Therapeutic hypothermia: from lab to NICU

Association Between Increased Seizures During Rewarming After Hypothermia for Neonatal Hypoxic Ischemic Encephalopathy and Abnormal Neurodevelopmental Outcomes at 2-Year Follow-up: A Nested Multisite Cohort Study

Importance

Compared with normothermia, hypothermia has been shown to reduce death or disability in neonatal hypoxic ischemic encephalopathy but data on seizures during rewarming and associated outcomes are scarce.

Objective

To determine whether electrographic seizures are more likely to occur during rewarming compared with the preceding period and whether they are associated with abnormal outcomes in asphyxiated neonates receiving hypothermia therapy.

Design, Setting, and Participants

This prespecified nested cohort study of infants enrolled in the Optimizing Cooling (OC) multicenter Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Neonatal Research Network trial from December 2011 to December 2013 with 2 years' follow-up randomized infants to either 72 hours of cooling (group A) or 120 hours (group B). The main trial included 364 infants. Of these, 194 were screened, 10 declined consent, and 120 met all predefined inclusion criteria. A total of 112 (90%) had complete data for death or disability. Data were analyzed from January 2018 to January 2020.

Interventions

Serial amplitude electroencephalography recordings were compared in the 12 hours prior and 12 hours during rewarming for evidence of electrographic seizure activity by 2 central amplitude-integrated electroencephalography readers blinded to treatment arm and rewarming epoch. Odds ratios and 95% CIs were evaluated following adjustment for center, prior seizures, depth of cooling, and encephalopathy severity.

Main Outcomes and Measures

The primary outcome was the occurrence of electrographic seizures during rewarming initiated at 72 or 120 hours compared with the preceding 12-hour epoch. Secondary outcomes included death or moderate or severe disability at age 18 to 22 months. The hypothesis was that seizures during rewarming were associated with higher odds of abnormal neurodevelopmental outcomes.

Results

A total of 120 newborns (70 male [58%]) were enrolled (66 in group A and 54 in group B). The mean (SD) gestational age was 39 (1) weeks. There was excellent interrater agreement (κ, 0.99) in detection of seizures. More infants had electrographic seizures during the rewarming epoch compared with the preceding epoch (group A, 27% vs 14%; P = .001; group B, 21% vs 10%; P = .03). Adjusted odd ratios (95% CIs) for seizure frequency during rewarming were 2.7 (1.0-7.5) for group A and 3.2 (0.9-11.6) for group B. The composite death or moderate to severe disability outcome at 2 years was significantly higher in infants with electrographic seizures during rewarming (relative risk [95% CI], 1.7 [1.25-2.37]) after adjusting for baseline clinical encephalopathy and seizures as well as center.

Conclusions and Relevance

Findings that higher odds of electrographic seizures during rewarming are associated with death or disability at 2 years highlight the necessity of electroencephalography monitoring during rewarming in infants at risk.

Trial Registration

ClinicalTrials.gov Identifier: NCT01192776.

The Role of Extracellular Vesicles in the Developing Brain: Current Perspective and Promising Source of Biomarkers and Therapy for Perinatal Brain Injury

This comprehensive review focuses on our current understanding of the proposed physiological and pathological functions of extracellular vesicles (EVs) in the developing brain. Furthermore, since EVs have attracted great interest as potential novel cell-free therapeutics, we discuss advances in the knowledge of stem cell- and astrocyte-derived EVs in relation to their potential for protection and repair following perinatal brain injury. This review identified 13 peer-reviewed studies evaluating the efficacy of EVs in animal models of perinatal brain injury; 12/13 utilized mesenchymal stem cell-derived EVs (MSC-EVs) and 1/13 utilized astrocyte-derived EVs. Animal model, method of EV isolation and size, route, timing, and dose administered varied between studies. Notwithstanding, EV treatment either improved and/or preserved perinatal brain structures both macroscopically and microscopically. Additionally, EV treatment modulated inflammatory responses and improved brain function. Collectively this suggests EVs can ameliorate, or repair damage associated with perinatal brain injury. These findings warrant further investigation to identify the optimal cell numbers, source, and dosage regimens of EVs, including long-term effects on functional outcomes.

Applications of advanced signal processing and machine learning in the neonatal hypoxic-ischemic electroencephalogram

Perinatal hypoxic-ischemic-encephalopathy significantly contributes to neonatal death and life-long disability such as cerebral palsy. Advances in signal processing and machine learning have provided the research community with an opportunity to develop automated real-time identification techniques to detect the signs of hypoxic-ischemic-encephalopathy in larger electroencephalography/amplitude-integrated electroencephalography data sets more easily. This review details the recent achievements, performed by a number of prominent research groups across the world, in the automatic identification and classification of hypoxic-ischemic epileptiform neonatal seizures using advanced signal processing and machine learning techniques. This review also addresses the clinical challenges that current automated techniques face in order to be fully utilized by clinicians, and highlights the importance of upgrading the current clinical bedside sampling frequencies to higher sampling rates in order to provide better hypoxic-ischemic biomarker detection frameworks. Additionally, the article highlights that current clinical automated epileptiform detection strategies for human neonates have been only concerned with seizure detection after the therapeutic latent phase of injury. Whereas recent animal studies have demonstrated that the latent phase of opportunity is critically important for early diagnosis of hypoxic-ischemic-encephalopathy electroencephalography biomarkers and although difficult, detection strategies could utilize biomarkers in the latent phase to also predict the onset of future seizures.

Neuroprotective Effects of AG490 in Neonatal Hypoxic-Ischemic Brain Injury

In infants and children, neonatal hypoxic-ischemic (HI) brain injury represents a major cause of chronic neurological morbidity. The transient receptor potential melastatin 2 (TRPM2), a non-selective cation channel that conducts calcium, can mediate neuronal death following HI brain injury. An important endogenous activator of TRPM2 is H₂O₂, which has previously been reported to be upregulated in the neonatal brain after hypoxic ischemic injury. Here, incorporating both in vitro (H₂O₂-induced neuronal cell death model) and in vivo (mouse HI brain injury model) approaches, we examined the effects of AG490, which can inhibit the H₂O₂-induced TRPM2 channel. We found that AG490 elicited neuroprotective effects. We confirmed that AG490 reduced H₂O₂-induced TRPM2 currents. Specifically, application of AG490 to neurons ameliorated H₂O₂-induced cell injury in vitro. In addition, AG490 administration reduced brain damage and improved neurobehavioral performance following HI brain injury in vivo. The neuroprotective benefits of AG490 suggest that pharmacological inhibition of H₂O₂-activated TRPM2 currents can be exploited as a potential therapeutic strategy to treat HI-induced neurological complications.

The prognostic value of proton magnetic resonance spectroscopy in term newborns treated with therapeutic hypothermia following asphyxia

OBJECTIVE

The purpose of this study was to correlate brain metabolism assessed shortly after therapeutic hyperthermia by ¹H magnetic resonance spectroscopy (MRS), with neurodevelopmental outcome.

METHODS

At the age of 6.0±1.8days, brain metabolites of 35 term asphyxiated newborns, treated with therapeutic hypothermia, were quantified by multivoxel proton MRS of a volume cranial to the corpus callosum, containing both gray and white matter. At the age of 30months the Bayley Scale of Infant Development-III was performed.

RESULTS

Infants that died had lower gray matter NAA levels than infants that survived (P=0.005). In surviving infants (28 of 35) there was a trend of negative correlation between gray matter choline levels and gross motor outcome (r=-0.45). In the white matter, choline correlated negatively with fine motor skills (r=-0.40), and creatine positively with gross motor skills (r=0.58, P=0.02). There was no relationship between lactate levels and outcome.

CONCLUSION

MRS of asphyxiated neonates treated by therapeutic hypothermia can serve as predictor of outcome. Unlike previously reported associations in untreated asphyxiates, lactate levels had no relationship with outcome, which indicates that one of the working mechanisms of therapeutic hypothermia is reduction of the metabolic rate.

Neonatal Hypoxia Ischaemia: Mechanisms, Models, and Therapeutic Challenges

Neonatal hypoxia-ischaemia (HI) is the most common cause of death and disability in human neonates, and is often associated with persistent motor, sensory, and cognitive impairment. Improved intensive care technology has increased survival without preventing neurological disorder, increasing morbidity throughout the adult population. Early preventative or neuroprotective interventions have the potential to rescue brain development in neonates, yet only one therapeutic intervention is currently licensed for use in developed countries. Recent investigations of the transient cortical layer known as subplate, especially regarding subplate's secretory role, opens up a novel set of potential molecular modulators of neonatal HI injury. This review examines the biological mechanisms of human neonatal HI, discusses evidence for the relevance of subplate-secreted molecules to this condition, and evaluates available animal models. Neuroserpin, a neuronally released neuroprotective factor, is discussed as a case study for developing new potential pharmacological interventions for use post-ischaemic injury.

Effects of Neonatal Hypoxic-Ischemic Injury and Hypothermic Neuroprotection on Neural Progenitor Cells in the Mouse Hippocampus

Neonatal hypoxic-ischemic injury (HI) results in widespread cerebral encephalopathy and affects structures that are essential for neurocognitive function, such as the hippocampus. The dentate gyrus contains a reservoir of neural stem and progenitor cells (NSPCs) that are critical for postnatal development and normal adult function of the hippocampus, and may also facilitate the recovery of function after injury. Using a neonatal mouse model of mild-to-moderate HI and immunohistochemical analysis of NSPC development markers, we asked whether these cells are vulnerable to HI and how they respond to both injury and hypothermic therapy. We found that cleaved caspase-3 labeling in the subgranular zone, where NSPCs are located, is increased by more than 30-fold after HI. The population of cells positive for both proliferating cell nuclear antigen and nestin (PCNA+Nes+), which represent primarily actively proliferating NSPCs, are acutely decreased by 68% after HI. The NSPC population expressing NeuroD1, a marker for NSPCs transitioning to become fate-committed neural progenitors, was decreased by 47%. One week after HI, there was a decrease in neuroblasts and immature neurons in the dentate gyrus, as measured by doublecortin (DCX) immunolabeling, and at the same time PCNA+Nes+ cell density was increased by 71%. NSPCs expressing Tbr2, which identifies a highly proliferative intermediate neural progenitor population, increased by 107%. Hypothermia treatment after HI partially rescues both the acute decrease in PCNA+Nes+ cell density at 1 day after injury and the chronic loss of DCX immunoreactivity and reduction in NeuroD1 cell density measured at 1 week after injury. Thus, we conclude that HI causes an acute loss of dentate gyrus NSPCs, and that hypothermia partially protects NSPCs from HI.

Fault and blame, insults to the perinatal brain may be remote from time of birth

There is a certainty in malpractice cases that neurodevelopmental deficits are caused by preventable events at birth when the onset, nature, and timing of the insult in the antenatal and natal period are unknown. The biggest problem is determining timing. Electronic fetal monitoring is given excessive importance in legal cases. Before assigning fault on events at birth, a better understanding of developmental neurobiology and limitations of the present clinical biomarkers is warranted. The issues of single versus repeated episodes, timing of antenatal insults, pros and cons of legal arguments, interaction of various etiologic and anatomic factors are discussed.

Stem cell therapy to protect and repair the developing brain: a review of mechanisms of action of cord blood and amnion epithelial derived cells

In the research, clinical, and wider community there is great interest in the use of stem cells to reduce the progression, or indeed repair brain injury. Perinatal brain injury may result from acute or chronic insults sustained during fetal development, during the process of birth, or in the newborn period. The most readily identifiable outcome of perinatal brain injury is cerebral palsy, however, this is just one consequence in a spectrum of mild to severe neurological deficits. As we review, there are now clinical trials taking place worldwide targeting cerebral palsy with stem cell therapies. It will likely be many years before strong evidence-based results emerge from these trials. With such trials underway, it is both appropriate and timely to address the physiological basis for the efficacy of stem-like cells in preventing damage to, or regenerating, the newborn brain. Appropriate experimental animal models are best placed to deliver this information. Cell availability, the potential for immunological rejection, ethical, and logistical considerations, together with the propensity for native cells to form teratomas, make it unlikely that embryonic or fetal stem cells will be practical. Fortunately, these issues do not pertain to the use of human amnion epithelial cells (hAECs), or umbilical cord blood (UCB) stem cells that are readily and economically obtained from the placenta and umbilical cord discarded at birth. These cells have the potential for transplantation to the newborn where brain injury is diagnosed or even suspected. We will explore the novel characteristics of hAECs and undifferentiated UCB cells, as well as UCB-derived endothelial progenitor cells (EPCs) and mesenchymal stem cells (MSCs), and how immunomodulation and anti-inflammatory properties are principal mechanisms of action that are common to these cells, and which in turn may ameliorate the cerebral hypoxia and inflammation that are final pathways in the pathogenesis of perinatal brain injury.

Passive cooling during transport of asphyxiated term newborns

OBJECTIVE

To evaluate the efficacy and safety of passive cooling during transport of asphyxiated newborns.

STUDY DESIGN

Retrospective medical record review of newborns with perinatal asphyxia transported for hypothermia between July 2007 and June 2010.

RESULT

Of 43 newborns transported, 27 were passively cooled without significant adverse events. Twenty (74%) passively cooled newborns arrived with temperature between 32.5 and 34.5 °C. One newborn arrived with a temperature <32.5, and 6 (22%) had temperatures >34.5 °C. Time from birth to hypothermia was significantly shorter among passively cooled newborns compared with newborns not cooled (215 vs 327 min, P<0.01), even though time from birth to admission to Boston Children's Hospital was similar (252 vs 259 min, P=0.77). Time from birth to admission was the only significant predictor of increased time to reach target temperature (P=0.001).

CONCLUSION

Exclusive passive cooling achieves significantly earlier initiation of effective hypothermia for asphyxiated newborns but should not delay transport for active cooling.

Early predictors of short term neurodevelopmental outcome in asphyxiated cooled infants. A combined brain amplitude integrated electroencephalography and near infrared spectroscopy study

BACKGROUND

Brain Cooling (BC) represents the elective treatment in asphyxiated newborns. Amplitude Integrated Electroencephalography (aEEG) and Near Infrared Spectroscopy (NIRS) monitoring may help to evaluate changes in cerebral electrical activity and cerebral hemodynamics during hypothermia.

OBJECTIVES

To evaluate the prognostic value of aEEG time course and NIRS data in asphyxiated cooled infants.

METHODS

Twelve term neonates admitted to our NICU with moderate-severe Hypoxic-Ischemic Encephalopathy (HIE) underwent selective BC. aEEG and NIRS monitoring were started as soon as possible and maintained during the whole hypothermic treatment. Follow-up was scheduled at regular intervals; adverse outcome was defined as death, cerebral palsy (CP) or global quotient <88.7 at Griffiths' Scale.

RESULTS

2/12 Infants died, 2 developed CP, 1 was normal at 6 months of age and then lost at follow-up and 7 showed a normal outcome at least at 1 year of age. The aEEG background pattern at 24 h of life was abnormal in 10 newborns; only 4 of them developed an adverse outcome, whereas the 2 infants with a normal aEEG developed normally. In infants with adverse outcome NIRS showed a higher Tissue Oxygenation Index (TOI) than those with normal outcome (80.0±10.5% vs 66.9±7.0%, p=0.057; 79.7±9.4% vs 67.1±7.9%, p=0.034; 80.2±8.8% vs 71.6±5.9%, p=0.069 at 6, 12 and 24 h of life, respectively).

CONCLUSIONS

The aEEG background pattern at 24h of life loses its positive predictive value after BC implementation; TOI could be useful to predict early on infants that may benefit from other innovative therapies.

Quantitative cranial magnetic resonance imaging in neonatal hypoxic-ischemic encephalopathy

The volume of acute injury detected by diffusion-weighted imaging and quantitative brain growth on serial cranial magnetic resonance imaging was not previously used to predict neurodevelopmental outcomes in infants with neonatal hypoxic-ischemic encephalopathy treated with head cooling. Our longitudinal study involved 16 head-cooled term infants with hypoxic-ischemic encephalopathy who underwent early and follow-up cranial magnetic resonance imaging and follow-up neurologic evaluations, out of 105 infants who received therapeutic hypothermia. The volume of acute injury was measured on initial cranial magnetic resonance imaging, using diffusion-weighted images. Total brain volumes were measured in both early and follow-up magnetic resonance imaging studies. Acute injury volume in the corpus callosum >0.5 cm(3) was associated with developing epilepsy (odds ratio, 20; 95% confidence interval, 1.01-1059.6; P = 0.013). Follow-up whole brain volume was reduced in those with unfavorable outcomes (i.e., epilepsy, cerebral palsy, and delayed developmental milestones), compared with infants without all three outcomes. Although acute brain injury volume and brain growth measurements may be useful predictors of outcomes in neonatal hypoxic-ischemic encephalopathy, the evolution of brain injury in these infants has yet to be fully understood and should be studied prospectively.

Implementation and conduct of therapeutic hypothermia for perinatal asphyxial encephalopathy in the UK--analysis of national data

BACKGROUND

Delay in implementing new treatments into clinical practice results in considerable health and economic opportunity costs. Data from the UK TOBY Cooling Register provides the opportunity to examine how one new effective therapy for newborn infants suspected of suffering asphyxial encephalopathy--therapeutic hypothermia- was implemented in the UK.

METHODOLOGY/PRINCIPAL FINDINGS

We analysed returned data forms from inception of the Register in December 2006 to the end of July 2011. Data forms were received for 1384 (67%) of the 2069 infants registered. The monthly rate of notifications increased from median {IQR} 18 {15-31} to 33 {30-39} after the announcement of the results of the recent TOBY trial, and to 50 {36-55} after their publication. This rate further increased to 70 {64-83} following official endorsement of the therapy, and is now close to the expected numbers of eligible infants. Cooling was started at 3.3 {1.5-5.5} hours after birth and the time taken to achieve the target 33-34 °C rectal temperature was 1 {0-3} hours. The rectal temperature was in the target range in 83% of measurements. From 2006 to 2011 there was evidence of extension of treatment to slightly less severely affected infants. 278 of 1362 (20%) infants died at 2.9 {1.4-4.1} days of age. The rates of death fell slightly over the period of the Register and, at two years of age cerebral palsy was diagnosed in 22% of infants; half of these were spastic bilateral. Factors independently associated with adverse outcome were clinical seizures prior to cooling (p<0.001) and severely abnormal amplitude integrated EEG (p<0.001).

CONCLUSIONS/SIGNIFICANCE

Therapeutic hypothermia was implemented appropriately within the UK, with significant benefit to patients and the health economy. This may be due in part to participation by neonatal units in clinical trials, the establishment of the national Register, and its endorsement by advisory bodies.

The instrumented fetal sheep as a model of cerebral white matter injury in the premature infant

Despite advances in neonatal intensive care, survivors of premature birth remain highly susceptible to unique patterns of developmental brain injury that manifest as cerebral palsy and cognitive-learning disabilities. The developing brain is particularly susceptible to cerebral white matter injury related to hypoxia-ischemia. Cerebral white matter development in fetal sheep shares many anatomical and physiological similarities with humans. Thus, the fetal sheep has provided unique experimental access to the complex pathophysiological processes that contribute to injury to the human brain during successive periods in development. Recent refinements have resulted in models that replicate major features of acute and chronic human cerebral injury and have provided access to complex clinically relevant studies of cerebral blood flow and neuroimaging that are not feasible in smaller laboratory animals. Here, we focus on emerging insights and methodologies from studies in fetal sheep that have begun to define cellular and vascular factors that contribute to white matter injury. Recent advances include spatially defined measurements of cerebral blood flow in utero, the definition of cellular maturational factors that define the topography of injury and the application of high-field magnetic resonance imaging to define novel neuroimaging signatures for specific types of chronic white matter injury. Despite the higher costs and technical challenges of instrumented preterm fetal sheep models, they provide powerful access to clinically relevant studies that provide a more integrated analysis of the spectrum of insults that appear to contribute to cerebral injury in human preterm infants.

Brain perfusion in asphyxiated newborns treated with therapeutic hypothermia

BACKGROUND AND PURPOSE

Induced hypothermia is thought to work partly by mitigating reperfusion injury in asphyxiated term neonates. The purpose of this study was to assess brain perfusion in the first week of life in these neonates.

MATERIALS AND METHODS

In this prospective cohort study, MR imaging and ASL-PI were used to assess brain perfusion in these neonates. We measured regional CBF values on 1-2 MR images obtained during the first week of life and compared these with values obtained in control term neonates. The same or later MR imaging scans were obtained to define the extent of brain injury.

RESULTS

Eighteen asphyxiated and 4 control term neonates were enrolled; 11 asphyxiated neonates were treated with hypothermia. Those developing brain injury despite being treated with induced hypothermia usually displayed hypoperfusion on DOL 1 and then hyperperfusion on DOL 2-3 in brain areas subsequently exhibiting injury. Asphyxiated neonates not treated with hypothermia who developed brain injury also displayed hyperperfusion on DOL 1-6 in brain areas displaying injury.

CONCLUSIONS

Our data show that ASL-PI may be useful for identifying asphyxiated neonates at risk of developing brain injury, whether or not hypothermia is administered. Because hypothermia for 72 hours may not prevent brain injury when hyperperfusion is found early in the course of neonatal hypoxic-ischemic encephalopathy, such neonates may be candidates for adjustments in their hypothermia therapy or for adjunctive neuroprotective therapies.

Post-traumatic seizure susceptibility is attenuated by hypothermia therapy

Traumatic brain injury (TBI) is a major risk factor for the subsequent development of epilepsy. Currently, chronic seizures after brain injury are often poorly controlled by available antiepileptic drugs. Hypothermia treatment, a modest reduction in brain temperature, reduces inflammation, activates pro-survival signaling pathways, and improves cognitive outcome after TBI. Given the well-known effect of therapeutic hypothermia to ameliorate pathological changes in the brain after TBI, we hypothesized that hypothermia therapy may attenuate the development of post-traumatic epilepsy and some of the pathomechanisms that underlie seizure formation. To test this hypothesis, adult male Sprague Dawley rats received moderate parasagittal fluid-percussion brain injury, and were then maintained at normothermic or moderate hypothermic temperatures for 4 h. At 12 weeks after recovery, seizure susceptibility was assessed by challenging the animals with pentylenetetrazole, a GABA(A) receptor antagonist. Pentylenetetrazole elicited a significant increase in seizure frequency in TBI normothermic animals as compared with sham surgery animals and this was significantly reduced in TBI hypothermic animals. Early hypothermia treatment did not rescue chronic dentate hilar neuronal loss nor did it improve loss of doublecortin-labeled cells in the dentate gyrus post-seizures. However, mossy fiber sprouting was significantly attenuated by hypothermia therapy. These findings demonstrate that reductions in seizure susceptibility after TBI are improved with post-traumatic hypothermia and provide a new therapeutic avenue for the treatment of post-traumatic epilepsy.

Neurocritical care for neonates

BACKGROUND

To describe the concept, implementation, patient characteristics, and preliminary outcomes of a Neonatal Neurocritical Care Service (NNCS) recently established at the University of California, San Francisco.

METHODS

The NNCS was developed to better address the special needs of neonates at risk for neurological injury. The service combines dedicated neurological care, specialized neonatal medical and nursing expertise, neuromonitoring, neuroimaging, neurodevelopmental care, and long-term follow up. Newborns evaluated by the NNCS between July 2008 and June 2009 were included in the analysis. Demographic data (gestational age at birth, sex, admission diagnosis, and reason for consult), outcome (mortality, length of stay), and neurophysiology and imaging resources were extracted from patient charts.

RESULTS

Over the 12-month period, 155 newborns were evaluated (approximately 25% of all admissions); of these, 51 were preterm (<36 weeks gestation) and 104 were term. Approximately half were admitted for primary medical diagnoses, such as preterm birth, congenital malformations or apnea/apparent life-threatening event (ALTE), with the remainder admitted for primary neurological problems, including perinatal asphyxia, seizures/possible seizures, or congenital cerebral malformation. The most common neurological diagnoses were hypoxic-ischemic encephalopathy (38%) and seizure (35%). Among preterm newborns, intraventricular hemorrhage grade III and periventricular hemorrhagic infarction were most common. Mortality was approximately 20% in both preterm and term populations.

CONCLUSIONS

While specialized neurocritical care has improved outcomes in adult populations, longitudinal studies are needed to determine whether specialized neurocritical care services will also result in improved neurodevelopmental outcomes for newborns.

Serial MRI and neurodevelopmental outcome in 9- to 10-year-old children with neonatal encephalopathy

OBJECTIVE

To assess the relation between patterns of brain injury on neonatal and childhood magnetic resonance imaging (MRI) and long-term neurodevelopmental outcome.

STUDY DESIGN

Neonatal (n = 34) and childhood MRIs (n = 77) were analyzed for 80 children with neonatal encephalopathy and for 51 control subjects during childhood. MRIs were graded as normal, mildly abnormal (white matter lesions), or moderately/severely abnormal (watershed injury, lesions in basal ganglia/thalamus or focal infarction). Severity of brain injury was related to different aspects of neurologic outcome: Total impairment score of the Movement Assessment Battery for Children, intelligence quotient score, cerebral palsy, postneonatal epilepsy, and need for special education. Seven children with neonatal encephalopathy required extracorporeal membrane oxygenation treatment.

RESULTS

Neonatal and childhood MRI were comparable in 25/33 children (75.8%, P < .001). Children with moderate/severe lesions on neonatal or childhood MRI more often had a total impairment score <or= 15th percentile, an intelligence quotient <or= 85, and cerebral palsy, and attended special education.

CONCLUSION

Different patterns of injury seen on neonatal MRI after neonatal encephalopathy can still be recognized on childhood MRI. Children with moderate to severe brain lesions on neonatal or childhood MRI significantly more often have impaired motor and cognitive outcomes.

Neuroprotection for ischemic stroke: past, present and future

Neuroprotection for ischemic stroke refers to strategies, applied singly or in combination, that antagonize the injurious biochemical and molecular events that eventuate in irreversible ischemic injury. There has been a recent explosion of interest in this field, with over 1000 experimental papers and over 400 clinical articles appearing within the past 6 years. These studies, in turn, are the outgrowth of three decades of investigative work to define the multiple mechanisms and mediators of ischemic brain injury, which constitute potential targets of neuroprotection. Rigorously conducted experimental studies in animal models of brain ischemia provide incontrovertible proof-of-principle that high-grade protection of the ischemic brain is an achievable goal. Nonetheless, many agents have been brought to clinical trial without a sufficiently compelling evidence-based pre-clinical foundation. At this writing, around 160 clinical trials of neuroprotection for ischemic stroke have been initiated. Of the approximately 120 completed trials, two-thirds were smaller early-phase safety-feasibility studies. The remaining one-third were typically larger (>200 subjects) phase II or III trials, but, disappointingly, only fewer than one-half of these administered neuroprotective therapy within the 4-6h therapeutic window within which efficacious neuroprotection is considered to be achievable. This fact alone helps to account for the abundance of "failed" trials. This review presents a close survey of the most extensively evaluated neuroprotective agents and classes and considers both the strengths and weakness of the pre-clinical evidence as well as the results and shortcomings of the clinical trials themselves. Among the agent-classes considered are calcium channel blockers; glutamate antagonists; GABA agonists; antioxidants/radical scavengers; phospholipid precursor; nitric oxide signal-transduction down-regulator; leukocyte inhibitors; hemodilution; and a miscellany of other agents. Among promising ongoing efforts, therapeutic hypothermia, high-dose human albumin therapy, and hyperacute magnesium therapy are considered in detail. The potential of combination therapies is highlighted. Issues of clinical-trial funding, the need for improved translational strategies and clinical-trial design, and "thinking outside the box" are emphasized.

Hypothermia

Experimental studies show that, following hypoxic ischaemic injury, mild induced hypothermia-a reduction of body temperature by about 3 degrees C -- preserves cerebral energy metabolism, reduces cerebral tissue injury and improves neurological function. Randomized trials in full-term and near-full-term newborns suggest that treatment with mild hypothermia is safe and improves survival without disabilities up to 18 months of age. Although the optimal time of initiation, the depth and duration, and the method of cooling are uncertain, in the absence of specific treatments many clinicians will wish to consider treating asphyxiated infants with hypothermia. Guidance now needs to be provided to promote uniform practice, to avoid inappropriate treatment and to foster continuing collaboration in future studies of neuroprotection following asphyxia. If the promising results of the current trials are confirmed by the findings from other on-going studies, with longer follow-up, the impact of such a treatment on the babies, their families and health resources in the shorter and longer terms will be considerable.

Beware: the misuse of technology and the law of unintended consequences

Electronic monitoring of the fetal heart rate during labor (EFM), originally designed to assess fetal stress and allow the early detection of the compromised fetus, has instead led to increasing maternal morbidity without decreasing fetal morbidity. The unintended consequences of this technologic advance have led to the creation of a pseudodisease and unwarranted intervention in response to its detection. Is it ethical to introduce a new technology without adequate assessment of its possible consequences? Are we about to repeat this (error resulting from the introduction of EFM?) There is increasing interest in monitoring the function of the newborn brain, to enable the early detection of subclinical seizures. The monitor may also be used for assessing brain function in older children and adults who are comatose or paralyzed and cannot appropriately respond to stimuli. Use of this amplitude-integrated electroencephalography (aEEG) in the newborn for detection of seizures and other brain abnormalities is not dissimilar to the use of electronic fetal heart rate monitoring. Whether seizures or subclinical seizures themselves cause harm to the developing nervous system is unclear. The effectiveness of medications for treatment of seizures in the newborn has not been established. Therefore, the consequences of introducing automated EEG for the detection of subclinical neonatal seizures are likely to be similar to the results of the introduction of EFM: creation of another pseudodisease, followed by unwarranted intervention, and increased legal liability. What are the ethics of continued approval and introduction of unevaluated technology? What is the wisdom of its use? Beware of the unintended consequences.

A review of progress in understanding the pathophysiology and treatment of brain edema

Object

Brain edema resulting from traumatic brain injury (TBI) or ischemia if uncontrolled exhausts volume reserve and leads to raised intracranial pressure and brain herniation. The basic types of edema—vasogenic and cytotoxic—were classified 50 years ago, and their definitions remain intact.

Methods

In this paper the author provides a review of progress over the past several decades in understanding the pathophysiology of the edematous process and the success and failures of treatment. Recent progress focused on those manuscripts that were published within the past 5 years.

Results

Perhaps the most exciting new findings that speak to both the control of production and resolution of edema in both trauma and ischemia are the recent studies that have focused on the newly described “water channels” or aquaporins. Other important findings relate to the predominance of cellular edema in TBI.

Conclusions

Significant new findings have been made in understanding the pathophysiology of brain edema; however, less progress has been made in treatment. Aquaporin water channels offer hope for modulating and abating the devastating effects of fulminating brain edema in trauma and stroke.

Induced cerebral hypothermia reduces post-hypoxic loss of phenotypic striatal neurons in preterm fetal sheep

Perinatal hypoxic-ischemic injury of the basal ganglia is a significant cause of disability in premature infants. Prolonged, moderate cerebral hypothermia has been shown to be neuroprotective after experimental hypoxia-ischemia; however, it has not been tested in the preterm brain. We therefore examined the effects of severe hypoxia and the potential neuroprotective effects of delayed hypothermia on phenotypic striatal neurons. Preterm (0.7 gestation) fetal sheep received complete umbilical cord occlusion for 25 min followed by cerebral hypothermia (fetal extradural temperature reduced from 39.4+/-0.3 degrees C to 29.5+/-2.6 degrees C) from 90 min to 70 h after the end of occlusion. Hypothermia was associated with a significant overall reduction in striatal neuronal loss compared with normothermia-occlusion fetuses (mean+/-SEM, 5.5+/-1.2% vs. 38.1+/-6.5%, P<0.01). Immunohistochemical studies showed that occlusion resulted in a significant loss of calbindin-28 kd, glutamic acid decarboxylase isoform 67 and neuronal nitric oxide synthase-immunopositive neurons (n=7, P<0.05), but not choline acetyltransferase-positive neurons, compared with sham controls (n=7). Hypothermia (n=7) significantly reduced the loss of calbindin-28 kd and neuronal nitric oxide synthase, but not glutamic acid decarboxylase-immunopositive neurons. In conclusion, delayed, prolonged moderate head cooling was associated with selective protection of particular phenotypic striatal projection neurons after severe hypoxia in the preterm fetus. These findings suggest that head cooling may help reduce basal ganglia injury in some premature babies.

The effect of cerebral hypothermia on white and grey matter injury induced by severe hypoxia in preterm fetal sheep

Prolonged, moderate cerebral hypothermia is consistently neuroprotective after experimental hypoxia-ischaemia; however, it has not been tested in the preterm brain. Preterm (0.7 gestation) fetal sheep received complete umbilical cord occlusion for 25 min followed by cerebral hypothermia (fetal extradural temperature reduced from 39.4 +/- 0.3 to 29.5 +/- 2.6 degrees C) from 90 min to 70 h after the end of occlusion or sham cooling. Occlusion led to severe acidosis and profound hypotension, which recovered rapidly after release of occlusion. After 3 days recovery the EEG spectral frequency, but not total intensity, was increased in the hypothermia-occlusion group compared with normothermia-occlusion. Hypothermia was associated with a significant overall reduction in loss of immature oligodendrocytes in the periventricular white matter (P < 0.001), and neuronal loss in the hippocampus and basal ganglia (P < 0.001), with suppression of activated caspase-3 and microglia (isolectin-B4 positive). Proliferation was significantly reduced in periventricular white matter after occlusion (P < 0.05), but not improved after hypothermia. In conclusion, delayed, prolonged head cooling after a profound hypoxic insult in the preterm fetus was associated with a significant reduction in loss of neurons and immature oligodendroglia, with evidence of EEG and haemodynamic improvement after 3 days recovery, but also with a persisting reduction in proliferation of cells in the periventricular region. Further studies are required to evaluate the long-term impact of cooling on brain growth and maturation.

Predicting outcomes of neonates diagnosed with hypoxemic-ischemic encephalopathy

OBJECTIVE

The goals were to identify predictor variables and to develop scoring systems and classification trees to predict death/disability or death in infants with hypoxic-ischemic encephalopathy.

METHODS

Secondary analysis of data from the multicenter, randomized, controlled, National Institute of Child Health and Human Development Neonatal Research Network trial of hypothermia in hypoxic-ischemic encephalopathy was performed. Data for 205 neonates diagnosed as having hypoxic-ischemic encephalopathy were studied. Logistic regression analysis was performed by using clinical and laboratory variables available within 6 hours of birth, with death or moderate/severe disability at 18 to 22 months or death as the outcomes. By using the identified variables and odds ratios, scoring systems to predict death/disability or death were developed, weighting each predictor in proportion to its odds ratio. In addition, classification and regression tree analysis was performed, with recursive partitioning and automatic selection of optimal cutoff points for variables. Correct classification rates for the scoring systems, classification and regression tree models, and early neurologic examination were compared.

RESULTS

Correct classification rates were 78% for death/disability and 71% for death with the scoring systems, 80% and 77%, respectively, with the classification and regression tree models, and 67% and 73% with severe encephalopathy in early neurologic examination. Correct classification rates were similar in the hypothermia and control groups.

CONCLUSIONS

Among neonates diagnosed as having hypoxic-ischemic encephalopathy, the classification and regression tree model, but not the scoring system, was superior to early neurologic examination in predicting death/disability. The 3 models were comparable in predicting death. Only a few components of the early neurologic examination were associated with poor outcomes. These scoring systems and classification trees, if validated, may help in assessments of prognosis and may prove useful for risk-stratification of infants with hypoxic-ischemic encephalopathy for clinical trials.

Fetal hypoxic and ischemic injuries

PURPOSE OF REVIEW

The principles of neonatal neurological protection following intrapartum hypoxia are briefly reviewed. The physiological principles behind the use of cardiotocograph patterns in defining the timing and mechanism of fetal hypoxia and injury are then demonstrated.

RECENT FINDINGS

Fetal neurological injury may result from progressive hypoxemia, acidosis, diminished cardiac output and cerebral ischemia, manifested at birth as low Apgar scores, multisystem compromise, severe acidosis and encephalopathy. More commonly, however, intrapartum injury results from often intermittent, regional ischemia secondary to umbilical cord or head compression resulting in hemorrhage or infarction. Under these circumstances, the amount of umbilical acidosis and neonatal encephalopathy varies and the potential candidate for neuroprotection may escape recognition and timely treatment. Selecting infants likely to benefit from neuroprotection requires information on the timing, duration and mechanism of hypoxia. Neonatal parameters, including low Apgar scores, acidosis, even seizures, lack sensitivity and specificity. Cardiotocograph patterns are capable of determining the duration, mechanism and severity of hypoxia and occasionally, the timing of neurological injury.

SUMMARY

Protecting the newborn from the neurological consequences of intrapartum hypoxia requires critical definition of the mechanism and timing of this exposure. cardiotocograph tracings offer the opportunity to refine the selection of candidates for neonatal rescue.

Relationship between evolving epileptiform activity and delayed loss of mitochondrial activity after asphyxia measured by near-infrared spectroscopy in preterm fetal sheep

Early onset cerebral hypoperfusion after birth is highly correlated with neurological injury in premature infants, but the relationship with the evolution of injury remains unclear. We studied changes in cerebral oxygenation, and cytochrome oxidase (CytOx) using near-infrared spectroscopy in preterm fetal sheep (103-104 days of gestation, term is 147 days) during recovery from a profound asphyxial insult (n= 7) that we have shown produces severe subcortical injury, or sham asphyxia (n= 7). From 1 h after asphyxia there was a significant secondary fall in carotid blood flow (P < 0.001), and total cerebral blood volume, as reflected by total haemoglobin (P < 0.005), which only partially recovered after 72 h. Intracerebral oxygenation (difference between oxygenated and deoxygenated haemoglobin concentrations) fell transiently at 3 and 4 h after asphyxia (P < 0.01), followed by a substantial increase to well over sham control levels (P < 0.001). CytOx levels were normal in the first hour after occlusion, was greater than sham control values at 2-3 h (P < 0.05), but then progressively fell, and became significantly suppressed from 10 h onward (P < 0.01). In the early hours after reperfusion the fetal EEG was highly suppressed, with a superimposed mixture of fast and slow epileptiform transients; overt seizures developed from 8 +/- 0.5 h. These data strongly indicate that severe asphyxia leads to delayed, evolving loss of mitochondrial oxidative metabolism, accompanied by late seizures and relative luxury perfusion. In contrast, the combination of relative cerebral deoxygenation with evolving epileptiform transients in the early recovery phase raises the possibility that these early events accelerate or worsen the subsequent mitochondrial failure.