Persistent increases in cerebral lactate concentration after birth asphyxia

Longitudinal perturbations of plasma nuclear magnetic resonance profiles in neonatal encephalopathy

BACKGROUND

Neonatal encephalopathy (NE) is a major cause of mortality and severe neurological disability in the neonatal period and beyond. We hypothesized that the degree of brain injury is reflected in the molecular composition of peripheral blood samples.

METHODS

A sub-cohort of 28 newborns included in the HYPOTOP trial was studied. Brain injury was assessed by magnetic resonance imaging (MRI) once per patient and neurodevelopment at 24 months of age was evaluated using the Bayley III Scales of Infant and Toddler Development. The nuclear magnetic resonance (NMR) profile of 60 plasma samples collected before, during, and after cooling was recorded.

RESULTS

In total, 249 molecular features were quantitated in plasma samples from newborns and postnatal age showed to affect detected NMR profiles. Lactate, beta-hydroxybutyrate, pyruvate, and three triglyceride biomarkers showed the ability to discern between different degrees of brain injury according to MRI scores. The prediction performance of lactate was superior as compared to other clinical and biochemical parameters.

CONCLUSIONS

This is the first longitudinal study of an ample compound panel recorded by NMR spectroscopy in plasma from NE infants. The serial determination of lactate confirms its solid position as reliable candidate biomarker for predicting the severity of brain injury.

IMPACT

The use of nuclear magnetic resonance (NMR) spectroscopy enables the simultaneous quantitation of 249 compounds in a small volume (i.e., 100 μL) of plasma. Longitudinal perturbations of plasma NMR profiles were linked to magnetic resonance imaging (MRI) outcomes of infants with neonatal encephalopathy (NE). Lactate, beta-hydroxybutyrate, pyruvate, and three triglyceride biomarkers showed the ability to discern between different degrees of brain injury according to MRI scores. Lactate is a minimally invasive candidate biomarker for early staging of MRI brain injury in NE infants that might be readily implemented in clinical guidelines for NE outcome prediction.

A Metabolomic Approach in Search of Neurobiomarkers of Perinatal Asphyxia: A Review of the Current Literature

Perinatal asphyxia and the possible sequelae of hypoxic-ischemic encephalopathy (HIE), are associated with high morbidity and mortality rates. The use of therapeutic hypothermia (TH) commencing within the first 6 h of life-currently the only treatment validated for the management of HIE-has been proven to reduce the mortality rate and disability seen at follow up at 18 months. Although there have been attempts to identify neurobiomarkers assessing the severity levels in HIE; none have been validated in clinical use to date, and the lack thereof limits the optimal treatment for these vulnerable infants. Metabolomics is a promising field of the "omics technologies" that may: identify neurobiomarkers, help improve diagnosis, identify patients prone to developing HIE, and potentially improve targeted neuroprotection interventions. This review focuses on the current evidence of metabolomics, a novel tool which may prove to be a useful in the diagnosis, management and treatment options for this multifactorial complex disease. Some of the most promising metabolites analyzed are the group of acylcarnitines: Hydroxybutyrylcarnitine (Malonylcarnitine) [C3-DC (C4-OH)], Tetradecanoylcarnitine [C14], L-Palmitoylcarnitine [C16], Hexadecenoylcarnitine [C16:1], Stearoylcarnitine [C18], and Oleoylcarnitine [C18:1]. A metabolomic "fingerprint" or "index," made up of 4 metabolites (succinate × glycerol/(β-hydroxybutyrate × O-phosphocholine)), seems promising in identifying neonates at risk of developing severe HIE.

Acute symptomatic neonatal seizures, brain injury, and long-term outcome: The role of neuroprotective strategies

INTRODUCTION

Neonatal seizures are frequent but underdiagnosed manifestations of acute brain dysfunction and an important contributor to unfavorable outcomes. Etiology and severity of brain injury are the single strongest outcome determinants.

AREAS COVERED

The authors will discuss the prognostic role of acute symptomatic seizures versus brain injury and the main neuroprotective and neurorestorative strategies for full-term and preterm infants.

EXPERT OPINION

Prolonged acute symptomatic seizures likely contribute to long-term outcomes by independently adding further brain injury to initial insults. Correct timing and dosing of therapeutic interventions, depending on etiology and gestational ages, need careful evaluation. Although promising strategies are under study, the only standard of care is whole-body therapeutic hypothermia in full-term newborns with hypoxic-ischemic encephalopathy.

The prognostic value of the level of lactate in umbilical cord blood in predicting complications of neonates with meconium aspiration syndrome

BACKGROUND

In spite of significant advances in therapeutic, diagnostic and even medical modalities, meconium management continues to be a concern for management. It has been recently assumed that trace of lactate in both serum and urine can be a sign of the asphyxia in neonates. However, no study has been done on the prognostic value of increasing lactate concentration in umbilical cord blood for predicting the outcomes of meconium aspiration syndrome (MAS), which was our aim in this study.

METHODS

Thin cross-sectional study was performed on 150 neonates suffering meconium aspiration syndrome who were admitted to Akbar Abadi hospital in Tehran between 2016 and 2018. Samples of umbilical cord blood were extracted from neonates and sent to the reference laboratory to measure lactate level as well as arterial blood gas analysis. The neonatal characteristics as well as postdelivery complications were also collected by reviewing the hospital recorded files.

RESULTS

Thick meconium stained amniotic fluid (TKMSF) was found in 40.0% and thin meconium stained amniotic fluid (TNMSF) in 60.0%. The mean level of lactate was significantly higher in those neonates with morbidities including pulmonary hemorrhage, persistent pulmonary hypertension of the neonate (PPHN), intraventricular hemorrhage (IVH), and respiratory failure requiring ventilation support. According to the ROC curve analysis, increasing lactate in umbilical cord blood could predict occurrence of pulmonary hemorrhage (AUC = 0.885), PPHN (AUC = 0.832), IVH (AUC = 0.898), and requiring ventilation (AUC = 0.833). Comparing the two groups with TKMSF and TNMSF showed higher gestational age, lower Apgar score, lower BE, higher PCO₂, lower PO₂, lower PH as well as higher serum lactate. In this regard and using the ROC curve analysis (Table 4), increased lactate could effectively discriminate TKMSF from TNMSF (AUC = 0.998) with the best cut-off value of 4.10.

CONCLUSION

The increase in lactate in the umbilical cord blood (>4.1 mmol/L with high sensitivity and specificity) can distinguish between thick meconium and thin meconium forms in amniotic acid and thus can determine the severity of MAS. Also, increasing serum lactate levels is an accurate indicator for predicting complications such as pulmonary hemorrhage, PPHN, IVH, and need for ventilation in newborns with this syndrome. This diagnostic accuracy is even beyond the usual markers for arterial gas analysis, such as PH, PCO₂, PO₂ and BE.

Assessing Cerebral Metabolism in the Immature Rodent: From Extracts to Real-Time Assessments

Brain development is an energy-expensive process. Although glucose is irreplaceable, the developing brain utilizes a variety of substrates such as lactate and the ketone bodies, β-hydroxybutyrate and acetoacetate, to produce energy and synthesize the structural components necessary for cerebral maturation. When oxygen and nutrient supplies to the brain are restricted, as in neonatal hypoxia-ischemia (HI), cerebral energy metabolism undergoes alterations in substrate use to preserve the production of adenosine triphosphate. These changes have been studied by in situ biochemical methods that yielded valuable quantitative information about high-energy and glycolytic metabolites and established a temporal profile of the cerebral metabolic response to hypoxia and HI. However, these analyses relied on terminal experiments and averaging values from several animals at each time point as well as challenging requirements for accurate tissue processing.More recent methodologies have focused on in vivo longitudinal analyses in individual animals. The emerging field of metabolomics provides a new investigative tool for studying cerebral metabolism. Magnetic resonance spectroscopy (MRS) has enabled the acquisition of a snapshot of the metabolic status of the brain as quantifiable spectra of various intracellular metabolites. Proton (1H) MRS has been used extensively as an experimental and diagnostic tool of HI in the pursuit of markers of long-term neurodevelopmental outcomes. Still, the interpretation of the metabolite spectra acquired with 1H MRS has proven challenging, due to discrepancies among studies, regarding calculations and timing of measurements. As a result, the predictive utility of such studies is not clear. 13C MRS is methodologically more challenging, but it provides a unique window on living tissue metabolism via measurements of the incorporation of 13C label from substrates into brain metabolites and the localized determination of various metabolic fluxes. The newly developed hyperpolarized 13C MRS is an exciting method for assessing cerebral metabolism in vivo, that bears the advantages of conventional 13C MRS but with a huge gain in signal intensity and much shorter acquisition times. The first part of this review article provides a brief description of the findings of biochemical and imaging methods over the years as well as a discussion of their associated strengths and pitfalls. The second part summarizes the current knowledge on cerebral metabolism during development and HI brain injury.

Biomarkers in neonatal hypoxic-ischemic encephalopathy-Review of the literature to date and future directions for research

The widespread introduction of therapeutic hypothermia as a standard of care in hypoxic-ischemic encephalopathy (HIE) has brought increasing pressure on clinicians to make an early and accurate assessment of the degree of hypoxic injury (HI) that has occurred and the severity of the encephalopathy that will ensue. No single blood-based marker is currently robust enough to detect significant HI or predict outcome. However, research in the field has been active in the last 10 years and we know that HIE is associated with predictable alterations in the expression of a number of inflammatory proteins, neuron-specific proteins, metabolite pathways, and microRNA. These alterations evolve quickly over the first hours and days of life. Predictive power varies depending on the timing of measurement of the biomarker, the sample type, and the case mix of the cohort examined. Combining clinical data with biochemical measurements is currently the most likely path toward improved detection and prediction of outcome in neonatal HIE.

Fetal and neonatal neuroimaging

Magnetic resonance imaging (MRI) can provide detail of the soft tissues of the fetal and neonatal brain that cannot be obtained by any other imaging modality. Conventional T1 and T2 weighted sequences provide anatomic detail of the normally developing brain and can demonstrate lesions, including those associated with preterm birth, hypoxic ischemic encephalopathy, perinatal arterial stroke, infections, and congenital malformations. Specialized imaging techniques can be used to assess cerebral vasculature (magnetic resonance angiography and venography), cerebral metabolism (magnetic resonance spectroscopy), cerebral perfusion (arterial spin labeling), and function (functional MRI). A wealth of quantitative tools, most of which were originally developed for the adult brain, can be applied to study the developing brain in utero and postnatally including measures of tissue microstructure obtained from diffusion MRI, morphometric studies to measure whole brain and regional tissue volumes, and automated approaches to study cortical folding. In this chapter, we aim to describe different imaging approaches for the fetal and neonatal brain, and to discuss their use in a range of clinical applications.

What is MR spectroscopy?

¹H-Magnetic Resonance Spectroscopy (MRS) is a novel advanced imaging technique used as an adjunct to MRI to reveal complementary non-invasive information about the biochemical composition of imaged tissue. Clinical uses in paediatrics include aiding diagnosis of brain tumours, neonatal disorders such as hypoxic-ischaemic encephalopathy, inherited metabolic diseases, traumatic brain injury, demyelinating conditions and infectious brain lesions. MRS has potential to improve diagnosis and treatment monitoring of childhood brain tumours and other CNS diseases, facilitate biopsy and surgical planning, and provide prognostic biomarkers. MRS is employed as a research tool outside the brain in liver disease and disorders of muscle metabolism. The range of clinical uses is likely to increase with growing evidence for added value. Multicentre trials are needed to definitively establish the benefits of MRS in specific clinical scenarios and integrate this promising new technique into routine practice to improve patient care. This article gives a brief overview of MRS and its potential clinical applications, and addresses challenges surrounding translation into practice.

Changes in Brain Metabolite Concentrations after Neonatal Hypoxic-ischemic Encephalopathy

Purpose To investigate the time-course changes and predictive utility of brain metabolite concentrations in neonatal hypoxic-ischemic encephalopathy (HIE). Materials and Methods Sixty-eight neonates (age, 35-41 gestational weeks) with HIE were admitted to a neonatal intensive care unit between September 2009 and March 2016 and examined by using proton MR spectroscopy at 18-96 hours (n = 25) and 7-14 days (n = 64) after birth (35-43 postmenstrual weeks) to estimate metabolite concentrations in the deep gray matter. Adverse outcome was defined as death or neurodevelopmental impairment at 18-22 months of age. Areas under the receiver operating characteristic curves were calculated to evaluate the prognostic values of metabolites. Results At 18-96 hours, N-acetylaspartate and creatine concentrations were lower, whereas lactate, and glutamate and glutamine (Glx) concentrations were higher in neonates with adverse outcomes than in those with favorable outcomes. Metabolite concentrations at 18-96 hours decreased during days 7-14 in neonates with adverse outcomes but did not change in those with favorable outcomes. For N-acetylaspartate, creatine, lactate, and Glx concentrations measured at 18-96 hours to predict adverse outcomes, areas under the receiver operating characteristic curve were 0.98, 0.89, 0.96, and 0.88, respectively, whereas at 7-14 days, the areas under the receiver operating characteristic curve were 0.97, 0.97, 0.59, and 0.36, respectively. Conclusion Time-dependent reductions in N-acetylaspartate and creatine concentrations at both 18-96 hours and 7-14 days accurately predicted adverse outcomes. However, higher lactate and glutamate and glutamine concentrations were often transient.

Cerebral Lactate Concentration in Neonatal Hypoxic-Ischemic Encephalopathy: In Relation to Time, Characteristic of Injury, and Serum Lactate Concentration

Background

Cerebral lactate concentration can remain detectable in neonatal hypoxic-ischemic encephalopathy (HIE) after hemodynamic stability. The temporal resolution of regional cerebral lactate concentration in relation to the severity or area of injury is unclear. Furthermore, the interplay between serum and cerebral lactate in neonatal HIE has not been well defined. The study aims to describe cerebral lactate concentration in neonatal HIE in relation to time, injury, and serum lactate.

Design/methods

Fifty-two newborns with HIE undergoing therapeutic hypothermia (TH) were enrolled. Magnetic resonance imaging and spectroscopy (MRI + MR spectroscopy) were performed during and after TH at 54.6 ± 15.0 and 156 ± 57.6 h of life, respectively. Severity and predominant pattern of injury was scored radiographically. Single-voxel ¹H MR spectra were acquired using short-echo (35 ms) PRESS sequence localized to the basal ganglia (BG), thalamus (Thal), gray matter (GM), and white matter. Cerebral lactate concentration was quantified by LCModel software. Serum and cerebral lactate concentrations were plotted based on age at time of measurement. Multiple comparisons of regional cerebral lactate concentration based on severity and predominant pattern of injury were performed. Spearman's Rho was computed to determine correlation between serum lactate and cerebral lactate concentration at the respective regions of interest.

Results

Overall, serum lactate concentration decreased over time. Cerebral lactate concentration remained low for less severe injury and decreased over time for more severe injury. Cerebral lactate remained detectable even after TH. During TH, there was a significant higher concentration of cerebral lactate at the areas of injury and also when injury was more severe. However, these differences were no longer observed after TH. There was a weak correlation between serum lactate and cerebral lactate concentration at the BG (r_s = 0.3, p = 0.04) and Thal (r_s = 0.35, p = 0.02). However, in infants with moderate-severe brain injury, a very strong correlation exists between serum lactate and cerebral lactate concentration at the BG (r_s = 0.7, p = 0.03), Thal (r_s = 0.9 p = 0.001), and GM (r_s = 0.6, p = 0.04) regions.

Conclusion

Cerebral lactate is most significantly different between regions and severity of injury during TH. There is a moderate correlation between serum and cerebral lactate concentration measured in the deep gray nuclei during TH. Differences in injury and altered regional cerebral metabolism may account for these differences.

MRI and spectroscopy in (near) term neonates with perinatal asphyxia and therapeutic hypothermia

BACKGROUND

Previous studies have demonstrated the association of abnormalities on diffusion-weighted MRI (DW-MRI) and proton magnetic resonance spectroscopy (¹H-MRS) in infants with perinatal asphyxia. The use of therapeutic hypothermia might change this association.

AIM

To study the association between DW-MRI and ¹H-MRS and outcome after perinatal asphyxia and therapeutic hypothermia in infants with a gestational age of ≥36 weeks.

PATIENTS AND METHODS

Infants with perinatal asphyxia and therapeutic hypothermia (n=88) were included when an MR examination was performed within 7 days after birth. Apparent diffusion coefficient (ADC) values of the basal ganglia and thalamus were calculated, as were lactate/N-acetylaspartate (LAC/NAA) and N-acetylaspartate/choline (NAA/Cho) ratios. Death or an abnormal neurodevelopment at ≥24 months was considered an adverse outcome. Receiver operating characteristic analysis was performed to determine cut-off levels.

RESULTS

Of the 88 infants, 22 died and 7 had an adverse neurodevelopmental outcome. In infants with an adverse outcome, ADC values of the basal ganglia and thalamus were significantly lower, and Lac/NAA ratios were significantly higher than in infants with a normal outcome. Areas under the curve of ADC of the basal ganglia, thalami and Lac/NAA ratio were 0.89, 0.88 and 0.87, respectively. NAA/Cho ratios were in this cohort not associated with outcome.

CONCLUSIONS

During and after therapeutic hypothermia, low ADC values and high Lac/NAA ratios of the basal ganglia and thalamus are associated with an adverse outcome in infants with perinatal asphyxia.

Fifty years of brain imaging in neonatal encephalopathy following perinatal asphyxia

In the past brain imaging of term infants with hypoxic-ischemic encephalopathy (HIE) was performed with cranial ultrasound (cUS) and computed tomography (CT). Both techniques have several disadvantages sensitivity and specificity is limited compared with magnetic resonance imaging (MRI) and CT makes use of radiation. At present MRI including diffusion weighted MRI during the first week of life, has become the method of choice for imaging infants with HIE. In addition to imaging, blood vessels and blood flow can be visualized using MR angiography, MR venography, and arterial spin labeling. Since the use of these techniques additional lesions in infants with HIE, such as arterial ischemic stroke, sinovenous thrombosis, and subdural hemorrhages can be diagnosed, and the incidence appears to be higher than shown previously. Phosphorus magnetic resonance spectroscopy (MRS) has led to the concept of secondary energy failure in infants with HIE, but has not been widely used. Proton MRS of the basal ganglia and thalamus is one of the best predictors of neurodevelopmental outcome. cUS should still be used for screening infants admitted to a NICU with neonatal encephalopathy. In the future magnetic resonance techniques will be increasingly used as early biomarkers of neurodevelopmental outcome in trials of neuroprotective strategies.

Basic Principles and Clinical Applications of Magnetic Resonance Spectroscopy in Neuroradiology

Magnetic resonance spectroscopy is a powerful tool to assist daily clinical diagnostics. This review is intended to give an overview on basic principles of the technology, discuss some of its technical aspects, and present typical applications in daily clinical routine in neuroradiology.

Metabolic Alterations in Developing Brain After Injury: Knowns and Unknowns

Brain development is a highly orchestrated complex process. The developing brain utilizes many substrates including glucose, ketone bodies, lactate, fatty acids and amino acids for energy, cell division and the biosynthesis of nucleotides, proteins and lipids. Metabolism is crucial to provide energy for all cellular processes required for brain development and function including ATP formation, synaptogenesis, synthesis, release and uptake of neurotransmitters, maintaining ionic gradients and redox status, and myelination. The rapidly growing population of infants and children with neurodevelopmental and cognitive impairments and life-long disability resulting from developmental brain injury is a significant public health concern. Brain injury in infants and children can have devastating effects because the injury is superimposed on the high metabolic demands of the developing brain. Acute injury in the pediatric brain can derail, halt or lead to dysregulation of the complex and highly regulated normal developmental processes. This paper provides a brief review of metabolism in developing brain and alterations found clinically and in animal models of developmental brain injury. The metabolic changes observed in three major categories of injury that can result in life-long cognitive and neurological disabilities, including neonatal hypoxia-ischemia, pediatric traumatic brain injury, and brain injury secondary to prematurity are reviewed.

Metabolic Alterations in Developing Brain After Injury: Knowns and Unknowns

Brain development is a highly orchestrated complex process. The developing brain utilizes many substrates including glucose, ketone bodies, lactate, fatty acids and amino acids for energy, cell division and the biosynthesis of nucleotides, proteins and lipids. Metabolism is crucial to provide energy for all cellular processes required for brain development and function including ATP formation, synaptogenesis, synthesis, release and uptake of neurotransmitters, maintaining ionic gradients and redox status, and myelination. The rapidly growing population of infants and children with neurodevelopmental and cognitive impairments and life-long disability resulting from developmental brain injury is a significant public health concern. Brain injury in infants and children can have devastating effects because the injury is superimposed on the high metabolic demands of the developing brain. Acute injury in the pediatric brain can derail, halt or lead to dysregulation of the complex and highly regulated normal developmental processes. This paper provides a brief review of metabolism in developing brain and alterations found clinically and in animal models of developmental brain injury. The metabolic changes observed in three major categories of injury that can result in life-long cognitive and neurological disabilities, including neonatal hypoxia-ischemia, pediatric traumatic brain injury, and brain injury secondary to prematurity are reviewed.

Metabolomic profiling in perinatal asphyxia: a promising new field

Metabolomics, the latest “omic” technology, is defined as the comprehensive study of all low molecular weight biochemicals, “metabolites” present in an organism. As a systems biology approach, metabolomics has huge potential to progress our understanding of perinatal asphyxia and neonatal hypoxic-ischaemic encephalopathy, by uniquely detecting rapid biochemical pathway alterations in response to the hypoxic environment. The study of metabolomic biomarkers in the immediate neonatal period is not a trivial task and requires a number of specific considerations, unique to this disease and population. Recruiting a clearly defined cohort requires standardised multicentre recruitment with broad inclusion criteria and the participation of a range of multidisciplinary staff. Minimally invasive biospecimen collection is a priority for biomarker discovery. Umbilical cord blood presents an ideal medium as large volumes can be easily extracted and stored and the sample is not confounded by postnatal disease progression. Pristine biobanking and phenotyping are essential to ensure the validity of metabolomic findings. This paper provides an overview of the current state of the art in the field of metabolomics in perinatal asphyxia and neonatal hypoxic-ischaemic encephalopathy. We detail the considerations required to ensure high quality sampling and analysis, to support scientific progression in this important field.

Early hyperglycemia is associated with poor gross motor outcome in asphyxiated term newborns

BACKGROUND

Hyperglycemia after ischemic stroke in adults and after near-drowning in children is associated with a poor neurological outcome. Anaerobic metabolism of glucose leads to buildup of lactic acid, free radical production, mitochondrial failure, and ultimately an increase in neurological injury. In asphyxiated infants, high lactate peaks are seen in the basal ganglia with magnetic resonance spectroscopy. Because motor disability in asphyxiated full-term newborns often relates to injury in the basal ganglia, we hypothesized that hyperglycemia and associated buildup of lactic acid may lead to worse gross motor outcome.

METHODS

Glucose, blood gas values, and demographic data were abstracted from the medical records of 41 term infants with asphyxia and without confounding diagnoses. Their Gross Motor Function Classification System scores were determined from the medical record or by structured telephone interviews.

RESULTS

The outcomes of 14 infants were considered poor on the basis of death within the first 6 months or moderate-to-severe cerebral palsy (Gross Motor Function Classification System score 1-5). The other 27 infants had no gross motor disability (Gross Motor Function Classification System score 0). The highest recorded blood glucose correlated with poor outcome (P = 0.046 by logistic regression). Infants with hyperglycemia (blood glucose > 150 mg/dL) were more likely to have poor outcome (P = 0.017; odds ratio: 5.9; 95% confidence interval: 1.4-24.7).

CONCLUSIONS

High blood glucose in the first 12 hours is associated with poor gross motor outcome in this cohort of asphyxiated term infants. Clinicians should avoid hyperglycemia in managing term infants with asphyxia.

Clinical proton MR spectroscopy in central nervous system disorders

A large body of published work shows that proton (hydrogen 1 [(1)H]) magnetic resonance (MR) spectroscopy has evolved from a research tool into a clinical neuroimaging modality. Herein, the authors present a summary of brain disorders in which MR spectroscopy has an impact on patient management, together with a critical consideration of common data acquisition and processing procedures. The article documents the impact of (1)H MR spectroscopy in the clinical evaluation of disorders of the central nervous system. The clinical usefulness of (1)H MR spectroscopy has been established for brain neoplasms, neonatal and pediatric disorders (hypoxia-ischemia, inherited metabolic diseases, and traumatic brain injury), demyelinating disorders, and infectious brain lesions. The growing list of disorders for which (1)H MR spectroscopy may contribute to patient management extends to neurodegenerative diseases, epilepsy, and stroke. To facilitate expanded clinical acceptance and standardization of MR spectroscopy methodology, guidelines are provided for data acquisition and analysis, quality assessment, and interpretation. Finally, the authors offer recommendations to expedite the use of robust MR spectroscopy methodology in the clinical setting, including incorporation of technical advances on clinical units.

Neonatal exposure to sevoflurane causes significant suppression of hippocampal long-term potentiation in postgrowth rats

BACKGROUND

The inhaled anesthetic sevoflurane is commonly used for neonates in the clinical setting. Recent studies have indicated that exposure of neonatal rodents to sevoflurane causes acute widespread neurodegeneration and long-lasting neurocognitive dysfunction. Although acute toxic effects of sevoflurane on cellular viability in the hippocampus have been reported in some studies, little is known about the effects of neonatal sevoflurane exposure on long-term hippocampal synaptic plasticity, which has been implicated in the processes of learning and memory formation. Our study is the first to examine the long-term electrophysiological impact of neonatal exposure to a clinically relevant concentration of sevoflurane.

METHODS

On postnatal day 7, rats were exposed to sevoflurane (1% or 2% for 2 hours) with oxygen. To eliminate the influence of blood gas abnormalities caused by sevoflurane-induced respiratory suppression, a group of rats were exposed to a high concentration of carbon dioxide (8% for 2 hours) to duplicate respiratory disturbances caused by 2% sevoflurane exposure.

RESULTS

Exposure of neonatal rats to 2% sevoflurane for 2 hours caused significant suppression of long-term potentiation (LTP) induction in the postgrowth period. There was no significant difference between the control group and the CO2-exposed group in LTP induction, indicating that sevoflurane-induced LTP suppression was not caused by blood gas abnormalities.

CONCLUSION

Our present findings indicate that neonatal exposure to sevoflurane at a higher concentration can cause alterations in the hippocampal synaptic plasticity that persists into adulthood.

Magnetic resonance spectroscopy as a prognostic marker in neonatal hypoxic-ischemic encephalopathy: a study protocol for an individual patient data meta-analysis

BACKGROUND

The prognostic accuracy of 1H (proton) magnetic resonance spectroscopy (MRS) in neonatal hypoxic-ischemic encephalopathy has been assessed by a criticized study-based meta-analysis. An individual patient data meta-analysis may overcome some of the drawbacks encountered in the aggregate data meta-analysis. Moreover, the prognostic marker can be assessed quantitatively and the effect of covariates can be estimated.

METHODS

Diagnostic accuracy studies relevant to the study topic were retrieved. The primary authors will be invited to share the raw de-identified study data. These individual patient data will be analyzed using logistic regression analysis. A prediction tool calculating the individualized risk of very adverse outcome will be devised.

DISCUSSION

The proposed individual patient data meta-analysis provides several advantages. Inclusion and exclusion criteria can be applied more uniformly. Furthermore, adjustment is possible for confounding factors and subgroup analyses can be conducted. Our goal is to develop a prediction model for outcome in newborns with hypoxic-ischemic encephalopathy.

Brain development in infants born preterm: looking beyond injury

Infants born very preterm are high risk for acquired brain injury and disturbances in brain maturation. Although survival rates for preterm infants have increased in the last decades owing to improved neonatal intensive care, motor disabilities including cerebral palsy persist, and impairments in cognitive, language, social, and executive functions have not decreased. Evidence from neuroimaging studies exploring brain structure, function, and metabolism has indicated abnormalities in the brain development trajectory of very preterm-born infants that persist through to adulthood. In this chapter, we review neuroimaging approaches for the identification of brain injury in the preterm neonate. Advances in medical imaging and availability of specialized equipment necessary to scan infants have facilitated the feasibility of conducting longitudinal studies to provide greater understanding of early brain injury and atypical brain development and their effects on neurodevelopmental outcome. Improved understanding of the risk factors for acquired brain injury and associated factors that affect brain development in this population is setting the stage for improving the brain health of children born preterm.

Hypoxic–ischemic brain injury and neuroprotection in the newborn infant

Recent clinical trials have confirmed that in term infants with moderate-to-severe hypoxic–ischemic encephalopathy, death and severe developmental disability can be reduced by early treatment with hypothermia. However, meta-analysis of these trials has confirmed that two-thirds of the survivors remain seriously impaired. The search for new neuroprotective interventions has therefore continued. Extensive research has identified the important biochemical pathways that result in neuronal loss, and the subsequent repair and regeneration processes. The most promising neuroprotective agents that limit the former, and promote the latter, are being tested in animal models of hypoxic–ischemic brain injury and are awaiting clinical trials. It is likely that a ‘cocktail’ of agents, affecting a number of pathways, will ultimately prove to be the most effective intervention. The latest additions to a long list of proposed substances are various stem cells that promote neurogenesis by releasing trophic substances into the injured brain. Future clinical trials are likely to employ early biomarkers, of which MRI and proton spectroscopy are probably the most predictive of long-term neurodevelopmental outcome. In conclusion, the exponential increase in knowledge in this field can be expected to provide many more neuroprotective agents within the next decade.

Neonatal exposure to high concentration of carbon dioxide produces persistent learning deficits with impaired hippocampal synaptic plasticity

Although respiratory complications with blood gas abnormalities contribute significantly to neurodevelopment in the immature brain, little is known about the mechanisms via which blood gas abnormalities, such as hypoxic hypercapnia, impair neurocognitive outcomes. To investigate the possible long-term consequences of neonatal exposure to hypoxic hypercapnia regarding learning ability, we investigated the effect of neonatal hypoxic hypercapnia on later functions in the hippocampus, which is a structure that has been implicated in many learning and memory processes. Neonatal rat pups (postnatal day 7; P7) were exposed to a high concentration of carbon dioxide (CO2; 13%) for 2 or 4h. Exposure to CO2 in P7 rat pups caused blood gas abnormalities, including hypercapnia, hypoxia, and acidosis, and disrupted later learning acquisition, as assessed in 10-week-old adult rats subjected to a Morris water maze test. Induction of long-term potentiation (LTP) in the synapses of the hippocampal CA1 area was also impaired, whereas the paired-pulse responses of population spikes exhibited a significant increase, in CO2-exposed rats, suggesting decreased recurrent inhibition in the hippocampus. Such long-lasting modifications in hippocampal synaptic plasticity may contribute to the learning impairments associated with perinatal hypoxic hypercapnia and acidosis.

Noninvasive monitoring of lactate dynamics in human forearm muscle after exhaustive exercise by (1)H-magnetic resonance spectroscopy at 7 tesla

Despite its importance in energy metabolism, lactate in human skeletal muscle has been difficult to detect by noninvasive (1)H-magnetic resonance spectroscopy mainly due to interference from large water and lipid signals. Long echo-time acquisitions at 7 T effectively attenuates the water and lipid signals in forearm muscle allowing direct observation of both lactate resonances, the methine at 4.09 ppm and the methyl at 1.31 ppm. Using this approach, we were able to monitor lactate dynamics at a temporal resolution of 32 s. While lactate was not detectable at rest, immediately after an acute period of exercise to fatigue the forearm muscle, lactate rose to a level comparable to that of creatine (∼30 mmol/kg wet weight). In a typical (1)H-magnetic resonance spectrum collected using a echo-time of 140 ms, the lactate methine and methyl resonances both appear as doublets with an unusually large splitting of ∼20 Hz due to residual dipolar coupling. During muscle recovery following exercise, the lactate signals decay rapidly with a time constant of t½ = 2.0 ± 0.6 min (n = 12 subjects). This fast and simple lactate detection method may prove valuable for monitoring lactate metabolism in cancer and in sports medicine applications.

Neonatal encephalopathy: an inadequate term for hypoxic-ischemic encephalopathy

This Point of View article addresses neonatal encephalopathy (NE) presumably caused by hypoxia-ischemia and the terminology currently in wide use for this disorder. The nonspecific term NE is commonly utilized for those infants with the clinical and imaging characteristics of neonatal hypoxic-ischemic encephalopathy (HIE). Multiple magnetic resonance imaging studies of term infants with the clinical setting of presumed hypoxia-ischemia near the time of delivery have delineated a topography of lesions highly correlated with that defined by human neuropathology and by animal models, including primate models, of hypoxia-ischemia. These imaging findings, coupled with clinical features consistent with perinatal hypoxic-ischemic insult(s), warrant the specific designation of neonatal HIE.

Magnetic resonance biomarkers of neuroprotective effects in infants with hypoxic ischemic encephalopathy

Evaluation of infants with hypoxic ischemic encephalopathy by magnetic resonance spectroscopy and imaging is useful to direct clinical care, and may assist the evaluation of candidate neuroprotective therapies. Cerebral metabolites measured by magnetic resonance spectroscopy, and visual analysis of magnetic resonance images during the first 30 days after birth accurately predict later neurological outcome and are valid biomarkers of the key physiological processes underlying brain injury in neonatal hypoxic ischemic encephalopathy. Visual assessment of magnetic resonance images may also be a suitable surrogate outcome in studies of neuroprotective therapies but current magnetic resonance methods are relatively inefficient for use in early phase, first in human infant studies of novel neuroprotective therapies. However, diffusion tensor imaging and analysis of fractional anisotropy with tract-based spatial statistics promises to be a highly efficient biomarker and surrogate outcome for rapid preliminary evaluation of promising therapies for neonatal hypoxic ischemic injury. Standardisation of scanning protocols and data analysis between different scanners is essential.

Experimental treatments for hypoxic ischaemic encephalopathy

Hypoxic ischaemic encephalopathy continues to be a significant cause of death and disability worldwide. In the last 1-2 years, therapeutic hypothermia has entered clinical practice in industrialized countries and neuroprotection of the newborn has become a reality. The benefits and safety of cooling under intensive care settings have been shown consistently in trials; therapeutic hypothermia reduces death and neurological impairment at 18 months with a number needed to treat of approximately nine. Unfortunately, around half the infants who receive therapeutic hypothermia still have abnormal outcomes. Recent experimental data suggest that the addition of another agent to cooling may enhance overall protection either additively or synergistically. This review discusses agents such as inhaled xenon, N-acetylcysteine, melatonin, erythropoietin and anticonvulsants. The role of biomarkers to speed up clinical translation is discussed, in particular, the use of the cerebral magnetic resonance spectroscopy lactate/N-acetyl aspartate peak area ratios to provide early prognostic information. Finally, potential future therapies such as regeneration/repair and postconditioning are discussed.

Neonatal ECMO Study of Temperature (NEST)--a randomised controlled trial

BACKGROUND

Existing evidence indicates that once mature neonates with severe cardio-respiratory failure become eligible for Extra Corporeal Membrane Oxygenation (ECMO) their chances of intact survival are doubled if they actually receive ECMO. However, significant numbers survive with disability. NEST is a multi-centre randomised controlled trial designed to test whether, in neonates requiring ECMO, cooling to 34 degrees C for the first 48 to 72 hours of their ECMO course leads to improved later health status. Infants allocated to the control group will receive ECMO at 37 degrees C throughout their course, which is currently standard practice around the world. Health status of both groups will be assessed formally at 2 years corrected age.

METHODS/DESIGN

All infants recruited to the study will be cared for in one of the four United Kingdom (UK) ECMO centres. Babies who are thought to be eligible will be assessed by the treating clinician who will confirm eligibility, ensure that consent has been obtained and then randomise the baby using a web based system, based at the National Perinatal Epidemiology Unit (NPEU) Clinical Trials Unit. Trial registration.Babies allocated ECMO without cooling will receive ECMO at 37 degrees C +/- 0.2 degrees C. Babies allocated ECMO with cooling will be managed at 34 degrees C +/- 0.2 degrees C for up to 72 hours from the start of their ECMO run. The minimum duration of cooling will be 48 hours. Rewarming (to 37 degrees C) will occur at a rate of no more than 0.5 degrees C per hour. All other aspects of ECMO management will be identical.

PRIMARY OUTCOME

Cognitive score from the Bayley Scales of Infant and Toddler Development, 3rd edition (Bayley-III) at age of 2 years (24 - 27 months).

DISCUSSION

For the primary analysis, children will be analysed in the groups to which they are assigned, comparing the outcome of all babies allocated to "ECMO with cooling" with all those allocated to "ECMO" alone, regardless of deviation from the protocol or treatment received. For the primary outcome the analysis will compare the mean scores for each group of surviving babies. The rationale for this choice of primary analysis is to give a fair representation of the average ability of assessable children, accepting the limitation that excluding deaths might impose.The consistency of the effect of cooling on the group of babies recruited to the trial will be explored to see whether cooling is of particular help, or not, to specific subgroups of infants, using the statistical test of interaction. Therefore pre-specified subgroup analyses include: (i) whether the ECMO is veno-arterial or veno-venous; (ii) whether the child's oxygenation index at the time of recruitment is <60 or > or = 60; (iii) initial aEEG pattern shown on the cerebral function monitor, and (iv) primary diagnostic group.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN72635512.

Effects of acute perinatal asphyxia in the rat hippocampus

In the present work, we have used a rat animal model to study the early effects of intrauterine asphyxia occurring no later than 60 min following the cesarean-delivery procedure. Transitory hypertonia accompanied by altered posture was observed in asphyxiated pups, which also showed appreciably increased lactate values in plasma and hippocampal tissues. Despite this, there was no difference in terms of either cell viability or metabolic activities such as oxidation of lactate, glucose, and glycine in the hippocampus of those fetuses submitted to perinatal asphyxia with respect to normoxic animals. Moreover, a significant decrease in glutamate, but not GABA uptake was observed in the hippocampus of asphyctic pups. Since intense ATP signaling especially through P2X(7) purinergic receptors can lead to excitotoxicity, a feature which initiates neurotransmission failure in experimental paradigms relevant to ischemia, here we assessed the expression level of the P2X(7) receptor in the paradigm of perinatal asphyxia. A three-fold increase in P2X(7) protein was transiently observed in hippocampus immediately following asphyxia. Nevertheless, further studies are needed to delineate whether the P2X(7) receptor subtype is involved in the pathogenesis, contributing to ongoing brain injury after intrapartum asphyxia. In that case, new pharmacologic intervention strategies providing neuroprotection during the reperfusion phase of injury might be identified.

Evolving understanding of hypoxic-ischemic encephalopathy in the term infant

Our aim was to document changes in the evaluation and prognosis of term-born infants with neonatal encephalopathy of hypoxic-ischemic origin, with particular reference to our own experiences and influences, and to summarize the debate on causation and the relative importance of antenatal and perinatal factors. High quality neonatal cranial ultrasound and magnetic resonance imaging and spectroscopy have enabled the accurate early visualization of different patterns of hypoxic-ischemic brain injury and prediction of their associated outcomes. Long-term follow-up shows that cognitive and memory difficulties may follow even in children without motor deficits. The very early use of electrophysiologic methods has allowed broad prognostic categorization of infants when this is not possible from clinical assessment or imaging, providing a rationale for entry into intervention trials, such as therapeutic hypothermia. This work has also shown that most of these infants have evidence of acute hypoxic-ischemic brain injury that explains their symptoms and outcomes.

Apoptotic mechanisms in the immature brain: involvement of mitochondria

Brain injury after hypoxic-ischemic encephalopathy often develops with delayed appearance, opening a therapeutic window. Clinical studies in newborns show that post-hypoxic-ischemic hypothermia improves outcome. This has generated renewed interest in the molecular mechanisms of hypoxic-ischemic brain injury. In this brief review, we propose that mitochondrial permeabilization is crucial for injury to advance beyond the point of no return. We suggest that excitatory amino acids, nitric oxide, inflammation, trophic factor withdrawal, and an increased pro- versus antiapoptotic Bcl-2 protein ratio will trigger Bax-dependent mitochondrial outer membrane permeabilization. Mitochondrial outer membrane permeabilization, in turn, elicits mitochondrial release of cytochrome C, apoptosis-inducing factor, second mitochondria-derived activator of caspase/Diablo, and HtrA2/Omi. Cytochrome C efflux activates caspase-9/-3, leading to DNA fragmentation. Apoptosis-inducing factor interacts with cyclophilin A and induces chromatinolysis. Blockage of mitochondrial outer membrane permeabilization holds promise as a strategy for perinatal brain protection.

Human fetal brain chemistry as detected by proton magnetic resonance spectroscopy

Magnetic resonance spectroscopy represents an invaluable tool for the in vivo study of brain development at the chemistry level. Whereas magnetic resonance spectroscopy has received wide attention in pediatric and adult settings, only a few studies were performed on the human fetal brain. They revealed changes occurring throughout gestation in the levels of the main metabolites detected by proton magnetic resonance spectroscopy (N-acetylaspartate, choline, myo-inositol, creatine, and glutamate), providing a reference for the normal metabolic brain development. Throughout the third trimester of gestation, N-acetylaspartate gradually increases, whereas choline undergoes a slow reduction during the process of myelination. Less clear are the modifications in creatine, myo-inositol, and glutamate levels. Under conditions of fetal distress, the meaning of lactate detection is unclear, and further studies are needed. Another field for investigation involves the possibility of early detection of glutamate levels in fetuses at risk for hypoxic-ischemic encephalopathy, because the role of glutamate excitotoxicity in this context is well-established. Because metabolic modifications may precede functional or morphologic changes in the central nervous system, magnetic resonance spectroscopy may likely serve as a powerful, noninvasive tool for the early diagnosis and prognosis of different pathologic conditions.

Severe chronic morbidity following childbirth

Three special, chronic morbidities of childbirth are reviewed with the most up-to-date knowledge in this article. Firstly, obstetric fistulas secondary to prolonged obstructed labour are still prevalent tragedies in underdeveloped countries. The damage is not only physical but psychosexual and social. The surgical skill and technology required to prevent and to treat obstetric fistulas are simple, but culture-social antagonism, geographic distance, political instability and financial constraint have to be overcome before effective management can take place. Congenital brachial plexus palsy is associated with shoulder dystocia and macrosomia, and both excessive exogenous traction and strong endogenous pushing forces contribute to its occurrence. As shoulder dystocia and macrosomia are not easily predictable, regular training and drill is essential to ensure proper management of shoulder dystocia. Most of the babies with brachial palsy will recover in 3 months but a minority of patients will suffer a more severe degree of damage, requiring early micro-neurosurgical intervention. Finally, although birth asphyxia is not the major cause of cerebral palsy, brain injury resulting from acute intrapartum hypoxic-ischemic insult is potentially alleviated by early neonatal hypothermic therapy. Both clinical and radiological assessments are essential in selecting suitable candidates for this innovative neuroprotective strategy.

Anatomic changes and imaging in assessing brain injury in the term infant

Encephalopathy from hypoxic-ischemic injury is a major cause of morbidity and mortality in term infants. MRI is the gold standard in evaluating the nature and extent of injury. Although imaging this population is challenging, important information can be obtained safely. Patterns of injury and the likely mechanisms that cause them are reviewed. Conventional images combined with additional techniques provide clues to cause, timing, and long-term prognosis. As altering acute neurologic damage with interventions in the acute period becomes a reality, MRI will play a crucial role in delineating which infants have the most to gain and act as a biomarker to gauge response.

Proton magnetic resonance spectroscopy in neonates with hypoxic-ischemic injury and its prognostic value

It is difficult to predict the neurologic outcome of neonates with hypoxic-ischemic encephalopathy (HIE). Our goal was to investigate the prognostic values of magnetic resonance spectroscopy (MRS) in neonatal HIE. During this study, 46 neonates with HIE underwent magnetic resonance imaging (MRI) and proton MRS ((1)HMRS). The sample included 25 cases of mild HIE, 11 cases of moderate HIE, and 10 cases of severe HIE. Nine healthy neonates without asphyxia served as controls. (1)HMRS techniques included single-voxel MRS and 2-D-point-resolved spatially localized spectroscopy (PRESS) multivoxel chemical shift spectroscopy imaging. Then, 31 of 46 neonates with HIE were divided into 3 groups according to their prognosis: dead, abnormal, and normal outcome. Abnormal and normal outcome were defined by follow-up MRI. Metabolic changes were analyzed and compared with HIE grading and prognosis. As a result, the GLx-alpha peak was markedly increased in the moderate and severe HIE groups. The GLx-alpha/Cr ratio in the control, mild, moderate, and severe HIE groups was 0.18, 0.21, 0.64, 1.31, respectively. The Lac/Cr ratio was 0.12, 0.14, 0.19, and 0.26, respectively. A Spearman rank correlation test confirmed that the ratio of GLx-alpha/Cr and Lac/Cr had significant positive correlation with clinical grading of HIE (P < 0.01). The GLx-alpha/Cr ratio in the dead, abnormal, and normal outcome groups was 1.28, 0.82, and 0.25, respectively; the Lac/Cr ratio was 0.34, 0.19, and 0.14, respectively. An anaylsis of variance demonstrated that the differences were significant (both P < 0.01). A Spearman rank correlation test confirmed that the ratio of GLx-alpha/Cr and Lac/Cr had significant negative correlation with prognosis of HIE; GLx-alpha/Cr showed a much stronger correlation than the Lac/Cr ratio (P < 0.01). The formula of the relationship between the poor prognosis of HIE and the ratio of GLx-alpha/Cr in basal ganglia was established by the logistic regression model. In conclusion, (1)HMRS is a useful tool for evaluating the severity and prognosis of HIE. The higher ratio of GLx-alpha/Cr in the basal ganglia and thalamus may predict a poor outcome in neonates with HIE.

The TOBY Study. Whole body hypothermia for the treatment of perinatal asphyxial encephalopathy: a randomised controlled trial

Background

A hypoxic-ischaemic insult occurring around the time of birth may result in an encephalopathic state characterised by the need for resuscitation at birth, neurological depression, seizures and electroencephalographic abnormalities. There is an increasing risk of death or neurodevelopmental abnormalities with more severe encephalopathy. Current management consists of maintaining physiological parameters within the normal range and treating seizures with anticonvulsants.

Studies in adult and newborn animals have shown that a reduction of body temperature of 3–4°C after cerebral insults is associated with improved histological and behavioural outcome. Pilot studies in infants with encephalopathy of head cooling combined with mild whole body hypothermia and of moderate whole body cooling to 33.5°C have been reported. No complications were noted but the group sizes were too small to evaluate benefit.

Methods/Design

TOBY is a multi-centre, prospective, randomised study of term infants after perinatal asphyxia comparing those allocated to "intensive care plus total body cooling for 72 hours" with those allocated to "intensive care without cooling".

Full-term infants will be randomised within 6 hours of birth to either a control group with the rectal temperature kept at 37 +/- 0.2°C or to whole body cooling, with rectal temperature kept at 33–34°C for 72 hours. Term infants showing signs of moderate or severe encephalopathy +/- seizures have their eligibility confirmed by cerebral function monitoring. Outcomes will be assessed at 18 months of age using neurological and neurodevelopmental testing methods.

Sample size

At least 236 infants would be needed to demonstrate a 30% reduction in the relative risk of mortality or serious disability at 18 months.

Recruitment was ahead of target by seven months and approvals were obtained allowing recruitment to continue to the end of the planned recruitment phase. 325 infants were recruited.

Primary outcome

Combined rate of mortality and severe neurodevelopmental impairment in survivors at 18 months of age. Neurodevelopmental impairment will be defined as any of:

• Bayley mental developmental scale score less than 70

• Gross Motor Function Classification System Levels III – V

• Bilateral cortical visual impairments

Trial Registration

Current Controlled Trials ISRCTN89547571

The Timing of Neonatal Brain Damage

Although neonatal morbidity and mortality are less than in the past, the risk of pre-natal and neonatal brain damage has not been eliminated. In order to optimize pre-natal, perinatal and neonatal care, it is necessary to detect factors responsible for brain damage and obtain information about their timing. Knowledge of the timing of asphyxia, infections and circulatory abnormalities would enable obstetricians and neonatologists to improve prevention in pre-term and full-term neonates. Cardiotocography has been criticized as being too indirect a sign of fetal condition and as having various technical pitfalls, though its reliability seems to be improved by association with pulse oximetry, fetal blood pH and electrocardiography. Neuroimaging is particularly useful to determine the timing of hypoxic-ischemic brain damage. Cranial ultrasound has been used to determine the type and evolution of brain damage. Magnetic resonance has also been used to detect antenatal, perinatal and neonatal abnormalities and timing on the basis of standardized assessment of brain maturation. Advances in the interpretation of neonatal electroencephalograms have also made this technique useful for determining the timing of brain lesions. Nucleated red blood cell count in cord blood has been recognized as an important indication of the timing of pre-natal hypoxia, and even abnormal lymphocyte and thrombocyte counts may be used to establish pre-natal asphyxia. Cord blood pH and base excess are well-known markers of fetal hypoxia, but are best combined with heart rate and blood pressure. Other markers of fetal and neonatal hypoxia useful for determining the timing of brain damage are assays of lactate and markers of oxidative stress in cord blood and neonatal blood. Cytokines in blood and amniotic fluid may indicate chorioamnionitis or post-natal infections. The determination of activin and protein S100 has also been proposed. Obstetricians and neonatologists can therefore now rely on various methods for monitoring the risk of brain damage in the antenatal and post-natal periods.

MR imaging of the neonatal brain

The advent of modern neuroimaging tools and methods has revolutionized the evaluation of the brain in neonates. The development of magnetic resonance (MR)-compatible monitoring tools and incubators has alleviated concerns regarding transportation of these unstable infants. The development of dedicated neonatal imaging coils has increased signal-to-noise ratios dramatically in images of the neonatal brain; this has made high-quality anatomic imaging, diffusion tensor imaging, and proton MR spectroscopy feasible in a normal imaging time. In centers that are equipped properly for neonatal MR imaging, MR is now unquestionably the study of choice for neonates who have encephalopathy or suspected brain injury. This article discusses the application of modern MR techniques to some of the causes of encephalopathy in neonates.

Prognostic value of 1H-MRS in neonatal encephalopathy

The aim of this study was to determine the prognostic value of proton magnetic resonance spectroscopy in neonatal encephalopathy. Studies were carried out in 11 consecutive term newborns with encephalopathy probably caused by hypoxic-ischemic injury. The clinical evaluation included pregnancy data, labor conditions, encephalopathy grade, presence of seizures, and necessity of antiepileptic drug therapy. Polygraphic recordings were obtained in all cases. Interest areas evaluated by spectroscopy were the basal ganglia and thalami. Among the cases, N-acetylaspartate/creatine, choline/creatine, and lactate/creatine ratios were calculated and related to the clinical variables, polygraphic recordings, and 6-month neurodevelopmental outcome. Abnormal follow-up occurred in 5 of 11 patients (45.4%) and was clearly related to an Apgar score <5 at 5 minutes (P = 0.003), encephalopathy grade (P = 0.02), early neonatal seizures (P = 0.02), and antiepileptic therapy (P = 0.01). No relationship was observed between spectroscopy results and polygraphic recordings profile. The lowest mean N-acetylaspartate/creatine ratio was observed in four of five patients with an adverse outcome and, although not statistically significant, demonstrated a clear trend to unfavorable follow-up (t test = 0.06). The choline/creatine ratios could not be related to follow-up in our sample. The most consistently observed abnormality on the spectra was the presence of the lactate peak in four of five patients with unfavorable outcome, with a high relative risk to determine evolution in the sample, relative risk 7.0 (chi2 = 0.01, 95% confidence interval = 1.1-42.9).

Lactate: creatinine ratio in babies with thin meconium staining of amniotic fluid

BACKGROUND

ACOG states meconium stained amniotic fluid (MSAF) as one of the historical indicators of perinatal asphyxia. Thick meconium along with other indicators is used to identify babies with severe intrapartum asphyxia. Lactate creatinine ratio (L:C ratio) of 0.64 or higher in first passed urine of babies suffering severe intrapartum asphyxia has been shown to predict Hypoxic Ischaemic Encephalopathy (HIE). Literature review shows that meconium is passed in distress and thin meconium results from mixing and dilution over time, which may be hours to days. Thin meconium may thus be used as an indicator of antepartum asphyxia. We tested L:C ratios in a group of babies born through thin and thick meconium, and for comparison, in a group of babies without meconium at birth.

METHODS

86 consecutive newborns, 36 to 42 weeks of gestation, with meconium staining of liquor, were recruited for the study. 52 voided urine within 6 hours of birth; of these 27 had thick meconium and 25 had thin meconium at birth. 42 others, who did not have meconium or any other signs of asphyxia at birth provided controls. Lactate and creatinine levels in urine were tested by standard enzymatic methods in the three groups.

RESULTS

Lactate values are highest in the thin MSAF group followed by the thick MSAF and controls. Creatinine was lowest in the thin MSAF, followed by thick MSAF and controls. Normal babies had an average L:C ratio of 0.13 (+/- 0.09). L:C ratio was more among thin MSAF babies (4.3 +/- 11.94) than thick MSAF babies (0.35 +/- 0.35). Median L:C ratio was also higher in the thin MSAF group. Variation in the values of these parameters is observed to be high in the thin MSAF group as compared to other groups. L:C ratio was above the cutoff of 0.64 of Huang et al in 40% of those with thin meconium. 2 of these developed signs of HIE with convulsions (HIE Sarnat and Sarnat Stage II) during hospital stay. One had L:C Ratio of 93 and the other of 58.6. A smaller proportion (20%) of those with thick meconium had levels above the cutoff and 2 developed HIE and convulsions with L:C ratio of 1.25 and 1.1 respectively.

CONCLUSION

In evolving a cutoff of L:C ratios that would be highly sensitive and specific (0.64), Huang et al studied it in a series of babies with severe intrapartum asphyxia. Our study shows that the specificity may not be as good if babies born through thin meconium are also included. L:C ratios are much higher in babies with thin meconium. It may be that meconium alone is not a good indicator of asphyxia and the risk of HIE. However, if the presence of meconium implies asphyxia then perhaps a higher cut-off than 0.64 is needed. L:C ratios should be tested in a larger sample that includes babies with thin meconium, before L:C ratios can be applied universally.

Oxidative metabolism, apoptosis and perinatal brain injury

Perinatal hypoxic-ischaemic injury (HII) is a significant cause of neurodevelopmental impairment and disability. Studies employing 31P magnetic resonance spectroscopy to measure phosphorus metabolites in situ in the brains of newborn infants and animals have demonstrated that transient hypoxia-ischaemia leads to a delayed disruption in cerebral energy metabolism, the magnitude of which correlates with the subsequent neurodevelopmental impairment. Prominent among the biochemical features of HII is the loss of cellular ATP, resulting in increased intracellular Na+ and Ca2+, and decreased intracellular K+. These ionic imbalances, together with a breakdown in cellular defence systems following HII, can contribute to oxidative stress with a net increase in reactive oxygen species. Subsequent damage to lipids, proteins, and DNA and inactivation of key cellular enzymes leads ultimately to cell death. Although the precise mechanisms of neuronal loss are unclear, it is now clear both apoptosis and necrosis are the significant components of cell death following HII. A number of different factors influence whether a cell will undergo apoptosis or necrosis, including the stage of development, cell type, severity of mitochondrial injury and the availability of ATP for apoptotic execution. This review will focus on some pathological mechanisms of cell death in which there is a disruption to oxidative metabolism. The first sections will discuss the process of damage to oxidative metabolism, covering the data collected both from human infants and from animal models. Following sections will deal with the molecular mechanisms that may underlie cerebral energy failure and cell death in this form of brain injury, with a particular emphasis on the role of apoptosis and mitochondria.

Brain injury in the term infant

Perinatal brain injury in the term infant is a relatively uncommon event. The principal lesions are intracranial hemorrhage including subarachnoid, subdural, intraparenchymal, intraventricular, focal cerebral infarction and hypoxic ischemic cerebral injury secondary to intrapartum hypoxia-ischemia. Both intracranial hemorrhage and focal cerebral infarction are invariably identified at the time of clinical symptoms, ie, seizures or apnea. This clearly limits the potential for prevention. The mechanisms contributing to brain injury secondary to intrapartum hypoxia-ischemia have become more clearly defined. Secondary or reperfusion injury is potentially amenable to neuroprotective strategies. Modest hypothermia is one such therapy that has been studied in high-risk newborn infants with some initial success. Future studies need to focus on additional neuroprotective strategies.

Hypoxic-ischemic brain injury in the term infant-current concepts

An enhanced understanding of the cellular characteristics contributing to ongoing brain injury following intrapartum hypoxia-ischemia has resulted in the implementation of targeted neuroprotective strategies in the newborn period. This review briefly covers the pathogenesis of hypoxic-ischemic injury with an emphasis on reperfusion injury; the role of magnetic resonance imaging in the detection of such injury, and focuses on potential strategies both supportive and neuroprotective to prevent ongoing injury with a specific emphasis on modest hypothermia.

A pilot investigation of mild hypothermia in neonates receiving extracorporeal membrane oxygenation (ECMO)

OBJECTIVE

To investigate the safety and feasibility of using mild hypothermia in neonates receiving extracorporeal membrane oxygenation (ECMO). Study design A prospective, nonrandomized pilot study of 25 neonates referred for ECMO. Whole body cooling was achieved by adjustment of the temperature of the extracorporeal circuit water bath. Five groups (N=5 per group) were each studied for the first 5 days of ECMO. The first group was maintained at 37 degrees C throughout the study period. Subsequent groups were cooled to 36 degrees C, to 35 degrees C, and, finally, to 34 degrees C, respectively, for 24 hours and the final group to 34 degrees C for 48 hours before being rewarmed to 37 degrees C. Patients were carefully assessed clinically and biologically. In addition to routine laboratory tests, cytokines (IL-6 and IL-8), complement (C3a), and molecular markers of coagulation (thrombin/antithrombin III [TAT], antithrombin III, and plasmin-alpha2plasminogen) were measured.

RESULTS

No major clinical or circuit problems were noted during cooling or rewarming. In particular, there were no problems of bleeding or cardiac arrhythmia. No significant difference was found between groups in terms of molecular markers of coagulation, complement, cytokines, and platelet transfusions.

CONCLUSIONS

Applying mild hypothermia (34 degrees C) for 24 or 48 hours to neonates receiving ECMO is both feasible and safe.

Prediction of adverse outcome with cerebral lactate level and apparent diffusion coefficient in infants with perinatal asphyxia

PURPOSE

To compare the predictive value for adverse outcome of quantitative cerebral lactate level and of apparent diffusion coefficient (ADC) in infants with perinatal asphyxia in the early postnatal period.

MATERIALS AND METHODS

Lactate-choline ratios determined with proton magnetic resonance (MR) spectroscopy and ADC determined with diffusion MR imaging in basal ganglia and thalami in 26 full-term neonates (age range, 1-10 days) were compared with severity of acute hypoxic-ischemic encephalopathy and long-term clinical outcome. Differences in metabolites between outcome groups were evaluated with the nonparametric Kruskal-Wallis test and the Dunn test. Logistic regression was performed to examine the predictive value of each metabolite for differentiating normal from abnormal or fatal clinical outcome. The likelihood ratio test was used to assess the statistical significance of each metabolite.

RESULTS

Logistic regression confirmed that lactate-choline ratio could be used to differentiate normal (n = 5) from abnormal (n = 14) or fatal (n = 6) outcome (P <.001). The probability of an adverse outcome exceeded 95% for a lactate-choline ratio of 1.0. Even when analyses were restricted to the early postnatal period, lactate-choline ratio was still a significant predictor of adverse outcome (P =.001). Although ADC images were useful in clinical examination of these infants, quantitative ADCs were not predictive of outcome (P =.82).

CONCLUSION

Higher lactate-choline ratios in basal ganglia and thalami of infants with perinatal asphyxia were predictive of worse clinical outcomes. Absolute ADC in the same brain regions did not indicate a statistically significant relationship with clinical outcome. Cerebral lactate level is useful in identifying infants who would benefit from early therapeutic intervention.

Advances in postnatal neuroimaging: relevance to pathogenesis and treatment of brain injury

The human brain is susceptible to a wide variety of insults. The permanent residua of these abnormalities are represented in dysfunction of one or more areas of neurodevelopment. A full understanding of normal brain development, mechanisms of brain injury, and consequences for subsequent brain development is required to determine which infants are at risk for neurodevelopmental handicap, and to monitor the effects of new treatments and management regimens designed to prevent these disabilities. Advanced magnetic resonance techniques, such as quantitative morphometric magnetic resonance techniques, diffusion-weighted magnetic resonance techniques, and magnetic resonance spectroscopy applied to the study of early human brain development have given us a better understanding of the pathophysiologic mechanisms of brain injury and its effects on subsequent brain development. Magnetic resonance imaging has provided an invaluable tool for the study of the fetal and newborn brain in vivo.

Predictors of 30-month outcome after perinatal depression: role of proton MRS and socioeconomic factors

The objective was to determine in infants with perinatal depression whether the relative concentrations of N-acetylaspartate and lactate in the neonatal period are associated with (1) neurodevelopmental outcome at 30 mo of age or (2) deterioration in outcome from age 12 to 30 mo; and to determine whether socioeconomic factors are associated with deterioration in outcome. Thirty-seven term neonates were prospectively studied with single-voxel proton magnetic resonance spectroscopy of the basal nuclei and intervascular boundary zones. Thirty-month outcomes were classified as normal [if Mental Development Index of the Bayley Scales of Infant Development (MDI) >85 and neuromotor scores (NMS) <3; n = 15], abnormal [if MDI <or=85 and/or NMS >or=3 at 12 and 30 mo; n = 11], or deteriorated [if normal at 12 mo and abnormal at 30 mo (MDI <or=85 or NMS >or=3); n = 11]. Thirty percent (11/37) of our cohort deteriorated between 12 and 30 mo. N-acetylaspartate/choline decreased across the groups ordered as normal, deteriorated, and abnormal [in basal nuclei (p <or= 0.001) and intervascular boundary zones (p = 0.04)], but was not different between the normal and deteriorated groups (p = 0.08). Lactate/choline similarly increased across the groups [in basal nuclei (p = 0.01) and intervascular boundary zones (p = 0.05)]. The odds of deterioration, if normal at 12 mo, increased by a factor of 5.1 (95% confidence interval: 1.3-19.8) with each decrease in one of four household income strata. Infants with perinatal depression are at high risk of developmental deterioration between 12 and 30 mo of age, particularly if in a lower income home or with intermediate values of cerebral metabolites on neonatal proton magnetic resonance spectroscopy.

Mechanisms of hypoxic neurodegeneration in the developing brain

Asphyxia and other insults to the developing brain are responsible for several human neurodevelopmental disorders. The pattern of neonatal brain injury differs from that seen in the adult nervous system, and there are wide differences in regional vulnerability. Recent evidence suggests that two events that contribute to this pattern of selective vulnerability are developmental changes in excitatory glutamate-containing neurotransmitter circuits and the propensity for immature neurons to die by apoptosis rather than necrosis. Developmental up-regulation of NMDA receptors with enhanced function and increased expression of caspase-3 at critical periods in development are linked to these mechanisms. Although these molecular changes enhance the developing brain's capacity for plasticity by helping to prune redundant synapses and neurons, they can become "Achilles heels" in the face of a brain energy crisis.