Resuscitation of newborn infants with room air or oxygen

Nup133 and ERα mediate the differential effects of hyperoxia-induced damage in male and female OPCs

Background

Hyperoxia is a well-known cause of cerebral white matter injury in preterm infants with male sex being an independent and critical risk factor for poor neurodevelopmental outcome. Sex is therefore being widely considered as one of the major decisive factors for prognosis and treatment of these infants. But unfortunately, we still lack a clear view of the molecular mechanisms that lead to such a profound difference. Hence, using mouse-derived primary oligodendrocyte progenitor cells (OPCs), we investigated the molecular factors and underlying mechanisms behind the differential response of male and female cells towards oxidative stress.

Results

We demonstrate that oxidative stress severely affects cellular functions related to energy metabolism, stress response, and maturation in the male-derived OPCs, whereas the female cells remain largely unaffected. CNPase protein level was found to decline following hyperoxia in male but not in female cells. This impairment of maturation was accompanied by the downregulation of nucleoporin and nuclear lamina proteins in the male cells. We identify Nup133 as a novel target protein affected by hyperoxia, whose inverse regulation may mediate this differential response in the male and female cells. Nup133 protein level declined following hyperoxia in male but not in female cells. We show that nuclear respiratory factor 1 (Nrf1) is a direct downstream target of Nup133 and that Nrf1 mRNA declines following hyperoxia in male but not in female cells. The female cells may be rendered resistant due to synergistic protection via the estrogen receptor alpha (ERα) which was upregulated following hyperoxia in female but not in male cells. Both Nup133 and ERα regulate mitochondrial function and oxidative stress response by transcriptional regulation of Nrf1.

Conclusions

These findings from a basic cell culture model establish prominent sex-based differences and suggest a novel mechanism involved in the differential response of OPCs towards oxidative stress. It conveys a strong message supporting the need to study how complex cellular processes are regulated differently in male and female brains during development and for a better understanding of how the brain copes up with different forms of stress after preterm birth.

While waiting: early recognition and initial management of neonatal hypoxic-ischemic encephalopathy

Hypoxic-ischemic encephalopathy (HIE) occurring during the perinatal period is one of the primary causes of severe, long-term neurological deficits in children. Initial systemic supportive therapy remains a critical aspect of HIE management. In addition to support therapy, the widespread use of hypothermia has demonstrated a reduction in death and neurodevelopmental disability in infants with moderate to severe HIE. Neonates with HIE born outside of tertiary care centers must be rapidly identified as hypothermia candidates and have emergent transport arranged. While waiting for the transport team to arrive, these neonates often require intensive stabilization, including meticulous temperature management. This article examines the need for HIE outreach teaching programs, assists in the identification of a neonate for hypothermia therapy, and supplies evidence-based recommendations for the initial stabilization and care of neonates delivered at nontertiary care facilities. The guidelines and materials supplied represent the outreach model used by our regional hypothermia center and disseminated to the surrounding referral hospitals.

Green tea catechins and their oxidative protection in the rat eye

Catechins, active constituents of green tea, are well-known antioxidative natural products. It was proposed that green tea extract (GTE) consumption could benefit the eye, and the pharmacokinetics of catechins and oxidation status in rat eye were investigated after oral administration. Sprague-Dawley rats were fed GTE and sacrificed at different time intervals. Their eyes were dissected into cornea, lens, retina, choroid-sclera, vitreous humor, and aqueous humor for analysis of catechins and 8-epi-isoprostane by HPLC-ECD and GC-NCI-MS, respectively. Catechins were differentially distributed in eye tissues. Gallocatechin was present at the highest concentration in the retina, 22729.4 +/- 4229.4 pmol/g, and epigallocatechin in aqueous humor at 602.9 +/- 116.7 nM. The corresponding area-under-curves were 207,000 pmol x h/g and 2035.0 +/- 531.7 nM x h, respectively. The time of maximum concentration of the catechins varied from 0.5 to 12.2 h. Significant reductions in 8-epi-isoprostane levels were found in the compartments except the choroid-sclera or plasma, indicating antioxidative activities of catechins in these tissues.

Is 100% oxygen necessary for the resuscitation of newborn infants?

This paper reproduces in detail the debate 'pro-and-con' regarding the use of 100% oxygen or room air in the resuscitation of the asphyxiated newly born infants, celebrated in Oslo at the 2002 European Association of Perinatal Medicine (EAPM) meeting, in which both co-authors participated as featured speakers. The authors describe their arguments which are based on medical tradition, clinical experience, basic science, and prospective randomized and pseudo-randomized clinical studies that have been reported in the past years. Both authors stress the importance of the long-term consequences of the use of high oxygen concentrations in the perinatal period and conclude that there is a need for further research in the way of ample prospective randomized clinical trials.

Four million newborn deaths: is the global research agenda evidence-based?

Four million neonates die each year. These deaths are mostly in low-income countries, but neonatal mortality and morbidity are also a priority burden in high-income countries. Epidemiological evidence suggests newborn research would prioritise the poorest families; birth and the first days of life; major causes particularly infections, preterm birth and asphyxia; and include preventive strategies as well as improved care. However research investment is not commensurate to burden, and there is a mismatch with current research priorities. South Asia and sub Saharan Africa, with 75% of the burden, expend around US$20 million per year on newborn research, a fraction of what is spent on a smaller proportion of health problem in rich countries. We propose a research pipeline of description, discovery, development of solutions and delivery of research with scale-up to reach the poorest families. Listing research options and applying quantitative scoring enables systematic, transparent research prioritisation. As well as a research pipeline, a "people pipeline" is required to generate research capacity in low-income countries.

Oxygen in neonatal and infant anesthesia--current practice in the UK

BACKGROUND

There is an increasing awareness of the role of oxygen free radicals in the pathogenesis of many conditions associated with prematurity, which has led to caution in the use of oxygen in neonatal resuscitation. We surveyed the practice of UK pediatric anesthetists with regard to oxygen use in neonatal and infant anesthesia.

METHODS

A postal questionnaire survey of 460 UK-based members of the Association of Pediatric Anesthetists of Great Britain and Ireland.

RESULTS

Responses were received from 247 pediatric anesthetists (54%). Seventy-five percent of anesthetists aim to avoid the use of 100% oxygen during routine infant anesthesia and 52% aim for an FiO(2) of < 0.4 in neonates. The factors most influencing choice of carrier gas are optimal oxygenation and the avoidance of pulmonary atelectasis. Sixteen percent stated that unavailability of medical air is a factor. Opinion was divided on concern about the effects of anesthetic agents on the developing brain. Moderate levels of concern were expressed about the potential toxic effects of oxygen on the eyes and lungs of premature newborns but this concern does not extend to term newborns. Only 20% of anesthetists had any recent knowledge of these issues.

CONCLUSIONS

This survey indicates that there is no consistency in attitudes and practices and demonstrates considerable variation in the use of oxygen during anesthesia in premature and newborn babies and infants. This may reflect the paucity of evidence in the anesthetic literature on the potential harmful effects of high concentrations of oxygen in vulnerable groups of infants.

Oxygen as a neonatal health hazard: call for détente in clinical practice

Education in oxygenation and in how oxygen is given to newborns needs to increase. Treatment with oxygen should no longer be considered proverbial and customary, regardless of our 'past experience' or consensus recommendations in clinical guidelines, since oxygen may lead to acute or chronic health effects.

CONCLUSION

Inappropriate oxygen use is a neonatal health hazard associated with aging, DNA damage and cancer, retinopathy of prematurity, injury to the developing brain, infection and others. Neonatal exposure to pure O2, even if brief, or to pulse oximetry >95% when breathing supplemental O2 must be avoided as much as possible.

Reventilation with room air or 100% oxygen after asphyxia differentially affects cerebral neuropathology in newborn pigs

AIM

To test if reventilation with room air (RA) or 100% oxygen (O2) after asphyxia would differentially affect neuronal damage in different brain areas of newborn pigs.

METHODS

Anaesthetized piglets were subjected to 10 min asphyxia (n=27) or served as time controls (n=7). Reventilation started with either RA or O2 for 1 h, and was continued with RA for an additional 1-3 h. Cortical or cerebellar blood flow was assessed with laser-Doppler flowmetry (LDF). Haematoxylin/eosin-stained sections from six brain regions were prepared for blinded neuropathological examination and scoring.

RESULTS

Asphyxia resulted in significant neuronal damage compared to time controls in all areas examined except the pons. O2 ventilation elicited greater neuronal lesions in the hippocampus and the cerebellum but smaller damage in the basal ganglia compared to RA. The assessed physiological parameters including the LDF signals were similar in both ventilation groups, except for PaO2 in the first hour of reventilation (RA 75+/-5 mmHg, O2 348+/-57 mmHg; p<0.05). Interestingly, however, reactive hyperaemia was much higher in the O2-sensitive cerebellum as compared with the cortex (1101+/-227 vs 571+/-73; p<0.05, area under the curve).

CONCLUSION

O2 toxicity after asphyxia was demonstrated in the piglet hippocampus and cerebellum but not in the cerebral cortex or basal ganglia. The observed regional differences may be associated with local haemodynamic factors.

The evolution of neonatology

In 1960, the terms "neonatology" and "neonatologist" were introduced. Thereafter, an increasing number of pediatricians devoted themselves to full-time neonatology. In 1975, the first examination of the Sub-Board of Neonatal-Perinatal Medicine of the American Board of Pediatrics and the first meeting of the Perinatal Section of the American Academy of Pediatrics were held. One of the most important factors that improved the care of the neonate was the miniaturization of blood samples needed to determine blood gases, serum electrolytes, glucose, calcium, bilirubin, and other biochemical measurements. Another factor was the ability to provide nutrition intravenously, and the third was the maintenance of normal body temperature. The management of respiratory distress syndrome improved with i.v. glucose and correction of metabolic acidosis, followed by assisted ventilation, continuous positive airway pressure, antenatal corticosteroid administration, and the introduction of exogenous surfactant. Pharmacologic manipulation of the ductus arteriosus, support of blood pressure, echocardiography, and changes in the management of persistent pulmonary hypertension, including the use of nitric oxide and extracorporeal membrane oxygenation, all have influenced the cardiopulmonary management of the neonate. Regionalization of neonatal care; changes in parent-infant interaction; and technological changes such as phototherapy, oxygen saturation monitors, and brain imaging techniques are among the important advances reviewed in this report. Most remarkable, a 1-kg infant who was born in 1960 had a mortality risk of 95% but had a 95% probability of survival by 2000. However, errors in neonatology are acknowledged, and potential directions for the future are explored.

Complement C5a is a key mediator of meconium-induced neutrophil activation

Meconium aspiration syndrome is a serious condition of the newborn characterized by pulmonary inflammation with substantial neutrophil infiltration. We recently showed that meconium is a potent activator of complement. The aim of the present study was to investigate a possible role for complement in meconium-induced neutrophil activation. Meconium was incubated in human whole blood anticoagulated with lepirudin, a specific thrombin inhibitor that does not affect complement activation. Complement activation was detected by measuring the terminal complement complex. Neutrophil oxidative burst and changes in CD11b and L-selectin expression were measured by flow cytometry. Complement was inhibited using the MAb 166-32 and 137-26, which block factor D and neutralize C5a, respectively. Meconium markedly activated the neutrophils, as revealed by up-regulation of CD11b, accentuation of L-selectin shedding, and induction of oxidative burst. Complement inhibition using the anti-factor D antibody completely (95-100%) blocked meconium-induced changes in CD11b and L-selectin expression, whereas oxidative burst was reduced by 60-70%. The anti-C5a antibody inhibited the neutrophil activation to the same extent as anti-factor D. The data suggest that complement activation is largely responsible for the neutrophil inflammatory responses induced by meconium in vitro and that C5a is a key mediator of this response.

Clinical risk management in newborn and neonatal resuscitation

This chapter aims to provide an overview of aspects of risk management as they might be applied to the practice of resuscitation of the newborn using general principles of risk management and specific standards where they apply. Section 1 considers the matter of hazard and risk and how they may be classified. Figures are presented to provide a clinical perspective on resuscitation with a discussion on the hierarchy of clinical risks operating upon the baby. Section 2 centres on a discussion of those aspects that operate to modify the risks to the baby during a resuscitation, including environmental considerations (location, clinical setting and equipment); staffing issues (establishment, competency, induction and training) and logistics (process, communication and documentation). Section 3 debates the place of cord gases in the context of the diagnosis of perinatal hypoxaemia.

Resuscitation of Depressed Newborn Infants with Ambient Air or Pure Oxygen: A Meta-Analysis

BACKGROUND

It is discussed whether depressed newborn infants should be resuscitated with room air or 100% O2.

OBJECTIVE

To perform a systematic review and meta-analysis including studies that report resuscitation of depressed newly born infants with 21 or 100% O2.

METHODS

Inclusion criterion was randomized or pseudo-randomized, blinded or not, studies of depressed newborn infants resuscitated with either 21 or 100% O2. The literature was searched in Medline/Pubmed/EMBASE and The Cochrane library databases. All identified studies were included.

RESULTS

Five studies fulfilled the inclusion criterion in which 881 infants were resuscitated with 21% O2 and 856 with 100% O2. Neonatal mortality was 8.0 vs. 13.0% in the 21 and 100% O2 groups respectively, OR 0.57, 95% CI 0.42-0.78. In term infants neonatal mortality was 5.9% in the 21% O2 group and 9.8% in the 100% O2 group, OR 0.59, 95% CI 0.40-0.87. The figures for the premature infants were very similar. In infants with 1-min Apgar score <4, OR for neonatal mortality was 0.81 (95% CI 0.54-1.21). Apgar score at 5 min and heart rate at 90 s were significantly higher, and time to first breath significantly earlier in infants given 21% O2 compared with 100% O2.

CONCLUSIONS

A systematic review and meta-analysis demonstrated that neonatal mortality is significantly reduced when depressed newly born infants are resuscitated with ambient air instead of pure oxygen. For infants with low 1-min Apgar score (<4), no significant difference in neonatal mortality was found. Recovery was faster in infants resuscitated with 21% O2 than 100% O2.

EARLY MECHANICAL VENTILATION IS DELETERIOUS AFTER ASPIRATION-INDUCED LUNG INJURY IN RABBITS

We investigated whether mechanical ventilation after aspiration is deleterious when started before surfactant therapy. Gas exchange and lung mechanics were measured in rabbits after aspiration either mechanically ventilated before or after lavage with diluted surfactant or Ringer's solution. Lung injury was induced by intratracheal instillation of 2 mL/kg of a betain/HCl pepsin mixture. After 30 min of spontaneous breathing, ventilation was started in 12 rabbits, which were then treated by lavage with diluted surfactant (15 mL/kg body weight; 5.3 mg/mL, group MVpre S) or with Ringer's solution (1 mL/kg; group MVpre R). Another 12 rabbits were treated by lavage while spontaneously breathing and were then connected to the ventilator (MVpost S and MVpost R). Sham control rabbits were mechanically ventilated for 4 h. At the end of experiment, PaO2/FiO2 ratio in MVpost S was five times higher than in MVpre S (P=0.0043). Lung mechanics measurements showed significant difference between MVpre S and MVpost S (P=0.0072). There was histopathologic evidence of decreased lung injury in MVpost S. Immediate initiation of ventilation is harmful when lung injury is induced by aspiration. Further investigations are needed to clarify whether the timing of lavage with diluted surfactant has an impact on the treatment of patients with aspiration or comparable types of direct lung injury.

Do hyperoxaemia and hypocapnia add to the risk of brain injury after intrapartum asphyxia?

BACKGROUND

Episodes of hyperoxaemia and hypocapnia, which may contribute to brain injury, occur unintentionally in severely asphyxiated neonates in the first postnatal hours.

OBJECTIVE

To determine whether hyperoxaemia and/or hypocapnia during the first 2 hours of life add to the risk of brain injury after intrapartum asphyxia.

METHODS

Retrospective cohort study in term infants with post-asphyxial hypoxic ischaemic encephalopathy (HIE) born between 1985 and 1995. Severe and moderate hyperoxaemia were defined as Pao(2) >26.6 and Pao(2) >13.3 kPa (200 and 100 mm Hg). Severe and moderate hypocapnia were defined as Paco(2) <2.6 and Paco(2) <3.3 kPa (20 and 25 mm Hg). Adverse outcome ascertained by age 24 months was defined as death, severe cerebral palsy, or any cerebral palsy with blindness, deafness, or developmental delay. With outcome as the dependent variable, multivariate analyses were performed including hyperoxaemic and hypocapnic variables, and factors adjusted for initial disease severity.

RESULTS

Of 244 infants, 218 had known outcomes, 127 of which were adverse (64 deaths, 63 neurodevelopmental deficits). Multivariate analyses showed an association between adverse outcome and episodes of severe hyperoxaemia (odds ratio (OR) 3.85, 95% confidence interval (CI) 1.67 to 8.88, p = 0.002), and severe hypocapnia (OR 2.34, 95% CI 1.02 to 5.37, p = 0.044). The risk of adverse outcome was highest in infants who had both severe hyperoxaemia and severe hypocapnia (OR 4.56, 95% CI 1.4 to 14.9, p = 0.012).

CONCLUSIONS

Severe hyperoxaemia and severe hypocapnia were associated with adverse outcome in infants with post-asphyxial HIE. During the first hours of life, oxygen supplementation and ventilation should be rigorously controlled.

The role of oxygen in neonatal resuscitation

New knowledge has accumulated in recent years making it prudent to ask questions regarding current oxygenation policies and guidelines. Because new-born resuscitation affects so many individuals, and because resuscitation procedures may have dramatic consequences on infant and child health, intensified discussion and research in this field are not only necessary but are a requirement. In particular, there is a lack of data on infants born before term. It is difficult to give absolute recommendations on which oxygen concentration should be applied for newborn resuscitation; however, it seems that ambient air is safe. It is easy to handle, is always at hand, and is inexpensive. Conversely, regarding 100% O2, I believe we have sufficient data to conclude that this should not be given routinely at birth to depressed infants; however, whether it is beneficial or harmful to start out resuscitation with 30%, 40%, or 60% O2 is not known. No data exist to answer this question. A call for more research in this area is timely. The effect of pure oxygen on cell growth and cell death, gene activation, and possibly DNA damage should be carefully investigated. Even before such data are collected, it is known that pure oxygen at birth triggers long-term and poorly understood effects. Oxygen obviously is more toxic than previously thought, and oxygen given to small infants has a 50-year history of uncertain benefits. Table 1 summarizes the pros and cons of using 21%versus 100% 02 for newborn resuscitation. Brain circulation as assessed by microspheres is restored as quickly with 21% O2 as it is with 100% O2; however, microcirculation is somewhat slower. Metabolism, pulmonary flow, and myocardial performance are normalized just as quickly by 21% and 100% O2. Brain injury as assessed by glycerol augmentation, matrix injury, and neonatal mortality is less in infants given 21% versus 100% O2.

Positive end expiratory pressure during resuscitation of premature lambs rapidly improves blood gases without adversely affecting arterial pressure

Positive end expiratory pressure (PEEP) is important for neonatal ventilation but is not considered in guidelines for resuscitation. Our aim was to investigate the effects of PEEP on cardiorespiratory parameters during resuscitation of very premature lambs delivered by hysterotomy at approximately 125 d gestation (term approximately 147 d). Before delivery, they were intubated and lung fluid was drained. Immediately after delivery, they were ventilated with a Dräger Babylog plus ventilator in volume guarantee mode with a tidal volume of 5 mL/kg. Lambs were randomized to receive 0, 4, 8, or 12 cm H(2)O of PEEP. They were ventilated for a 15-min resuscitation period followed by 2 h of stabilization at the same PEEP. Tidal volume, peak inspiratory pressure, PEEP, arterial pressure, oxygen saturation, and blood gases were measured regularly, and respiratory system compliance and alveolar/arterial oxygen differences were calculated. Lambs that received 12 cm H(2)O of PEEP died from pneumothoraces; all others survived without pneumothoraces. Oxygenation was significantly improved by 8 and 12 cm H(2)O of PEEP compared with 0 and 4 cm H(2)O of PEEP. Lambs with 0 PEEP did not oxygenate adequately. The compliance of the respiratory system was significantly higher at 4 and 8 cm H(2)O of PEEP than at 0 PEEP. There were no significant differences in partial pressure of carbon dioxide in arterial blood between groups. Arterial pressure was highest with 8 cm H(2)O of PEEP, and there was no cardiorespiratory compromise at any level of PEEP. Applying PEEP during resuscitation of very premature infants might be advantageous and merits further investigation.

Preterm outcomes research: a critical component of neonatal intensive care

While early preterm outcome studies described the lives of preterm survivors to justify the efforts required to save them, subsequent studies demonstrated their increased incidence of cerebral palsy, mental retardation, sensory impairments, minor neuromotor dysfunction, language delays, visual-perceptual disorders, learning disability and behavior problems compared to fullterm controls. Because infants born at the lower limit of viability require the most resources and have the highest incidence of neurodevelopmental disability, there is concern that resources have gone primarily to neonatal intensive care and are not available for meeting the followup, health, educational and emotional needs of these fragile infants and their families. Despite many methodological concerns, preterm outcome studies have provided insight into risk factors for and causes of CNS injury in preterm infants. Nevertheless, it remains difficult to predict neurodevelopmental outcome for individual preterm infants. Perinatal and neonatal risk factors are inadequate proxies for neurodevelopmental disability. Recent randomized controlled trials with one to five year neurodevelopmental followup have provided valuable information about perinatal and neonatal treatments. Recognizing adverse longterm neurodevelopmental effects of pharmacological doses of postnatal steroids is a sobering reminder of the need for longterm neurodevelopmental followup in all neonatal randomized controlled trials. Ongoing longterm preterm neurodevelopmental studies, analysis of changes in outcomes over time and among centers, and evaluation of the longterm safety, efficacy and effectiveness of many perinatal and neonatal management strategies and proposed neuroprotective agents are all necessary for further medical and technological advances in neonatal intensive care.

Use of an oxygen concentrator in a Nigerian neonatal unit: economic implications and reliability

A 3-year experience of using an oxygen concentrator in a Nigerian newborn unit and economic appraisal of its effectiveness is reported. The oxygen concentrator is a device that absorbs nitrogen from ambient air, with a resultant oxygen concentration of 85 to 95% at different flow rates. The oxygen concentrator met our oxygen needs which averaged 18 hours a day, and had a huge cost advantage over the oxygen cylinders. The cost of oxygen via cylinder for just one patient for a year exceeds the initial capital outlay for a concentrator. The Puritan-Bennett oxygen concentrator has a lifespan of at least 7 years and is virtually maintenance-free for the 1st 26,400 hours of use, after which some major components might need replacement. We conclude that in developing countries oxygen concentrators are a more cost-effective, reliable and convenient means of oxygen supply than oxygen cylinders, and recommend their use where there is a high demand for oxygen.

Recent advances in neonatology

This update focuses on recent neonatal research of potential interest to obstetricians. Accurate information on outcomes for infants born at the edges of viability is critical to informing management decisions. New research, population based, gives guidance on short-term survival and long-term neurodevelopmental outcome. Recent research has also highlighted the variation in attitudes to end-of-life decision-making and important influences on this that cross different boundaries. Although research is dominated by issues related to prematurity, some important developments relevant to term infants will be covered. There is accumulating evidence that challenges the traditional approach of using 100% O2 in resuscitation. For infants suffering intrapartum asphyxia there are new approaches to neuroprotection actively being explored. Therapeutic interventions such as extracorporeal membrane oxygenation and inhaled nitric oxide, available for some time, are having their place in neonatal intensive care more clearly defined.