Use of brain lactate levels to predict outcome after perinatal asphyxia

Comparison of Sodium Lactate Infusion and Carbon Dioxide Inhalation Panic Provocation Tests: A Meta-analysis

BACKGROUND

Sodium lactate (NaL) infusion and carbon dioxide (CO₂) inhalation are proven to provoke acute panic attacks (PAs) in patients with panic disorder (PD). A systematic literature search and meta-analysis were performed to compare the effect sizes of these methods.

METHODS

Odds ratios were calculated for each of the original studies and were pooled using the random-effects model.

RESULTS

Either NaL or CO₂ provocations significantly increased the rates of PAs in individuals with PD compared to those in healthy controls. However, the effect size of NaL infusion (OR=25.13, 95% CI=15.48-40.80) was significantly greater than that of CO₂ inhalation (OR=10.58, 95%CI=7.88-14.21).

CONCLUSION

The evidence for the efficacy of the two panic provocation tests is very strong. Yet, the results support the superiority of NaL infusion over CO₂ inhalation challenge as a panic provocation test. Thus, lactate seems a much stronger stimulus than CO₂ for the brain suffocation detector.

MR spectroscopy in pediatric neuroradiology

Magnetic resonance spectroscopy (MRS), being able to identify and measure some brain components (metabolites) in pathologic lesions and in normal-appearing tissue, offers a valuable additional diagnostic tool to assess several pediatric neurological diseases. In this review we will illustrate the basic principles and clinical applications of brain proton (H¹; hydrogen) MRS (H¹MRS), by now the only MRS method widely available in clinical practice. Performing H¹MRS in the brain is inherently less complicated than in other tissues (e.g., liver, muscle), in which spectra are heavily affected by magnetic field inhomogeneities, respiration artifacts, and dominating signals from the surrounding adipose tissues. H¹MRS in pediatric neuroradiology has some advantages over acquisitions in adults (lack of motion due to children sedation and lack of brain iron deposition allow optimal results), but it requires a deep knowledge of pediatric pathologies and familiarity with the developmental changes in spectral patterns, particularly occurring in the first two years of life. Examples from our database, obtained mainly from a 1.5 Tesla clinical scanner in a time span of 15 years, will demonstrate the efficacy of H¹MRS in the diagnosis of a wide range of selected pediatric pathologies, like brain tumors, infections, neonatal hypoxic-ischemic encephalopathy, metabolic and white matter disorders.

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.

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.

Neurologic Injury in Acidemic Term Infants

Objective To determine whether arterial umbilical cord gas (aUCG) pH, in anatomically normal-term infants, could select infants at risk for brain injury identified on magnetic resonance imaging (MRI). Study Design We performed a nested case-control within a prospective cohort of 8,580 women. Cases, with an aUCG pH < 7.10, were temporally, age, and sex matched to controls with an aUCG pH ≥ 7.20. Bi- and multivariable analyses compared the presence and severity of brain injury. Secondary analyses estimated whether elevated arterial base excess or lactate were associated with brain injury. Results Fifty-five cases were matched to 165 controls. There was no statistical difference in brain injury between the groups (adjusted odds ratio [aOR]: 1.8, 95% confidence interval [CI]: 0.7-4.4]). Base excess ≥ -8 mEq/L was not significantly associated with brain injury (p = 0.12). There was no increase in risk of injury based on elevation of arterial lactate ≥ 4 mmol ⁄L (p = 1.00). Cases were significantly more likely to have an abnormal score in several domains of the Dubowitz neurologic examination. Conclusion The aUCG acid-base parameters alone are not sufficient clinical markers to identify term infants that might benefit from MRI of the brain to identify injury.

Umbilical Artery Lactate Correlates with Brain Lactate in Term Infants

Objective The objective of this study was to determine the correlation between umbilical artery lactate with brain lactate in nonanomalous term infants. Study Design We performed a nested case-control study within an on-going prospective cohort of more than 8,000 consecutive singleton term (≥ 37 weeks) nonanomalous infants. Neonates underwent cerebral magnetic resonance imaging (MRI) within the first 72 hours of life. Cases (umbilical artery pH ≤ 7.10) were gender and race matched 1:3 to controls (umbilical artery pH > 7.20). Single voxel magnetic resonance spectroscopy (MRS), lactate, and N-acetyl aspartate (NAA) for normalization were calculated using Siemens software (Plano, TX). Linear regression estimated the association between incremental change in umbilical artery lactate and brain lactate, both directly and as a ratio with NAA. Results Of 175 infants who underwent MRI with spectral sequencing, 52 infants had detectable brain lactate. The 52 infants with brain lactate peaks had umbilical artery lactate values of 1.6 to 11.4 mmol/L. For every 1.0 mmol/L increase in umbilical artery lactate, there was an increase in brain lactate of 0.02, which remained significant even when corrected for NAA. Conclusion MRS measured brain lactate is significantly correlated with umbilical artery lactate in nonanomalous term infants, which may help explain the observed association between umbilical artery lactate and neurologic morbidity.

Brain metabolite alterations in Eisenmenger syndrome: Evaluation with MR proton spectroscopy

OBJECTIVE

Eisenmenger syndrome (ES) is a life-threatening disease characterized by pulmonary hypertension and cyanosis in patients with congenital heart diseases. The aim of this study was to determine the brain metabolite changes in Eisenmenger syndrome compared with a control group using MR proton spectroscopy.

METHODS AND MATERIALS

The study included 10 children (3 male, 7 female) with congenital heart diseases and a diagnosis of Eisenmenger syndrome. The control group consisted of 10 healthy volunteer children. All were examined with a 1.5T MRI scanner and single voxel spectroscopy was performed to obtain spectra from three different regions; left frontal subcortical white matter, left lentiform nucleus and left thalamus. Peak integral values obtained from the spectra were used as quantitative data.

RESULTS

The ages of the children with ES were between 5 and 16 years, and between 5 and 15 years in the control group. Periventricular white matter hyperintensities were observed in 3 patients. On MR spectroscopy study, significantly lower levels of Choline metabolite (Cho) were detected in the frontal subcortical region and thalamus regions of the patients compared with the control group. There was no statistically significant difference between the levels of other metabolites (NAA, Cr, mI and Glx). In the lentiform nucleus, although the average value of Cho in ES patients was lower than that of the control group, it was not statistically significant.

CONCLUSION

Cho metabolite was determined to have an important role in brain metabolism in Eisenmenger syndrome patients. Oral Cho treatment may help to extend survival.

Secondary Increase of Lactate Levels in Asphyxiated Newborns during Hypothermia Treatment: Reflect of Suboptimal Hemodynamics (A Case Series and Review of the Literature)

Objective To evaluate whether a secondary increase of serum lactate levels in asphyxiated newborns during hypothermia treatment may reflect suboptimal dynamics. Methods-Retrospective case series and review of the literature. We present the clinical course of four asphyxiated newborns treated with hypothermia who presented with hypotension requiring inotropic support, and who displayed a secondary increase of serum lactate levels during hypothermia treatment. Serial serum lactate levels are correlated with blood pressure and inotropic support within the first 96 hours of life. Results Lactate levels initially decreased in the four patients. However, each of them started to present lower blood pressure, and lactate levels started to increase again. Inotropic support was started to raise blood pressure. The introduction of an epinephrine drip consistently worsened the increase of lactate levels in these newborns, whereas dopamine and dobutamine enabled the clearance of lactate in addition to raising the blood pressure. Rewarming was associated with hemodynamics perturbations (a decrease of blood pressure and/or an increase of lactate levels) in the three newborns who survived. Conclusions Lactate levels during the first 4 days of life should be followed as a potential marker for suboptimal hemodynamic status in term asphyxiated newborns treated with hypothermia, for whom the maintenance of homeostasis during hypothermia treatment is of utmost importance to alleviate brain injury.

MRI evaluation and safety in the developing brain

Magnetic resonance imaging (MRI) evaluation of the developing brain has dramatically increased over the last decade. Faster acquisitions and the development of advanced MRI sequences, such as magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI), perfusion imaging, functional MR imaging (fMRI), and susceptibility-weighted imaging (SWI), as well as the use of higher magnetic field strengths has made MRI an invaluable tool for detailed evaluation of the developing brain. This article will provide an overview of the use and challenges associated with 1.5-T and 3-T static magnetic fields for evaluation of the developing brain. This review will also summarize the advantages, clinical challenges, and safety concerns specifically related to MRI in the fetus and newborn, including the implications of increased magnetic field strength, logistics related to transporting and monitoring of neonates during scanning, and sedation considerations, and a discussion of current technologies such as MRI conditional neonatal incubators and dedicated small-foot print neonatal intensive care unit (NICU) scanners.

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.

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.

Basic principles and concepts underlying recent advances in magnetic resonance imaging of the developing brain

Over the last decade, magnetic resonance (MR) imaging has become an essential tool in the evaluation of both in vivo human brain development and perinatal brain injury. Recent technology including MR-compatible neonatal incubators, neonatal head coils, advanced MR pulse sequences, and 3-T field strength magnets allow high-quality MR imaging studies to be performed on sick neonates. This article will review basic principles and concepts underlying recent advances in MR spectroscopy, diffusion, perfusion, and volumetric MR imaging. These techniques provide quantitative assessment and novel insight of both brain development and brain injury in the immature brain. Knowledge of normal developmental changes in quantitative MR values is also essential to interpret pathologic cases.

Magnetic resonance spectroscopy in pediatric neuroradiology: clinical and research applications

Magnetic resonance spectroscopy (MRS) offers a unique, noninvasive approach to assess pediatric neurological abnormalities at microscopic levels by quantifying cellular metabolites. The most widely available MRS method, proton ((1)H; hydrogen) spectroscopy, is FDA approved for general use and can be ordered by clinicians for pediatric neuroimaging studies if indicated. There are a multitude of both acquisition and post-processing methods that can be used in the implementation of MR spectroscopy. MRS in pediatric neuroimaging is challenging to interpret because of dramatic normal developmental changes that occur in metabolites, particularly in the first year of life. Still, MRS has been proven to provide additional clinically relevant information for several pediatric neurological disease processes such as brain tumors, infectious processes, white matter disorders, and neonatal injury. MRS can also be used as a powerful quantitative research tool. In this article, specific research applications using MRS will be demonstrated in relation to neonatal brain injury and pediatric brain tumor imaging.

Pediatric neuroimaging

This article provides clinical neurologists with an overview of pediatric neuroimaging. Pediatric neuroimaging is a broad subject, and its details are beyond the scope of any short review article. First this article briefly highlights different stages of brain development and explains how these stages correlate with various congenital brain anomalies. It then focuses on the safety of pediatric neuroimaging, discussing important issues in pediatric sedation and hazards of exposure of ionizing radiation. Last, it describes the advent of modern neuroimaging tools, such as diffusion tensor imaging and MR spectroscopy, and their emerging role in evaluating multiple pediatric brain disorders.

Brain metabolite levels assessed by lactate-edited MR spectroscopy in premature neonates with and without pentobarbital sedation

BACKGROUND AND PURPOSE

Pentobarbital is known to affect cerebral metabolism; pentobarbital sedation is, however, frequently used for MR imaging and MR spectroscopy, especially in children. Accurate assessment of the brain metabolite levels is important, particularly in neonates with suspected brain injury. We investigated whether pentobarbital sedation has any effect on the ratios of spectral metabolites lactate, N-acetylaspartate, or choline in a group of premature neonates.

MATERIALS AND METHODS

MR spectroscopy was performed in 43 premature neonates, all with normal concurrent MR imaging and normal neurodevelopmental outcome at 12 months of age. Of those neonates, 14 (33%) required pentobarbital (Nembutal 1 mg/kg) sedation during MR spectroscopy; the remaining 29 neonates did not receive any sedation. Ratios of lactate, choline, and N-acetylaspartate were calculated in the basal ganglia, thalami, and corticospinal tracts and compared between those neonates with and without sedation.

RESULTS

Small amounts of brain lactate were detected in all of the premature neonates. The basal ganglia lactate/choline and lactate/N-acetylaspartate ratios were significantly lower, by 17% and 25% respectively, in the neonates with pentobarbital sedation compared with the age-matched neonates without sedation (P < .05). Sedation did not affect the lactate level in the thalami or the corticospinal tracts. The N-acetylaspartate/choline ratios were unaffected by pentobarbital sedation.

CONCLUSION

Pentobarbital sedation is associated with lower lactate/choline and lactate/N-acetylaspartate ratios in the basal ganglia of premature neonates, as determined by proton MR spectroscopy. Investigators should be aware of this phenomenon for accurate interpretation of their MR spectroscopy results.

Advances in magnetic resonance neuroimaging techniques in the evaluation of neonatal encephalopathy

Magnetic resonance (MR) imaging has become an essential tool in the evaluation of neonatal encephalopathy. Magnetic resonance-compatible neonatal incubators allow sick neonates to be transported to the MR scanner, and neonatal head coils can improve signal-to-noise ratio, critical for advanced MR imaging techniques. Refinement of conventional imaging techniques include the use of PROPELLER techniques for motion correction. Magnetic resonance spectroscopic imaging and diffusion tensor imaging provide quantitative assessment of both brain development and brain injury in the newborn with respect to metabolite abnormalities and hypoxic-ischemic injury. Knowledge of normal developmental changes in MR spectroscopy metabolite concentration and diffusion tensor metrics is essential to interpret pathological cases. Perfusion MR and functional MR can provide additional physiological information. Both MR spectroscopy and diffusion tensor imaging can provide additional information in the differential of neonatal encephalopathy, including perinatal white matter injury, hypoxic-ischemic brain injury, metabolic disease, infection, and birth injury.

Magnetic resonance spectroscopic imaging of human brain development

MR spectroscopy (MRS) can provide the noninvasive detection of a number of biologically important cellular metabolites. Recently, this technique has been applied to provide unique assessments of maturational changes in brain biochemistry. Significant variations in the concentration of intracellular metabolite levels have been observed in the neonatal brain with anatomic location and with development. These changes are critical to define in normal neonatal populations so as to provide improved understanding of brain maturation as well as to establish normative values for the differentiation of abnormal metabolism in cases of brain injury. This article includes the description of MRS techniques for neonatal studies and results in the study of the premature and term newborn brain.

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.

The role of functional neuroimaging in pediatric brain injury

The aim of this article is to review empirical studies published in the last 10 years that used various functional neuroimaging techniques to assess pediatric patients with brain injury. Overall, these studies have demonstrated the ability of functional neuroimaging to offer unique information concerning the diagnosis, clinical outcome, and recovery mechanisms after pediatric brain injury. Future research using functional neuroimaging is recommended to better understand the functional reorganization and neurodevelopmental consequences resulting from brain injury. Such research might allow clinicians to design tailored early-intervention and rehabilitation programs to maximize the recovery process for pediatric patients. Limitations and advantages associated with the use of functional neuroimaging in pediatric populations are discussed.

On-line monitoring of striatum glucose and lactate in the endothelin-1 rat model of transient focal cerebral ischemia using microdialysis and flow-injection analysis with biosensors

In vivo studies on cerebral glucose and lactate metabolism following a brain insult require fast and sensitive monitoring techniques. Here we report on-line monitoring of ischemic events and metabolic changes following reperfusion in striatum of freely moving rats subjected to endothelin-1 (60-240 pmol) induced, transient focal cerebral ischemia using slow microdialysis (0.5 microl/min), fast sampling (every minute) and flow-injection analysis with biosensors for glucose and lactate. The high-time resolution provides detailed information on lactate rise times and duration of low glucose. In rats, developing large striatal lesions, lactate increased from 1.0 +/- 0.1 to 4.2 +/- 0.7 mM within 37 +/- 1 min, whereas glucose dropped from 0.3 +/- 0.1 mM to below detection levels (<0.05 mM) for a period of 80 +/- 18 min. The lactate increase measured over a 2-h period after endothelin-1 infusion was highly correlated with striatal infarct size. In some rats oscillatory changes are observed which cannot be detected in traditional assays. The here-described monitoring technique applied in a clinically relevant rat model is a sensitive tool to study post-ischemic energy metabolism, effects of therapeutic interventions and its relationship with histological outcome.

Diffusion-weighted imaging and proton magnetic resonance spectroscopy in perinatal hypoxic-ischemic encephalopathy: association with neuromotor outcome at 18 months of age

We evaluated early diffusion-weighted imaging findings, the quantitative apparent diffusion coefficient, and magnetic resonance spectroscopy (the presence of lactate and ratios of N-acetylaspartate to total creatine and choline to total creatine) in the prediction of the 18-month neuromotor outcome of term newborns with hypoxic-ischemic encephalopathy. Conventional T1- and T2-weighted and diffusion-weighted imaging was performed in 20 asphyxiated term newborns, with additional basal ganglia magnetic resonance spectroscopy in 15 newborns between 2 and 18 days of life (mean 7.3 days). Neuromotor outcome was dichotomized into normal and abnormal for statistical analysis. Statistically significant differences in the ratios of N-acetylaspartate to total creatine, but not apparent diffusion coefficient values and ratios of choline to total creatine, were found between infants with a normal and an abnormal outcome (Mann-Whitney U-test, P = .010). There was a significant association between the presence of a lactate peak and an abnormal outcome (chi-square test, P = .017). The presence of a lactate peak for predicting an abnormal outcome had a sensitivity of 100% and a specificity of 80%, and the odds ratio was 37.4. Ischemic lesions were more conspicuous and/or extensive on diffusion-weighted imaging in all except one neonate. The presence of normal findings on both diffusion-weighted imaging and conventional magnetic resonance imaging is predictive of a normal neuromotor outcome, whereas lactate and a reduced ratio of N-acetylaspartate to total creatine in the basal ganglia, but not an apparent diffusion coefficient, are associated with an abnormal outcome at 18 months of age.

Hypoxia-ischemic encephalopathy in full-term neonate: correlation proton MR spectroscopy with MR imaging

INTRODUCTION

To evaluate 1H Magnetic Resonance Spectroscopy (1HMRS) in the diagnosis of hypoxia-ischemic encephalopathy (HIE) of full-term neonates correlated with Magnetic Resonance Imaging (MRI).

MATERIALS AND METHODS

Thirty-eight cases of full-term neonates diagnosed as HIE clinically were selected to perform MRI and 1HMRS examination. The ages ranged from 7 to 17 days, with median age of 8.2 days. In which, 26 cases were followed up and/or MRI reexamined at 6 months of age or later. Eight healthy neonates, with no evidence of birth asphyxia, also underwent 1HMRS for comparison. SE sequences were used for routine MR examination; point resolved spectroscopy sequence was required for 1HMRS. The metabolites in the spectra includes: N-acetylaspartate (NAA), choline compounds (CHO), creatine compounds (CR), myo-inositol (MI), lactate (LAC), glutamate and glutamine (Glu-Gln).

RESULTS

The peaks of NAA were fall in two cases; the peaks of LAC, which were elevated, appeared as typical double-peaks appearance in 26 cases; the peaks of Glu-Gln, which were also elevated, appeared as zigzag appearance in nine cases. The peaks of CR were decreased in 11 cases, while those of MI were increased in seven cases. Mild type of lesions was present on MRI in 12 cases whose LAC/CR ratio lower than 0.5; mild and moderate types of lesions were present in 15 cases whose LAC/CR ratio between 0.5 and 1.5. Whereas, nine cases of severe lesions and two cases of moderate lesions were present on MRI in 11 cases whose LAC/CR ratio greater than 1.5. Twenty-six of 38 cases were followed up and/or MRI reexamined after 6 months, in which, sequelae were present in 12 cases. Among them, eight cases of sequelae in nine cases whose LAC/CR ratio greater than 1.5 were present (account for 88.89%).

CONCLUSION

1HMRS plays an important role to diagnose and predict outcome of HIE.

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.

Lactacidosis in the neonate is minimized by prenatal detection of congenital heart disease

OBJECTIVES

To investigate the impact of prenatal detection of congenital heart disease on preventing severe preoperative lactacidosis.

DESIGN

Patients operated upon for congenital heart disease during the first 31 days of life (n = 209) were studied retrospectively, 21 were diagnosed prenatally and 188 patients had not been diagnosed prenatally. Preoperative lactate, pH and base excess were evaluated.

RESULTS

Differences were noted in preoperative pH (7.28 +/- 0.03 vs. 7.24 +/- 0.01, P = 0.29), base excess (-5.83 +/- 0.64 vs. -6.93 +/- 0.46 mmol/L, P = 0.10) and lactate (3.05 +/- 0.35 vs. 6.08 +/- 0.45 mmol/L, P < 0.001), indicating a significant difference in blood lactate values in favor of the prenatally diagnosed group.

CONCLUSIONS

Prenatal diagnosis of congenital heart disease and the resulting immediate postnatal care prevent lactate increase in the preoperative period of these patients. This may decrease the risk of cerebral damage and result in the patient being in better condition at surgery.

Lactate measurements in scalp and cord arterial blood

Lactate has been measured to evaluate fetal metabolic acidosis for some decades. However, not until the past few years have reliable lactate meters become available for bedside obstetric practice. The new technology, which requires only 5 microl blood, has reduced the sampling failure rate of fetal scalp blood to almost nil. A growing body of evidence has also shown lactate to be good at predicting neonatal outcome.

Quantitative apparent diffusion coefficient measurements in term neonates for early detection of hypoxic-ischemic brain injury: initial experience

PURPOSE

To determine the utility of using quantitative apparent diffusion coefficient (ADC) values as an objective means of early detection of brain injury caused by hypoxic-ischemic encephalopathy (HIE) in term neonates.

MATERIALS AND METHODS

Conventional images, diffusion-weighted images, ADC maps, and clinical charts from 13 term neonates clinically suspected of having HIE were retrospectively reviewed. Four term neonates without HIE served as control subjects. ADC values were calculated in predefined regions in patients and compared with those in control subjects. A Student t test was performed for each region to compare patients and control subjects.

RESULTS

Abnormalities were more easily detected on diffusion-weighted images and ADC maps, compared with conventional images. ADC values in patients with HIE were significantly different from those of control subjects in the posterior limb of the internal capsule, corona radiata, posterior frontal white matter, and parietal white matter bilaterally.

CONCLUSION

Evaluation of ADC maps can improve conspicuity of hypoxic-ischemic injury in the acute and/or subacute setting (within 12 days of insult), and calculation of ADC values can provide an objective measure of hypoxic-ischemic injury.

Value of (1)H-MRS using different echo times in neonates with cerebral hypoxia-ischemia

Previous studies have shown altered brain metabolism after cerebral hypoxia-ischemia, using magnetic resonance spectroscopy with echo times (TE) of 272 and 136 ms, based on peak-area or peak-height ratios. The present study examined the additional value of proton magnetic resonance spectroscopy with a short TE (31 ms) to predict a poor outcome in neonates with brain hypoxia-ischemia. Studies were performed in 21 full-term neonates with perinatal asphyxia in a 1.5 tesla magnetic field. Proton magnetic resonance spectroscopy was performed in a single volume of interest including the basal ganglia. TE of 272, 136 and 31 ms were used. After curve-fitting procedures, peak-areas as well as peak-height ratios of different brain metabolites were calculated, comparing patients with a poor versus a good outcome. Seven neonates out of 21 had a poor outcome. Neonates with a poor outcome showed a significantly lower N:-acetylaspartate/choline (NAA/Cho) and a significantly raised lactate/NAA (Lac/NAA) ratio using TE of 272 and 136 ms. Using a TE of 31 ms, no differences were found in glutamate/NAA (Glx/NAA), Glx/Cho, myo-inositol/NAA (mI/NAA), and mI/Cho ratios between neonates with a good and those with a poor outcome. Highest predictive values could be achieved for NAA/Cho with a TE of 136 ms. We conclude that low NAA/Cho and high Lac/NAA ratios predict a poor outcome in neonates with cerebral hypoxia-ischemia. TE of 272 and 136 ms have a better predictive value than a TE of 31 ms.

New radiographic techniques to evaluate cerebrovascular disorders in children

The radiographic evaluation of the pediatric patient with cerebrovascular disease has dramatically improved during the past decade. Few new technologies have been introduced, but significant new developments in data acquisition and post-processing have resulted from refinements in both software and, to a lesser extent, hardware. This review focuses on the advantages and limitations of the different imaging modalities and their recommended role in managing the pediatric patient who presents with signs or symptoms of cerebrovascular disease.

Cerebral mucormycosis: proton MR spectroscopy and MR imaging

Proton magnetic resonance spectroscopy (MRS) was integrated with magnetic resonance imaging (MRI) in the evaluation of a case of cerebral mucormycosis. MRS showed markedly elevated lactate, depleted N-acetyl aspartate and metabolite resonances attributable to succinate and acetate. The spectroscopy profile is essentially similar to that of bacterial abscess but without the commonly seen resonances of the amino acids valine, leucine and isoleucine. Our extensive literature review did not yield any reports of MRS findings on cerebral mucormycosis. MRS prospectively limited the differential diagnoses given the otherwise nonspecific and complex MR imaging findings in our immunosuppressed patient.

Proton MR spectroscopy in children with acute brain injury: comparison of short and long echo time acquisitions

The aim of this study was to evaluate comparatively the information given by proton magnetic resonance spectroscopy (MRS) with short echo time (TE 20 msec) stimulated echo acquisition mode and long TE (270 msec) point-resolved spectroscopy in predicting long-term outcome in children suffering from acute brain injury. At 1.5 T, we performed single-voxel proton MRS with both methods in occipital gray matter of 70 children. A linear discriminant analysis used to predict outcomes based on MRS variables was compared with actual neurologic outcome assigned at least 6 months after injury by a pediatric neurologist. Using peak area metabolite ratios and lactate presence, the short and long TE methods were equally predictive in children over 1 month of age. In neonates less than 1 month of age, the long TE method produced a higher percentage of correct outcome predictions (91%) than the short TE method (79%). The long TE method detected lactate more often in all age groups.

Neonatal neurologic prognostication: the asphyxiated term newborn

The pediatric neurologist is often requested to predict the neurologic outcome in an uncertain situation. A common and problematic clinical setting in which this occurs is the asphyxiated term newborn. This report reviews the predictive tools available for prognostication in this situation and formulates a practical paradigm that the authors hope will improve predictive accuracy and lessen uncertainty in this setting.

Effects of vaginal birth versus caesarean section birth with general anesthesia on blood gases and brain energy metabolism in neonatal rats

Using a rat model, several laboratories have demonstrated long-term effects of Caesarean section (C-section) birth or of global hypoxia during C-section birth on a variety of central nervous system (CNS) parameters. These studies used C-section delivery from rapidly decapitated dams, to avoid confounding anesthetic effects, or from dams anesthetized with halothane or ether under unspecified conditions. Systemic oxygenation or cerebral energy metabolites in the pups at birth have not been systematically measured in this model. To develop and characterize a C-section model with relevance to the human situation, the present study measured arterial/venous blood gases and pH and brain ATP and lactate, a widely accepted measure of CNS hypoxia, in pups born either vaginally, by C-section from decapitated dams, or by C-section from dams anesthetized with nitrous oxide (N2O) and increasing concentrations of isoflurane under well-defined conditions. Immediately after birth, pups born vaginally, by C-section with maternal decapitation, or by C-section with 2.5% isoflurane showed no group differences in systemic pO2 or pH or brain ATP levels, but pCO2 was elevated in the C-section/2.5% isoflurane group. Pups born by C-section with 3.0, 3.5, or 4.0% isoflurane, showed progressive reductions in blood pO2 and increases in pCO2 and blood pH was reduced with 3.5% isoflurane. Relative to vaginal birth, brain lactate levels were unchanged in pups born by C-section with any concentration (2.5-4.0%) of isoflurane, but reduced in pups born by C-section from decapitated dams. At 1 h (and 4 h) after birth, in both vaginally born controls and the 2.5% isoflurane group, brain lactate fell while blood pO2 and brain ATP remained stable. In the 3.0, 3.5, or 4.0% isoflurane groups, blood gases and pH and brain lactate also normalized to control values. In conclusion, rat neonates show minimal signs of systemic or CNS hypoxia following C-section birth under 2.5% isoflurane with N2O. However, there is a rather narrow window of isoflurane concentrations which produces effective maternal anesthesia without producing respiratory compromise in the neonate. Thus the results indicate that the level of maternal anesthesia employed is an important factor influencing neonatal systemic and CNS oxygenation during C-section birth.

Prenatal and perinatal striatal injury: a hypothetical cause of attention-deficit-hyperactivity disorder?

Experimental data indicate a particular vulnerability of striatal neurons in the developing brain, and together with the idea that the striatum is important for context recognition and behavior, these data have led the author to search for subtle striatal lesions, in the form of biochemical changes, in children who have suffered perinatal adverse events. Evidence is presented to demonstrate that the composition of metabolites in the striatum is altered, primarily in the form of an elevated level of lactate, in human neonates who have suffered various perinatal disorders, such as germinal matrix hemorrhage, intrauterine growth retardation, and asphyxia. An elevated level of lactate suggests tissue hypoxia, which may interfere with the formation of frontostriatal circuits and may play a role in the pathogenesis of the behavioral disturbances observed in a proportion of children with a history of perinatal adverse events.