Clinical applications of cerebral function monitoring in neonates

Introduction of Amplitude-Integrated Electroencephalography (aEEG) Monitoring in a Level 2 NICU: Improving the Quality of Care for Neurologically At-Risk Newborns

Amplitude-integrated electroencephalography (aEEG) is a bedside tool for continuous monitoring of brain activity with the possibility of real-time interpretation. Amplitude-integrated electroencephalography is routinely used in Canadian tertiary NICUs; however, its use in Level 2 NICUs has been limited. A bedside aEEG program was introduced in a Level 2 NICU in order to help facilitate the timely transfer of neurologically compromised infants and keep mother-infant dyads together where reassurance of appropriate neurological status could be attained. A monitoring guideline and educational program were developed. The introduction of aEEG monitoring enhanced the care provided to neurologically at-risk newborns. This experience can be used as a framework for other Level 2 NICUs who may wish to embark upon a similar initiative.

Prognostic neurobiomarkers in neonatal encephalopathy

Therapeutic hypothermia is now standard-care for infants with moderate-severe neonatal encephalopathy (NE), and improves brain damage on neuroimaging, and neurodevelopmental outcomes. Critically, for effective neuroprotection, hypothermia should be started within 6 h from birth. There is compelling evidence to suggest that a proportion of infants with mild NE have material risk of developing brain damage and poor outcomes. This cohort is increasingly being offered therapeutic hypothermia, despite lack of trial evidence for its benefit. In current practice, infants need to be diagnosed within 6 h of birth for therapeutic treatment, compared to retrospective NE grading in the pre-hypothermia era. This presents challenges as NE is a dynamic brain disorder that can worsen or resolve over time. Neurological symptoms of NE can be difficult to discern in the first few hours after birth, and confounded by analgesics and anesthetic treatment. Using current enrolment criteria, a significant number of infants with NE that would benefit from hypothermia are not treated, and vice versa, infants are receiving mild hypothermia when its benefit will be limited. Better biomarkers are needed to further improve management and treatment of these neonates. In the present review, we examine the latest research, and highlight a central limitation of most current biomarkers: that their predictive value is consistently greatest after most neuroprotective therapies are no longer effective.

Challenges in developing therapeutic strategies for mild neonatal encephalopathy

There is increasing evidence that infants with mild neonatal encephalopathy (NE) have significant risks of mortality, brain injury and adverse neurodevelopmental outcomes. In the era of therapeutic hypothermia, infants need to be diagnosed within 6 hours of birth, corresponding with the window of opportunity for treatment of moderate to severe NE, compared to the retrospective grading over 2 to 3 days, typically with imaging and formal electroencephalographic assessment in the pre-hypothermia era. This shift in diagnosis may have increased the apparent prevalence of brain damage and poor neurological outcomes seen in infants with mild NE in the era of hypothermia. Abnormal short term outcomes observed in infants with mild NE include seizures, abnormal neurologic examination at discharge, abnormal brain magnetic resonance imaging and difficulty feeding. At 2 to 3 years of age, mild NE has been associated with an increased risk of autism, language and cognitive deficits. There are no approved treatment strategies for these infants as they were not included in the initial randomized controlled trials for therapeutic hypothermia. However, there is already therapeutic creep, with many centers treating infants with mild NE despite the limited evidence for its safety and efficacy. The optimal duration of treatment and therapeutic window of opportunity for effective treatment need to be specifically established for mild NE as the evolution of injury is likely to be slower, based on preclinical data. Randomized controlled trials of therapeutic hypothermia for infants with mild NE are urgently required to establish the safety and efficacy of treatment. This review will examine the evidence for adverse outcomes after mild NE and dissect some of the challenges in developing therapeutic strategies for mild NE, before analyzing the evidence for therapeutic hypothermia and other strategies for treatment of these infants.

Methods for Monitoring Risk of Hypoxic Damage in Fetal and Neonatal Brains: A Review

Fetal, perinatal, and neonatal asphyxia are vital health issues for the most vulnerable groups in human beings, including fetuses, newborns, and infants. Severe reduction in oxygen and blood supply to the fetal brain can cause hypoxic-ischemic encephalopathy, leading to long-term neurological disorders, including mental impairment and cerebral palsy. Such neurological disorders are major healthcare concerns. Therefore, there has been a continuous effort to develop clinically useful diagnostic tools for accurately and quantitatively measuring and monitoring blood and oxygen supply to the fetal and neonatal brain to avoid severe consequences of asphyxia Hypoxic-Ischemic Encephalopathy (HIE) and Neonatal Encephalopathy (NE). Major diagnostic technologies used for this purpose include fetal heart rate monitoring (FHRM), fetus scalp blood sampling (FBS), ultrasound (US) imaging, magnetic resonance imaging (MRI), x-ray computed tomography (CT), and nuclear medicine. In addition, given the limitations and shortcomings of traditional diagnostic methods, emerging technologies such as near-infrared spectroscopy (NIRS) and photoacoustic (PA) imaging have also been introduced as stand-alone or complementary solutions to address this critical gap in fetal and neonatal care. This review provides a thorough overview of the traditional and emerging technologies for monitoring fetal and neonatal brain oxygenation status and describes their clinical utility, performance, advantages, and disadvantages.

Cooling in mild encephalopathy: Costs and perils of therapeutic creep

Increasing confidence in therapeutic hypothermia and ambiguity of cooling guidelines has led to many clinicians extending its use to untested populations like mild encephalopathy, or even no encephalopathy. Poor quality clinical neurological examination for encephalopathy staging coupled with a fear of litigation if a baby with mild encephalopathy progress to moderate or severe encephalopathy appears to be the primary driver for this therapeutic creep. Recent data suggesting increased apoptosis with cooling uninjured brains, and lack of hypothermic neuroprotection in partial prolonged hypoxia, implies that such therapeutic creeps may cause more harm than benefit. Currently available preclinical and clinical data do not support the clinical use of therapeutic hypothermia for mild encephalopathy, although phase II clinical trials are ongoing. We recommend that until further evidence from adequately powered randomised controlled trials are available, cooling in mild encephalopathy need to be considered experimental and parental consent should be obtained before providing this therapy.

A realistic flow phantom model of the carotid artery in preterm infants for training and research

Introduction

Cerebral blood flow is increasingly monitored in preterm infants. Doppler ultrasound of the carotid artery is a widely available method but is operator dependent. Our aim was to design and produce a realistic flow phantom model of the carotid artery of preterm infants.

Methods

Data from cerebral blood flow measurements using Doppler ultrasound of the right common carotid artery from 21 premature newborn infants were used to produce a Doppler flow phantom model with three different vessel diameters. Vessel diameter, continuous and pulsatile flow volume measurements were performed by two blinded observers (with more than eight and 20 years of experience).

Results

Vessel diameter measurements using the phantom were underestimated by 7%. Continuous flow volume measurements were overestimated by 7% by both observers (observer 1 mean difference 1.5 ± 1.96 SD -3.3 to 6.3 ml/min versus observer 2, 1.9 ± 1.96 SD -3.6 to 7.4 ml/min). Pulsatile flow measurements were overestimated by 12.6% by observer 1 (2.7 ± 1.96 SD -0.6 to 5.9 ml/min) and by 7.8% by observer 2 (1.7 ± 1.96 SD -1.6 to 4.9 ml/min). There was good interobserver and intraobserver reliability for the majority of measurements using continuous and pulsatile flow.

Conclusion

It is feasible to produce a realistic flow phantom model of the neonatal carotid artery of preterm infants. Diameter measurements were underestimated and flow measurements were overestimated. These errors fell within acceptable limits for in vivo measurements. If these limitations were related to materials, this could be explored using a wall-less model. The flow phantom could be utilised for research and training clinicians in measuring cerebral blood flow using the carotid artery in this vulnerable group of infants.

Preterm Brain Injury, Antenatal Triggers, and Therapeutics: Timing Is Key

With a worldwide incidence of 15 million cases, preterm birth is a major contributor to neonatal mortality and morbidity, and concomitant social and economic burden Preterm infants are predisposed to life-long neurological disorders due to the immaturity of the brain. The risks are inversely proportional to maturity at birth. In the majority of extremely preterm infants (<28 weeks' gestation), perinatal brain injury is associated with exposure to multiple inflammatory perinatal triggers that include antenatal infection (i.e., chorioamnionitis), hypoxia-ischemia, and various postnatal injurious triggers (i.e., oxidative stress, sepsis, mechanical ventilation, hemodynamic instability). These perinatal insults cause a self-perpetuating cascade of peripheral and cerebral inflammation that plays a critical role in the etiology of diffuse white and grey matter injuries that underlies a spectrum of connectivity deficits in survivors from extremely preterm birth. This review focuses on chorioamnionitis and hypoxia-ischemia, which are two important antenatal risk factors for preterm brain injury, and highlights the latest insights on its pathophysiology, potential treatment, and future perspectives to narrow the translational gap between preclinical research and clinical applications.

Swedish consensus reached on recording, interpretation and reporting of neonatal continuous simplified electroencephalography that is supported by amplitude-integrated trend analysis

Continuous monitoring of electroencephalography (EEG), with a focus on amplitude-integrated EEG (aEEG), has been used in neonatal intensive care for decades. A number of systems have been suggested for describing and quantifying aEEG patterns. Extensive full-montage EEG monitoring is used in specialised intensive care units. The American Clinical Neurophysiology Society published recommendations for defining and reporting EEG findings in critically ill adults and infants. Swedish neonatologists and clinical neurophysiologists collaborated to optimise simplified neonatal continuous aEEG and EEG recordings based on these American documents.

CONCLUSION

This paper describes the Swedish consensus document produced by those meetings.

Early Amplitude-Integrated Electroencephalogram as a Predictor of Brain Injury in Newborns With Very Low Birth Weight: A Cohort Study

PURPOSE

To evaluate the relationship between abnormal early amplitude integrated electroencephalography (EEG) and severe lesions in imaging tests performed during the neonatal period in very low birth weight infants.

METHODS

An amplitude-integrated EEG was performed in 70 patients with a mean birth weight of 1226 g during the first 48 hours of life. Severe lesions on magnetic resonance imaging (MRI) or ultrasonography (US) during the neonatal period were considered as adverse conditions. Variables were compared using the χ² test or analysis of variance. Sensitivity, specificity, and positive likelihood ratio were calculated.

RESULTS

Adverse outcomes were observed in 6 patients. There was a significant relationship ( P < .001) between abnormal amplitude-integrated EEG background and severe lesions on MRI and US. Sensitivity and specificity were 100% and 89%, respectively.

CONCLUSION

Early amplitude-integrated EEG with moderate/severe abnormalities in the background is associated with severe structural lesions detected in imaging studies and should be considered as an auxiliary screening tool for the detection of neonatal brain lesions in very low birth weight infants.

A review of the conundrum of mild hypoxic-ischemic encephalopathy: Current challenges and moving forward

A review of the conundrum called mild hypoxic-ischemic encephalopathy (HIE) is provided. During the past decades, the definition of HIE has evolved to accommodate the short window of time required for the initiation of therapeutic hypothermia. Also, neurological evaluations have changed with the use of simpler staging systems that can be applied within the first 6 h of life. In this review, we discuss the challenges in the identification of newborns with "mild HIE" within 6 h after birth, the limitations in the existing early biomarkers of brain injury, and the current knowledge gaps in the long term neurodevelopmental outcomes of infants diagnosed with mild HIE. Progress in the understanding of mild HIE and its sequelae continues to be hindered by the lack of a standardized definition for mild HIE that will reliably identify at-risk infants who may benefit from neuroprotective strategies.

Amplitude Integrated Electroencephalography Compared With Conventional Video EEG for Neonatal Seizure Detection: A Diagnostic Accuracy Study

This diagnostic accuracy study compared the accuracy of seizure detection by amplitude-integrated electroencephalography with the criterion standard conventional video EEG in term and near-term infants at risk of seizures. Simultaneous recording of amplitude-integrated EEG (2-channel amplitude-integrated EEG with raw trace) and video EEG was done for 24 hours for each infant. Amplitude-integrated EEG was interpreted by a neonatologist; video EEG was interpreted by a neurologist independently. Thirty-five infants were included in the analysis. In the 7 infants with seizures on video EEG, there were 169 seizure episodes on video EEG, of which only 57 were identified by amplitude-integrated EEG. Amplitude-integrated EEG had a sensitivity of 33.7% for individual seizure detection. Amplitude-integrated EEG had an 86% sensitivity for detection of babies with seizures; however, it was nonspecific, in that 50% of infants with seizures detected by amplitude-integrated EEG did not have true seizures by video EEG. In conclusion, our study suggests that amplitude-integrated EEG is a poor screening tool for neonatal seizures.

Comparison of Amplitude-Integrated EEG and Conventional EEG in a Cohort of Premature Infants

OBJECTIVE

To compare amplitude-integrated EEG (aEEG) and conventional EEG (EEG) activity in premature neonates.

METHODS

Biweekly aEEG and EEG were simultaneously recorded in a cohort of infants born less than 34 weeks gestation. aEEG recordings were visually assessed for lower and upper border amplitude and bandwidth. EEG recordings were compressed for visual evaluation of continuity and assessed using a signal processing software for interburst intervals (IBI) and frequencies' amplitude. Ten-minute segments of aEEG and EEG indices were compared using regression analysis.

RESULTS

A total of 189 recordings from 67 infants were made, from which 1697 aEEG/EEG pairs of 10-minute segments were assessed. Good concordance was found for visual assessment of continuity between the 2 methods. EEG IBI, alpha and theta frequencies' amplitudes were negatively correlated to the aEEG lower border while conceptional age (CA) was positively correlated to aEEG lower border ( P < .001). IBI and all frequencies' amplitude were positively correlated to the upper aEEG border ( P ≤ .001). CA was negatively correlated to aEEG span while IBI, alpha, beta, and theta frequencies' amplitude were positively correlated to the aEEG span.

CONCLUSIONS

Important information is retained and integrated in the transformation of premature neonatal EEG to aEEG.

SIGNIFICANCE

aEEG recordings in high-risk premature neonates reflect reliably EEG background information related to continuity and amplitude.