Systems Biology Model of Cerebral Oxygen Delivery and Metabolism During Therapeutic Hypothermia: Application to the Piglet Model.

Hypoxic ischaemic encephalopathy (HIE) is a significant cause of death and disability. Therapeutic hypothermia (TH) is the only available standard of treatment, but 45-55% of cases still result in death or neurodevelopmental disability following TH. This work has focussed on developing a new brain tissue physiology and biochemistry systems biology model that includes temperature effects, as well as a Bayesian framework for analysis of model parameter estimation. Through this, we can simulate the effects of temperature on brain tissue oxygen delivery and metabolism, as well as analyse clinical and experimental data to identify mechanisms to explain differing behaviour and outcome. Presented here is an application of the model to data from two piglets treated with TH following hypoxic-ischaemic injury showing different responses and outcome following treatment. We identify the main mechanism for this difference as the Q10 temperature coefficient for metabolic reactions, with the severely injured piglet having a median posterior value of 0.133 as opposed to the mild injury value of 5.48. This work demonstrates the use of systems biology models to investigate underlying mechanisms behind the varying response to hypothermic treatment.

Diagnostic accuracy and limitations of post-mortem MRI for neurological abnormalities in fetuses and children.

AIM: To compare the diagnostic accuracy of non-invasive cerebral post-mortem magnetic resonance imaging (PMMRI) specifically for cerebral and neurological abnormalities in a series of fetuses and children, compared to conventional autopsy. MATERIALS AND METHODS: Institutional ethics approval and parental consent was obtained. Pre-autopsy cerebral PMMRI was performed in a sequential prospective cohort (n = 400) of fetuses (n = 277; 185 ≤ 24 weeks and 92 > 24 weeks gestation) and children <16 years (n = 123) of age. PMMRI and conventional autopsy findings were reported blinded and independently of each other. RESULTS: Cerebral PMMRI had sensitivities and specificities (95% confidence interval) of 88.4% (75.5 to 94.9), and 95.2% (92.1 to 97.1), respectively, for cerebral malformations; 100% (83.9 to 100), and 99.1% (97.2 to 99.7) for major intracranial bleeds; and 87.5% (80.1 to 92.4) and 74.1% (68 to 79.4) for overall brain pathology. Formal neuropathological examination was non-diagnostic due to maceration/autolysis in 43/277 (16%) fetuses; of these, cerebral PMMRI imaging provided clinically important information in 23 (53%). The sensitivity of PMMRI for detecting significant ante-mortem ischaemic injury was only 68% (48.4 to 82.8) overall. CONCLUSIONS: PMMRI is an accurate investigational technique for identifying significant neuropathology in fetuses and children, and may provide important information even in cases where autolysis prevents formal neuropathological examination; however, PMMRI is less sensitive at detecting hypoxic-ischaemic brain injury, and may not detect rarer disorders not encountered in this study.

Brain mitochondrial oxidative metabolism during and after cerebral hypoxia-ischemia studied by simultaneous phosphorus magnetic-resonance and broadband near-infrared spectroscopy.

BACKGROUND: Multimodal measurements combining broadband near-infrared spectroscopy (NIRS) and phosphorus magnetic resonance spectroscopy ((31)P MRS) assessed associations between changes in the oxidation state of cerebral mitochondrial cytochrome-c-oxidase (Δ[oxCCO]) and (31)P metabolite peak-area ratios during and after transient cerebral hypoxia-ischemia (HI) in the newborn piglet. METHODS: Twenty-four piglets (aged<24 h) underwent transient HI (inspired oxygen fraction 9% and bilateral carotid artery occlusion for ~20 min). Whole-brain (31)P MRS and NIRS data were acquired every minute. Inorganic phosphate (Pi)/epp, phosphocreatine (PCr)/epp, and total nucleotide triphosphate (NTP)/epp were measured by (31)P MRS and were plotted against Δ[oxCCO] during HI and recovery (epp=exchangeable phosphate pool=Pi+PCr+2γ-NTP+ß-NTP). RESULTS: During HI Δ[oxCCO], PCr/epp and NTP/epp declined and Pi/epp increased. Significant correlations were seen between (31)P ratios and Δ[oxCCO]; during HI a threshold point was identified where the relationship between Δ[oxCCO] and both NTP/epp and Pi/epp changed significantly. Outcome at 48 h related to recovery of Δ[oxCCO] and (31)P ratios 1h post-HI (survived: 1-h NTP/epp 0.22 ± 0.02, Δ[oxCCO] -0.29 ± 0.50 µM; died: 1-h NTP/epp 0.10 ± 0.04, Δ[oxCCO] -2.41 ± 1.48 µM). CONCLUSIONS: Both lowered Δ[oxCCO] and NTP/epp 1h post-HI indicated mitochondrial impairment. Animals dying before 48 h had slower recovery of both Δ[oxCCO] and (31)P ratios by 1 h after HI.

Pharmacokinetics of dexmedetomidine combined with therapeutic hypothermia in a piglet asphyxia model.

BACKGROUND: The highly selective α2 -adrenoreceptor agonist, dexmedetomidine, exerts neuroprotective, analgesic, anti-inflammatory and sympatholytic properties that may be beneficial for perinatal asphyxia. The optimal safe dose for pre-clinical newborn neuroprotection studies is unknown. METHODS: Following cerebral hypoxia-ischaemia, dexmedetomidine was administered to nine newborn piglets in a de-escalation dose study in combination with hypothermia (whole body cooling to 33.5°C). Dexmedetomidine was administered with a loading dose of 1 µg/kg and maintenance infusion at doses from 10 to 0.6 µg/kg/h. One additional piglet was not subjected to hypoxia-ischaemia. Blood for pharmacokinetic analysis was sampled pre-insult and frequently post-insult. A one-compartment linear disposition model was used to fit data. Population parameter estimates were obtained using non-linear mixed effects modelling. RESULTS: All dexmedetomidine infusion regimens led to plasma concentrations above those associated with sedation in neonates and children (0.4-0.8 µg/l). Seven out of the nine piglets with hypoxia-ischaemia experienced periods of bradycardia, hypotension, hypertension and cardiac arrest; all haemodynamic adverse events occurred in piglets with plasma concentrations greater than 1 µg/l. Dexmedetomidine clearance was 0.126 l/kg/h [coefficient of variation (CV) 46.6.%] and volume of distribution was 3.37 l/kg (CV 191%). Dexmedetomidine clearance was reduced by 32.7% at a temperature of 33.5°C. Dexmedetomidine clearance was reduced by 55.8% following hypoxia-ischaemia. CONCLUSIONS: Dexmedetomidine clearance was reduced almost tenfold compared with adult values in the newborn piglet following hypoxic-ischaemic brain injury and subsequent therapeutic hypothermia. Reduced clearance was related to cumulative effects of both hypothermia and exposure to hypoxia. High plasma levels of dexmedetomidine were associated with major cardiovascular complications.

Impact of anaesthetics and surgery on neurodevelopment: an update.

Accumulating preclinical and clinical evidence suggests the possibility of neurotoxicity from neonatal exposure to general anaesthetics. Here, we review the weight of the evidence from both human and animal studies and discuss the putative mechanisms of injury and options for protective strategies. Our review identified 55 rodent studies, seven primate studies, and nine clinical studies of interest. While the preclinical data consistently demonstrate robust apoptosis in the nervous system after anaesthetic exposure, only a few studies have performed cognitive follow-up. Nonetheless, the emerging evidence that the primate brain is vulnerable to anaesthetic-induced apoptosis is of concern. The impact of surgery on anaesthetic-induced brain injury has not been adequately addressed yet. The clinical data, comprising largely retrospective cohort database analyses, are inconclusive, in part due to confounding variables inherent in these observational epidemiological approaches. This places even greater emphasis on prospective approaches to this problem, such as the ongoing GAS trial and PANDA study.

Minimally invasive fetal postmortem examination using magnetic resonance imaging and computerised tomography: current evidence and practical issues.

For a variety of reasons, acceptance of traditional postmortem examination following foetal or neonatal death has declined significantly in recent years in the UK. Here, we review the case for the development of less invasive autopsy using combined investigations including imaging techniques, in particular, magnetic resonance imaging and computerised tomography.

[Neonatal hypoxia-ischemia: cellular and molecular brain damage and therapeutic modulation of neurogenesis]. / Hipoxia-isquemia neonatal: bases celulares y moleculares del daño cerebral y modulacion terapeutica de la neurogenesis.

INTRODUCTION: Perinatal asphyxia remains a major cause of both mortality and neurological morbidity. Neonatal encephalopathy affects to 1-3/1,000 newborns, leading to significant brain damage and childhood disability. The only standard therapy is moderate hypothermia, whose efficacy, despite proved, is limited, being partially effective. DEVELOPMENT: The capacity of hypothermia in promoting cell proliferation in the neurogenic niches of the central nervous system remains subject of investigation. The use of therapeutic agents such as erythropoietin and cannabinoids and mesenchymal stem cells have shown promising results in experimental models of perinatal asphyxia, being able of modulate neurogenesis, neuronal plasticity and neuroreparation processes after hypoxic-ischemic brain injury. CONCLUSIONS: The effects of these therapies in clinics are still unknown, so as if the newborn cells will be able to effectively integrate in the existing neuronal networks or if they will develop their proper functions in a brain-damaged microenvironment, thus being necessary new works focused on the evaluation of the real potential of these therapies in the modulation of neurogenesis after neonatal hypoxia-ischemia.

TITLE: Hipoxia-isquemia neonatal: bases celulares y moleculares del daño cerebral y modulacion terapeutica de la neurogenesis.Introduccion. La asfixia perinatal continua siendo una de las mayores causas de morbimortalidad neurologica. La encefalopatia neonatal derivada constituye una causa importante de daño cerebral, que afecta de manera moderada-grave a 1-3 de cada 1.000 recien nacidos y comporta un alto riesgo de deficits neurologicos permanentes. La unica aproximacion terapeutica actual consiste en la hipotermia moderada, cuya eficacia, aunque constatada, no siempre consigue una recuperacion funcional total. Desarrollo. Se desconoce con certeza si la hipotermia tiene la capacidad de promover la proliferacion celular en los nichos neurogenicos cerebrales, donde permanecen celulas madre neuronales con capacidad de proliferacion y diferenciacion. El empleo de agentes terapeuticos, como la eritropoyetina o los cannabinoides, y de celulas madre mesenquimales ha mostrado resultados prometedores en diversos modelos experimentales de asfixia perinatal y es capaz de modular los procesos de neurogenesis, de plasticidad neuronal y de neurorreparacion tras un daño cerebral hipoxico-isquemico. Conclusiones. Aun se desconocen los efectos de estas terapias en modelos clinicos y si las celulas recien formadas seran capaces de integrarse de forma efectiva en las redes neuronales existentes o si podran desarrollar sus funciones adecuadamente en un microambiente de lesion cerebral, por lo que se hace necesario el desarrollo de nuevos trabajos enfocados a evaluar el potencial real de estos agentes en la modulacion terapeutica de la neurogenesis tras una hipoxia-isquemia neonatal.

Postmortem magnetic resonance imaging as an adjunct to perinatal autopsy for renal-tract abnormalities.

The aim of this study was to compare postmortem magnetic resonance imaging (MRI) of the renal system with autopsy in perinatal and fetal deaths. 37 deaths were studied and renal abnormalities were found in five of these cases. Postmortem MRI provided information of diagnostic utility comparable to that obtained by autopsy.

Proton MR spectroscopy in neonates with perinatal cerebral hypoxic-ischemic injury: metabolite peak-area ratios, relaxation times, and absolute concentrations.

BACKGROUND: Results from cerebral proton (1)H-MR spectroscopy studies of neonates with perinatal hypoxic-ischemic injury have generally been presented as metabolite peak-area ratios, which are T1- and T2-weighted, rather than absolute metabolite concentrations. We hypothesized that compared with (1)H-MR spectroscopy peak-area ratios, calculation of absolute metabolite concentrations and relaxation times measured within the first 4 days after birth (1) would improve prognostic accuracy and (2) enhance the understanding of underlying neurochemical changes in neonates with neonatal encephalopathy. METHODS: Seventeen term infants with neonatal encephalopathy and 10 healthy controls were studied at 2.4T at 1 (1-3) and 2 (2-4) (median [interquartile range]) days after birth, respectively. Infants with neonatal encephalopathy were classified into 2 outcome groups (normal/mild and severe/fatal), according to neurodevelopmental assessments at 1 year. The MR spectroscopy peak-area ratios, relaxation times, absolute concentrations, and concentration ratios of lactate (Lac), creatine plus phosphocreatine (Cr), N-acetylaspartate (NAA), and choline-containing compounds (Cho) from a voxel centered on the thalami were analyzed according to outcome group. RESULTS: Comparing the severe/fatal group with the controls (significance assumed with P < 0.05), we found that Lac/NAA, Lac/Cho, and Lac/Cr peak-area ratios increased and NAA/Cr and NAA/Cho decreased; Lac, NAA, and Cr T2s were increased; [Lac] was increased and [Cho], [Cr], and [NAA] decreased; and among the concentration ratios, only [Lac]/[NAA] was increased. Comparison of the normal/mild group with controls revealed no differences in peak-area ratios, relaxation times, or concentration ratios but decreased [NAA], [Cho], and [Cr] were observed in the infants with normal/mild outcome. Comparison of the normal/mild and severe/fatal groups showed increased Lac/NAA and Lac/Cho and decreased NAA/Cr and NAA/Cho peak-area ratios, reduced [NAA], and increased Lac T2 in the infants with the worse outcome. CONCLUSIONS: Metabolite concentrations, in particular [NAA], enhance the prognostic accuracy of cerebral (1)H-MR spectroscopy-[NAA] was the only measurable to discriminate among all (control, normal/mild, and severe/fatal outcome) groups. However, peak-area ratios are more useful prognostic indicators than concentration ratios because they depend on metabolite concentrations and T2s, both of which are pathologically modulated. Concentration ratios depend only on the concentrations of the constituent metabolites. Increased Cr T2 may provide an indirect marker of impaired cellular energetics, and similarly, NAA T2 may constitute an index of exclusively neuronal energy status. Our recommendation is to collect data that enable calculation of brain metabolite concentrations. However, if time constraints make this impossible, metabolite peak-area ratios provide the next best method of assigning early prognosis in neonatal encephalopathy.

Brain Perfusion Imaging in Neonates: An Overview.

The development of cognitive function in children has been related to a regional metabolic increase and an increase in regional brain perfusion. Moreover, brain perfusion plays an important role in the pathogenesis of brain damage in high-risk neonates, both preterm and full-term asphyxiated infants. In this article, we will review and discuss several existing imaging techniques for assessing neonatal brain perfusion.

Neonatal neurological examination in well newborn term Ugandan infants.

BACKGROUND: Newborn neurological examinations have mostly been developed in high-resource settings with cohorts comprising predominantly white Caucasian infants. No comparison has been made with different populations. AIMS: To (i) establish the range of neurological findings in apparently well newborn term Ugandan infants, (ii) compare these findings to published data for equivalent term UK infants and (iii) correlate the neurological findings with perinatal characteristics and cranial ultrasound (cUS) imaging. METHODS: Low-risk term Ugandan infants were recruited from the postnatal ward at Mulago Hospital, Kampala, Uganda. Neurological examination (1) and cUS were performed. The raw data and neurological optimality scores were compared to published data from UK infants (1). Gestational age, postnatal age, sex, maternal parity and HIV status, mode of delivery, birth weight and head circumference were correlated with raw scores. RESULTS: Ugandan infants showed significantly stronger palmar grasp, better auditory and visual orientation, less irritability and less need for consoling but had poorer tone, poorer quality of spontaneous movements and more abnormal signs than UK infants. No correlation was found between raw scores and cUS findings, gestational age, sex, birth weight and head circumference. Significantly fewer Ugandan infants had optimal scores based on the UK data. CONCLUSION: The neurological status of low-risk hospital-born term Ugandan infants differs from that of low-risk UK infants. The study findings have implications for assessing normality in Ugandan infants and raise concerns about the use of this UK "optimality" score in other research settings. Further work is needed to understand fully the reasons for the differences.

Characterization of cerebral white matter damage in preterm infants using 1H and 31P magnetic resonance spectroscopy.

The biochemical characteristics of white matter damage (WMD) in preterm infants were assessed using magnetic resonance spectroscopy (MRS). The authors hypothesized that preterm infants with WMD at term had a persisting cerebral lactic alkalosis and reduced N-acetyl aspartate (NAA)/ creatine plus phosphocreatine (Cr), similar to that previously documented in term infants weeks after perinatal hypoxiaischemia (HI). Thirty infants (gestational age 27.9 +/- 3.1 weeks, birth weight 1,122 +/- 445 g) were studied at postnatal age of 9.8 +/- 4.1 weeks (corrected age 40.3 +/- 3.9 weeks). Infants were grouped according to the presence or absence of WMD on magnetic resonance (MR) images. The peak area ratios of lactate/Cr, NAA/Cr, myo-inositol/Cr, and choline (Cho)/Cr were measured from an 8-cm3 voxel in the posterior periventricular white matter (WM) using proton MRS. Intracellular pH (pHi) was calculated using phosphorus MRS. Eighteen infants had normal WM on MR imaging; 12 had WMD. For infants with WMD, lactate/Cr and myo-inositol/Cr were related (P < 0.01); lactate/Cr and pHi were not (P = 0.8). In the WMD group, mean lactate/Cr and myo-inositol/Cr were higher (P < 0.001, P < 0.05, respectively) than the normal WM group. There was no difference in the NAA/Cr, Cho/Cr, or pHi between the two groups, although pHi was not measured in all infants. These findings suggest that WMD in the preterm infant at term has a different biochemical profile compared with the term infant after perinatal HI.

Liver giant mitochondria revisited.

AIMS: To examine the correlation between the severity of alcohol induced liver damage and the presence of intracytoplasmic red bodies (defined as periodic acid-Schiff diastase negative, globular, hyaline cytoplasmic inclusions larger in size than the hepatocyte nucleolus). To investigate the incidence of intracytoplasmic red bodies (ICRBs) in non-alcoholic liver disease. METHODS: Liver biopsy specimens from 53 patients with alcoholic liver disease and 50 patients with a variety of nonalcohol related liver diseases were examined by light microscopy for the presence of ICRBs. For the 53 patients with alcoholic liver disease an assessment of recent alcohol consumption was made indirectly from measurements of red cell volume (MCV) and plasma gamma-glutamyl transferase (GGT). In addition, 10 liver biopsies with alcohol induced changes and ICRBs were examined by electron microscopy for the presence of mitochondrial aberrations including enlargement. RESULTS: ICRBs were detected in 18 of the 53 liver biopsy specimens showing alcohol induced changes, and were more abundant in those showing more advanced changes. Those patients whose liver specimens contained ICRBs were found to have a significantly higher mean plasma GGT activity and mean MCV than those individuals whose liver biopsy specimens did not contain ICRBs. Two of the 50 liver biopsy specimens showing non-alcohol induced changes contained ICRBs. Giant mitochondria were not detected by electron microscopy, but this may reflect sampling. CONCLUSIONS: The results of this study indicate that ICRBs are definitely associated with alcoholic liver disease and are more likely to be found in liver biopsy specimens showing more advanced alcohol induced damage, and when recent alcohol consumption has been high.

Intravascular synovial sarcoma.

A case of intravascular biphasic synovial sarcoma arising from the wall of the left femoral vein in a 34 year old woman is described. This is the third case of an intravascular synovial sarcoma known to be reported in the medical literature. The two previous cases arose from the left femoral vein and inferior vena cava in women of 34 and 31 years old, respectively. A characteristic clinical pattern appears to be emerging--that is, location in large veins of the lower extremity and trunk in young adult females. Synovial sarcoma must be considered in the differential diagnosis of intravascular "tumours".

Amphibian organ culture in experimental toxicology: the effects of paracetamol and phenacetin on cultured tissues from urodele and anuran amphibians.

Organ cultures of various tissues from urodele amphibians deacetylate paracetamol to p-aminophenol, which polymerises to form a brown precipitate. Paracetamol addition results in a loss of glycogen and lactate dehydrogenase (LDH) from urodele liver cultures and an increase in glucose release, and in LDH loss from kidney cultures. Organ cultures from anuran amphibians are unable to metabolise paracetamol and are not affected by its presence in the culture medium. The addition of unpolymerised p-aminophenol resulted in a loss of LDH from urodele and anuran organ cultures, whilst the addition of polymerised p-aminophenol had no such effects. This suggests that the toxic effects which follow the addition of paracetamol to urodele organ cultures are caused by unpolymerised p-aminophenol, a known toxicant in mammals. Cultures from both urodele and anuran amphibians are able to deacetylate phenacetin to p-phenetidine, but p-phenetidine was found to be much less toxic to amphibian tissues than p-aminophenol, causing LDH loss from kidney cultures only at very high dose levels.

Randomised trial of elective continuous positive airway pressure (CPAP) compared with rescue CPAP after extubation.

AIM: To determine if a weaning regimen on flow driver continuous positive airway pressure (CPAP) would decrease the number of ventilator days but increase the number of CPAP days when compared with a rescue regimen. METHODS: Fifty eight babies of 24-32 weeks gestation with respiratory distress syndrome (RDS) were studied prospectively. After extubation they were randomly allocated to receive CPAP for 72 hours (n = 29) according to a weaning regimen, or were placed in headbox oxygen and received CPAP only if present "start CPAP" criteria were met (n = 29, rescue group). RESULTS: There was no difference in successful extubation at 72 hours, 1 and 2 weeks, between the groups in terms of the number of reventilation episodes, reventilation days, or in total days of CPAP. Birthweight, gestational age, race, day of first extubation, antenatal or postnatal steroids, patent ductus arteriosus status and maximal mean airway pressure used were of no value in predicting success or failure at 72 hours, 1, or 2 weeks. CONCLUSION: The weaning regimen did not decrease the number of ventilator days or days on CPAP compared with the rescue regimen. The rescue regimen on flow driver CPAP seems to be a safe and effective method of managing a baby of 24-32 weeks gestation who has been ventilated for RDS or immature lung disease.

Nasal deformities resulting from flow driver continuous positive airway pressure.

Over a period of six months, seven cases were documented of trauma to the nose as a result of flow driver continuous positive airway pressure in babies of very low birthweight (VLBW). There was a complication rate of 20% in the babies who required it. Deformities consisted of columella nasi necrosis which can occur within three days, flaring of nostrils which worsens with duration of continuous positive airway pressure, and snubbing of the nose which persists after prolonged continuous positive airway pressure. These complications should be preventable by modifications to the mechanism and method of use.

Developments in vapour cloud explosion blast modeling.

TNT Equivalency methods are widely used for vapour cloud explosion blast modeling. Presently, however, other types of models are available which do not have the fundamental objections TNT Equivalency models have. TNO Multi-Energy method is increasingly accepted as a more reasonable alternative to be used as a simple and practical method. Computer codes based on computational fluid dynamics (CFD) like AutoReaGas, developed by TNO and Century Dynamics, could be used also in case a more rigorous analysis is required. Application of the Multi-Energy method requires knowledge of two parameters describing the explosion: a charge size and a charge strength. During the last years, research has led to an improved determination of the charge strength (i.e., the class number or source overpressure) to be chosen to apply the blast charts. A correlation has been derived relating the charge strength to a set of parameters describing the boundary conditions of the flammable cloud and the fuel in the cloud. A simple approach may not be satisfactory in all situations. The overpressure distribution inside a vapour cloud explosion is generally not homogeneous and the presence of obstructions causes directional blast propagation in the near field. A CFD approach, in which the actual situation is modeled, supplies case-specific results. An overview of the key aspects relevant to the application of the Multi-Energy method and CFD modeling is provided. Then the application of the two methods is demonstrated for an example problem involving the calculation of the explosion blast load on a structure at some distance from the explosion in an offshore platform complex.

Ethical and practical issues relating to the global use of therapeutic hypothermia for perinatal asphyxial encephalopathy.

In intensive care settings in the developed world, therapeutic hypothermia is established as a therapy for term infants with moderate to severe neonatal encephalopathy due to perinatal asphyxia. Several preclinical, pilot and clinical trials conducted in such settings over the last decade have demonstrated that this therapy is safe and effective. The greatest burden of birth asphyxia falls, however, in low- and middle-income countries; it is still unclear whether therapeutic hypothermia is safe and effective in this context. In this paper, the issues around treatments that may be proven safe and effective in the developed world and the caution needed in translating these into different settings and populations are explored. It is argued that there are strong scientific and ethical reasons supporting the conduct of rigorous, randomised controlled trials of therapeutic hypothermia in middle-income settings. There also needs to be substantial and sustainable improvements in all facets of antenatal care and in the basic level of newborn resuscitation in low income countries. This will reduce the burden of disease and allow health workers to determine rapidly which infants are most eligible for potential neuroprotection.