M Chandrasekaran

Cerebral Magnetic Resonance Biomarkers in Neonatal Encephalopathy: A Meta-analysis

OBJECTIVE: Accurate prediction of neurodevelopmental outcome in neonatal encephalopathy (NE) is important for clinical management and to evaluate neuroprotective therapies. We undertook a meta-analysis of the prognostic accuracy of cerebral magnetic resonance (MR) biomarkers in infants with neonatal encephalopathy. METHODS: We reviewed all studies that compared an MR biomarker performed during the neonatal period with neurodevelopmental outcome at ≥1 year. We followed standard methods recommended by the Cochrane Diagnostic Accuracy Method group and used a random-effects model for meta-analysis. Summary receiver operating characteristic curves and forest plots of each MR biomarker were calculated. χ2 tests examined heterogeneity. RESULTS: Thirty-two studies (860 infants with NE) were included in the meta-analysis. For predicting adverse outcome, conventional MRI during the neonatal period (days 1–30) had a pooled sensitivity of 91% (95% confidence interval [CI]: 87%–94%) and specificity of 51% (95% CI: 45%–58%). Late MRI (days 8–30) had higher sensitivity but lower specificity than early MRI (days 1–7). Proton MR spectroscopy deep gray matter lactate/N-acetyl aspartate (Lac/NAA) peak-area ratio (days 1–30) had 82% overall pooled sensitivity (95% CI: 74%–89%) and 95% specificity (95% CI: 88%–99%). On common study analysis, Lac/NAA had better diagnostic accuracy than conventional MRI performed at any time during neonatal period. The discriminatory powers of the posterior limb of internal capsule sign and brain-water apparent diffusion coefficient were poor. CONCLUSIONS: Deep gray matter Lac/NAA is the most accurate quantitative MR biomarker within the neonatal period for prediction of neurodevelopmental outcome after NE. Lac/NAA may be useful in early clinical management decisions and counseling parents and as a surrogate end point in clinical trials that evaluate novel neuroprotective therapies.

Melatonin augments hypothermic neuroprotection in a perinatal asphyxia model

Despite treatment with therapeutic hypothermia, almost 50% of infants with neonatal encephalopathy still have adverse outcomes. Additional treatments are required to maximize neuroprotection. Melatonin is a naturally occurring hormone involved in physiological processes that also has neuroprotective actions against hypoxic-ischaemic brain injury in animal models. The objective of this study was to assess neuroprotective effects of combining melatonin with therapeutic hypothermia after transient hypoxia-ischaemia in a piglet model of perinatal asphyxia using clinically relevant magnetic resonance spectroscopy biomarkers supported by immunohistochemistry. After a quantified global hypoxic-ischaemic insult, 17 newborn piglets were randomized to the following: (i) therapeutic hypothermia (33.5°C from 2 to 26 h after resuscitation, n = 8) and (ii) therapeutic hypothermia plus intravenous melatonin (5 mg/kg/h over 6 h started at 10 min after resuscitation and repeated at 24 h, n = 9). Cortical white matter and deep grey matter voxel proton and whole brain (31)P magnetic resonance spectroscopy were acquired before and during hypoxia-ischaemia, at 24 and 48 h after resuscitation. There was no difference in baseline variables, insult severity or any physiological or biochemical measure, including mean arterial blood pressure and inotrope use during the 48 h after hypoxia-ischaemia. Plasma levels of melatonin were 10 000 times higher in the hypothermia plus melatonin than hypothermia alone group. Melatonin-augmented hypothermia significantly reduced the hypoxic-ischaemic-induced increase in the area under the curve for proton magnetic resonance spectroscopy lactate/N-acetyl aspartate and lactate/total creatine ratios in the deep grey matter. Melatonin-augmented hypothermia increased levels of whole brain (31)P magnetic resonance spectroscopy nucleotide triphosphate/exchangeable phosphate pool. Correlating with improved cerebral energy metabolism, TUNEL-positive nuclei were reduced in the hypothermia plus melatonin group compared with hypothermia alone in the thalamus, internal capsule, putamen and caudate, and there was reduced cleaved caspase 3 in the thalamus. Although total numbers of microglia were not decreased in grey or white matter, expression of the prototypical cytotoxic microglial activation marker CD86 was decreased in the cortex at 48 h after hypoxia-ischaemia. The safety and improved neuroprotection with a combination of melatonin with cooling support phase II clinical trials in infants with moderate and severe neonatal encephalopathy.

Xenon augmented hypothermia reduces early lactate/N-acetylaspartate and cell death in perinatal asphyxia

Additional treatments for therapeutic hypothermia are required to maximize neuroprotection for perinatal asphyxial encephalopathy. We assessed neuroprotective effects of combining inhaled xenon with therapeutic hypothermia after transient cerebral hypoxia–ischemia in a piglet model of perinatal asphyxia using magnetic resonance spectroscopy (MRS) biomarkers supported by immunohistochemistry.

Diagnostic accuracy of post-mortem magnetic resonance imaging in fetuses, children and adults: A systematic review

To determine, in a systematic review, the diagnostic accuracy, acceptability and cost-effectiveness of less invasive autopsy by post-mortem MR imaging, in fetuses, children and adults. We searched Medline, Embase, the Cochrane library and reference lists to identify all studies comparing post-mortem MR imaging with conventional autopsy, published between January 1990 and March 2009. 539 abstracts were identified; 15 papers met the inclusion criteria; data from 9 studies were extracted (total: 146 fetuses, 11 children and 24 adults). In accurately identifying the final cause of death or most clinically significant abnormality, post-mortem MR imaging had a sensitivity and specificity of 69% (95% CI-56%, 80%) and 95% (95% CI-88%, 98%) in fetuses, and 28% (95% CI-13%, 47%) and 64% (95% CI-23%, 94%) in children and adults, respectively; however the published data is limited to small, heterogenous and poorly designed studies. Insufficient data is available on acceptability and economic evaluation of post-mortem MR imaging. Well designed, large, prospective studies are required to evaluate the accuracy of post-mortem MR imaging, before it can be offered as a clinical tool.

Brain Cell Death Is Reduced With Cooling by 3.5°C to 5°C but Increased With Cooling by 8.5°C in a Piglet Asphyxia Model

Background and Purpose— In infants with moderate to severe neonatal encephalopathy, whole-body cooling at 33°C to 34°C for 72 hours is standard care with a number needed to treat to prevent a adverse outcome of 6 to 7. The precise brain temperature providing optimal neuroprotection is unknown. Methods— After a quantified global cerebral hypoxic-ischemic insult, 28 piglets aged <24 hours were randomized (each group, n=7) to (1) normothermia (38.5°C throughout) or whole-body cooling 2 to 26 hours after insult to (2) 35°C, (3) 33.5°C, or (4) 30°C. At 48 hours after hypoxia-ischemia, delayed cell death (terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling and cleaved caspase 3) and microglial ramification (ionized calcium-binding adapter molecule 1) were evaluated. Results— At 48 hours after hypoxia-ischemia, substantial cerebral injury was found in the normothermia and 30°C hypothermia groups. However, with 35°C and 33.5°C cooling, a clear reduction in delayed cell death and microglial activation was observed in most brain regions (P<0.05), with no differences between 35°C and 33.5°C cooling groups. A protective pattern was observed, with U-shaped temperature dependence in delayed cell death in periventricular white matter, caudate nucleus, putamen, hippocampus, and thalamus. A microglial activation pattern was also seen, with inverted U-shaped temperature dependence in periventricular white matter, caudate nucleus, internal capsule, and hippocampus (all P<0.05). Conclusions— Cooling to 35°C (an absolute drop of 3.5°C as in therapeutic hypothermia protocols) or to 33.5°C provided protection in most brain regions after a cerebral hypoxic-ischemic insult in the newborn piglet. Although the relatively wide therapeutic range of a 3.5°C to 5°C drop in temperature reassured, overcooling (an 8.5°C drop) was clearly detrimental in some brain regions.

Early clinical signs in neonates with hypoxic ischemic encephalopathy predict an abnormal amplitude-integrated electroencephalogram at age 6 hours

BackgroundAn early clinical score predicting an abnormal amplitude-integrated electroencephalogram (aEEG) or moderate-severe hypoxic ischemic encephalopathy (HIE) may allow rapid triage of infants for therapeutic hypothermia. We aimed to determine if early clinical examination could predict either an abnormal aEEG at age 6 hours or moderate-severe HIE presenting within 72 hours of birth.MethodsSixty infants ≥ 36 weeks gestational age were prospectively enrolled following suspected intrapartum hypoxia and signs of encephalopathy. Infants who were moribund, had congenital conditions that could contribute to the encephalopathy or had severe cardio-respiratory instability were excluded. Predictive values of the Thompson HIE score, modified Sarnat encephalopathy grade (MSEG) and specific individual signs at age 3–5 hours were calculated.ResultsAll of the 60 infants recruited had at least one abnormal primitive reflex. Visible seizures and hypotonia at 3–5 hours were strongly associated with an abnormal 6-hour aEEG (specificity 88% and 92%, respectively), but both had a low sensitivity (47% and 33%, respectively). Overall, 52% of the infants without hypotonia at 3–5 hours had an abnormal 6-hour aEEG. Twelve of the 29 infants (41%) without decreased level of consciousness at 3–5 hours had an abnormal 6-hour aEEG (sensitivity 67%; specificity 71%). A Thompson score ≥ 7 and moderate-severe MSEG at 3–5 hours, both predicted an abnormal 6-hour aEEG (sensitivity 100 vs. 97% and specificity 67 vs. 71% respectively). Both assessments predicted moderate-severe encephalopathy within 72 hours after birth (sensitivity 90%, vs. 88%, specificity 92% vs. 100%). The 6-hour aEEG predicted moderate-severe encephalopathy within 72 hours (sensitivity 75%, specificity 100%) but with lower sensitivity (p = 0.0156) than the Thompson score (sensitivity 90%, specificity 92%). However, all infants with a normal 3- and 6-hour aEEG with moderate-severe encephalopathy within 72 hours who were not cooled had a normal 24-hour aEEG.ConclusionsThe encephalopathy assessment described by the Thompson score at age 3–5 hours is a sensitive predictor of either an abnormal 6-hour aEEG or moderate-severe encephalopathy presenting within 72 hours after birth. An early Thompson score may be useful to assist with triage and selection of infants for therapeutic hypothermia.

Methyl‐isobutyl amiloride reduces brain Lac/NAA, cell death and microglial activation in a perinatal asphyxia model

Na+/H+ exchanger (NHE) blockade attenuates the detrimental consequences of ischaemia and reperfusion in myocardium and brain in adult and neonatal animal studies. Our aim was to use magnetic resonance spectroscopy (MRS) biomarkers and immunohistochemistry to investigate the cerebral effects of the NHE inhibitor, methyl isobutyl amiloride (MIA) given after severe perinatal asphyxia in the piglet. Eighteen male piglets (aged < 24 h) underwent transient global cerebral hypoxia‐ischaemia and were randomized to (i) saline placebo; or (ii) 3 mg/kg intravenous MIA administered 10 min post‐insult and 8 hourly thereafter. Serial phosphorus‐31 (31P) and proton (1H) MRS data were acquired before, during and up to 48 h after hypoxia‐ischaemia and metabolite‐ratio time‐series Area under the Curve (AUC) calculated. At 48 h, histological and immunohistochemical assessments quantified regional tissue injury. MIA decreased thalamic lactate/N‐acetylaspartate and lactate/creatine AUCs (both p < 0.05) compared with placebo. Correlating with improved cerebral energy metabolism, transferase mediated biotinylated d‐UTP nick end‐labelling (TUNEL) positive cell density was reduced in the MIA group in cerebral cortex, thalamus and white matter (all p < 0.05) and caspase 3 immunoreactive cells were reduced in pyriform cortex and caudate nucleus (both p < 0.05). Microglial activation was reduced in pyriform and midtemporal cortex (both p < 0.05). Treatment with MIA starting 10 min after hypoxia‐ischaemia was neuroprotective in this perinatal asphyxia model.

Early clinical predictors of a severely abnormal amplitude-integrated electroencephalogram at 48 hours in cooled neonates

There is a need to identify infants with hypoxic ischaemic encephalopathy who have a poor outcome despite therapeutic hypothermia. A severely abnormal amplitude‐integrated electroencephalogram at 48 h predicts death or disability. Our aim was to determine whether clinical assessment at age 3–5 h predicts a severely abnormal amplitude‐integrated electroencephalogram at 48 h or death in cooled infants.

PS-339 Therapeutic Hypothermia In The Asphyctic Newborn: Immunohistochemical Comparison Of Three Cooling Target Temperatures In The Piglet Brain

Background and aims Therapeutic hypothermia has now become standard of care for neonatal hypoxic-ischaemic brain injury, as it reduces death and neurological sequelae without neurodevelopmental disabilities. There are however around 40% of infants who, despite treatment, have an adverse neurodevelopmental outcome. We aimed to assess brain regional cell death and microglial activation with cooling to 35°C, 33.5°C, and 30°C after hypoxia-ischemia (HI) in the piglet asphyxia model. Methods Following HI and resuscitation, 28 newborn piglets were randomised to: (i) normothermia (38.5°C throughout), or whole-body cooling 2–26 h post-insult to (ii) 35°C, (iii) 33.5°C, or (iv) 30°C (all groups n = 7). At 48 h after HI, regional neuropathological analysis was performed to assess delayed cell death (quantitative analyses of both TUNEL-positive cells and cleaved caspase 3 immunoreactivity) and microglial activation (Iba-1 staining). Results Compared with normothermia, cooling to 33.5°C showed a strong reduction in delayed cell death in periventricular white matter, hippocampus, caudate, putamen, thalamus and midtemporal cortex, a beneficial effect also extended to other cortical areas when analysing microglial activation. Cooling to 35°C was also beneficial, but in fewer regions than at 33.5°C. On the contrary, cooling to 30°C neither reduced delayed cell death nor maintained the microglial ramification index, showing a global neuropathological pattern similar to that observed in the normothermic group. Conclusions In our piglet perinatal asphyxia model, the optimum therapeutic hypothermia temperature is 33.5°C, thus suggesting that the extent of neuroprotection might not proportionately increase with temperature decreases.

Systemic effects of whole-body cooling to 35, 33 and 30 deg c in a piglet model of perinatal asphxyia

Background Therapeutic hypothermia reduces neurological damage and improves survival in neonatal encephalopathy. Despite treatment, however, 50% infants have adverse outcomes. Clinical trials are investigating lower cooling temperatures as tailoring cooling may be beneficial. Objective To assess systemic effects of cooling to 35, 33 and 30°C in a piglet model of perinatal asphyxia. Design/methods 28 male piglets, <24 h, underwent hypoxia-ischaemia and randomized (groups n=7), with intervention from 2 to 26 h to (i) normothermia; (ii) hypothermia (35°C); (iii) hypothermia (33.5°C); intravenous) hypothermia (30°C). Heart rate (HR), mean arterial blood pressure (MABP) and rectal temperature (Trec) were recorded continuously; blood chemistry every 6 h. Results Five animals in the 30°C group died before 48 h due to cardiac arrest, no piglets died prematurely in other groups. During cooling, HR was similar at 30°C versus 35 and 33.5°C and MABP did not differ between groups. However, inotrope and volume replacement were higher at 30°C versus all other groups (p<0.001). Blood pH was lower at 12 and 24 h (p<0.001) at 30°C versus all other groups (figure 1A). Blood glucose, lactate and BE were abnormal at 24 h (all p< 0.05) at 30°C versus all other groups (figures 1B–D). Abstract 8B.2 Figure 1 Mean (SD) saline bolus and inotrope infusions over 48 h in the four groups. *p<0.001. Conclusions Cooling to 30°C required extensive cardiovascular support and led to significant metabolic derangement and more cardiac arrests. Despite similar MABP in all groups, systemic effects at 30°C were considerable and may be deleterious to the brain.