Refining the role of oxygen administration during delivery room resuscitation: what are the future goals?

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.

Prise en charge périnatale du nouveau-né lors d’une naissance en milieu extrahospitalier

Les accouchements inopinés extrahospitaliers représentent environ 0,3 % des accouchements en France. La prise en charge du nouveau-né en préhospitalier par une équipe Smur fait partie de l’activité courante. L’évaluation initiale du nouveau-né comprend systématiquement la mesure de sa fréquence cardiaque (FC) et respiratoire (FR), l’appréciation de son tonus ainsi que la mesure de sa température axillaire. En cas de doute ou de transition incomplète un monitoring cardiorespiratoire sera immédiatement mis en place (FC, FR, SpO2). Nous faisons ici une mise au point sur les données connues et avons adapté les pratiques, si besoin, au contexte extrahospitalier, car la majeure partie des données rapportées dans la littérature concernent les prises en charge en maternité ou en milieu hospitalier. Nous abordons les points essentiels de la prise en charge des nouveau-nés, à savoir la réanimation cardiopulmonaire, le clampage tardif du cordon ombilical, la lutte contre l’hypothermie et l’hypoglycémie; ainsi que des situations particulières comme la prématurité, la conduite à tenir en cas de liquide méconial ou de certaines malformations congénitales. Nous proposons aussi quels peuvent être : le matériel nécessaire à la prise en charge des nouveau-nés en extrahospitalier, les critères d’engagement d’un renfort pédiatrique à la régulation ainsi que les méthodes de ventilation et d’abord vasculaire que l’urgentiste doit maîtriser. L’objectif de cette mise au point est de proposer des prises en charge les plus adaptées au contexte préhospitalier.

Oxygen Therapy for Neonatal Resuscitation in the Delivery Room

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

Newborn Resuscitation in Settings Without Access to Supplemental Oxygen

Low- and middle-income countries and resource-limited regions are major contributors to perinatal and infant mortality. Oxygen is widely used for resuscitation in high- and middle-income settings. However, oxygen supplementation is not available in resource-limited regions. Oxygen supplementation for resuscitation at birth has adverse effects in human/animal model studies. There has been a change with resultant recommendations for restrictive oxygen use in neonatal resuscitation. Neonatal resuscitation without supplemental oxygen decreases mortality and morbidities. Oxygen in resource-limited settings for neonatal resuscitation is ideal as a backup for selected resuscitations but should not be a limiting factor for implementing basic life-saving efforts.

The Goldilocks principle. Oxygen in the delivery room: When is it too little, too much, and just right?

Oxygen has been used to stabilize newborn infants for more than a century. Over the last two decades, a paradigm shift towards using less oxygen has occurred but without firm evidence of benefit. Using lower levels of oxygen has also added new conundrums to clinical care. Can oxygen delivery to sick newborn babies meet the Goldilocks principle, of being "just right"? This review discusses the history of oxygen use in the delivery room and the impetus to change from the long-established practice of using pure oxygen to using lower oxygen concentrations. The review also highlights knowledge gaps, particularly for oxygen exposure and monitoring, as well as the sequelae of oxygen administration, including short- and long-term outcomes.

One oxygen breath shortened the time to return of spontaneous circulation in severely asphyxiated piglets

AIM

Asphyxiated neonates should be resuscitated with air, but it remains unclear if oxygen supplementation is needed in ineffectively ventilated newborn infants. We studied the return of spontaneous circulation (ROSC) with oxygen or air in an experimental model of inadequate ventilation.

METHODS

Asphyxia was induced in 16 newborn piglets until their heart rate was <60 bpm or mean arterial pressure (MAP) <30 mmHg. During the first 10 minutes of resuscitation, they received one breath per minute of oxygen (n = 8) or air (n = 8). Tidal volume was 7.5 mL/kg. If MAP was <30 mmHg for 15 seconds, closed-chest cardiac massage (CCCM) was performed for 45 seconds. From 10 minutes onward, all piglets received normal ventilation with air. ROSC was defined as a heart rate >150 bpm, MAP >40 mmHg and no subsequent CCCM.

RESULTS

Before resuscitation, the median arterial pH was 6.73. At 10 minutes, no piglets in the oxygen group needed CCCM, while all did in the air group (p < 0.001). The median time to ROSC was 60 seconds with oxygen and 845 seconds with air (p < 0.001). No brain tissue hyperoxia occurred.

CONCLUSION

When ventilation was inadequate, one oxygen breath reduced time to ROSC in piglets with severe metabolic and respiratory acidosis.

Neonatal self-inflating bags: achieving titrated oxygen delivery using low flows: an experimental study

AIM

To determine delivered O2 concentration (dFiO2) during manual inflations using neonatal self-inflating resuscitation bags (SIBs) at oxygen (O2) flow rates <1 L/min.

METHODS

This experimental study, determined dFiO2 during 216 sets of manual inflations at different O2 flow rate (L/min; 0.2, 0.4, 0.6, 0.8, 1.0 and 5.0), controlling peak inspiratory pressures (PIP; cm of H2O; 10-15, 15-20 and 20-25), inflation rates (per min; 30, 40 and 60), with and without O2 reservoir using two SIBs--the Laerdal infant resuscitator (240 mL) and Ambu Mark IV resuscitator (300 mL). A leak proof circuit connecting the SIB in series with pressure transducer, O2 analyzer and test lung was used. All possible combinations were tested four times each. The dFiO2 with each possible combination was compared using generalised estimating equation.

RESULTS

The mean dFiO2 with SIB even without reservoirs varied with rates and PIP from 75 to 93% at O2 flow rate of 5 L/min. At 1 L/min flow itself, 65-85% O2 is delivered. The dFiO2 was reduced to approximately 40% with flow of 0.2 L/min, PIP 20-25 cmH2O and inflations 40-60 per min.

CONCLUSION

During manual breaths using neonatal SIBs, the delivered O2 concentration of nearly 40% is attained at clinically used inflation pressures and rates by using lower flows. A graded increase in O2 delivery from 40 to 99% was obtained with flow varying from 0.2 to 5 L/min and addition of reservoir. However, even at such low flows, reduction in O2 concentration below 40% was unattained.

The role of oxygen in the delivery room

As recently as the year 2000, 100% oxygen was recommended to begin resuscitation of depressed newborns in the delivery room. However, the most recent recommendations of the International Liaison Committee on Resuscitation counsel the prudent use of oxygen during resuscitation. In term and preterm infants, oxygen therapy should be guided by pulse oximetry that follows the interquartile range of preductal saturations of healthy term babies after vaginal birth at sea level. This article reviews the literature in this context, which supports the radical but judicious curtailment of the use of oxygen in resuscitation at birth.

Antioxidant protects against increases in low molecular weight hyaluronan and inflammation in asphyxiated newborn pigs resuscitated with 100% oxygen

BACKGROUND

Newborn resuscitation with 100% oxygen is associated with oxidative-nitrative stresses and inflammation. The mechanisms are unclear. Hyaluronan (HA) is fragmented to low molecular weight (LMW) by oxidative-nitrative stresses and can promote inflammation. We examined the effects of 100% oxygen resuscitation and treatment with the antioxidant, N-acetylcysteine (NAC), on lung 3-nitrotyrosine (3-NT), LMW HA, inflammation, TNFα and IL1ß in a newborn pig model of resuscitation.

METHODS & PRINCIPAL FINDINGS

Newborn pigs (n = 40) were subjected to severe asphyxia, followed by 30 min ventilation with either 21% or 100% oxygen, and were observed for the subsequent 150 minutes in 21% oxygen. One 100% oxygen group was treated with NAC. Serum, bronchoalveolar lavage (BAL), lung sections, and lung tissue were obtained. Asphyxia resulted in profound hypoxia, hypercarbia and metabolic acidosis. In controls, HA staining was in airway subepithelial matrix and no 3-NT staining was seen. At the end of asphyxia, lavage HA decreased, whereas serum HA increased. At 150 minutes after resuscitation, exposure to 100% oxygen was associated with significantly higher BAL HA, increased 3NT staining, and increased fragmentation of lung HA. Lung neutrophil and macrophage contents, and serum TNFα and IL1ß were higher in animals with LMW than those with HMW HA in the lung. Treatment of 100% oxygen animals with NAC blocked nitrative stress, preserved HMW HA, and decreased inflammation. In vitro, peroxynitrite was able to fragment HA, and macrophages stimulated with LMW HA increased TNFα and IL1ß expression.

CONCLUSIONS & SIGNIFICANCE

Compared to 21%, resuscitation with 100% oxygen resulted in increased peroxynitrite, fragmentation of HA, inflammation, as well as TNFα and IL1ß expression. Antioxidant treatment prevented the expression of peroxynitrite, the degradation of HA, and also blocked increases in inflammation and inflammatory cytokines. These findings provide insight into potential mechanisms by which exposure to hyperoxia results in systemic inflammation.

Impact of delivery room resuscitation on outcomes up to 18 months in very low birth weight infants

OBJECTIVE

To examine the relationships between intensity of delivery room resuscitation and short- and long-term outcomes of very low birth weight infants enrolled in the Caffeine for Apnea of Prematurity (CAP) Trial.

STUDY DESIGN

The CAP Trial enrolled 2006 infants with birthweights between 500 and 1250 g who were eligible for caffeine therapy. All levels of delivery room resuscitation were recorded in study participants. We divided infants in 4 groups of increasing intensity of resuscitation: minimal, n = 343; bag-mask ventilation, n = 372; endotracheal intubation, n = 1205; and cardiopulmonary resuscitation (chest compressions/epinephrine), n = 86. We used multivariable logistic regression models to compare outcomes across the 4 groups.

RESULTS

The observed rates of death or disability, death, cerebral palsy, cognitive deficit, and hearing loss at 18 months increased with higher levels of resuscitation. Risk of bronchopulmonary dysplasia, severe retinopathy of prematurity, and brain injury also increased with higher levels of resuscitation. Adjustment for prognostic variables reduced the differences between the groups for most outcomes. Only the adjusted rates of bronchopulmonary dysplasia and severe retinopathy remained significantly higher after more intense resuscitation.

CONCLUSIONS

In CAP Trial participants, the risk of death or neurodevelopmental disability at 18 months did not increase substantially with increasing intensity of delivery room resuscitation.

Oxygen supplementation in the delivery room: updated information

Resuscitation is the most common procedure performed in neonatology. However, new contributions based on scientific evidence challenge the traditional procedures. Of these new contributions, the use of room-air instead of 100% oxygen and titration of the oxygen inspiratory fraction according to oximetry and heart rate represent a new approach in the resuscitation of both term and preterm newborns.

Oxygen concentration and pulmonary hemodynamics in newborn lambs with pulmonary hypertension

The effect of oxygen concentration on lowering pulmonary vascular resistance (PVR) during resuscitation in a model of persistent pulmonary hypertension of the newborn (PPHN) is not known. PPHN was induced in fetal lambs by ductal ligation 9 d before delivery. After delivery by cesarean section, resuscitation of PPHN lambs with 21%, 50%, or 100% O2 (n = 6 each) for 30 min produced similar decreases in PVR. Lambs were then ventilated with 50% O2 for 60 min and exposed to inhaled nitric oxide (iNO, 20 ppm). Initial resuscitation with 100% O2 significantly impaired the subsequent response to iNO compared with 21% O2 (42 +/- 9% vs 22 +/- 4% decrease from baseline PVR). Finally, each lamb was randomly and sequentially ventilated with 10%, 21%, 50%, or 100% O2. PVR decreased with increased concentrations of inhaled O2 up to 50%, there being no additional decrease in PVR with 100% O2. When PVR was correlated with Pao2, the maximal change in PVR was achieved at Pao2 values <60 mm Hg. We conclude that resuscitation with 100% O2 does not enhance pulmonary vasodilation compared with 21% and 50% O2, but impairs the subsequent response to iNO in PPHN lambs. Hypoxia increases PVR but hyperoxia does not confer significant additional pulmonary vasodilation in lambs with PPHN.