxygen concentrations higher than those intrauterine, represents the initial pathogenetic trigger. The increase of oxygenation in a retina still incompletely vascularized promotes the downregulation of proangiogenic factors and finally the interruption of vascularization (ischemic phase). However, the increasing metabolic requirement of the ischemic retina induces, over the following weeks, a progressive hypoxia that specularly increases the levels of proangiogenic factors finally leading to proliferative retinopathy (proliferative phase). Considering non-modifiable the coupling between oxygen levels and vascularization, so far, neonatologists and ophthalmologists have “played defense”, meticulously searching the minimum necessary concentration of oxygen for individual newborns, refining their diagnostic ability, adopting a careful monitoring policy, ready to decisively intervene only in a very advanced stage of disease progression. However, recent advances have demonstrated the possibility to pharmacologically modulate the relationship between oxygen and vascularization, opening thus the perspective for new therapeutic or preventive opportunities. The perspective of a shift from a defensive towards an attack strategy is now at hand.

National trends in the incidence and management of retinopathy of prematurity in the United States, 2009 -2018

BACKGROUND

Retinopathy of prematurity is a major cause of morbidity in preterm infants but population-based studies to evaluate recent trends in incidence in the United States (US) are lacking. Moreover, previous studies did not include the use of anti-Vascular Endothelial Growth Factor medications. The objective was to examine the recent secular trends in the incidence and treatment of severe retinopathy of prematurity (sROP) in the United States (US) from 2009 to 2018.

METHODS

This was a population-based, serial cross-sectional study that utilized data from the National Inpatient Sample. The inclusion criteria were preterm infants with gestational age (GA) ≤30 weeks and length of stay > 28 days. The primary outcomes were trends in ROP surgery (photocoagulation, cryotherapy, scleral buckling, vitrectomy) and intravitreal injection of therapeutic (anti-VEGF) medications. The Cochrane-Armitage test was used to evaluate trends and P-value < 0.05 was considered significant.

RESULTS

Out of 279,664 hospitalizations that met the inclusion criteria, 12,942 (4.6%) had sROP. Those with sROP were more likely to have severe intraventricular hemorrhage (12.5% vs 6.1%), bronchopulmonary dysplasia (48.2% vs 25.9%), and pulmonary hypertension (10.7% vs 4.7%). From 2009-2018, sROP significantly increased from 3.4% to 5.3% (P < 0.001), ROP surgery decreased from 36.8% to 11.9% (P < 0.001) while intra-vitreal administration of therapeutic drugs increased from 2% to 7.6% (P < 0.001).

CONCLUSION

Surgery for sROP decreased while intra-vitreal administration of therapeutic drugs increased in the setting of increasing incidence of sROP in the US. Taken together, these findings suggest a gradual practice change and the long-term outcomes of intra-vitreal agents warrants future study.

Pulmonary Resilience: Moderating the Association between Oxygen Exposure and Pulmonary Outcomes in Extremely Preterm Newborns

Bronchopulmonary dysplasia (BPD) is a chronic lung disease of infancy associated with high morbidity and mortality. Although most prevalent following extremely preterm birth, BPD is diagnosed at 36 weeks post-menstrual age, when the disease trajectory is underway, and long-term physiological implications may be irreversible. There is an urgent and unmet need to identify how early exposures can be modified to decrease the risk of developing BPD before disease progression becomes irreversible. Extremely preterm newborns encounter a paradox at birth: oxygen is a life-sustaining component of ex utero life yet is undeniably toxic. Attempts at minimizing supplemental oxygen exposure by targeting lower oxygen saturations appear to decrease BPD but may increase mortality. Given the potential association between lower oxygen saturations and increased mortality, practice guidelines favor targeting higher saturations. This uniformly increases oxygen exposure, prompting a cascade of pathogenic mechanisms implicated in BPD development. In this review, we introduce the concept of pulmonary resilience: a homeostatic process driven by the autonomic nervous system (ANS) as a moderator of physiologic stress that when functional, could inform successful environmental adaptation following extremely preterm birth. We hypothesize that infants with early-life ANS dysfunction require a higher oxygen dose for survival; conversely, oxygen exposure could be safely limited in infants with more robust early-life ANS function, an indicator of pulmonary resilience. Characterizing the pulmonary resilience continuum to guide individualized supplemental oxygen dosing may reduce morbidity and mortality in this growing population of extremely preterm infants at risk for BPD.

Automated Oxygen Delivery in Neonatal Intensive Care

Oxygen is the most common drug used in the neonatal intensive care. It has a narrow therapeutic range in preterm infants. Too high (hyperoxemia) or low oxygen (hypoxemia) is associated with adverse neonatal outcomes. It is not only prudent to maintain oxygen saturations in the target range, but also to avoid extremes of oxygen saturations. In routine practice when done manually by the staff, it is challenging to maintain oxygen saturations within the target range. Automatic control of oxygen delivery is now feasible and has shown to improve the time spent with in the target range of oxygen saturations. In addition, it also helps to avoid extremes of oxygen saturation. However, there are no studies that evaluated the clinical outcomes with automatic control of oxygen delivery. In this narrative review article, we aim to present the current evidence on automatic oxygen control and the future directions.

Automation of oxygen titration in preterm infants: Current evidence and future challenges

For the preterm infant with respiratory insufficiency requiring supplemental oxygen, tight control of oxygen saturation (SpO₂) is advocated, but difficult to achieve in practice. Automated control of oxygen delivery has emerged as a potential solution, with six control algorithms currently embedded in commercially-available respiratory support devices. To date, most clinical evaluations of these algorithms have been short-lived crossover studies, in which a benefit of automated over manual control of oxygen titration has been uniformly noted, along with a reduction in severe SpO₂ deviations and need for manual FiO₂ adjustments. A single non-randomised study has examined the effect of implementation of automated oxygen control with the CLiO₂ algorithm as standard care for preterm infants; no clear benefits in relation to clinical outcomes were noted, although duration of mechanical ventilation was lessened. The results of randomised controlled trials are awaited. Beyond the gathering of evidence regarding a treatment effect, we contend that there is a need for a better understanding of the function of contemporary control algorithms under a range of clinical conditions, further exploration of techniques of adaptation to individualise algorithm performance, and a concerted effort to apply this technology in low resource settings in which the majority of preterm infants receive care. Attainment of these goals will be paramount in optimisation of oxygen therapy for preterm infants globally.

Diagnosis and management of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the most common chronic lung disease in infants and is associated with increased mortality, respiratory morbidity, neurodevelopmental impairment, and increased healthcare costs. In parallel with advances made in the field of neonatal intensive care, the phenotype of BPD has evolved from a fibrocystic disease affecting late preterm infants to one of impaired parenchymal development and dysregulated vascular growth predominantly affecting infants born before 29 weeks' gestational age. BPD has been shown to have significant lifelong consequences. Adults with BPD have been found to have abnormal lung function tests, reduced exercise tolerance, and may be at increased risk for developing chronic obstructive pulmonary disease. Evidence shows that BPD occurs secondary to genetic-environmental interactions in an immature lung. In this review, we evaluate the various clinical definitions, imaging modalities, and biomarker data that are helpful in making an early diagnosis of BPD. In addition, we evaluate recent evidence about the prevention and treatment of BPD. We discuss the invasive and non-invasive ventilation strategies and pharmacological agents used in the early, evolving, and established phases of BPD.

Oxygen Toxicity to the Immature Lung-Part II: The Unmet Clinical Need for Causal Therapy

Oxygen toxicity continues to be one of the inevitable injuries to the immature lung. Reactive oxygen species (ROS) production is the initial step leading to lung injury and, subsequently, the development of bronchopulmonary dysplasia (BPD). Today, BPD remains the most important disease burden following preterm delivery and results in life-long restrictions in lung function and further important health sequelae. Despite the tremendous progress in the pathomechanistic understanding derived from preclinical models, the clinical needs for preventive or curative therapies remain unmet. This review summarizes the clinical progress on guiding oxygen delivery to the preterm infant and elaborates future directions of research that need to take into account both hyperoxia and hypoxia as ROS sources and BPD drivers. Many strategies have been tested within clinical trials based on the mechanistic understanding of ROS actions, but most have failed to prove efficacy. The majority of these studies were tested in an era before the latest modes of non-invasive respiratory support and surfactant application were introduced or were not appropriately powered. A comprehensive re-evaluation of enzymatic, antioxidant, and anti-inflammatory therapies to prevent ROS injury is therefore indispensable. Strategies will only succeed if they are applied in a timely and vigorous manner and with the appropriate outcome measures.

The immunological link between neonatal lung and eye disease

Bronchopulmonary dysplasia (BPD) and retinopathy of prematurity (ROP) are two neonatal diseases of major clinical importance, arising in large part as a consequence of supplemental oxygen therapy used to promote the survival of preterm infants. The presence of coincident inflammation in the lungs and eyes of neonates receiving oxygen therapy indicates that a dysregulated immune response serves as a potential common pathogenic factor for both diseases. This review examines the current state of knowledge of immunological dysregulation in BPD and ROP, identifying similarities in the cellular subsets and inflammatory cytokines that are found in the alveoli and retina during the active phase of these diseases, indicating possible mechanistic overlap. In addition, we highlight gaps in the understanding of whether these responses emerge independently in the lung and retina as a consequence of oxygen exposure or arise because of inflammatory spill‐over from the lung. As BPD and ROP are anatomically distinct, they are often considered discreet disease entities and are therefore treated separately. We propose that an improved understanding of the relationship between BPD and ROP is key to the identification of novel therapeutic targets to treat or prevent both conditions simultaneously.

Study protocol for a multicentre, open-label, single-arm phase I/II trial to evaluate the safety and efficacy of ripasudil 0.4% eye drops for retinopathy of prematurity

INTRODUCTION

Retinopathy of prematurity (ROP) is a vascular proliferative disorder that occurs in preterm infants. Existing treatments are only indicated in severe ROP cases due to the high invasiveness and the potential risk of irreversible side effects. We previously elucidated that ripasudil, a selective inhibitor of the Rho-associated protein kinase, has the ability to inhibit abnormal retinal neovascularisation in animal models. In addition, ripasudil eye drops (Glanatec ophthalmic solution 0.4%) have been already used for the treatment of glaucoma. Since eye drop therapy is less invasive, early intervention for ROP is possible. The purpose of this phase I/II trial is to evaluate the safety and efficacy of ripasudil eye drops for preterm infants with ROP.

METHODS AND ANALYSIS

This is a multicentre, open-label, single-arm phase I/II trial. To evaluate the safety and efficacy of ripasudil as much as possible, ripasudil will be administered to all enrolled preterm infants with zone I/II, stage 1, or worse ROP. The safety and efficacy of ripasudil in treated patients will be assessed in comparison to a historical control group. Because this is the first trial of ripasudil in preterm infants, a dose-escalation study (once daily for 1 week, then two times per day for 2 weeks) will be conducted in phase I. After obtaining approval from the independent data and safety monitoring board to continue the trial after the completion of phase I, phase II will be conducted. In phase II, ripasudil eye drops will be administered two times per day for 12 weeks. The primary endpoint in phase II is also safety. Efficacy and pharmacokinetics will be evaluated as secondary endpoints.

ETHICS AND DISSEMINATION

This study protocol was approved by the institutional review board at each of the participating centres. Data will be presented at international conferences and published in peer-reviewed journals.

TRIAL REGISTRATION NUMBERS

NCT04621136 and jRCT2071200047.

Cerebral and splanchnic oxygenation during automated control of inspired oxygen (FiO2 ) in preterm infants

OBJECTIVES

Our aim in this study was to assess the effect of the Predictive Intelligent Control of Oxygenation (PRICO^® ) system on cerebral (rSO₂ C) and splanchnic (rSO₂ S) oxygenation in a cohort of preterm infants with frequent desaturations.

METHODS

Twenty infants with gestational age <32 weeks (n = 20) were assigned in random sequence to 12 h of automated or manual adjustment of FiO₂ . Over this period, they were studied continuously by near-infrared spectroscopy (NIRS).

RESULTS

We found that rSO₂ C [68.0% (60.5%-74.7%) vs. 68.5% (62%-72%); p = .824] and rSO₂ S [27.0% (17.3%-45.7%) vs. 27.0% (15%-53%); p = .878] were similar during automatic and manual control of FiO₂ . Time spent with SpO₂ 90%-95% was higher during the automatic than manual control of FiO₂ , while time spent with SpO₂ <80% or >95% was lower.

CONCLUSIONS

Automated control of FiO₂ with PRICO^® system did not improve brain and splanchnic oxygenation in comparison with manual control in a cohort of preterm infants, but it significantly decreased SpO₂ fluctuations and limited the duration of both hypoxemia and hyperoxemia.

New evidence on the protector effect of weight gain in retinopathy of prematurity

INTRODUCTION

Retinopathy of prematurity (ROP) is characterised by insufficient vascular development in the retina, and requires early treatment to avoid visual disability in severe cases. ROP is currently the second leading cause of preventable child blindness in the world.

PATIENTS AND METHODS

This was an observational, retrospective, case-control study including 233 preterm infants examined between 1999 and 2019.

RESULTS

Postnatal weight gain in the first 4 weeks of life, birth weight, gestational age, mechanical ventilation, transfusion, presence of sepsis, persistence of arterial ductus, necrotising enterocolitis, intraventricular haemorrhage, or periventricular leukomalacia were found to be significantly different between the ROP groups requiring and not requiring treatment. The mean postnatal weight gain in the ROP group not requiring treatment was 12.75 ± 5.99 g/day, whereas it was 9.50 ± 5.45 g/day in the ROP group requiring treatment. The risk of developing ROP that required treatment decreased with an increase in weight gain. The risk reduction was 2.76%-8.35% in preterm infants gaining 10 g/day, and 7.17%-12.76% in infants gaining 20 g/day.

CONCLUSIONS

The risk of developing ROP requiring treatment decreased with increasing weight gain in the first 4 weeks of life. This was applicable in infants with postnatal weight gain ≥14 g/day. However, gestational age, birth weight, time of mechanical ventilation, and comorbidity should be taken into account when evaluating the risk of ROP requiring treatment.

Pulmonary hypertension in a neonatologist-performed echocardiographic follow-up of bronchopulmonary dysplasia

Neonatologist-performed echocardiography (NPE) is an established tool for bedside hemodynamic evaluation, including pulmonary hypertension (PH). PH may complicate bronchopulmonary dysplasia (BPD) course. Aims of this retrospective study were to assess the feasibility of NPE follow-up of infants with BPD and to describe the course of PH of infants with moderate/severe BPD. Preterm infants <32 gestational weeks or birthweight ≤1500 g with moderate/severe BPD underwent NPE follow-up, from 36 weeks postmenstrual age up to 8 months postnatal age. Twenty-three preemies were included (birth weight 840 (213) g, gestational age 26.8 (2.3) weeks); 12/23 developed mild PH, 2/12 after discharge. PH resolved at 8.9 (3.9) months. Clinical and echocardiographic variables did not differ between infants with and without PH, except pulmonary artery acceleration time (PAAT) and PAAT/right ventricle ejection time (RVET) ratio (PAAT: 36 weeks, 68.9 (11.9) vs 52.0 (19.1), p = 0.0443; 6 months: 83.9 (38.9) vs 74.8 (16.9), p = 0.0372). No deaths or admissions for PH were reported. Neonatologist's Image Quality Assessment score attributed by the cardiologist assumed as gold standard was adequate or optimal (9.5/14 total score); inter-rater agreement was excellent (ICC 0.974).Conclusions: NPE follow-up seems to be feasible and safe in both intensive care and outpatient clinic. Mild PH is frequently detected in moderate/severe BPD, with good prognosis. What is Known: • Preterm infants with bronchopulmonary dysplasia (BPD) may develop pulmonary hypertension (PH) and have a late diagnosis. • Neonatologist-performed echocardiography (NPE) is an established tool for bedside hemodynamic evaluation of the neonate. What is New: • To our knowledge this is the first study of NPE follow-up of moderate/severe BPD, describing the course of mild PH from diagnosis to its resolution. • NPE follow-up of BPD seems to be safe and practicable, in both intensive care and outpatient clinic, as long as neonatologists maintain a sound collaboration with pediatric cardiologists.

Factors that impact the accuracy with which nurses place preterm infants with respiratory distress syndrome in the prone position

Prone positioning is an important treatment procedure for preterm infants with Respiratory Distress Syndrome (RDS). However, the accuracy with which preterm infants in the Neonatal Intensive Care Unit (NICU) are placed in the prone position is impacted by several factors. The current study aimed to identify these factors. One hundred and twenty-eight nurses were included in this cross-sectional study. Direct observations of the research subjects were used to collect the research data. The participants completed a research questionnaire that included their demographic data and three others to obtain information on their clinical experience, knowledge of positioning, caring behaviors, and efficacy. Independent factors likely to affect preterm infant positioning were evaluated using multivariate logistic regression. The alpha level was set at 5%. Knowledge (p=0.002) and caring behavior (p=0.009) significantly influenced the accuracy with which nurses placed preterm infants with RDS in the prone position. Nursing efficacy, infant’s bodyweight, gestational age, the institution, and DNR decisions did not significantly impact accuracy. NICU nursing staff require interventions to increase their knowledge of the accurate positioning of preterm infants with RDS.

Concurrent Physiological and Pathological Angiogenesis in Retinopathy of Prematurity and Emerging Therapies

Retinopathy of prematurity (ROP) is an ocular vascular disease affecting premature infants, characterized by pathological retinal neovascularization (RNV), dilated and tortuous retinal blood vessels, and retinal or vitreous hemorrhages that may lead to retinal detachment, vision impairment and blindness. Compared with other neovascular diseases, ROP is unique because of ongoing and concurrent physiological and pathological angiogenesis in the developing retina. While the disease is currently treated by laser or cryotherapy, anti-vascular endothelial growth factor (VEGF) agents have been extensively investigated but are not approved in the U.S. because of safety concerns that they negatively interfere with physiological angiogenesis of the developing retina. An ideal therapeutic strategy would selectively inhibit pathological but not physiological angiogenesis. Our group recently described a novel strategy that selectively and safely alleviates pathological RNV in animal models of ROP by targeting secretogranin III (Scg3), a disease-restricted angiogenic factor. The preclinical profile of anti-Scg3 therapy presents a high potential for next-generation disease-targeted anti-angiogenic therapy for the ROP indication. This review focuses on retinal vessel development in neonates, the pathogenesis of ROP and its underlying molecular mechanisms, including different animal models, and provides a summary of current and emerging therapies.

Optimisation of clinical workflow and monitor settings safely reduces alarms in the NICU

Aim

To address alarm fatigue, a new alarm management system which ensures a quicker delivery of alarms together with waveform information on nurses' handheld devices was implemented and settings optimised. The effects of this clinical implementation on alarm rates and nurses' responsiveness were measured in an 18‐bed single family rooms neonatal intensive care unit (NICU).

Methods

The technical implementation of the alarm management system was followed by clinical workflow optimisation. Alarms and vital parameters from October 2017 to December 2019 were analysed. Measures included monitoring alarms, nurses' response to alarms and time spent by patients in different saturation ranges. A survey among nurses was performed to evaluate changes in alarm rate and use of protocols.

Results

A significant reduction of monitoring alarms per patient days was detected after the optimisation phase (in particular for SpO2 ≤ 80%, P < .001). More time was spent by infants within the optimal peripheral oxygen saturation range (88% < SpO2 < 95%, P < .001). Results from the surveys showed that false alarms are less likely to cause an inappropriate response after the optimisation phase.

Conclusion

The implementation of an alarm management solution and an optimisation programme can safely reduce the alarm burden inside of the NICU environment.

The impact of targeted oxygen reduction test in preterm infants on reducing the oxygen exposure

BACKGROUND

Caring for infants on respiratory support is a challenge in the middle-income countries, applying a protocol of targeted oxygen reduction test (tORT) guided by daily assessment of oxygen histograms is novel and practical approach.

OBJECTIVE

To study the impact of tORT guided by daily assessment of oxygen histograms as a quality improvement project aiming to decrease days on oxygen support, and duration of hospital admission in preterm infants.

STUDY DESIGN

A quality project conducted in neonatal intensive care units (NICU) of two hospitals, from 2017- 2018 (Epochs II). After a period of observation of a cohort of preterm Infants, 2016-2017 (Epoch I). The main aims were to reduce days on oxygen and hospital admission days. All infants in Epoch II underwent daily assessment of oxygen histograms and a trial of oxygen reduction if applicable as per a predefined protocol. Comparison was made between these two Epochs, and the primary outcome was the time to successful discontinuation of oxygen support.

RESULTS

Fifty-nine infants were included; 30 underwent the protocolized tORT (Epoch II) with a median (IQR) of 4 (2-6) tORC per infant. Postanal age at presentation (time of initial tORT assessment was performed at the postnatal age of 8 (5, 13) days. Days on oxygen and total numbers of hospital days were significantly less in Epoch II. Oxygen histograms significantly improved after tORT.

CONCLUSIONS

Applying tORT guided by oxygen histograms may have a significant impact on oxygen exposure and hospitalization days of patients admitted to the NICU.

Translational Research in Retinopathy of Prematurity: From Bedside to Bench and Back Again

Retinopathy of prematurity (ROP), a vascular proliferative disease affecting preterm infants, is a leading cause of childhood blindness. Various studies have investigated the pathogenesis of ROP. Clinical experience indicates that oxygen levels are strongly correlated with ROP development, which led to the development of oxygen-induced retinopathy (OIR) as an animal model of ROP. OIR has been used extensively to investigate the molecular mechanisms underlying ROP and to evaluate the efficacy of new drug candidates. Large clinical trials have demonstrated the efficacy of anti-vascular endothelial growth factor (VEGF) agents to treat ROP, and anti-VEGF therapy is presently becoming the first-line treatment worldwide. Anti-VEGF therapy has advantages over conventional treatments, including being minimally invasive with a low risk of refractive error. However, long-term safety concerns and the risk of late recurrence limit this treatment. There is an unmet medical need for novel ROP therapies, which need to be addressed by safe and minimally invasive therapies. The recent progress in biotechnology has contributed greatly to translational research. In this review, we outline how basic ROP research has evolved with clinical experience and the subsequent emergence of new drugs. We discuss previous and ongoing trials and present the candidate molecules expected to become novel targets.

Strategies to Prevent Severe Retinopathy of Prematurity: A 2020 Update and Meta-analysis

The incidence of retinopathy of prematurity (ROP) is showing an increasing trend in the United States. This may be because of increasing survival rates among extremely preterm infants (<25 weeks' gestation) and targeting higher oxygen saturation. Five randomized clinical trials of low versus high oxygen saturation target ranges found increased mortality in the low oxygen saturation target group and an increased incidence of ROP in the high oxygen saturation target group. The American Academy of Pediatrics recommends using an oxygen saturation target range of 90% to 95% in extremely low-birthweight infants. The change of practice to target this higher oxygen saturation range, from admission until discharge, may be contributing to the increasing incidence of ROP in extremely preterm infants. To decrease the incidence of ROP without increasing mortality, 2 new cohort trials suggest gradually increasing oxygen saturation targets as preterm infants mature. There is evidence that human milk, vitamin A, and omega-3 fatty acids can help, in addition to continuous oxygen saturation monitoring, to decrease the risk of ROP. We review this literature and provide a meta-analysis to evaluate the evidence.

Early oxygen levels contribute to brain injury in extremely preterm infants

BACKGROUND

Extremely low gestational age newborns (ELGANs) are at risk of neurodevelopmental impairments that may originate in early NICU care. We hypothesized that early oxygen saturations (SpO₂), arterial pO₂ levels, and supplemental oxygen (FiO₂) would associate with later neuroanatomic changes.

METHODS

SpO₂, arterial blood gases, and FiO₂ from 73 ELGANs (GA 26.4 ± 1.2; BW 867 ± 179 g) during the first 3 postnatal days were correlated with later white matter injury (WM, MRI, n = 69), secondary cortical somatosensory processing in magnetoencephalography (MEG-SII, n = 39), Hempel neurological examination (n = 66), and developmental quotients of Griffiths Mental Developmental Scales (GMDS, n = 58).

RESULTS

The ELGANs with later WM abnormalities exhibited lower SpO₂ and pO₂ levels, and higher FiO₂ need during the first 3 days than those with normal WM. They also had higher pCO₂ values. The infants with abnormal MEG-SII showed opposite findings, i.e., displayed higher SpO₂ and pO₂ levels and lower FiO₂ need, than those with better outcomes. Severe WM changes and abnormal MEG-SII were correlated with adverse neurodevelopment.

CONCLUSIONS

Low oxygen levels and high FiO₂ need during the NICU care associate with WM abnormalities, whereas higher oxygen levels correlate with abnormal MEG-SII. The results may indicate certain brain structures being more vulnerable to hypoxia and others to hyperoxia, thus emphasizing the role of strict saturation targets.

IMPACT

This study indicates that both abnormally low and high oxygen levels during early NICU care are harmful for later neurodevelopmental outcomes in preterm neonates. Specific brain structures seem to be vulnerable to low and others to high oxygen levels. The findings may have clinical implications as oxygen is one of the most common therapies given in NICUs. The results emphasize the role of strict saturation targets during the early postnatal period in preterm infants.

Survival rate dependent variations in retinopathy of prematurity treatment rates in very low birth weight infants

As increased oxidative stress causes increased mortality and morbidities like bronchopulmonary dysplasia (BPD) and retinopathy of prematurity (ROP) in very low birth weight infants (VLBWIs), the conundrum of improved survival but increased ROP observed with the high oxygen saturation target range of 91–95% is difficult to explain. To determine the survival rate-dependent variation in ROP treatment rate, 6292 surviving eligible VLBWIs registered in the Korean Neonatal Network were arbitrarily grouped according to the survival rate of infants at 23–24 weeks’ gestation as group I (> 70%, n = 1626), group II (40–70%, n = 2984) and group III (< 40%, n = 1682). Despite significantly higher survival and lower BPD rates in group I than in groups II and III, the ROP treatment rate was higher in group I than in groups II and III. However, the adjusted odds ratios for ROP treatment were not significantly different between the study groups, and the ROP treatment rate in the infants at 23–24 weeks’ gestation was 21-fold higher than the infants at ≥ 27 weeks’ gestation. The controversial association between improved survival and reduced BPD reflecting quality improvement of neonatal intensive care but increased ROP treatment rate might be primarily attributed to the improved survival of the most immature infants.

A safety review of drugs used for the treatment of retinopathy of prematurity

INTRODUCTION

Retinopathy of Prematurity (ROP) is a sight-threatening disease representing one of the main disabling diseases affecting premature newborns. Presently, ROP is treated by surgical interventions and drug therapies are limited to the off-label use of a little amount of molecules approved for other pathologies.

AREAS COVERED

Many drugs that may potentially be used in treating ROP are recently proposed, in many cases after the demonstration of their effectiveness in preclinical studies. In this review, the authors discuss safety and effectiveness of the main proposed approaches in the pharmacologic treatment of the disease, including approaches based on oxygen therapy and nutritional interventions.

EXPERT OPINION

Surgical approaches to ROP are not without side effects. However, most of the proposed pharmacologic interventions can also raise specific concerns. In particular, these approaches follow a curative paradigm and are proposed in patients once the disease has progressed, with an effectiveness that is often smaller than expected. A goal in the treatment of ROP would be moving the paradigm toward a preventive approach that could be potentially effective in treating extremely low birth weight preterm infants before ROP becomes manifest.

The Various Oximetric Techniques Used for the Evaluation of Blood Oxygenation

Adequate oxygen delivery to a tissue depends on sufficient oxygen content in arterial blood and blood flow to the tissue. Oximetry is a technique for the assessment of blood oxygenation by measurements of light transmission through the blood, which is based on the different absorption spectra of oxygenated and deoxygenated hemoglobin. Oxygen saturation in arterial blood provides information on the adequacy of respiration and is routinely measured in clinical settings, utilizing pulse oximetry. Oxygen saturation, in venous blood (SvO₂) and in the entire blood in a tissue (StO₂), is related to the blood supply to the tissue, and several oximetric techniques have been developed for their assessment. SvO₂ can be measured non-invasively in the fingers, making use of modified pulse oximetry, and in the retina, using the modified Beer–Lambert Law. StO₂ is measured in peripheral muscle and cerebral tissue by means of various modes of near infrared spectroscopy (NIRS), utilizing the relative transparency of infrared light in muscle and cerebral tissue. The primary problem of oximetry is the discrimination between absorption by hemoglobin and scattering by tissue elements in the attenuation measurement, and the various techniques developed for isolating the absorption effect are presented in the current review, with their limitations.

Effect of Blood Transfusions on Intermittent Hypoxic Episodes in a Prospective Study of Very Low Birth Weight Infants

OBJECTIVES

To compare the number of intermittent hypoxia events before and after packed red blood cell (pRBC) and non-pRBC transfusions in very low birth weight infants, and to compare the time spent with saturations of ≤85% before and after transfusions in the same population.

STUDY DESIGN

This prospective observational study was conducted from April 2014 to August 2017. It included 92 transfusions (81 pRBC, 11 non-pRBC) from 41 very low birth weight infants between 23^0/7 and 28^6/7 weeks of gestation. The primary outcome was number of intermittent hypoxia events. Secondary outcomes included the percent time of Peripheral capillary oxygen saturation (SpO2)of ≤85%, ≤80%, and ≤75%. A mixed ANOVA model was used to examine the relationship between event rate and covariates.

RESULTS

The mean number of intermittent hypoxia events per hour decreased from 5.27 ± 5.02 events per hour before pRBC transfusion to 3.61 ± 3.17 per hour after pRBC transfusions (P < .01) and intermittent hypoxia did not change after non-RBC transfusions (before, 4.45 ± 3.19 vs after, 4.47 ± 2.78; P = NS). The percent time with saturations of ≤80% and ≤75% significantly decreased after pRBC transfusions (P = .01). The time with saturations of ≤85% did not significantly change after non-pRBC transfusion.

CONCLUSIONS

In very low birth weight infants with a hematocrit of 20%-42%, pRBC transfusions are associated with decreased frequency of intermittent hypoxia. No such diminution of intermittent hypoxia events was observed in infants who had received a non-pRBC transfusion. This finding suggests that the observed beneficial effects of RBC transfusions on apnea and its clinical manifestations of intermittent hypoxia are mediated through an enhanced oxygen carrying capacity.

Thresholds for oximetry alarms and target range in the NICU: an observational assessment based on likely oxygen tension and maturity

BACKGROUND

Continuous monitoring of SpO₂ in the neonatal ICU is the standard of care. Changes in SpO₂ exposure have been shown to markedly impact outcome, but limiting extreme episodes is an arduous task. Much more complicated than setting alarm policy, it is fraught with balancing alarm fatigue and compliance. Information on optimum strategies is limited.

METHODS

This is a retrospective observational study intended to describe the relative chance of normoxemia, and risks of hypoxemia and hyperoxemia at relevant SpO₂ levels in the neonatal ICU. The data, paired SpO₂-PaO₂ and post-menstrual age, are from a single tertiary care unit. They reflect all infants receiving supplemental oxygen and mechanical ventilation during a 3-year period. The primary measures were the chance of normoxemia (PaO₂ 50-80 mmHg), risks of severe hypoxemia (PaO₂ ≤ 40 mmHg), and of severe hyperoxemia (PaO₂ ≥ 100 mmHg) at relevant SpO₂ levels.

RESULTS

Neonates were categorized by postmenstrual age: < 33 (n = 155), 33-36 (n = 192) and > 36 (n = 1031) weeks. From these infants, 26,162 SpO₂-PaO₂ pairs were evaluated. The post-menstrual weeks (median and IQR) of the three groups were: 26 (24-28) n = 2603; 34 (33-35) n = 2501; and 38 (37-39) n = 21,058. The chance of normoxemia (65, 95%-CI 64-67%) was similar across the SpO₂ range of 88-95%, and independent of PMA. The increasing risk of severe hypoxemia became marked at a SpO₂ of 85% (25, 95%-CI 21-29%), and was independent of PMA. The risk of severe hyperoxemia was dependent on PMA. For infants < 33 weeks it was marked at 98% SpO₂ (25, 95%-CI 18-33%), for infants 33-36 weeks at 97% SpO₂ (24, 95%-CI 14-25%) and for those > 36 weeks at 96% SpO₂ (20, 95%-CI 17-22%).

CONCLUSIONS

The risk of hyperoxemia and hypoxemia increases exponentially as SpO₂ moves towards extremes. Postmenstrual age influences the threshold at which the risk of hyperoxemia became pronounced, but not the thresholds of hypoxemia or normoxemia. The thresholds at which a marked change in the risk of hyperoxemia and hypoxemia occur can be used to guide the setting of alarm thresholds. Optimal management of neonatal oxygen saturation must take into account concerns of alarm fatigue, staffing levels, and FiO₂ titration practices.

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.

Achieved oxygen saturations and retinopathy of prematurity in extreme preterms

OBJECTIVE

To identify achieved oxygen saturations (SpO₂) associated with increased risk of severe retinopathy of prematurity (ROP).

DESIGN

This is a secondary analysis of the Surfactant Positive Airway Pressure and Pulse Oximetry Trial (SUPPORT)randomised controlled trial. SpO₂ was recorded up to 36 weeks' postmenstrual age. Saturations through 9 postnatal weeks were explored graphically, and logistic regression models were created to predict severe ROP.

SETTING

20 centres of the Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Research Network.

PATIENTS

984 surviving infants of 24-27 weeks' gestational age born in 2005-2009.

INTERVENTIONS

SUPPORT targeted SpO₂ to a lower (85%-89%) or higher (91%-95%) range through 36 weeks' postmenstrual age or off respiratory support.

MAIN OUTCOME MEASURES

Severe ROP defined as threshold ROP, ophthalmological surgery or bevacizumab treatment.

RESULTS

There were statistically significant interactions between duration of oxygen supplementation and percentage of time in certain achieved saturation ranges. Specifically, for infants who spent at least 2 weeks on oxygen in postnatal weeks 1-5, a higher percentage of time at 91%-96% SpO₂ was associated with increased odds of severe ROP. For infants who spent at least 3 weeks on oxygen in postnatal weeks 6-9, a higher percentage of time at 97%-100% SpO₂ was associated with increased odds of severe ROP. Other significant risk factors were lower gestational age and birth weight, non-Hispanic white versus black race, prospectively defined severe illness, late-onset sepsis or meningitis, and clinical centre.

CONCLUSIONS

Among extremely preterm survivors to discharge, the association between SpO₂ and severe ROP depended on the timing and duration of oxygen supplementation.

Current Recommendations and Practice of Oxygen Therapy in Preterm Infants

This narrative review identified 23 publications in 2011 to 2019 discussing randomized trials of oxygen saturation targets of 85% to 89% versus 91% to 95% in infants below 28 weeks' gestation. Of 18 commentaries or consensus statements, 17 recommended saturation targets above 89%. Five systematic reviews reported that the 85% to 89% target increased mortality but not the composite of death or disability. The evidence for increased mortality was assessed as of "high", "moderate," or "low," quality, reflecting substantial differences in interpreting the GRADE guidelines. Systematic reviews and guidelines without biostatisticians or epidemiologists as co-authors should be considered potentially problematic.