Oxygen Resuscitation Research Articles

Cortical 5HT2A Receptor Function under Hypoxia in Neonatal Rats: Role of Glucose, Oxygen, and Epinephrine Resuscitation

Neonatal hypoxia induces brain injury through alterations in neurotransmitters and its receptors. Molecular processes regulating serotonergic receptors play an important role in the control of respiration under hypoxia. The present study evaluates the serotonergic regulation of neonatal hypoxia and its resuscitation methods. Receptor binding assays and gene expression studies were done to evaluate the changes in 5HT(2A) receptors and its transporter in the cerebral cortex of hypoxic neonatal rats and hypoxic rats resuscitated with glucose, oxygen, and epinephrine. Hypoxic stress increased total 5HT and 5HT(2A) receptor number along with an upregulation of 5HT(2A) receptor and 5HT transporter gene in the cortex. The enhanced cortical 5HT(2A) receptors may act as a modulator of ventilatory response to hypoxia. These alterations were reversed to near control by glucose supplementation. Glucose supplementation helped in managing the serotonergic functional alterations. Hypoxia-induced adenosine triphosphate depletion causes a reduction in blood glucose levels which can be encountered by glucose administration, and oxygenation helps in overcoming the anaerobic condition. The adverse effect of immediate oxygenation and epinephrine supplementation was also reported. This has immense clinical significance in establishing a proper resuscitation for the management of neonatal hypoxia.

Titrating Oxygen During and After Cardiopulmonary Resuscitation

SEVERAL INVESTIGATIONS HAVE REKINDLED IMPORtant concern that administration of 100% oxygen during and early after resuscitation from experimental cardiopulmonary arrest might be deleterious to the brain. In a canine model of ventricular fibrillation cardiopulmonary arrest, use of 100% oxygen compared with use of room air early during resuscitation was associated with increased neuronal death in selectively vulnerable brain regions and worse neurological outcome. Several studies have focused on oxidative injury to key mitochondrial enzymes (such as pyruvate dehydrogenase or manganese superoxide dismutase) or mitochondrial lipids (such as cardiolipin) in mediating these deleterious effects. Concern about the use of 100% oxygen in resuscitation is not new. In neonatal resuscitation, detrimental effects of 100% oxygen have been described in case reports and randomized controlled trials. However, infants have compromised antioxidant defenses and age-related differences in endogenous defenses against hypoxemia, including fetal hemoglobin, among others. Thus, the potential risk of 100% oxygen and the potential benefit of room air may be greatly magnified in neonates compared with adults. In this issue of JAMA, Kilgannon et al report the results of an important multicenter cohort study generated from a critical care database of intensive care units (ICUs) in 120 US hospitals. The authors studied 6326 adults with nontraumatic cardiopulmonary arrest and analyzed the relationship between in-hospital mortality and hypoxia (PaO2 60 mm Hg), normoxia (PaO2 300 mm Hg), or hyperoxia (PaO2 300 mm Hg) as assessed on the first ICU arterial blood gas. Hyperoxia was associated with a significantly increased mortality rate compared with normoxia (proportion difference, 18%; 95% confidence interval [CI], 14%-22%). Moreover, the hyperoxia group showed increased mortality vs the hypoxia group (proportion difference, 6%; 95% CI, 3%-9%). In a model controlling for a predefined set of confounders, hyperoxia exposure had an odds ratio for death of 1.8 (95% CI, 1.5-2.2). In this study, 18% of the patients had hyperoxia based on the first arterial blood gas determination in the ICU. Given the rather conservative definition of hyperoxia (PaO2 300 mm Hg), the true incidence of more moderate levels of hyperoxia is likely to be quite high. Even though mechanisms producing secondary deleterious effects after cardiac arrest can be successfully manipulated (as evidenced by the use of induction of mild hypothermia), this finding underscores the possibility that further meaningful improvements in outcome might result from careful attention to appropriately titrating basic aspects of extracerebral physiology at the bedside, such as prevention of hyperoxia. The authors acknowledge the limitations of this observational study. For instance, it would have been informative to have provided an assessment of the temporal relationship of hyperoxia with outcomes because experimental work suggests the possibility that early hyperoxia rather than delayed postresuscitation hyperoxia is deleterious to the brain. The first PaO2 value in this study was obtained within 24 hours of ICU arrival, precluding assessment of the temporal effects of hyperoxia. Moreover, cause of death and neurological outcome were both lacking in the database, limiting any inferences regarding the contribution of cerebral vs extracerebral effects to the reported findings. The authors suggest putative deleterious effects of hyperoxia on pulmonary function, but (based on experimental data) tissue hyperoxia early postreperfusion also could adversely affect other organ systems. This study also showed an association between hypoxia and mortality after cardiopulmonary arrest. Many underlying pathologies that may require high levels of fraction of inspired oxygen to achieve normal arterial saturation can either cause or represent comorbidities in adults with cardiopulmonary arrest, such as drowning or pulmonary embolism. This complicates the ability to make sweeping recommendations against the use of 100% oxygen early in resuscitation. Similarly, it is not clear that arterial hyperoxia necessarily results in brain tissue hyperoxia. As

Use of Oxygen for Resuscitation of the Extremely Low Birth Weight Infant

The practice of mouth-to-mouth resuscitation was the first natural experiment using hypoxic gas mixtures for resuscitation. Although supplemental oxygen is now the standard during neonatal resuscitation, this practice has never been validated in prospective controlled trials. Neonatal resuscitation is primarily directed toward establishing early lung aeration and maintaining lung volume during expiration to overcome the initial vagal and hypoxic bradycardia. It remains unclear whether supplemental oxygen facilitates this process or contributes to potential hypoxia/reoxygenation injury, inhibition of breathing, and possible aggravation of atelectasis by the attenuation of nitrogen splinting. Accumulating evidence over the last decade has challenged clinicians to reconsider the optimal oxygen concentration for resuscitation of the newborn term infant. A critical review of 6 randomized trials that compared the use of room air (RA) and 100% oxygen reported that RA was associated with a significant lowering of mortality rate from 13% to 8% ( P = .0021), with a typical odds ratio (OR) of 0.57 (95% confidence interval [CI]: 0.42–0.78); however, no difference was observed for infants with a 1-minute Apgar score of <4 (typical OR: 0.81 [95% CI: 0.54–1.21]).1 In most of these trials, up to 30% of the infants in the RA group met prespecified failure criteria and received additional oxygen. However, a similar proportion of the oxygen-resuscitated infants also met the failure criteria. In term infants, the neonatal mortality rate was 5.9% in the RA group and 9.8% in the 100% O2 group (typical OR: 0.59 [95% CI: 0.40–0.870]). These results are similar to those reported in the Cochrane review by Tan et al.2 Subgroup analysis confined to preterm infants (all > 1000gm) revealed a greater reduction in mortality rate in the RA group, from 35% in the 100% O2 group to 21% in the RA group (typical OR: 0.51 [95% CI: … Address correspondence to Neil Finer, MD, UCSD Medical Center, 402 W Dickinson St, MPF Building, Suite 1-140, San Diego, CA 92103-8774. E-mail: nfiner{at}ucsd.edu

Impact of docosahexaenoic acid on oxidation in newborn rats with high oxygen resuscitation

Objective To evaluate the impact of docosahexaenoic acid (DHA) on the level of oxidative and ant+oxidative factors in newborn rats with high oxygen resuscitation. Methods Pregnant rats were divided randomly into regular diet group and DHA supplement group (DHA 100 mg/d, Qd, administrated through gavage). Within 24 h after birth, the newborn rats were given low concentration oxygen (8%) for 2 h. Then, the newborn rats were divided into groups exposed to 100% O2 or room air. There were 4 groups: regular diet + hyperoxia-exposed group, regular diet + room air group, DHA + hyperoxia-exposed group and DHA+room air group. The activities of superoxide dismutase (SOD), maleic dialdehyde (MDA) and glutathione peroxidase (GSH-Px) in newborn rats exposed to high oxygen or room air for 1 d, 3 d, 7 d and at the time of immediately after asphyxia were measured by spectrophotometry. Results At day 1,3 and 7, SOD activities in newborn rats of DHA+ hyperoxia-exposed group were (93. 7± 16.8) U/ml, (128.2±11.5) U/ml and (170.9±9.0) U/ml, higher than those in DHA+room air group [(73.7± 21.5) U/mt, (112.2±19. 9) U/ml and (124.2±24. 6) U/ml, respectively] (P 0. 05). Conclusions Dietary DHA during pregnancy and breast feeding period might protect newborn rats against hyperoxic damage by increasing antioxidase level and decreasing peroxide level when exposed to high oxygen. Key words: Docosahexaenoic acids; Hyperoxia; Asphyxia; Animals, newborn

Normobaric hyperoximia increases hypoxia‐induced cerebral injury: DTI study in rats

Perinatal hypoxia affects normal neurological development and can lead to motor, behavioral and cognitive deficits. A common acute treatment for perinatal hypoxia is oxygen resuscitation (hyperoximia), a controversial treatment. Magnetic resonance imaging (MRI), including diffusion tensor imaging (DTI), was performed in a P7 rat model of perinatal hypoxia to determine the effect of hyperoximia. These studies were performed on two groups of animals: 1) animals which were subjected to ischemia followed by hypoxia (HI), and 2) HI followed by hyperoximic treatment (HHI). Lesion volumes on high resolution MRI and DTI derived measures, fractional anisotropy (FA), mean diffusivity (MD), and axial and radial diffusivities (lambda(l) and lambda(t), respectively) were measured in vivo one day, one week, and three weeks after injury. Most significant differences in the MRI and DTI measures were found at three weeks after injury. Specifically, three weeks after HHI injury resulted in significantly larger hyperintense lesion volumes (95.26 +/- 50.42 mm(3)) compared to HI (22.25 +/- 17.62 mm(3)). The radial diffusivity lambda(t) of the genu of corpus callosum was significantly larger in HHI (681 +/- 330 x 10(-6) mm(2)/sec) than in HI (486 +/- 96 x 10(-6) mm(2)/sec). Over all, most significant differences in all the DTI metrics (FA, MD, lambda(t), lambda(l)) at all time points were found in the corpus callosum. Our results suggest that treatment of perinatal hypoxia with normobaric oxygen does not ameliorate, but exacerbates damage.

Neonatal outcomes associated with planned vaginal versus planned primary cesarean delivery

To determine whether planned route of delivery leads to differences in neonatal morbidity. Analysis was based on planned route of delivery, not actual route of delivery. A total of 4048 subjects were divided into two groups: planned vaginal delivery and planned cesarean delivery. Primary outcomes were neonatal intensive care unit (NICU) admission, respiratory morbidity and neurologic morbidity. There were 3868 planned vaginal and 180 planned cesarean deliveries. Planned vaginal delivery had decreased NICU admission (P<0.0001), oxygen resuscitation (P=0.001) and jaundice (P<0.0001) but increased meconium passage (P<0.0001) and 1 min Apgar <or=5 (P=0.02). After multivariable regression, NICU admission remained lower and meconium passage remained higher in the planned vaginal group. Planned vaginal delivery led to more meconium passage and low 1 min Apgar but less NICU admissions, oxygen resuscitation and jaundice. Multicenter trials are needed to assess rare but serious outcomes based on planned route of delivery.

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

Oxygen was discovered more than 200 years ago and was thought to be both essential and beneficial for all animal life. Although it is now over 100 years since oxygen was first shown to damage biological tissues exposed to high concentrations, and more than 50 years since it was implicated in the aetiology of retinopathy of prematurity, the use of 100% oxygen was still recommended for the resuscitation of all babies at birth as recently as 2000. However, the 2005 International Liaison Committee on Resuscitation (ILCOR) recommendations allow for the initiation of resuscitation with concentrations of oxygen between 21 and 100%. There are strong arguments in favour of a radical curtailment of the use of oxygen in resuscitation at birth, and for devoting resources to defining the margins of safety for its use in the neonatal period in general.

Resuscitation with 100%, compared with 21%, oxygen following brief, repeated periods of apnea can protect vulnerable neonatal brain regions from apoptotic injury

To determine the effect of repeated intermittent apnea and resuscitation with 100% vs. 21% oxygen enriched gas on levels of key regulatory proteins contributing to cell death (Bax, Caspase-3) or protecting neurons from hypoxic/ischemic injury (Bcl-2, p-Akt, p-CREB). The anaesthetized, mechanically ventilated newborn piglets underwent 10 episodes of apnea with resuscitation either with 100% or with 21% oxygen. Following 6h recovery the animals were sacrificed painlessly, the brain dissected out and used to determine levels of Bcl-2, Bax, Caspase-3, p-Akt and p-CREB in the striatum, frontal cortex, midbrain and hippocampus were studied. In hippocampus and striatum, Bcl-2 expression was higher with 100% vs. 21% group (173+/-29% vs. 121+/-31%, p<0.05 and 189+/-10% vs. 117+/-47%, p<0.01, respectively) whereas the Bax expression was lower (88+/-3% vs. 100+/-9%, p<0.05 and 117+/-5% vs. 133+/-10%, p<0.05, respectively). Expression of Caspase-3 in the striatum, was lower with 100% vs. 21% group (197+/-35% vs. 263+/-33%, p<0.05, respectively) but not different in the hippocampus. p-Akt expression was higher with 100% vs. 21% oxygen in the hippocampus and striatum (225+/-44% vs. 108+/-35%, p<0.01 and 215+/-12% vs. 164+/-16%, p<0.01, respectively). The p-CREB expression was higher with 100% vs. 21% oxygen resuscitation in the hippocampus (217+/-41% vs. 132+/-30%, p<0.01) with no changes in striatum. Much smaller or insignificant differences between 100% vs. 21% oxygen groups were observed in the frontal cortex and midbrain, respectively. In neonatal piglet model of intermittent apnea, selectively vulnerable regions of brain (striatum and hippocampus) are better protected from apoptotic injury when resuscitation was conducted with 100%, rather than 21%, oxygen.

Earlier Apgar Score Increase in Severely Depressed Term Infants Cared for in Swedish Level III Units with 40% Oxygen Versus 100% Oxygen Resuscitation Strategies: A Population-Based Register Study

In 1997, guidelines for Swedish neonatologists attempting to resuscitate markedly depressed term infants were altered to provide for starting resuscitation with 40% oxygen rather than the previously accepted 100% oxygen. Most Swedish hospitals complied with the revised guideline; the few that did not provided an opportunity to compare the two regimens. Four perinatal level III centers provided data from the years 1998 to 2003 on 1223 live-born singleton term infants with birth weights appropriate for gestational age whose 1-minute Apgar score was less than 4. Infants with major malformations were excluded. Two of the centers used 100% oxygen, and two, 40% oxygen for resuscitation. Cesarean section rates were similar in the two treatment groups. Neither nonparametric analysis nor analysis of covariance demonstrated any difference between the treatment strategies for 1- and 10-minute Apgar scores, but the mean 5-minute score was significantly higher for infants breathing 40% oxygen. Adjusting for possible confounding factors did not substantially alter these findings. Apgar scores increased more rapidly in the 40% oxygen group, but there was no difference 10 minutes after birth. A significant association was found between 100% oxygen treatment and a 5-minute Apgar score below 7; the odds ratio was 1.5. No significant differences between the treatment strategies were found in rates of neonatal death, hypoxic ischemic encephalopathy, or seizures. The study findings did not change when infants with meconium aspiration, sepsis, or pneumonia were excluded from analysis. Resuscitating severely depressed term infants with 40% oxygen proved to be as efficient as using pure oxygen in this population-based register study. In addition, Apgar scores recovered more rapidly with 40% oxygen.

Evidence-Based Practices for the Fetal to Newborn Transition

Many common care practices during labor, birth, and the immediate postpartum period impact the fetal to neonatal transition, including medication used during labor, suctioning protocols, strategies to prevent heat loss, umbilical cord clamping, and use of 100% oxygen for resuscitation. Many of the care practices used to assess and manage a newborn immediately after birth have not proven efficacious. No definitive outcomes have been obtained from studies on maternal analgesia effects on the newborn. Although immediate cord clamping is common practice, recent evidence from large randomized, controlled trials suggests that delayed cord clamping may protect the infant against anemia. Skin-to-skin care of the newborn after birth is recommended as the mainstay of newborn thermoregulation and care. Routine suctioning of infants at birth was not been found to be beneficial. Neither amnioinfusion, suctioning of meconium-stained babies after the birth of the head, nor intubation and suctioning of vigorous infants prevents meconium aspiration syndrome. The use of 100% oxygen at birth to resuscitate a newborn causes increased oxidative stress and does not appear to offer benefits over room air. This review of evidence on newborn care practices reveals that more often than not, less intervention is better. The recommendations support a gentle, physiologic birth and family-centered care of the newborn.

The Need to Assess Benefits and Not Just Risks of 100% Oxygen for Newborn Resuscitation

To the Editor.—The commentary “Oxygen for Newborn Resuscitation: How Much Is Enough?” by Saugstad et al1 provides a compendium of what these authors, in particular, have studied and published over the last 15 years. To their credit, they have diligently brought scientific examination to what has been the long-standing but unjustified practice of delivering 100% oxygen to asphyxiated newborns. Although I have a few concerns about their interpretation of the risk side of the risk/benefit equation, of greater concern is the absence of any information in their article about potential benefits. This makes it difficult to fully and fairly assess the practice.The first piece of negative evidence cited by the authors is the reduction in neonatal mortality in room-air–resuscitated infants.2 The vast majority of subjects in the studies included in the meta-analysis were from countries with significantly higher neonatal mortality rates. This would mean that the number needed to treat to demonstrate an equal reduction in the mortality rate would be much higher in countries with lower baseline mortality. Next, the effects of oxygen resuscitation on markers of oxidative stress and on biochemical markers of heart and kidney injury,3 although provocative, do not correlate with short-term or long-term effects on organ function or other morbidities. Regarding the delay in response to resuscitative efforts in the hyperoxia-exposed infants,1,4 Kattwinkel5 pointed out that this may be an innocent byproduct of the therapy in which hyperoxia suppressed the infant's own drive.The link between childhood cancer and oxygen exposure was demonstrated by a case-control study from Sweden.6 Retrospective analysis of the participants in the Collaborative Perinatal Project from 1959 to 1966 also showed a significant but small increased risk for childhood cancers after the first year of life if oxygen duration was >3 minutes, after adjustment for low 5-minute Apgar scores, an association the investigators themselves called “weak” and “ambiguous.”7 In addition, there was a narrow window for oxygen exposure as a risk, >3 minutes but not, according to the Swedish study, after more prolonged postnatal oxygen therapy. Generally, findings from case-control studies and retrospective analyses of old databases can demonstrate association, but they are not as strong at defining a causal relationship.Even without those caveats, to decide if these risks outweigh the benefits, one has to examine the other side of the equation, and that is what is missing from the Saugstad et al commentary. None of the referenced studies specifically addressed developmental outcome. The most extensive follow-up study examined a little over 40% of the original cohort and, with only 213 subjects, was not large enough to determine if oxygen provides any long-term benefit to asphyxiated infants and, if so, to what degree.8 If the purpose of using oxygen (at any fraction of inspired oxygen >0.21) at delivery is to prevent significant hypoxic brain injury, then information on the developmental follow-up of subjects from randomized, blinded clinical trails is necessary. Only with that kind of data can we properly assess the risks documented in the commentary within the complete scientific context.

Earlier Apgar Score Increase in Severely Depressed Term Infants Cared for in Swedish Level III Units With 40% Oxygen Versus 100% Oxygen Resuscitation Strategies: A Population-Based Register Study

The aim of this study was to evaluate whether a resuscitation strategy based on administration of 40% oxygen influences mortality rates and rates of improvement in 5-minute Apgar scores, compared with a strategy based on 100% oxygen administration. A population-based study evaluated data from 4 Swedish perinatal level III centers during the period of 1998 to 2003. During this period, the centers used either of 2 resuscitation strategies (initial oxygen administration of 40% or 100%). Live-born, singleton, term infants with 1-minute Apgar scores of <4, with a birth weight appropriate for gestational age, and without major malformations were included in the study (n = 1223). Infants born in hospitals using a 40% oxygen strategy had a more rapid Apgar score increase than did infants born in hospitals using a 100% oxygen strategy; however, no difference remained at 10 minutes. The mean Apgar score increased from 2.01 at 1 minute to 6.74 at 5 minutes in the 2 hospitals initiating resuscitation with 40% oxygen, compared with 2.01 to 6.38 in the 2 hospitals using 100% oxygen, with a mean difference in Apgar score increases of 0.36. At 5 minutes, 44.3% of infants born in the hospitals using 100% oxygen had an Apgar score of <7, compared with 34.0% of infants at the hospitals using 40% oxygen. At 10 minutes, the mean Apgar scores were 8.16 at the hospitals using 40% oxygen and 8.07 at the hospitals using 100% oxygen. There were no significant differences in rates of neonatal death, hypoxic ischemic encephalopathy, or seizures in relation to the 2 oxygen strategies. Severely depressed term infants born in hospitals initiating resuscitation with 40% oxygen had earlier Apgar score recovery than did infants born in hospitals using a 100% oxygen strategy.

Re-interpreting conventional interval estimates taking into account bias and extra-variation

BackgroundThe study design with the smallest bias for causal inference is a perfect randomized clinical trial. Since this design is often not feasible in epidemiologic studies, an important challenge is to model bias properly and take random and systematic variation properly into account. A value for a target parameter might be said to be "incompatible" with the data (under the model used) if the parameter's confidence interval excludes it. However, this "incompatibility" may be due to bias and/or extra-variation.DiscussionWe propose the following way of re-interpreting conventional results. Given a specified focal value for a target parameter (typically the null value, but possibly a non-null value like that representing a twofold risk), the difference between the focal value and the nearest boundary of the confidence interval for the parameter is calculated. This represents the maximum correction of the interval boundary, for bias and extra-variation, that would still leave the focal value outside the interval, so that the focal value remained "incompatible" with the data. We describe a short example application concerning a meta analysis of air versus pure oxygen resuscitation treatment in newborn infants. Some general guidelines are provided for how to assess the probability that the appropriate correction for a particular study would be greater than this maximum (e.g. using knowledge of the general effects of bias and extra-variation from published bias-adjusted results).SummaryAlthough this approach does not yet provide a method, because the latter probability can not be objectively assessed, this paper aims to stimulate the re-interpretation of conventional confidence intervals, and more and better studies of the effects of different biases.

Severe Carbon Monoxide Poisoning Treated by Hyperbaric Oxygen Therapy—A Case Report

Carbon monoxide (CO) poisoning is an important cause of mortality and late neurological sequelae such as memory loss, personality changes, psychosis, dementia, and so on. The benefits of hyperbaric oxygen (HBO) therapy are still discussed, but the majority of trials recommend it in severe cases with coma and/or hemodynamic instability, irrespective of carboxyhemoglobin (COHb) level, to prevent permanent neurological deficits. We present a 35-yr-old woman who underwent accidental CO poisoning. Although breathing 100% oxygen by mask during transfer to the hospital, she was in deep coma, hypotensive, cyanotic, and hypoxic (arterial pO2 7,41 kPa, HbO2 87.8%), with serum COHb 26.7% on hospital admission. Orotracheal intubation, mechanical ventilation, iv fluids, dobutamin, and norepinephrine were administered. COHb level decreased to 17.2% within 1 h. To prevent severe neurological sequelae, the patient was transferred as soon as possible to an HBO center 60 km distant to perform HBO therapy twice at 3.0 and once at 2.2 atm within 24 h. After the second HBO session, the patient regained consciousness, and respiratory failure and shock resolved. She was transferred to our hospital and discharged few weeks later with discrete paresis of peripheral nerves, discrete ischemic brain lesions on computed tomography (CT) scan, and moderately abnormal electroencephalogram (EEG) without cognitive disturbances. She was able to resume her daily activities. We conclude that in severe CO poisoning, normobaric oxygen therapy and resuscitation by fluids, inotropic agents, and catecholamines is essential for survival, but additional HBO therapy seems to prevent major neurological sequelae.

Commentary on ‘Air versus oxygen for resuscitation of infants at birth’

This is a commentary on a Cochrane review, published in this issue of EBCH, first published as: Tan A, Schulze A, O'Donnell CPF, Davis PG. Air versus oxygen for resuscitation of infants at birth. The Cochrane Database of Systematic Reviews 2005, Issue 2. Art. No.: CD002273. DOI: 10.1002/14651858.CD002273.pub3. Copyright © 2006 John Wiley & Sons, Ltd.

Air versus oxygen for resuscitation of infants at birth

Air versus oxygen for resuscitation of infants at birth

Summary of ‘Air versus oxygen for resuscitation of infants at birth’

This is a summary of a Cochrane review, published in this issue of EBCH, first published as: Tan A, Schulze A, O'Donnell CPF, Davis PG. Air versus oxygen for resuscitation of infants at birth. The Cochrane Database of Systematic Reviews 2005, Issue 2. Art. No.: CD002273. DOI: 10.1002/14651858.CD002273.pub3. Copyright © 2006 John Wiley & Sons, Ltd.

Pulmonary Arterial Contractility in Neonatal Lambs Increases with 100% Oxygen Resuscitation

The optimal Fi(O2) during neonatal resuscitation is a subject of controversy. The effect of exposure to high levels of inspired oxygen on pulmonary arterial (PA) contractility is not known. We studied differences in PA vasoreactivity in term lambs initially ventilated with 21% or 100% oxygen, followed by continued ventilation using oxygen as needed for 24 h, or ventilated with 100% oxygen for 24 h and room air breathing 1-d-old lambs. Term lambs were delivered by cesarean section, intubated, and ventilated with 21% (21%Res) or 100% oxygen (100%Res) for the first 30 min of life. Subsequently, the ventilator Fi(O2) was adjusted to maintain a Pa(O2) between 45 and 65 mm Hg for 24 h. Five lambs were ventilated continuously with 100% oxygen (100%24h). Six spontaneously breathing newborn lambs (RA Spont) were studied for comparison. Lambs were killed at 24 h of life and PA rings were isolated and contracted with norepinephrine (NE) and KCl and some were relaxed with A23187 and SNAP in tissue baths. NE and KCl induced contractions were highest in PA isolated from 100%24h lambs, and were significantly higher in 100%Res lambs than PA from 21%Res lambs. Contraction responses in PA from RA Spont lambs were similar to 21%Res lambs. Relaxations to A23187 and SNAP were similar among all ventilated groups. PA contractility to NE and KCl is increased following both brief (30 min) and prolonged (24 h) exposure to 100% oxygen during mechanical ventilation. In contrast, normoxic resuscitation and ventilation do not increase PA contractility.

Major Changes in the 2005 AHA Guidelines for CPR and ECC

The emergency cardiovascular care (ECC) scientists involved in the 2005 evidence evaluation process and the revision of the 2005 AHA Guidelines for CPR and ECC began and ended the process aware of the limitations of the resuscitation scientific evidence, optimistic about emerging data that documents the benefits of high-quality cardiopulmonary resuscitation (CPR), and determined to make recommendations that would increase survival from cardiac arrest and life-threatening emergencies. This editorial summarizes the factors that contributed to the tipping point, the point at which information and discussion either triggered support for major changes in the guidelines or reaffirmed existing recommendations. The scientists critically reviewed the sequence and priorities of the steps of CPR to identify those factors with the greatest potential impact on survival. They then developed recommendations to support those interventions that should be performed frequently and well. There was unanimous support for increased emphasis on ensuring that rescuers deliver high-quality CPR: rescuers need to provide an adequate number and depth of compressions, allow complete chest recoil after each compression, and minimize interruptions in chest compressions. The 2005 AHA Guidelines for CPR and ECC are based on the most comprehensive review of resuscitation literature ever published.1 The evidence evaluation process incorporated the input of 281 international resuscitation experts who evaluated research, topics, and hypotheses over a 36-month period before the 2005 Consensus Conference. The process included structured evidence evaluation, analysis, and documentation of the literature.2 It also included rigorous disclosure and management of potential conflicts of interest, a process summarized in two editorials.3,4 Cardiopulmonary resuscitation and emergency cardiovascular care is a relatively new field. The epidemiologic data is incomplete, and high-level evidence is insufficient to support many recommendations. Although sudden cardiac arrest (SCA) is responsible for an estimated 250 000 deaths out of the hospital in the United …

Room Air Resuscitation Versus Oxygen Resuscitation in the Delivery Room

The use of 100% oxygen for delivery room resuscitation is currently the recommended standard of the American Academy of Pediatrics and the Neonatal Resuscitation Program. However, there is mounting evidence from animal and human studies suggesting that resuscitation with room air (RA, 21% oxygen), including positive pressure ventilation with bag and face mask, may be as effective as that with 100% oxygen, and that the use of 100% oxygen may pose a risk of adverse physiologic sequelae. Resuscitation with RA has been demonstrated to result in faster recovery and improved neonatal mortality in comparison to 100% oxygen resuscitation. In addition, studies of normal oxygen saturation immediately after birth suggest delivery room personnel may be rushing to high saturation unnecessarily. The question for perinatal medical and nursing personnel involved in newborn resuscitation in the delivery room is whether the use of RA reduces the possible adverse effects of 100% oxygen, including delay in short-term stabilization, death, neurological disability, and possible secondary oxygen free radical injury. A systematic synopsis of both animal studies and human studies involving the advantages, disadvantages, possible risks, and short- and long-term effects of these 2 methods of resuscitation is presented.