Meta-analysis of Oxygenation Saturation Targeting Trials: Do Infant Subgroups Matter?

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.

Preterm infant retinal OCT markers of perinatal health and retinopathy of prematurity

The increasing survival of preterm infants has led to the importance of improving long-term outcomes associated with preterm birth. Antenatal and perinatal insults not only impact mortality, but also long-term disability. While in the intensive care nursery, preterm infants are also exposed to various stressors that lead to long-term cognitive deficits. It is therefore critical to identify early, low-stress, non-invasive biomarkers for preterm infant health. Optical coherence tomography (OCT) is a powerful imaging modality that has recently been adapted to the infant population and provides noninvasive, high-resolution, cross-sectional imaging of the infant eye at the bedside with low stress relative to conventional examination. In this review we delve into discussing the associations between preterm systemic health factors and OCT-based retinal findings and their potential contribution to the development of non-invasive biomarkers for infant health and for retinopathy of prematurity (ROP).

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.

Systemic Factors Associated with a Thinner Choroid in Preterm Infants

Purpose

To identify systemic health factors associated with a thinner choroid, which has been hypothesized as a cause of poor visual outcomes in low–birth weight infants.

Design

The prospective, observational Study of Eye Imaging in Preterm Infants (BabySTEPS) enrolled infants recommended for retinopathy of prematurity screening based on the American Association of Pediatrics guidelines.

Participants

Infants who underwent imaging with investigational handheld OCT at 36 ± 1 weeks’ postmenstrual age (PMA) as part of BabySTEPS.

Methods

Average choroidal thickness was measured across the central subfoveal 1 mm. We concurrently collected maternal and infant clinical health data. Univariate and multivariate linear regression analyses were performed to evaluate factors associated with choroidal thickness. The left and right eyes showed similar thicknesses, so their average was used for analysis.

Main Outcomes Measures

Association between infant health factors and subfoveal choroidal thickness.

Results

Subfoveal choroidal thickness was measurable in 82 of 85 infants and 94% of eyes. Mean choroidal thickness was 231 ± 78 μm. In the univariate analysis, a thinner choroid was associated with decreased growth velocity (P < 0.001), lower birth weight (P < 0.001), smaller head circumference (P < 0.001), younger gestational age (P = 0.01), the presence of patent ductus arteriosus (P = 0.05), sepsis or necrotizing enterocolitis (P = 0.03), bronchopulmonary dysplasia (P = 0.03), pulmonary interstitial emphysema (P = 0.002), more days on oxygen support (P < 0.001), and being on oxygen support at 36 weeks (P < 0.001) and at the time of imaging (P < 0.001). In the multivariate analysis, growth velocity (P = 0.002) and oxygen support at the time of OCT imaging (P = 0.004) remained associated with a thinner choroid.

Conclusions

A thinner choroid is associated independently with growth velocity and receiving oxygen support at 36 ± 1 weeks PMA. This suggests that choroidal development in preterm infants may be related to growth rate in the first weeks of life and the prolonged use of supplemental oxygen. Longitudinal studies are needed to assess differences in choroidal thickness before 36 weeks PMA and to assess their impact on visual outcomes.

Incidence of Retinopathy of Prematurity in Botswana: A Prospective Observational Study

Background

Retinopathy of prematurity (ROP) is a widely recognized cause of blindness after preterm birth. The incidence of ROP is rising especially in low- and middle-income countries (LMIC) because of improved neonatal care and increased survival of very premature neonates. To date, there is no data on incidence of ROP in Botswana.

Objective

The purpose of this study was to provide initial data and determine ROP-associated risk factors from a single neonatal care center on the incidence of ROP in Gaborone, Botswana.

Methods

A prospective observational study was conducted at Princess Marina Hospital (PMH) in Gaborone, Botswana. Premature neonates with birth weights (BW) of <1,801 g or gestational age (GA) of <34 weeks were enrolled in this study. Diagnostic examinations were conducted using an indirect ophthalmoscope with 28D lens. ROP findings were classified according to the most advanced stage of ROP reached using the International Classification of ROP (2005). Data were entered into STATA version 15 statistical software for analysis.

Results

There were 264 premature infants enrolled in the study. ROP screening was performed on 200 (75.8%). Of all 264 enrolled patients 133 (50.4%) were female. The mean GA was 30.3±2.6 (range 24–37) weeks and the mean BW was 1302.2±285.9 g (range 725–2035). Out of 200 who were screened, we identified 22 with ROP with a ROP incidence of 11%. The incidence of type 1 ROP (sight-threatening) was found to be 3.5%. This study identified a significant difference in possible ROP risk factors between those infants who develop ROP and those who do not, eg, BW (p<0.001), GA (p=0.024) and blood transfusion (p=0.001).

Conclusion

This study demonstrates that ROP is a treatable cause of blindness in Botswana. Lack of a proper screening protocol, delay in diagnosis and management are plausible reasons for poor outcome in those who were diagnosed with type 1 ROP.