Why are we still using oxygen to resuscitate term infants?

Collaboration in Regulatory Science to Facilitate Therapeutic Development for Neonates

BACKGROUND

Historically, neonatal therapeutic interventions were derived from adult therapeutics, and tragedies resulting from this approach have demonstrated differences in the pathophysiologic and developmental processes between neonates and older patients. Over the past 3 decades, researchers and collaborative research networks have made progress in the systematic evaluation of neonatal therapies, yet most neonatal therapeutic products have been incompletely assessed for safety and efficacy, and remain unlabeled and unapproved.

APPROACH

This work describes the legislative initiatives that have stimulated an increase in pediatric and neonatal studies. It highlights examples of successful neonatal drug studies that have resulted in informative neonatal labeling changes, as well as studies that have produced incomplete information. Strategies that support the design of successful studies, including targeting specific subpopulations, modeling and simulation to inform dose selection, innovative design strategies, biomarkers, and endpoints are discussed. Multi-stakeholder consortia such as the International Neonatal Consortium (INC), are working to improve the tools needed for the development of neonatal therapies. These research tools may be used by trial networks to inform consistent and efficient multicenter studies.

CONCLUSION

More data are needed to support safe and effective use of drugs in neonates, and to obtain these data, a thorough understanding of pathophysiology, drug disposition, biomarkers, and clinically-meaningful endpoints is required. This information will be derived from clinical trials, registries, real-world evidence, and the medical literature. Collaboration of consortia and the development of research networks are essential to achieving these goals.

A Review of Oxygen Physiology and Appropriate Management of Oxygen Levels in Premature Neonates

Background:

Although oxygen is the most widely used therapeutic agent in neonatal care, optimal oxygen management remains uncertain.

Purpose:

We reviewed oxygen physiology and balance, key studies evaluating oxygen saturation targets, and strategies for oxygen use in the neonatal intensive care unit.

Results:

Oxygen is a potent vasodilator involved in the transition at birth to breathing. Supplemental oxygen is administered to reverse/prevent hypoxia; however, excessive oxygen can be toxic owing to the formation of reactive oxygen species. Current neonatal resuscitation guidelines recommend using room air for term infants in need of support, with titration to achieve oxygen saturation levels similar to uncompromised term infants. In premature infants, targeting a higher oxygen saturation range (eg, 91%-95%) may be safer than targeting a lower range (eg, 85%-89%), but more evidence is needed. In combined analyses, lower oxygen saturation levels increased mortality, suggesting that the higher target may be safer, but higher targets are associated with an increased risk of developing disorders of oxidative stress.

Implications for Practice:

Need for supplemental oxygen should be assessed according to the American Heart Association guidelines. If appropriate, oxygen should be administered using room air, with the goal of preventing hypoxia and avoiding hyperoxia. Use of oximeter alarms may help achieve this goal. Pulmonary vasodilators may improve oxygenation and reduce supplemental oxygen requirements.

Implications for Research:

Implementation of wider target ranges for oxygen saturation may be more practical and lead to improved outcomes; however, controlled trials are necessary to determine the impact on mortality and disability.

Current Practices and Attitudes Regarding Use of Inhaled Nitric Oxide in the NICU: Results From a Survey of Members of the National Association of Neonatal Nurse Practitioners

Background:

Excessive supplemental oxygen exposure in the neonatal intensive care unit (NICU) can be associated with oxygen-related toxicities, which can lead to negative clinical consequences. Use of inhaled nitric oxide (iNO) can be a successful strategy for avoiding hyperoxia in the NICU. iNO selectively produces pulmonary vasodilation and has been shown to improve oxygenation parameters across the spectrum of disease severity, from mild to very severe, in neonates with hypoxic respiratory failure associated with persistent pulmonary hypertension of the newborn.

Purpose:

An online survey was conducted among members of the National Association of Neonatal Nurse Practitioners to gain insight into the level of understanding and knowledge among neonatal nurse practitioners (NNPs) about optimizing supplemental oxygen exposure and the use of iNO in the NICU setting.

Results:

Of 937 NNP respondents, 51% reported that their healthcare team typically waits until the fraction of inspired oxygen level is 0.9 or more before adding iNO in patients not responding to oxygen ventilation alone. Among respondents with 1 or more iNO-treated patients per month, only 35% reported they know the oxygenation index level at which iNO should be initiated. Less than 20% of NNPs reported perceived benefits associated with early initiation of iNO for preventing progression to use of extracorporeal membrane oxygenation or reducing the length of hospital stay, and about one-third of respondents reported they believe early iNO use minimizes hyperoxia.

Implications for Practice:

More education is needed for NNPs regarding the negative effects of oxidative stress in neonates.

Implications for Research:

Additional clinical trials investigating the most beneficial strategies for avoiding neonatal hyperoxia are warranted.

Pulse oximetry in very low birth weight infants

Pulse oximetry has become ubiquitous and is used routinely during neonatal care. Emerging evidence highlights the continued uncertainty regarding definition of the optimal range to target pulse oximetry oxygen saturation levels in very low birth weight infants. Furthermore, maintaining optimal oxygen saturation targets is a demanding and tedious task because of the frequency with which oxygenation changes, especially in these small infants receiving prolonged respiratory support. This article addresses the historical perspective, basic physiologic principles behind pulse oximetry operation, and the use of pulse oximetry in targeting different oxygen ranges at various time-points throughout the neonatal period.

Increased inspired oxygen in the first hours of life is associated with adverse outcome in newborns treated for perinatal asphyxia with therapeutic hypothermia

OBJECTIVE

To assess whether increased inspired oxygen and/or hypocarbia during the first 6 hours of life are associated with adverse outcome at 18 months in term neonates treated with therapeutic hypothermia.

STUDY DESIGN

Blood gas values and ventilatory settings were monitored hourly in 61 newborns for 6 hours after birth. We investigated if there was an association between increased inspired oxygen and/or hypocarbia and adverse outcome (death or disability by Bayley Scales of Newborn Development II examination at 18-20 months).

RESULTS

Hypothermia was started from 3 hours 45 minutes (10 minutes-10 hours) and median lowest Pco(2) level within the first 6 hours of life was 30 mm Hg (16.5-96 mm Hg). The median highest fraction of inspiratory oxygen within the first hour of life was 0.43 (0.21-1.00). The area under the curve fraction of inspiratory oxygen and Pao(2) for hours 1-6 of life was 0.23 (0.21-1.0) and 86 mm Hg (22-197 mm Hg), respectively. We did not find any association between any measures of hypocapnia and adverse outcome (P > .05), but increased inspired oxygen correlated with adverse outcome, even when excluding newborns with initial oxygenation failure (P < .05).

CONCLUSION

Increased fraction of inspired oxygen within the first 6 hours of life was significantly associated with adverse outcome in newborns treated with therapeutic hypothermia following hypoxic ischemic encephalopathy.

The developing human preterm neonatal immune system: a case for more research in this area

Neonates, particularly those born prematurely, are among the most vulnerable age group for morbidity and mortality due to infections. Immaturity of the innate immune system and a high need for invasive medical procedures in the context of a preterm birth make these infants highly susceptible to common neonatal pathogens. Preterm infants who survive may also suffer permanent disabilities due to organ damage resulting from either the infection itself or from the inflammatory response generated under an oxidative stress. Infections in preterm infants continue to pose important healthcare challenges. Yet, developmental maturation events in the innate immune system that underlie their excessively high vulnerability to infection remain largely understudied. In this review article, we identify pertinent knowledge gaps that must be filled in order to orient future translational research.

Short- and long-term behavioral effects of exposure to 21%, 40% and 100% oxygen after perinatal hypoxia-ischemia in the rat

Until recently, supplementation with 100% oxygen was standard therapy for newborns who required resuscitation at birth or suffered later hypoxic-ischemic events. Exposure to high concentrations of oxygen, however, may worsen oxidative stress induced by ischemic injury. In this study we investigated the short- and long-term behavioral outcomes in rats that had undergone hypoxic-ischemic brain injury on postnatal day 7, followed by 2h exposure to 21%, 40%, or 100% oxygen, compared to normal controls. There were no differences in the development of walking, head lifting and righting reflexes from postnatal days 9 to 15. Cliff avoidance showed some abnormal responses in the H21 animals. From postnatal days 28 to 56, three tests of sensorimotor coordination were performed weekly: ledged tapered beam, cylinder, and bilateral tactile stimulation. The ledged tapered beam test without prior training of animals was sensitive to injury, but did not distinguish between treatment groups. The cylinder test showed a greater use of the unimpaired limb in female 21% and 40% oxygen groups compared to controls. Performance in both cylinder and the beam tests showed a correlation with the degree of brain injury. The bilateral tactile stimulation test showed that the male 21% oxygen groups had worse sensory asymmetry than male 40% or 100% oxygen groups, but was not statistically significantly different from controls. We thus found a minor benefit to post-hypoxia-ischemic treatment with 100% and 40% oxygen compared to 21% in one test of early motor skills. Our results for long-term sensorimotor behavior, however, showed conflicting results, however, as males treated with 40% or 100% oxygen had less sensory asymmetry (better performance) in the bilateral tactile stimulation test than males treated with 21% oxygen, while females had impaired motor performance in the cylinder test with both 21% and 40% oxygen.