Prophylactic phenobarbital and whole-body cooling for neonatal hypoxic-ischemic encephalopathy

Long-Term Outcomes Following Hypoxic Ischemic Encephalopathy

Hypoxic ischemic encephalopathy (HIE) is the most common cause of neonatal encephalopathy and results in significant morbidity and mortality. Long-term outcomes of the condition encompass impairments across all developmental domains. While therapeutic hypothermia (TH) has improved outcomes for term and late preterm infants with moderate to severe HIE, trials are ongoing to investigate the use of TH for infants with mild or preterm HIE. There is no evidence that adjuvant therapies in combination with TH improve long-term outcomes. Numerous trials of various adjuvant therapies are underway in the quest to further improve outcomes for infants with HIE.

Midazolam Prevents the Adverse Outcome of Neonatal Asphyxia

OBJECTIVE

Birth asphyxia (BA) is the most frequent cause of neonatal death as well as central nervous system (CNS) injury. BA is often associated with neonatal seizures, which only poorly respond to anti-seizure medications and may contribute to the adverse neurodevelopmental outcome. Using a non-invasive rat model of BA, we have recently reported that the potent benzodiazepine, midazolam, prevents neonatal seizures in ~50% of rat pups. In addition to its anti-seizure effect, midazolam exerts anti-inflammatory actions, which is highly relevant for therapeutic intervention following BA. The 2 major aims of the present study were to examine (1) whether midazolam reduces the adverse outcome of BA, and (2) whether this effect is different in rats that did or did not exhibit neonatal seizures after drug treatment.

METHODS

Behavioral and cognitive tests were performed over 14 months after asphyxia, followed by immunohistochemical analyses.

RESULTS

All vehicle-treated rats had seizures after asphyxia and developed behavioral and cognitive abnormalities, neuroinflammation in gray and white matter, neurodegeneration in the hippocampus and thalamus, and hippocampal mossy fiber sprouting in subsequent months. Administration of midazolam (1 mg/kg i.p.) directly after asphyxia prevented post-asphyctic seizures in ~50% of the rats and resulted in the prevention or decrease of neuroinflammation and the behavioral, cognitive, and neurodegenerative consequences of asphyxia. Except for neurodegeneration in the thalamus, seizures did not seem to contribute to the adverse outcome of asphyxia.

INTERPRETATION

The disease-modifying effect of midazolam identified here strongly suggests that this drug provides a valuable option for improving the treatment and outcome of BA. ANN NEUROL 2023;93:226-243.

Hypothermia combined with neuroprotective adjuvants shortens the duration of hospitalization in infants with hypoxic ischemic encephalopathy: Meta-analysis

Objective: Therapeutic hypothermia (TH) is the current standard of care for neonatal hypoxic-ischemic encephalopathy (HIE), yet morbidity and mortality remain significant. Adjuvant neuroprotective agents have been suggested to augment hypothermic-mediated neuroprotection. This analysis aims to identify the classes of drugs that have been used in combination with hypothermia in the treatment of neonatal HIE and determine whether combination therapy is more efficacious than TH alone. Methods: A systematic search of PubMed, Embase and Medline from conception through December 2022 was conducted. Randomized- and quasi-randomized controlled trials, observational studies and retrospective studies evaluating HIE infants treated with combination therapy versus TH alone were selected. Primary reviewers extracted information on mortality, neurodevelopmental impairment and length of hospitalization for meta-analyses. Effect sizes were pooled using a random-effects model and measured as odds ratio (OR) or mean difference (MD) where applicable, and 95% confidence intervals (CI) were calculated. Risk of bias was assessed using the tool from the Cochrane Handbook for Systematic Reviews of Interventions. Results: The search strategy collected 519 studies, 16 of which met analysis inclusion criteria. HIE infants totaled 1,288 infants from included studies, 646 infants received some form of combination therapy, while 642 received TH alone. GABA receptor agonists, NMDA receptor antagonists, neurogenic and angiogenic agents, stem cells, glucocorticoids and antioxidants were identified as candidate adjuvants to TH that have been evaluated in clinical settings compared to TH alone. Length of hospitalization was significantly reduced in infants treated with combination therapy (MD -4.81, 95% CI [-8.42. to -1.19], p = .009) compared to those treated with TH alone. Risk of mortality and neurodevelopmental impairment did not differ between combination therapy and TH alone groups. Conclusion: Compared to the current standard of care, administration of neuroprotective adjuvants with TH reduced the duration of hospitalization but did not impact the risk of mortality or neurodevelopmental impairment in HIE infants. Meta-analysis was limited by a moderate risk of bias among included studies and small sample sizes. This analysis highlights the need for preclinical trials to conduct drug development studies in hypothermic settings to identify relevant molecular targets that may offer additive or synergistic neuroprotection to TH, and the need for larger powered clinical trials to determine the dose and timing of administration at which maximal clinical benefits are observed for adjuvant neuroprotectants.

Interventions for the Management of Pain and Sedation in Newborns Undergoing Therapeutic Hypothermia for Hypoxic-Ischemic Encephalopathy: A Systematic Review

BACKGROUND

Newborn infants undergoing therapeutic hypothermia (TH) are exposed to multiple painful and stressful procedures. The aim of this systematic review was to assess benefits and harms of pharmacological and non-pharmacological interventions for the management of pain and sedation in newborn infants undergoing TH for hypoxic-ischemic encephalopathy.

METHODS

We included randomized and observational studies reporting any intervention (either drugs or non-pharmacological interventions) to manage pain and sedation in newborn infants (> 33 weeks' gestational age) undergoing TH. We included any dose, duration and route of administration. We also included any type and duration of non-pharmacological interventions. Our prespecified primary outcomes were analgesia and sedation assessed using validated pain scales in the neonatal population; circulatory instability; mortality to discharge; and neurodevelopmental disability. A systematic literature search was conducted in the PubMed, Embase, CINAHL, Cochrane CENTRAL, Scopus, and Web of Science databases, with no language restrictions. Included studies underwent risk-of-bias assessment (Cochrane risk-of-bias tool and ROBINS-I) and data extraction performed by two authors independently. The plan had been to use effect measures such as mean difference for continuous outcomes and risk ratio for dichotomous outcomes, however the included studies are presented in a narrative synthesis due to their paucity and heterogeneity.

RESULTS

Ten studies involving 3551 infants were included-one trial and nine observational studies. Most studies examined the use of phenobarbital or other antiepileptic drugs with primary outcomes related to seizure activity. The single trial that was included compared pentoxifylline with placebo. Among the primary outcomes, six studies reported circulatory instability and five reported mortality to discharge without relevant differences; two studies reported on neurodevelopmental disability and one study reported on pain scale. Three studies were ongoing.

CONCLUSIONS

We found limited evidence to establish the benefits and harms of the interventions for the management of pain and sedation in newborn infants undergoing TH. Long-term outcomes were not reported. Given the very low certainty of evidence-due to imprecision of the estimates, inconsistency and limitations in study design (all nine observational studies with overall serious risk of bias)-for all outcomes, clinical trials are required to determine the most effective interventions in this population.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number: CRD42020205755.

A combination of phenobarbital and the bumetanide derivative bumepamine prevents neonatal seizures and subsequent hippocampal neurodegeneration in a rat model of birth asphyxia

OBJECTIVES

Bumetanide was suggested as an adjunct to phenobarbital for suppression of neonatal seizures. This suggestion was based on the idea that bumetanide, by reducing intraneuronal chloride accumulation through inhibition of the Na-K-2Cl cotransporter NKCC1, may attenuate or abolish depolarizing γ-aminobutyric acid (GABA) responses caused by birth asphyxia. However, a first proof-of-concept clinical trial failed. This could have had several reasons, including bumetanide's poor brain penetration, the wide cellular NKCC1 expression pattern in the brain, and problems with the general concept of NKCC1's role in neonatal seizures. We recently replicated the clinical failure of bumetanide to potentiate phenobarbital's effect in a novel rat model of birth asphyxia. In this study, a clinically relevant dose (0.3 mg/kg) of bumetanide was used that does not lead to NKCC1-inhibitory brain levels. The aim of the present experiments was to examine whether a much higher dose (10 mg/kg) of bumetanide is capable of potentiating phenobarbital in this rat model. Furthermore, the effects of the two lipophilic bumetanide derivatives, the ester prodrug N,N-dimethylaminoethylester of bumetanide (DIMAEB) and the benzylamine derivative bumepamine, were examined at equimolar doses.

METHODS

Intermittent asphyxia was induced for 30 min by exposing male and female P11 rat pups to three 7 + 3 min cycles of 9% and 5% O₂ at constant 20% CO₂ . All control pups exhibited neonatal seizures after the asphyxia.

RESULTS

Even at 10 mg/kg, bumetanide did not potentiate the effect of a submaximal dose (15 mg/kg) of phenobarbital on seizure incidence, whereas a significant suppression of neonatal seizures was determined for combinations of phenobarbital with DIMAEB or, more effectively, bumepamine, which, however, does not inhibit NKCC1. Of interest, the bumepamine/phenobarbital combination prevented the neurodegenerative consequences of asphyxia and seizures in the hippocampus.

SIGNIFICANCE

Both bumepamine and DIMAEB are promising tools that may help to develop more effective lead compounds for clinical trials.

Evaluation of the Neonate with Seizures

Neonatal seizures are common, occurring in 2 to 5 of 1,000 live births in the United States. The neonatal brain is thought to be predisposed toward seizures due to a combination of excessive excitatory and deficient inhibitory neuronal activity. The seizures tend to be focal or multifocal without secondary generalization, resulting in subtle seizure appearance. There are five main categories of neonatal seizures: focal clonic, focal tonic, myoclonic, subtle, and generalized tonic. An electroencephalogram is recommended to diagnose and treat neonatal seizures due to poor reliability of the clinical examination. Causes of neonatal seizures are broad, including trauma, structural brain anomalies, infections, metabolic disorders, drug withdrawal or intoxication, and neonatal epilepsy syndromes. Treatment of neonatal seizures involves management of cardiorespiratory status, correction of metabolic derangements, and antiepileptics as needed. The most common antiepileptics used in neonates are phenobarbital, levetiracetam, and fosphenytoin. The long-term risk of neurodevelopmental disability varies depending upon the etiology of neonatal seizures. Close attention to developmental milestones and neurology follow-up is recommended for all neonates with seizures. [Pediatr Ann. 2020;49(7):e292-e298.].

Provision of Sedation and Treatment of Seizures During Neonatal Therapeutic Hypothermia

Hypoxic-ischemic encephalopathy (HIE) produces a high rate of long-term neurodevelopmental disability in survivors. Therapeutic hypothermia dramatically improves the incidence of intact survival, but does not eliminate adverse outcomes. The ideal provision of sedation and treatment of seizures during therapeutic hypothermia represent therapeutic targets requiring optimization in practice. Physiologic stress from therapeutic hypothermia may obviate some of the benefits of this therapy. Morphine is commonly utilized to provide comfort, despite limited empiric evidence supporting safety and efficacy. Dexmedetomidine represents an interesting alternative, with preclinical data suggesting direct efficacy against shivering during induced hypothermia and neuroprotection in the setting of HIE. Pharmacokinetic properties must be considered when utilizing either agent, with safety dependent on conservative dosing and careful monitoring. HIE is the leading cause of neonatal seizures. Traditional therapies, including phenobarbital, fosphenytoin, and benzodiazepines, control seizures in the vast majority of neonates. Concerns about the acute and long-term effects of these agents have led to the exploration of alternative anticonvulsants, including levetiracetam. Unfortunately, levetiracetam is inferior to phenobarbital as first-line therapy for neonatal seizures. Considering both the benefits and risks of traditional anticonvulsant agents, treatment should be limited to the shortest duration indicated, with maintenance therapy reserved for neonates at high risk for recurrent seizures.

Electroencephalographic monitoring for seizure identification and prognosis in term neonates

Seizures represent a manifestation of neurological disease in the neonatal period. Historically, neonatal seizures were identified by direct clinical observation. However, since most seizures are electroencephalographic (EEG)-only (subclinical, non-convulsive) and clinical manifestations may be subtle, many clinicians place increasing importance on EEG data including conventional EEG or amplitude-integrated EEG to identify seizures in neonates. Beyond seizure identification, the EEG is a robust source of information about brain function that can be useful for neurobehavioral prognostication in some neonates. This review summarizes the available data regarding EEG for neonatal seizure diagnosis and brain function assessment.

The effects of adding prophylactic phenobarbital to therapeutic hypothermia in the term-equivalent hypoxic-ischemic rat

BackgroundHypoxic-ischemic encephalopathy (HIE) is a major cause of neonatal morbidity and mortality. Therapeutic hypothermia (TH) is the only available intervention, but neuroprotection is incomplete and variable. Seizures are common in infants with HIE undergoing TH and may worsen outcome. Phenobarbital (PB) is sometimes added, although use of prophylactic PB is controversial in the neonate. We hypothesize that prophylactic PB will not reduce, and may enhance, the neuroprotective effects of TH on brain injury and motor outcomes in the postnatal day 10 (P10) hypoxic-ischemic (HI) rat.MethodsP10 rat pups were subjected to unilateral HI and 4 h recovery with: normothermia (N); hypothermia (TH); and hypothermia with phenobarbital (TH+PB). Brain damage was assessed longitudinally at 24 h and 2 weeks using brain magnetic resonance imaging and 12 weeks using histochemical analysis. Motor function was assessed with the beam walk and cylinder tests.ResultsTH and TH+PB induced neuroprotection, as measured by global brain damage score and improved motor function. Exploratory analyses suggest that TH+PB may confer enhanced protection, especially to the extent of damage.ConclusionProphylactic PB with TH is not deleterious and may provide additional long-term neuroprotection, including improvement of motor outcomes following HI in the term-equivalent, neonatal rat.

The use of phenobarbital and other anti-seizure drugs in newborns

Neonatal seizures constitute the most frequent presenting neurologic sign encountered in the neonatal intensive care unit. Despite limited efficacy and safety data, phenobarbital continues to be used near-universally as the first-line anti-seizure drug (ASD) in neonates. The choice of second-line ASDs varies by provider and institution, and is still not supported by sufficient scientific evidence. In this review, we discuss the available evidence supporting the efficacy, mechanism of action, potential adverse effects, key pharmacokinetic characteristics such as interaction with therapeutic hypothermia, logistical issues, and rationale for use of neonatal ASDs. We describe the widely used neonatal ASDs, namely phenobarbital, phenytoin, midazolam, and levetiracetam, in addition to potential ASDs, including lidocaine, topiramate, and bumetanide.

Neuroprotective Strategies after Neonatal Hypoxic Ischemic Encephalopathy

Neonatal hypoxic ischemic encephalopathy (HIE) is a devastating disease that primarily causes neuronal and white matter injury and is among the leading cause of death among infants. Currently there are no well-established treatments; thus, it is important to understand the pathophysiology of the disease and elucidate complications that are creating a gap between basic science and clinical translation. In the development of neuroprotective strategies and translation of experimental results in HIE, there are many limitations and challenges to master based on an appropriate study design, drug delivery properties, dosage, and use in neonates. We will identify understudied targets after HIE, as well as neuroprotective molecules that bring hope to future treatments such as melatonin, topiramate, xenon, interferon-beta, stem cell transplantation. This review will also discuss some of the most recent trials being conducted in the clinical setting and evaluate what directions are needed in the future.

Strategies to prevent reperfusion injury to the brain following intrapartum hypoxia-ischemia

Hypoxia-ischemia is an infrequent event which may occur prior to or during delivery, following a period of decreased placental and/or fetal blood flow. Following recovery, a reperfusion phase and secondary energy failure may occur 6-48 h subsequent to the initial insult. Therapeutic hypothermia may be offered to infants at risk for evolving encephalopathy if identified within the 6 h therapeutic window, and should be instituted as early as possible for eligible infants. Additionally, the clinician must pay close attention to supportive measures such as avoidance of hyperthermia, as well as comprehensive management of clinical or electrographic seizures, blood pressure, blood glucoses, and carbon dioxide levels.

Treatment of neonatal seizures

Seizures occur more often during the neonatal period than at any other period of life. Precise incidence is difficult to delineate and depends on study population and criteria used for diagnosis of seizures. Controversy exists as to whether neonatal seizures themselves cause damage to the developing brain, or if the damage is primarily due to the underlying cause of the seizures. As a result of this controversy there is an ongoing discussion as to whether all seizures (both clinical and subclinical) should be treated. When (sub)clinical seizures are treated, there is no consensus about the most appropriate treatment for neonatal seizures and how to assess the efficacy of treatment. Current therapeutic options to treat neonatal seizures (i.e. primarily first generation antiepileptics) are relatively ineffective. There is an urgent need for prospective, randomized, controlled trials for efficacy and safety of these second-generation antiepileptic drugs in neonates. The aim of this review is to survey current knowledge regarding treatment of neonatal seizures in both term and preterm infants.

Cooling for newborns with hypoxic ischaemic encephalopathy

BACKGROUND

Newborn animal studies and pilot studies in humans suggest that mild hypothermia following peripartum hypoxia-ischaemia in newborn infants may reduce neurological sequelae without adverse effects.

OBJECTIVES

To determine the effect of therapeutic hypothermia in encephalopathic asphyxiated newborn infants on mortality, long-term neurodevelopmental disability and clinically important side effects.

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review Group as outlined in The Cochrane Library (Issue 2, 2007). Randomised controlled trials evaluating therapeutic hypothermia in term and late preterm newborns with hypoxic ischaemic encephalopathy were identified by searching the Oxford Database of Perinatal Trials, the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, 2007, Issue 2), MEDLINE (1966 to June 2007), previous reviews including cross-references, abstracts, conferences, symposia proceedings, expert informants and journal handsearching. We updated this search in May 2012.

SELECTION CRITERIA

We included randomised controlled trials comparing the use of therapeutic hypothermia with standard care in encephalopathic term or late preterm infants with evidence of peripartum asphyxia and without recognisable major congenital anomalies. The primary outcome measure was death or long-term major neurodevelopmental disability. Other outcomes included adverse effects of cooling and 'early' indicators of neurodevelopmental outcome.

DATA COLLECTION AND ANALYSIS

Four review authors independently selected, assessed the quality of and extracted data from the included studies. Study authors were contacted for further information. Meta-analyses were performed using risk ratios (RR) and risk differences (RD) for dichotomous data, and weighted mean difference for continuous data with 95% confidence intervals (CI).

MAIN RESULTS

We included 11 randomised controlled trials in this updated review, comprising 1505 term and late preterm infants with moderate/severe encephalopathy and evidence of intrapartum asphyxia. Therapeutic hypothermia resulted in a statistically significant and clinically important reduction in the combined outcome of mortality or major neurodevelopmental disability to 18 months of age (typical RR 0.75 (95% CI 0.68 to 0.83); typical RD -0.15, 95% CI -0.20 to -0.10); number needed to treat for an additional beneficial outcome (NNTB) 7 (95% CI 5 to 10) (8 studies, 1344 infants). Cooling also resulted in statistically significant reductions in mortality (typical RR 0.75 (95% CI 0.64 to 0.88), typical RD -0.09 (95% CI -0.13 to -0.04); NNTB 11 (95% CI 8 to 25) (11 studies, 1468 infants) and in neurodevelopmental disability in survivors (typical RR 0.77 (95% CI 0.63 to 0.94), typical RD -0.13 (95% CI -0.19 to -0.07); NNTB 8 (95% CI 5 to 14) (8 studies, 917 infants). Some adverse effects of hypothermia included an increase sinus bradycardia and a significant increase in thrombocytopenia.

AUTHORS' CONCLUSIONS

There is evidence from the 11 randomised controlled trials included in this systematic review (N = 1505 infants) that therapeutic hypothermia is beneficial in term and late preterm newborns with hypoxic ischaemic encephalopathy. Cooling reduces mortality without increasing major disability in survivors. The benefits of cooling on survival and neurodevelopment outweigh the short-term adverse effects. Hypothermia should be instituted in term and late preterm infants with moderate-to-severe hypoxic ischaemic encephalopathy if identified before six hours of age. Further trials to determine the appropriate techniques of cooling, including refinement of patient selection, duration of cooling and method of providing therapeutic hypothermia, will refine our understanding of this intervention.

Cerebral oxygenation during subclinical seizures in neonatal hypoxic-ischaemic encephalopathy

Treatment of subclinical seizures in newborn HIE remains a contentious issue, especially in light of potential adverse effects of aggressive use of anticonvulsants. We report on the association of subclinical seizures with changes in cerebral oxygenation in an infant with HIE. Our results show that subclinical seizures of longer durations and with associated autonomic disturbance (increased blood pressure) are more likely to be associated with fluctuation in cerebral oxygenation, with some seizures resulting in cerebral hypoxia. Future studies should aim to delineate the effects of subclinical seizure and anticonvulsant treatment on cerebral oxygenation, and their relationships to developmental outcome. Level of cerebral oxygenation may play a role in refining anti-convulsant treatment and management of subclinical seizures in newborns.

Does phenobarbital improve the effectiveness of therapeutic hypothermia in infants with hypoxic-ischemic encephalopathy?

OBJECTIVE

To determine whether phenobarbital (PB) given before therapeutic hypothermia to infants with hypoxic-ischemic encephalopathy (HIE) augments the neuroprotective efficacy of hypothermia.

STUDY DESIGN

Records of 68 asphyxiated infants of 36 weeks' gestation, who received hypothermia for moderate or severe HIE were reviewed. Some of these infants received PB prophylactically or for clinical seizures. All surviving infants had later brain magnetic resonance imaging (MRI). The composite primary outcome of neonatal death related to HIE with worsening multiorgan dysfunction despite maximal treatment, and the presence of post-hypothermia brain MRI abnormalities consistent with hypoxic-ischemic brain injury, were compared between the infants who received PB before initiation of hypothermia (PB group, n=36) and the infants who did not receive PB before or during hypothermia (No PB group, n=32). Forward logistic regression analysis determined which of the pre-hypothermia clinical and laboratory variables predict the primary outcome.

RESULT

The two groups were similar for severity of asphyxia as assessed by Apgar scores, initial blood pH and base deficit, early neurologic examination, and presence of an intrapartum sentinel event. The composite primary outcome was more frequent in infants from the PB group (PB 78% versus No PB 44%, P=0.006, odds ratio 4.5, 95% confidence interval 1.6 to 12.8). Multivariate analysis identified only the PB receipt before initiation of hypothermia (P=0.002, odds ratio 9.5, 95% confidence interval 2.3 to 39.5), and placental abruption to be independently associated with a worse primary outcome.

CONCLUSION

PB treatment before cooling did not improve the composite outcome of neonatal death or the presence of an abnormal post-hypothermia brain MRI, but the long-term outcomes have not yet been evaluated.

Hypoxic ischemic encephalopathy--what can we learn from humans?

Hypoxic ischemic encephalopathy (HIE) is a condition that occurs in both human newborns and foals. The condition is the subject of extensive current research in human infants, but there have been no direct studies of HIE in foals, and hence, knowledge of the condition has been extrapolated from studies in humans and other animal models. The purpose of this review article is to highlight the most up-to-date and relevant research in the human field, and discuss how this potentially might have an impact in the management of foals with HIE.

A new neurological focus in neonatal intensive care

Advances in the care of high-risk newborn babies have contributed to reduced mortality rates for premature and term births, but the surviving neonates often have increased neurological morbidity. Therapies aimed at reducing the neurological sequelae of birth asphyxia at term have brought hypothermia treatment into the realm of standard care. However, this therapy does not provide complete protection from neurological complications and a need to develop adjunctive therapies for improved neurological outcomes remains. In addition, the care of neurologically impaired neonates, regardless of their gestational age, clearly requires a focused approach to avoid further injury to the brain and to optimize the neurodevelopmental status of the newborn baby at discharge from hospital. This focused approach includes, but is not limited to, monitoring of the patient's brain with amplitude-integrated and continuous video EEG, prevention of infection, developmentally appropriate care, and family support. Provision of dedicated neurocritical care to newborn babies requires a collaborative effort between neonatologists and neurologists, training in neonatal neurology for nurses and future generations of care providers, and the recognition that common neonatal medical problems and intensive care have an effect on the developing brain.

Pathophysiology of perinatal asphyxia: can we predict and improve individual outcomes?

Perinatal asphyxia occurs still with great incidence whenever delivery is prolonged, despite improvements in perinatal care. After asphyxia, infants can suffer from short- to long-term neurological sequelae, their severity depend upon the extent of the insult, the metabolic imbalance during the re-oxygenation period and the developmental state of the affected regions. Significant progresses in understanding of perinatal asphyxia pathophysiology have achieved. However, predictive diagnostics and personalised therapeutic interventions are still under initial development. Now the emphasis is on early non-invasive diagnosis approach, as well as, in identifying new therapeutic targets to improve individual outcomes. In this review we discuss (i) specific biomarkers for early prediction of perinatal asphyxia outcome; (ii) short and long term sequelae; (iii) neurocircuitries involved; (iv) molecular pathways; (v) neuroinflammation systems; (vi) endogenous brain rescue systems, including activation of sentinel proteins and neurogenesis; and (vii) therapeutic targets for preventing or mitigating the effects produced by asphyxia.

Treatment advances in neonatal neuroprotection and neurointensive care

Knowledge of the nature, prognosis, and ways to treat brain lesions in neonatal infants has increased remarkably. Neonatal hypoxic-ischaemic encephalopathy (HIE) in term infants, mirrors a progressive cascade of excito-oxidative events that unfold in the brain after an asphyxial insult. In the laboratory, this cascade can be blocked to protect brain tissue through the process of neuroprotection. However, proof of a clinical effect was lacking until the publication of three positive randomised controlled trials of moderate hypothermia for term infants with HIE. These results have greatly improved treatment prospects for babies with asphyxia and altered understanding of the theory of neuroprotection. The studies show that moderate hypothermia within 6 h of asphyxia improves survival without cerebral palsy or other disability by about 40% and reduces death or neurological disability by nearly 30%. The search is on to discover adjuvant treatments that can further enhance the effects of hypothermia.

Cooling for newborns with hypoxic ischaemic encephalopathy

BACKGROUND

Newborn animal and human pilot studies suggest that mild hypothermia following peripartum hypoxia-ischaemia in newborn infants may reduce neurological sequelae, without adverse effects.

OBJECTIVES

To determine whether therapeutic hypothermia in encephalopathic asphyxiated newborn infants reduces mortality and long-term neurodevelopmental disability, without clinically important side effects.

SEARCH STRATEGY

The standard search strategy of the Neonatal Review Group as outlined in the Cochrane Library (Issue 2, 2003) was used. Randomised controlled trials evaluating therapeutic hypothermia in term newborns with hypoxic ischaemic encephalopathy were identified by searching the Oxford Database of Perinatal Trials, the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library Issue Issue 2, 2003), MEDLINE (1966 to July 2003), previous reviews including cross-references, abstracts, conferences, symposia proceedings, expert informants and journal hand searching.

SELECTION CRITERIA

Randomised controlled trials comparing the use of therapeutic hypothermia with normothermia in encephalopathic newborn infants with evidence of peripartum asphyxia and without recognisable major congenital anomalies were included. The primary outcome measure was death or long-term major neurodevelopmental disability. Other outcomes included adverse effects of cooling and 'early' indicators of neurodevelopmental outcome.

DATA COLLECTION AND ANALYSIS

Three reviewers independently selected, assessed the quality of and extracted data from the included studies. Authors were contacted for further information. Meta-analyses were performed using relative risk and risk difference for dichotomous data, and weighted mean difference for continuous data with 95% confidence intervals.

MAIN RESULTS

Two randomised controlled trials were included in this review, comprising 50 term infants with moderate/ severe encephalopathy and evidence of intrapartum asphyxia. There was no significant effect of therapeutic hypothermia on the combined outcome of death or major neurodevelopmental disability in survivors followed. No adverse effects of hypothermia on short term medical outcomes or on some 'early' indicators of neurodevelopmental outcome were detected.

REVIEWER'S CONCLUSIONS

Although two small randomised controlled trials demonstrated neither evidence of benefit or harm, current evidence is inadequate to assess either safety or efficacy of therapeutic hypothermia in newborn infants with hypoxic ischaemic encephalopathy. Therapeutic hypothermia for encephalopathic asphyxiated newborn infants should be further evaluated in well designed randomised controlled trials.