Oxygen Saturation Targeting During Delivery Room Stabilization: What Does This Mean for Regional Cerebral Oxygenation?

Regional pulmonary oxygen saturations in late preterm and term infants with respiratory distress at birth

BACKGROUND

Measurement of regional pulmonary oxygen saturation by near-infrared spectroscopy is a novel monitorization method. This study aimed to determine the early regional pulmonary oxygen saturations in neonates with respiratory distress.

METHODS

This observational study was conducted at the delivery room in infants above 35 weeks of gestation who developed respiratory distress immediately after birth. Preductal oxygen saturation (Covidien Nellcor®) and regional oxygen saturations of both apical (raSO2 ) and basal regions (rbSO2 ) of right lung were measured (Covidien INVOS®) within the first 15 min of life and compared to those of healthy neonates.

RESULTS

Of the 165 infants included to the study, 15 were late preterm and 55 developed respiratory distress. Infants with respiratory distress had significantly lower gestational age and birth weight. Regional pulmonary oxygenations at both apex and basal lung areas were positively correlated with SpO2 in all infants. The rbSO2 was significantly lower than raSO2 until 10th minute of life regardless of respiratory distress. The fractionized tissue oxygen extraction of both apical and basal lung areas was significantly higher in infants with respiratory distress until 5th minute of life.

CONCLUSION

This study is one of the pioneer studies evaluating the early pulmonary oxygenation values of infants with respiratory distress. Oxygenation of apical lung regions are better than basal areas. Higher fractionized tissue oxygen extraction showed the impaired pulmonary perfusion in infants with respiratory distress.

Fetal to neonatal transition: what additional information can be provided by cerebral near infrared spectroscopy?

This narrative review focuses on the clinical use and relevance of cerebral oxygenation measured by NIRS during fetal to neonatal transition. Cerebral NIRS(cNIRS) offers the possibility of non-invasive, continuous, and objective brain monitoring in addition to the recommended routine monitoring. During the last decade, with growing interest in early and sensitive brain monitoring, many research groups worldwide have been working with cNIRS and verified the feasibility of cNIRS monitoring immediately after birth. Cerebral hypoxia during fetal to neonatal transition, defined as cerebral oxygenation values below10th percentile, seems to have an impact on neurological outcomes. Feasibility to guide clinical support using cNIRS to reduce the burden of cerebral hypoxia has been shown. It is well known that in some cases cerebral oxygenation follows different patterns than SpO2. Cerebral oxygenation does not only depend on systemic oxygenation, hemoglobin content and cerebral blood flow, but also on cardiocirculatory condition, ventilation, and metabolic parameters. Hence, measurement of cerebral oxygenation may uncover problems not detectable by standard monitoring. Therefore, applying NIRS can provide caregivers a more complete clinical overview, especially in critically ill neonates. In this review, we aim to describe the additional information which can be provided by cNIRS during fetal to neonatal transition. IMPACT: This narrative review focuses on the clinical use and relevance of cerebral oxygenation measured by near infrared spectroscopy (NIRS) during fetal to neonatal transition. During the last decade, interest on brain monitoring is growing continuously as the measurement of cerebral oxygenation may uncover problems which are not detectable by routine monitoring. Therefore, it will be crucial to have additional information to get a complete overview, especially in critically ill neonates in need of medical and respiratory support. In this review, we offer additional information which can be provided by cerebral NIRS during fetal to neonatal transition.

Normal regional tissue oxygen saturation in neonates: a systematic qualitative review

BACKGROUND

The aim of this systematic qualitative review was to give an overview of reference ranges defined as normal values or centile charts of regional tissue oxygen saturation measured by near-infrared spectroscopy (NIRS) in term and preterm neonates.

METHODS

A systematic search of MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials was performed. Additional articles were identified by manual search of cited references. Only human studies in neonates were included.

RESULTS

Nineteen studies were identified. Eight described regional tissue oxygen saturation during fetal-to-neonatal transition, six during the first 3 days after birth, four during the first 7 days after birth, and one during the first 8 weeks after birth. Nine described regional tissue oxygen saturation in term, nine in preterm neonates, and one in both. Eight studies published centile charts for cerebral regional tissue oxygen saturation, and only five included large cohorts of infants. Eleven studies described normal values for cerebral, muscle, renal, and abdominal regional tissue oxygen saturation, the majority with small sample sizes. Four studies of good methodological quality were identified describing centile charts of cerebral regional tissue oxygen saturation.

CONCLUSIONS

In clinical settings, quality centile charts are available and should be the preferred method when using NIRS monitoring.

IMPACT

Near-infrared spectroscopy (NIRS) enables a bed-side non-invasive continuous monitoring of tissue oxygenation. When using NIRS monitoring in a clinical setting, centile charts with good quality are available and should be preferred to normal values. High-quality reference ranges of regional tissue oxygenation in term and preterm born neonates are an important step toward routine clinical application of NIRS.

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.

Oxygen saturation (SpO2) targeting for newborn infants at delivery: Are we reaching for an impossible unknown?

For more than 200 years, pure oxygen was given ad libitum to newborn infants requiring resuscitation. Due to oxidative stress and injury concerns, a paradigm shift towards using "less" oxygen, including air (21% oxygen) instead of pure (100%) oxygen, occurred about twenty years ago. A decade later, clinicians were advised to adjust fractional inspired oxygen (FiO₂) to target oxygen saturations (SpO₂) that were derived from spontaneously breathing, healthy, mature infants. Whether these recommendations are achievable, beneficial, harmful or redundant is uncertain. The underlying pathology leading to resuscitation varies between infants and may considerably alter an infant's response to supplemental oxygen. In this review, we summarize available evidence for the use of SpO₂ monitoring at delivery for newborn infants, elucidate existing knowledge and service gaps, and suggest future research recommendations that will lead to the safest clinical strategies for this standard and important practice.

Intensive care management of right ventricular failure and pulmonary hypertension crises

Pulmonary hypertension (PH), an often unrelenting disease that carries with it significant morbidity and mortality, affects not only the pulmonary vasculature but, in turn, the right ventricle as well. The survival of patients with PH is closely related to the right ventricular function. Therefore, having an understanding of how to manage right ventricular failure (RVF) and acute pulmonary hypertensive crises is imperative for clinicians who encounter these patients. This review addresses the management of these patients in detail, addressing: (a) the pathophysiology of RVF, (b) intensive care monitoring of these patients in the intensive care unit, (c) imaging of the right ventricle, (d) intubation and mechanical ventilation, (e) inotrope and vasopressor selection, (f) pulmonary vasodilator use, (g) interventional and surgical procedures for the acutely failing right ventricle, and (h) mechanical support for RVF.

Oxygen in the First Minutes of Life in Very Preterm Infants

Even a few minutes of exposure to oxygen in the delivery room in very preterm and immature infants may have detrimental effects. The initial oxygenation in the delivery room should therefore be optimized, but knowledge gaps, including initial fraction of oxygen (FiO2) and how FiO2 should be changed to reach an optimal oxygen saturation measured by pulse oximetry (SpO2) target within the first 5-10 min of life, remain. In order to answer this question, we therefore reviewed relevant literature. For newly born infants with gestational age (GA) <32 weeks in need of positive pressure ventilation (PPV) immediately after birth, we identified 2 fundamental issues: (1) the optimal initial FiO2 and (2) the target SpO2 within the first 5-10 min of life. For newly born infants between 29 and 31 weeks of GA, an initial FiO2 of 0.3 hit the target defined by the International Liaison Committee on Resuscitation (ILCOR) best. Newborn infants with GA <29 weeks in need of PPV and supplementary oxygen, we suggest starting with FiO2 0.3 and adjusting the FiO2 to reach SpO2 of 80% within 5 min of life for best outcomes. Prolonged bradycardia (heart rate <100 bpm for >2 min) is associated with increased risk of adverse outcomes, including death. The combination of strict control of development of SpO2 in the first 10 min of life and a heart rate >100 bpm represents the best tool today to achieve the most optimal outcome in the delivery room of very preterm and immature newborn infants.

NIRS in the fetal to neonatal transition and immediate postnatal period

Near-infrared spectroscopy (NIRS) offers the non-invasive continuous monitoring of cerebral oxygenation and perfusion. Cerebral regional oxygen (crSO2) measured via NIRS represents a mixed tissue saturation value, thus enabling information on the balance of cerebral oxygen delivery and oxygen consumption. Cerebral oxygenation is influenced by pulse oximeter saturation (SpO2), hemoglobin content, and cerebral blood flow. Furthermore, cerebral oxygenation is dependent on metabolic parameters, cardio circulatory parameters, perinatal- and postnatal interventions. Reference ranges for healthy term born and late preterm infants have already been published. It is feasible to increase crSO2 values above the 10th percentile by guiding medical support during neonatal to fetal transition. Guiding oxygen supply based on NIRS monitoring in addition to SpO2 monitoring showed that a reduction of the burden of cerebral hypoxia was possible. A currently ongoing study will give further information whether additional NIRS monitoring guiding medical support during neonatal to fetal transition is effective in improving neonatal outcome.

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.

Oxygen Supplementation During Preterm Stabilization and the Relevance of the First 5 min After Birth

Fetal to neonatal transition entails cardiorespiratory, hemodynamic, and metabolic changes coinciding with the switch from placental to airborne respiration with partial pressures of oxygen of 4-5 kPa in utero raising to 8-9 kPa ex utero in few minutes. Preterm infants have immature lung and antioxidant defense system. Very preterm infants (<32 weeks' gestation) frequently require positive pressure ventilation and oxygen to establish lung aeration, a functional residual capacity, and overcome a tendency toward hypoxemia and bradycardia in the first minutes after birth. Recent studies have shown that prolonged bradycardia (heart rate <100 beats per minute) and/or hypoxemia (oxygen saturation <80%) are associated with increased mortality and/or intracranial hemorrhage. However, despite the accumulated evidence, the way in which oxygen should be supplemented in the first minutes after birth still has not yet been clearly established. The initial inspired fraction of oxygen and its adjustment within a safe arterial oxygen saturation range measured by pulse oximetry that avoids hyper-or-hypoxia is still a matter of debate. Herewith, we present a current summary aiming to assist the practical neonatologist who has to aerate the lung and establish an efficacious respiration in very preterm infants in the delivery room.