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

Brain injury in the infant: the old, the new, and the uncertain

Although neonatal brain injury occurs most frequently after a perinatal hypoxic-ischemic insult, recently studies have noted that variable causes such as metabolic and reperfusion events can result in, or aggravate, a brain insult. Current data suggest that about 2 to 5 of 1,000 live births in the United States and more so in developing countries experience a brain injury Approximately 20% to 40% of infants who survive the brain injury develop significant neurological and developmental impairments. The resulting impact on the child, family, and society presents a formidable challenge to health care professionals. Although several important insights have been gained in the last several years about the epidemiology, diagnosis, and mechanism of brain injury, management remains mostly a cocktail of controversial trials. This article provides a comprehensive review of the pathology, clinical manifestations, and timely management of infants with brain injury.

A survey of delivery room resuscitation practices in the United States

OBJECTIVE

To determine current resuscitation practices of neonatologists in the United States.

METHODS

A 15-question survey was developed and mailed to neonatal directors in May 2004.

RESULTS

Of the total of 797 surveys mailed, 84 were returned undeliverable or unanswered and 450 were returned completed (63% response rate). Respondents were mainly (70%) from level III NICUs. Most programs resuscitate newborns in the delivery room (83%), rather than in a separate room. The number and background of individuals attending deliveries vary greatly, with 31% of programs having <3 individuals attending deliveries. Flow-inflating bags are most commonly used (51%), followed by self-inflating bags (40%) and T-piece resuscitators (14%). Pulse oximeters are used during resuscitation by 52% of programs, and 23% of respondents indicated that there was a useful signal within 1 minute after application. Blenders are available for 42% of programs, of which 77% use pure oxygen for the initial resuscitation and 68% use oximeters to alter the fraction of inspired oxygen. Thirty-two percent of programs use carbon dioxide detectors to confirm intubation, 48% routinely and 43% when there is difficulty confirming intubation. Preterm infants are wrapped with plastic wrap to prevent heat loss in 29% of programs, of which 77% dry the infant before wrap application. A majority of programs (76%) attempt to provide continuous positive airway pressure or positive end expiratory pressure (PEEP) during resuscitation, most commonly with a flow-inflating bag (58%), followed by a self-inflating bag with PEEP valve (19%) and T-piece resuscitator (16%). A level of 5 cm H2O is used by 55% of programs.

CONCLUSIONS

Substantial variations exist in neonatal resuscitation practices, some of which are not addressed in standard guidelines. Future guidelines should include recommendations regarding the use of blenders, oximeters, continuous positive airway pressure/PEEP, and plastic wrap during resuscitation.

Delivery room and early postnatal management of neonates who have prenatally diagnosed congenital heart disease

Advances in fetal echocardiography are providing highly accurate diagnoses of congenital heart disease prior to delivery, making it possible to plan the delivery-room management of these newborns. Knowledge of the expected transitional circulation occurring with birth and the pathophysiologic implications of congenital heart disease increases the likelihood of providing efficient and effective therapies. The majority of neonates who have congenital heart disease will not require delivery room resuscitation in excess of routine care; however, a small number of prenatally diagnosed cardiac lesions are more likely to require urgent postnatal intervention immediately following delivery. These cardiac lesions include transposition of the great arteries with intact ventricular septum and restrictive atrial septum, hypoplastic left heart syndrome with intact atrial septum, obstructed total anomalous pulmonary venous return, and complete congenital heart block. Prenatal diagnosis allows for coordination of care surrounding delivery and during the early postnatal hours.

Reoxygenation of hypoxic mice with 100% oxygen induces brain nuclear factor-kappa B

Oxidative stress is closely related to inflammation, a pathologic process characterized by activation of the transcriptional factor nuclear factor-kappa B (NF-kappaB). We have used transgenic NF-kappaB luciferase reporter mice to assess brain NF-kappaB activity noninvasively in living mice. We have studied NF-kappaB activation in hypoxic mice reoxygenated with either 21% O2 (room air) or 100% O2. Forty-one mice exposed for 2 h to 4% oxygen and then randomized to reoxygenation with pure oxygen or room air were investigated. A control mouse was dedicated to every mouse exposed to hypoxia. In vivo luminescence originated from brain was measured from mice 2 d before hypoxia, and 3 h after reoxygenation. A change in luminescence between the mouse exposed to hypoxia and its control demonstrates an alteration in NF-kappaB activity. Because of high mortality among males, only females were included. Six female mice died. Nineteen female mice were reoxygenated with room air, 16 with pure oxygen. We observed a significantly higher luminescence in the brain of the 100% O2 group versus the 21% O2 group. Our data indicate that brain NF-kappaB activity is increased in mice subjected to 4% oxygen followed by reoxygenation with 100% oxygen. However, when reoxygenation occurs with 21% O2 (room air), no elevation in NF-kappaB activity is observed. Thus, reoxygenation with room air may induce less brain inflammation than reoxygenation with pure oxygen.

Feasibility of and delay in obtaining pulse oximetry during neonatal resuscitation

Application of the sensor to newly born infants before connection to a pulse oximeter increases the reliability and speed with which data are displayed. Data are available in most infants within 90 seconds of birth. Oximetry may be useful in guiding interventions during resuscitation.

Hyperoxia with 100% Oxygen following Hypoxia-Ischemia Increases Brain Damage in Newborn Rats

OBJECTIVE

To describe the effect of reoxygenation with 100% O2 as compared to the effect of room air in newborn rat brains after asphyxia.

METHODS

Experimental asphyxia (carotid artery ligation followed by hypoxic exposure with 8% O2 for 2 h) was performed on 7-day-old rats. After hypoxia-ischemia the rats were reoxygenated with either 100% O2 (hyperoxia group) or 21% O2 (room air group) for 24 h and then returned to the dam. The rats were killed 1 week after the experiment to study the cerebral cortex and hippocampus.

RESULTS

Rats reoxygenated with 100% O2 post-asphyxia showed more frequency of cortical damage (10 of 24 rats) than those reoxy genated with room air (3 of 24 rats) (chi2 test, p = 0.02).

CONCLUSION

We consider that hyperoxia with 100% oxygen after hypoxia-ischemia can cause more damage in the cerebral cortex than room air in newborn rats.

Use of supplementary equipment for resuscitation of newborn infants at tertiary perinatal centres in Australia and New Zealand

AIM

Neonatal resuscitation is a common and important intervention. International consensus statements advise how newborns should be resuscitated and suggest equipment to be used. Use of equipment not specifically recommended in these guidelines has been advocated. We wished to determine how widely this supplementary equipment is used in a geographically defined region.

METHODS

Each of the 25 tertiary perinatal centres with on-site deliveries in Australia and New Zealand was surveyed. The questionnaire asked about the use of the following items during delivery room resuscitation: pulse oximetry, exhaled carbon dioxide detection, polyethylene wrapping, oxygen blenders, laryngeal mask and oropharyngeal airways.

RESULTS

Data were obtained from all centres. Pulse oximetry is used at 12 (48%) centres. Exhaled CO2 detection is used to confirm endotracheal tube placement at three (12%) of the centres. Polyethylene wrapping is used to prevent heat loss in very-low-birthweight infants at delivery at 11 (44%) centres. Oxygen blenders are used to modify the amount of oxygen delivered at nine (36%) centres. Laryngeal mask airways are infrequently used at two (8%) centres. Oropharyngeal airways are infrequently used at five (20%) centres.

CONCLUSION

There is considerable variation in the equipment and techniques used to resuscitate newly born infants. Use of equipment not specifically recommended in international consensus statements is widespread. These are potentially effective tools to improve resuscitation. The evidence supporting their use is, however, limited. Urgent evaluation of their efficacy and safety is required before even more widespread use occurs.

Resuscitation of hypoxic piglets with 100% O2 increases pulmonary metalloproteinases and IL-8

We hypothesized that resuscitation with 100% O2 compared with 21% O2 is detrimental to pulmonary tissue. The pulmonary injury was assessed by matrix metalloproteinase (MMP) activity, oxidative stress, IL-8, and histology 2.5 h after resuscitation from a hypoxic state. In pulmonary tissue extracts, MMP activity was analyzed by broad matrix-degrading capacity (total MMP) and zymography. MMP-2 mRNA expression was evaluated by quantitative real-time PCR. Total endogenous antioxidant capacity was measured by the oxygen radical absorbance capacity (ORAC) assay, and IL-8 was analyzed by ELISA technique. In bronchoalveolar lavage (BAL) fluid, MMPs were analyzed by zymography. In pulmonary tissue, pro- and active MMP-2 levels were increased in piglets that were resuscitated with 100% O2 compared with 21% O2. Pro-MMP-9, total MMP activity, and MMP-2 mRNA levels were significantly increased in resuscitated piglets compared with baseline. Net gelatinolytic activity increased in submucosa and blood vessels after 100% O2 and only in the blood vessels after 21% O2. Compared with baseline, ORAC values were considerably lowered in the resuscitated piglets and significantly reduced in the 100% O2 versus 21% O2 group. In BAL fluid, both pro-MMP-9 and pro-MMP-2 increased 2-fold in the 100% O2 group compared with 21% O2. Moreover, IL-8 concentration increased significantly in piglets that were resuscitated with 100% O2 compared with 21% O2, suggesting a marked proinflammatory response in the pulmonary tissue. Altogether, these data strongly suggest that caution must be taken when applying pure O2 to the newborn infant.

Room-air resuscitation causes less damage to heart and kidney than 100% oxygen

RATIONALE

Pure oxygen causes more oxidative stress than room air in resuscitation of asphyctic neonates, and consequently could be associated with increased tissue damage.

OBJECTIVES

To compare damage caused to heart and kidneys on reoxygenation in severely asphyctic term neonates resuscitated with room air (RAR) or 100% oxygen (OxR). Nonasphyctic term newborn infants served as a control group.

METHODS AND MEASUREMENTS

This is a prospective randomized clinical trial masked for the gas mixture. Reduced glutathione (GSH), oxidized glutathione (GSSG), and superoxide dismutase (SOD) activity were measured to assess oxidative stress. Plasma cardiac troponin T (cTnT) and urinary N-acetyl-glucosaminidase (NAG) assessed cardiac and renal damage, respectively. Daily determinations of NAG for a 2-wk period were performed to monitor postasphyctic renal damage.

MAIN RESULTS

Both asphyctic groups showed oxidative stress when compared with the control group as evidenced by diminished GSH/GSSG ratios, adaptive increases in SOD activity, and higher values of NAG and cTnT (markers of tissue damage). However, the OxR group showed significantly higher values of NAG and cTnT, lower GSH/GSSG ratios, and higher SOD activity than the RAR group. Moreover, NAG values persisted in being higher than normal in the OxR group for 2 wk after birth, whereas NAG in the RAR group dropped to normal within the first week. A linear correlation between cTnT or NAG and GSSG was found.

CONCLUSIONS

The use of room air on resuscitation causes less oxidative stress and damage to heart and kidney than pure oxygen.

Focus on neonatal resuscitation--NOW

The paper by Saugstad et al. in this issue of Acta Paediatrica presents new and provocative data on the development of the child's physiological status during the first minutes of life. The data were extracted from the database of the Resair 2 study designed to investigate the outcome of resuscitation with air or 100% oxygen. The potential of these variables to predict the outcome of asphyxiated infants was evaluated.

CONCLUSION

The data--in spite of some technical limitations and lack of representative reference measurements--point out the potential value of sequential physiological observations in the early identification of newborn infants at risk of poor outcome, challenge the routine habit of giving ample oxygen to depressed neonates, and call for further studies.

Response to resuscitation of the newborn: early prognostic variables

AIM

To characterize the development of clinically relevant variables the first minutes after birth and identify early prognostic markers in newborn infants requiring resuscitation.

METHODS

A database of 591 infants resuscitated with either 21% or 100% oxygen was analysed. Time to first breath, development in heart rate, Apgar scores, arterial oxygen saturation (SaO(2)), and base deficit (BD) are described in relation to different degrees of birth depression and outcomes.

RESULTS

Heart rate and Apgar scores increased quickly even in the most depressed infants but were significantly lower in those having a poor outcome. By contrast, BD normalized at the same rate, 6-7 mmol/l/h, in the first hour of life regardless of the degree of birth depression and outcome. SaO(2) values increased as quickly in room air as in 100%-oxygen-resuscitated infants. Time to first breath was prolonged threefold, from 1 to 3 min, in the most depressed (1-min Apgar score < 4) compared with the less depressed infants. Highest odds ratio (OR) for death in the first week of life or for development of hypoxic-ischaemic encephalopathy (HIE) stage 2 and 3 was a 5-min heart rate < or =60 bpm (OR 16.5 for both death and HIE) and Apgar < 4 (OR 14 and 18.8). Neonatal survival for HIE stage 1, 2, and 3 was 93%, 63%, and 11%, respectively. OR for early neonatal death, if SaO(2) < or =60% at 1 min, was 8.6 (sensitivity 0.82 and specificity 0.65).

CONCLUSION

Apgar scores, heart rate, SaO(2), and time to first breath in newly born infants in need of resuscitation may be used for early identification of infants with a poor prognosis. These data may be helpful in describing the severity of depression in single infants and to select infants in need of interventional therapy.

Oxygen for newborns: how much is too much?

International guidelines for newborn resuscitation recommend the use of 100% oxygen. However, high concentrations of oxygen after asphyxiation activate reactive oxygen species that may contribute to a number of morbidities. Animal models have been useful in describing their mechanisms, but only large-scale clinical trials can provide evidence that may be used to alter clinical practice. It has been demonstrated that neonates recover faster when resuscitated with room air as opposed to pure oxygen and neonatal mortality rates are improved. Increases in saturation are equal with oxygen and room air resuscitation. Studies of normal oxygen saturation immediately after birth suggest that clinicians may unnecessarily be rushing to high saturations. In the first weeks of life, lower saturation targets in preterm infants reduce retinopathy of prematurity and pulmonary complications and may improve growth. The neonatologist would be well served to think of oxygen as a medication, and use it sparingly.

Restoration of cardiopulmonary function with 21% versus 100% oxygen after hypoxaemia in newborn pigs

OBJECTIVE

To assess the consequences of hypoxaemia and resuscitation with room air versus 100% O(2) on cardiac troponin I (cTnI), cardiac output (CO), and pulmonary artery pressure (PAP) in newborn pigs.

DESIGN

Twenty anaesthetised pigs (12-36 hours; 1.7-2.7 kg) were subjected to hypoxaemia by ventilation with 8% O(2). When mean arterial blood pressure fell to 15 mm Hg, or arterial base excess was < or = -20 mmol/l, resuscitation was performed with 21% (n = 10) or 100% (n = 10) O(2) for 30 minutes, then ventilation with 21% O(2) for 120 minutes. Blood was analysed for cTnI. Ultrasound examinations of CO and PAP (estimated from tricuspid regurgitation velocity (TR-Vmax)) were performed at baseline, during hypoxia, and at the start of and during reoxygenation.

RESULTS

cTnI increased from baseline to the end point (p<0.001), confirming a serious myocardial injury, with no differences between the 21% and 100% O(2) group (p = 0.12). TR-Vmax increased during the insult and returned towards baseline values during reoxygenation, with no differences between the groups (p = 0.11) or between cTnI concentrations (p = 0.31). An inverse relation was found between increasing age and TR-Vmax during hypoxaemia (p = 0.034). CO per kg body weight increased during the early phase of hypoxaemia (p<0.001), then decreased. Changes in CO per kg were mainly due to changes in heart rate, with no differences between the groups during reoxygenation (p = 0.298).

CONCLUSION

Hypoxaemia affects the myocardium and PAP. During this limited period of observation, reoxygenation with 100% O(2) showed no benefits compared with 21% O(2) in normalising myocardial function and PAP. The important issue may be resuscitation and reoxygenation without hyperoxygenation.

Air versus oxygen for resuscitation of infants at birth

BACKGROUND

100% oxygen is the commonly recommended gas for the resuscitation of infants at birth. There is growing evidence from both animal and human studies that room air is as effective as 100% oxygen and that 100% oxygen may have adverse effects on breathing physiology and cerebral circulation. There is also the theoretical risk of tissue damage due to free oxygen radicals when 100% oxygen is given. The use of room air has, therefore, been suggested as a safer and possibly more effective alternative.

OBJECTIVES

In newborn infants requiring resuscitation, does the use of room air reduce the incidence of death, neurological disability and short term morbidity when compared with the use of 100% oxygen?

SEARCH STRATEGY

This included searches of the Oxford Database of Perinatal Trials, Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 1, 2004) and MEDLINE PubMed 1966 to December 2003, and handsearches of reference lists of relevant articles and conference proceedings.

SELECTION CRITERIA

All randomised and quasi-randomised studies comparing the use of room air or any other concentration of oxygen versus 100% oxygen in the resuscitation of infants at birth.

DATA COLLECTION AND ANALYSIS

Three authors assessed the methodological quality of eligible trials and extracted data independently. When appropriate, meta-analysis was conducted to provide a pooled estimate of effect. For categorical data the relative risk (RR), risk difference (RD) and number needed to treat (NNT) with 95% confidence intervals (CI) were calculated. Continuous data were analysed using weighted mean difference (WMD).

MAIN RESULTS

Five studies were identified which enrolled a total of 1302 infants. In two studies allocation was randomised and the caregivers were blinded to intervention group. In the other three studies, allocation was quasi-randomised and the caregivers were not blinded. Pooled analysis of the four trials reporting effect on death showed a significant reduction in the rate of death in the group resuscitated with room air [typical RR 0.71 (0.54, 0.94), typical RD -0.05 (-0.08, -0.01), NNT 20 (12, 100)]. There were no significant differences between the groups with respect to rates of grade 2 or 3 hypoxic ischaemic encephalopathy. One of the four trials reported a statistically significant difference in median 5 minute Apgar scores, favouring the group allocated to room air. However, the absolute difference between the medians was small and there were no significant differences in the median 10 minute Apgar scores in the three trials reporting this outcome. One trial followed up a selected subgroup of survivors to 18-24 months. There were no significant differences in rates of adverse neurodevelopmental outcomes including cerebral palsy and failure to achieve various milestones; however, the proportion of eligible patients seen was less than 70%. Analyses that were planned for this review, but not able to be carried out because of lack of published data, included a sub-analysis stratified by gestational age and assessments of the effect on bronchopulmonary dysplasia and retinopathy of prematurity.

AUTHORS' CONCLUSIONS

There is insufficient evidence at present on which to recommend a policy of using room air over 100% oxygen, or vice versa, for newborn resuscitation. A reduction in mortality has been seen in infants resuscitated with room air, and no evidence of harm has been demonstrated. However, the small number of identified studies and their methodologic limitations dictate caution in interpreting and applying these results. We note the use of back-up 100% oxygen in more than a quarter of infants randomised to room air. Therefore, on the basis of currently available evidence, if one chooses room air as the initial gas for resuscitation, supplementary oxygen should continue to be made available.

[Air or oxygen for neonatal resuscitation in the delivery room?]

Most of the contemporary guidelines on newborn resuscitation are based on experience but lack scientific evidence. The use of 100% oxygen is one of the more evident. Today, these practices are questioned, particularly for the resuscitation of moderately depressed full term or near term newborns. Results of recent meta-analysis of trials that compared ventilation with air versus pure oxygen at birth suggests current practices should be revisited. On the basis of these data, air can be the initial gas to use for these babies. Large scale trials, including preterm and cause and/or severity of initial asphyxia, must now be undertaken before the publication of new guidelines for these populations. Particularly severely asphyxiated infants might require supplemental oxygen with titration of oxygen delivery and continuous monitoring of oxygen saturation.

Air or 100% oxygen for asphyxiated babies? Time to decide

Both experimental and clinical studies have demonstrated that room air is as efficient as 100% oxygen for newborn resuscitation and improves short-term recovery. The recent meta-analysis by Davis and colleagues in the Lancet includes five studies from the past 10 years where asphyxiated infants were randomised or pseudo-randomised to be resuscitated in room air or in 100% oxygen. A significant reduction in mortality was seen when infants were resuscitated in room air compared to 100% oxygen. It is astonishing that a brief exposure of only a few minutes to 100% oxygen may be so toxic to the newborn infant; this finding, however, is supported by increasing evidence from experimental work emphasising that resuscitation in 100% oxygen may be associated with an aggravation of cellular injury when compared with resuscitation in air. It is imperative that these findings are reflected in the new newborn resuscitation guidelines and that further research continues in this area of neonatal medicine. Key areas include defining the best resuscitation practice for the preterm infant, designing adequate multicentre, randomised and blinded studies of term newborn resuscitation with adequate outcome data, and pursuing intense experimental research into the mechanisms and prevention of injury from oxygen free radicals.

Management of infants with bronchopulmonary dysplasia in Germany

Although official guidelines for diagnosis and treatment of bronchopulmonary dysplasia (BPD) exist in Germany the practice in tertiary care neonatology centres differs considerably. There is no consensus about the appropriate level of oxygen saturation for infants at risk for BPD or infants with established BPD. Targeting oxygen saturation just below 90% in the first weeks and in the lower nineties thereafter seems to be a reasonable approach. Systemic corticosteroids must be used very restrictively because of adverse short- and long-term outcomes. Diuretics, inhaled corticosteroids, and bronchodilators may be used based on a stringent assessment of the individual response; their routine use cannot be recommended. Domiciliary oxygen is a therapy rarely prescribed in Germany although, if carefully planned and organised, it is safe and effective. Infants with home oxygen need a close follow-up by neonatologists and other specialists. Routine vaccination is recommended from the postnatal age of 3 months onwards.

Room air resuscitation-two decades of neonatal research

Experimental as well as clinical studies have demonstrated that room air is as efficient as pure oxygen for newborn resuscitation. Recent data even indicate that outcome is improved if pure oxygen is avoided. Thus, in a meta-analysis, neonatal mortality was significantly lower in those newly born infants resuscitated with 21% than with 100% oxygen. Short-term recovery is also improved in the room air group since time to first breath is shorter, heart rate at 90 s and 5 min Apgar score are higher. Animal data indicate that injury in a number of organs, including the brain, is aggravated by giving pure oxygen to newly born depressed infants even for a brief period. Although the optimal oxygen concentration probably is not known for newborn infants in need of resuscitation, pure oxygen should be avoided. These data should be reflected in new guidelines that are under way.