Electroencephalographic response to procedural pain in healthy term newborn infants

A machine learning artefact detection method for single-channel infant event-related potential studies

Objective. Automated detection of artefact in stimulus-evoked electroencephalographic (EEG) data recorded in neonates will improve the reproducibility and speed of analysis in clinical research compared with manual identification of artefact. Some studies use very short, single-channel epochs of EEG data with little recorded EEG per infant-for example because the clinical vulnerability of the infants limits access for recording. Current artefact-detection methods that perform well on adult data and resting-state and multi-channel data in infants are not suitable for this application. The aim of this study was to create and test an automated method of detecting artefact in single-channel 1500 ms epochs of infant EEG.Approach. A total of 410 epochs of EEG were used, collected from 160 infants of 28-43 weeks postmenstrual age. This dataset-which was balanced to include epochs of background activity and responses to visual, auditory, tactile and noxious stimuli-was presented to seven independent raters, who independently labelled the epochs according to whether or not they were able to visually identify artefacts. The data was split into a training set (340 epochs) and an independent test set (70 epochs). A random forest model was trained to identify epochs as either artefact or not artefact.Main results. This model performs well, achieving a balanced accuracy of 0.81, which is as good as manual review of data. Accuracy was not significantly related to the infant age or type of stimulus.Significance. This method provides an objective tool for automated artefact rejection for short epoch, single-channel EEG in neonates and could increase the utility of EEG in neonates in both the clinical and research setting.

How can cry acoustics associate newborns' distress levels with neurophysiological and behavioral signals?

Introduction

Even though infant crying is a common phenomenon in humans' early life, it is still a challenge for researchers to properly understand it as a reflection of complex neurophysiological functions. Our study aims to determine the association between neonatal cry acoustics with neurophysiological signals and behavioral features according to different cry distress levels of newborns.

Methods

Multimodal data from 25 healthy term newborns were collected simultaneously recording infant cry vocalizations, electroencephalography (EEG), near-infrared spectroscopy (NIRS) and videos of facial expressions and body movements. Statistical analysis was conducted on this dataset to identify correlations among variables during three different infant conditions (i.e., resting, cry, and distress). A Deep Learning (DL) algorithm was used to objectively and automatically evaluate the level of cry distress in infants.

Results

We found correlations between most of the features extracted from the signals depending on the infant's arousal state, among them: fundamental frequency (F0), brain activity (delta, theta, and alpha frequency bands), cerebral and body oxygenation, heart rate, facial tension, and body rigidity. Additionally, these associations reinforce that what is occurring at an acoustic level can be characterized by behavioral and neurophysiological patterns. Finally, the DL audio model developed was able to classify the different levels of distress achieving 93% accuracy.

Conclusion

Our findings strengthen the potential of crying as a biomarker evidencing the physical, emotional and health status of the infant becoming a crucial tool for caregivers and clinicians.

Feasibility of automated early postnatal sleep staging in extremely and very preterm neonates using dual-channel EEG

OBJECTIVE

To investigate the feasibility of automated sleep staging based on quantitative analysis of dual-channel electroencephalography (EEG) for extremely and very preterm infants during their first postnatal days.

METHODS

We enrolled 17 preterm neonates born between 25 and 30 weeks of gestational age. Three-hour behavioral sleep observations and simultaneous dual-channel EEG monitoring were conducted for each infant within their first 72 hours after birth. Four kinds of representative and complementary quantitative EEG (qEEG) metrics (i.e., bursting, synchrony, spectral power, and complexity) were calculated and compared between active sleep, quiet sleep, and wakefulness. All analyses were performed in offline mode.

RESULTS

In separate comparison analyses, significant differences between sleep-wake states were found for bursting, spectral power and complexity features. The automated sleep-wake state classifier based on the combination of all qEEG features achieved a macro-averaged area under the curve of receiver operating characteristic of 74.8%. The complexity features contributed the most to sleep-wake state classification.

CONCLUSIONS

It is feasible to distinguish between sleep-wake states within the first 72 postnatal hours for extremely and very preterm infants using qEEG metrics.

SIGNIFICANCE

Our findings offer the possibility of starting personalized care dependent on preterm infants' sleep-wake states directly after birth, potentially yielding long-run benefits for their developmental outcomes.

Can Event-Related Potentials Evoked by Heel Lance Assess Pain Processing in Neonates? A Systematic Review

To clarify the possibility of event-related potential (ERP) evoked by heel lance in neonates as an index of pain assessment, knowledge acquired by and problems of the methods used in studies on ERP evoked by heel lance in neonates were systematically reviewed, including knowledge about Aδ and C fibers responding to noxious stimuli and Aβ fibers responding to non-noxious stimuli. Of the 863 reports searched, 19 were selected for the final analysis. The following points were identified as problems for ERP evoked by heel lance in neonates to serve as a pain assessment index: (1) It is possible that the ERP evoked by heel lance reflected the activation of Aβ fibers responding to non-noxious stimuli and not the activation of Aδ or C fibers responding to noxious stimulation; (2) Sample size calculation was presented in few studies, and the number of stimulation trials to obtain an averaged ERP was small. Accordingly, to establish ERP evoked by heel lance as a pain assessment in neonates, it is necessary to perform a study to clarify ERP evoked by Aδ- and C-fiber stimulations accompanied by heel lance in neonates.

Using sensor-fusion and machine-learning algorithms to assess acute pain in non-verbal infants: a study protocol

INTRODUCTION

Objective pain assessment in non-verbal populations is clinically challenging due to their inability to express their pain via self-report. Repetitive exposures to acute or prolonged pain lead to clinical instability, with long-term behavioural and cognitive sequelae in newborn infants. Strong analgesics are also associated with medical complications, potential neurotoxicity and altered brain development. Pain scores performed by bedside nurses provide subjective, observer-dependent assessments rather than objective data for infant pain management; the required observations are labour intensive, difficult to perform by a nurse who is concurrently performing the procedure and increase the nursing workload. Multimodal pain assessment, using sensor-fusion and machine-learning algorithms, can provide a patient-centred, context-dependent, observer-independent and objective pain measure.

METHODS AND ANALYSIS

In newborns undergoing painful procedures, we use facial electromyography to record facial muscle activity-related infant pain, ECG to examine heart rate (HR) changes and HR variability, electrodermal activity (skin conductance) to measure catecholamine-induced palmar sweating, changes in oxygen saturations and skin perfusion, and electroencephalography using active electrodes to assess brain activity in real time. This multimodal approach has the potential to improve the accuracy of pain assessment in non-verbal infants and may even allow continuous pain monitoring at the bedside. The feasibility of this approach will be evaluated in an observational prospective study of clinically required painful procedures in 60 preterm and term newborns, and infants aged 6 months or less.

ETHICS AND DISSEMINATION

The Institutional Review Board of the Stanford University approved the protocol. Study findings will be published in peer-reviewed journals, presented at scientific meetings, taught via webinars, podcasts and video tutorials, and listed on academic/scientific websites. Future studies will validate and refine this approach using the minimum number of sensors required to assess neonatal/infant pain.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Registry (NCT03330496).

Comparison of conventional, amplitude-integrated and geodesic sensor net EEG used in premature neonates: a systematic review

INTRODUCTION

The use of methods to evaluate cortical activity in neonates has great importance in modern medicine, as it allows the observation and evaluation of several clinical aspects, which guarantees that the health team has knowledge about possible intervention measures that may be necessary in the treatment of newborns.

OBJECTIVE

This systematic review aimed to compare the main technologies available for the evaluation of brain functions in neonates, among them: the conventional electroencephalogram (EEG), the amplitude-integrated electroencephalogram (aEEG) and the geodesic sensor net EEG.

METHODS

A search was conducted forarticles from national and international periodicals included in the Web of Science, LILACS, SciELO and Medline electronic databases.

RESULTS

The search found 39 among 155 articles of interest and the analyses indicated that, in the clinical environment, the use of both conventional EEG and aEEG is highly recommended, as the combination of their functions allows, for example, a greater number of subclinical seizures to be detected. Conversely, the use of a geodesic sensor net EEG could be of great value, as it allows a large amount of data to be analyzed.

CONCLUSION

This analysis may be useful in studies and research related to diseases and symptoms, such as seizures, a current challenge for neonatal neuromonitoring, as well as aspects of neurological development and functional studies. However, despite many advances in technology, electroencephalography in preterm neonates remains a challenge worldwide and still requires more robust research and efforts towards the best clinical assistance in this extremely early stage of life.

Assessment of pain in newborn infants

Hospitalized newborn infants experience pain that can have negative short- and long-term consequences and thus should be prevented and treated. National and international guidelines state that adequate pain management requires valid pain assessment. Nociceptive signals cause a cascade of physical and behavioral reactions that alone or in combination can be observed and used to assess the presence and intensity of pain. Units that are caring for newborn infants must adopt sufficient pain assessment tools to cover the gestational ages and pain types that occurs in their setting. Pain assessment should be performed on a regular basis and any detection of pain should be acted on. Future research should focus on developing and validating pain assessment tools for specific situations.

Behavioral and Physiological Signs for Pain Assessment in Preterm and Term Neonates During a Nociception-Specific Response: A Systematic Review

BACKGROUND/GOAL

Assessment and treatment of neonatal pain is difficult because current scales are rarely validated against brain-based evidence. We sought to systematically evaluate published evidence to extract validation of the most promising markers of neonatal pain.

METHODS

We searched four databases using germane MeSH terms. We focused on assessments of pain and/or nociception that had at least two measures among behavioral, physiological, or cortical components in preterm and/or term neonates. We evaluated studies for quality of evidence and strength of recommendations using standardized tools.

RESULTS

Fifteen articles met our inclusion criteria. Among the behavioral components uncovered in this review, the withdrawal reflex and changes in facial expression are the most strongly associated with nociception-specific brain activity. These associations may be influenced by gestational age and change over time. Physiological signs, such heart rate and oxygen saturation, have little to no association with this type of response.

CONCLUSIONS

Current assessments of neonatal pain include behavioral components that are associated with nociceptive processing, but also other less valid components, while omitting newer measures based on neuroscientific research.

Neurophysiological assessment of acute pain in infants: a scoping review of research methods

A systematic scoping search to describe the neurophysiological methods used in infant acute pain assessment research was conducted. Of the 2411 abstracts screened, 19 articles were retained. Nine studies utilised near-infrared spectroscopy (NIRS), two utilised functional magnetic resonance imaging (fMRI), and eight utilised electroencephalography (EEG). There was methodological variability in studies utilising NIRS, whereas EEG and fMRI studies reported consistent methods. Of the eight EEG studies, six identified a nociceptive-specific event-related potential.

CONCLUSION

While more methodologically rigorous studies are needed, ERPs appear to hold some promise as indicators of infant nociception during clinical procedures to supplement existing measures.

Growth of Thalamocortical Fibers to the Somatosensory Cortex in the Human Fetal Brain

Thalamocortical (TH-C) fiber growth begins during the embryonic period and is completed by the third trimester of gestation in humans. Here we determined the timing and trajectories of somatosensory TH-C fibers in the developing human brain. We analyzed the periods of TH-C fiber outgrowth, path-finding, "waiting" in the subplate (SP), target selection, and ingrowth in the cortical plate (CP) using histological sections from post-mortem fetal brain [from 7 to 34 postconceptional weeks (PCW)] that were processed with acetylcholinesterase (AChE) histochemistry and immunohistochemical methods. Images were compared with post mortem diffusion tensor imaging (DTI)-based fiber tractography (code No NO1-HD-4-3368). The results showed TH-C axon outgrowth occurs as early as 7.5 PCW in the ventrolateral part of the thalamic anlage. Between 8 and 9.5 PCW, TH-C axons form massive bundles that traverse the diencephalic-telencephalic boundary. From 9.5 to 11 PCW, thalamocortical axons pass the periventricular area at the pallial-subpallial boundary and enter intermediate zone in radiating fashion. Between 12 and 14 PCW, the TH-C axons, aligned along the fibers from the basal forebrain, continue to grow for a short distance within the deep intermediate zone and enter the deep CP, parallel with SP expansion. Between 14 and 18 PCW, the TH-C interdigitate with callosal fibers, running shortly in the sagittal stratum and spreading through the deep SP ("waiting" phase). From 19 to 22 PCW, TH-C axons accumulate in the superficial SP below the somatosensory cortical area; this occurs 2 weeks earlier than in the frontal and occipital cortices. Between 23 and 24 PCW, AChE-reactive TH-C axons penetrate the CP concomitantly with its initial lamination. Between 25 and 34 PCW, AChE reactivity of the CP exhibits an uneven pattern suggestive of vertical banding, showing a basic 6-layer pattern. In conclusion, human thalamocortical axons show prolonged growth (4 months), and somatosensory fibers precede the ingrowth of fibers destined for frontal and occipital areas. The major features of growing TH-C somatosensory fiber trajectories are fan-like radiation, short runs in the sagittal strata, and interdigitation with the callosal system. These results support our hypothesis that TH-C axons are early factors in SP and CP morphogenesis and synaptogenesis and may regulate cortical somatosensory system maturation.

HELPinKids&Adults Knowledge Synthesis of the Management of Vaccination Pain and High Levels of Needle Fear: Limitations of the Evidence and Recommendations for Future Research

The HELPinKids&Adults knowledge synthesis for the management of vaccination-related pain and high levels of needle fear updated and expanded upon the 2010 HELPinKIDS knowledge synthesis and clinical practice guideline for pain mitigation during vaccine injections in childhood. Interventions for vaccine pain management in adults and treatment of individuals with high levels of needle fear, phobias, or both were included, thereby broadening the reach of this work. The present paper outlines the overarching limitations of this diverse evidence base and provides recommendations for future research. Consistent with the framing of clinical questions in the systematic reviews, the Participants, Intervention, Comparison, Outcome, Study design (PICOAS) framework was used to organize these predominant issues and research directions. The major limitations we identified across systematic reviews were an overall dearth of trials on vaccination, lack of methodological rigor, failure to incorporate important outcomes, poor study reporting, and various sources of heterogeneity. Future research directions in terms of conducting additional trials in the vaccination context, improving methodological quality and rigor, assessment of global acceptability and feasibility of interventions, and inclusion of outcomes that stakeholders consider to be important (eg, compliance) are recommended. Given concerns about pain and fear are known contributors to vaccine hesitancy, improving and expanding this evidence base will be integral to broader efforts to improve vaccine compliance and public health worldwide.

Biological and neurodevelopmental implications of neonatal pain

Nociceptive pathways are functional following birth. In addition to physiological and behavioral responses, neurophysiological measures and neuroimaging evaluate nociceptive pathway function and quantify responses to noxious stimuli in preterm and term neonates. Intensive care and surgery can expose neonates to painful stimuli when the developing nervous system is sensitive to changing input, resulting in persistent impacts into later childhood. Early pain experience has been correlated with increased sensitivity to subsequent painful stimuli, impaired neurodevelopmental outcomes, and structural changes in brain development. Parallel preclinical studies have elucidated underlying mechanisms and evaluate preventive strategies to inform future clinical trials.

Amplitude electroencephalogram characterization in preterm infants undergoing patent ductus arteriosus ligation

BACKGROUND

Recent studies suggest an increased risk of neurodevelopmental impairment following patent ductus arteriosus surgical ligation. The mechanisms are unclear, but intraoperative stress or pain may contribute. The objectives of this study were to determine if pain, evidenced by an increase in heart rate and blood pressure, during patent ductus arteriosus ligation would be accompanied by an increase in amplitude-integrated electroencephalogram (aEEG) voltage.

METHODS

This was an observational, pilot study of infants born at 22.6-35.1 weeks with patent ductus arteriosus requiring surgical ligation. The aEEG was recorded prior to, during surgery, and for 2 hours following surgery. Mean heart rate, blood pressure, and aEEG voltage were analyzed for each recording period.

RESULTS

Seventeen preterm infants were studied at a mean postmenstrual age of 26.6 weeks. Following anesthetic induction, aEEG became suppressed and remained suppressed during the postoperative period. Heart rate and blood pressure increased significantly intraoperatively. The aEEG voltage did not increase with an increase in heart rate. Infants received between 3.7-47 μg/kg of fentanyl.

CONCLUSIONS

There was no correlation between aEEG voltage and vital sign changes. aEEG is not a useful tool as a marker of pain during patent ductus arteriosus ligation, rather a more standardized approach to pain management should be considered.

Sucrose for procedural pain management in infants

The use of oral sucrose has been the most extensively studied pain intervention in newborn care to date. More than 150 published studies relating to sweet-taste-induced calming and analgesia in human infants have been identified, of which 100 (65%) include sucrose. With only a few exceptions, sucrose, glucose, or other sweet solutions reduced pain responses during commonly performed painful procedures in diverse populations of infants up to 12 months of age. Sucrose has been widely recommended for routine use during painful procedures in newborn and young infants, yet these recommendations have not been translated into consistent use in clinical practice. One reason may be related to important knowledge and research gaps concerning analgesic effects of sucrose. Notably, the mechanism of sweet-taste-induced analgesia is still not precisely understood, which has implications for using research evidence in practice. The aim of this article is to review what is known about the mechanisms of sucrose-induced analgesia; highlight existing evidence, knowledge gaps, and current controversies; and provide directions for future research and practice.

Assessing pain in preterm infants in the neonatal intensive care unit: moving to a 'brain-oriented' approach

Preterm infants in the neonatal intensive care unit undergo repeated exposure to procedural and ongoing pain. Early and long-term changes in pain processing, stress-response systems and development may result from cumulative early pain exposure. So that appropriate treatment can be given, accurate assessment of pain is vital, but is also complex because these infants' responses may differ from those of full-term infants. A variety of uni- and multidimensional assessment tools are available; however, many have incomplete psychometric testing and may not incorporate developmentally important cues. Near-infrared spectroscopy and/or EEG techniques that measure neonatal pain responses at a cortical level offer new opportunities to validate neonatal pain assessment tools.

Analgesic effects of sweet-tasting solutions for infants: current state of equipoise

OBJECTIVE

The goal was to review published studies of analgesic effects of sweet solutions, to ascertain areas with sufficient evidence of effectiveness and areas of uncertainty.

METHODS

Databases searched included Medline, Embase, the Cumulative Index to Nursing and Allied Health Literature database, and PsycINFO, using the terms pain*, infant*, neonat*, newborn*, sucrose, glucose, and alternative sugars. Publications were sorted according to type, year, painful procedure studied, placebo/no-treatment groups, population studied, and country of publication.

RESULTS

A total of 298 relevant unique publications involving human infants were identified; 125 (42%) were primary research studies, of which 116 (93%) were randomized controlled trials. Healthy preterm or term newborns were included in 82 studies (65%), and sick or very low birth weight infants were included in 22 (18%). Most studies included single episodes of painful procedures, with only 3 (2%) conducted over long periods. Procedures investigated most frequently were heel lance (49%), venipuncture (14%), and intramuscular injection (14%). Placebo or no-treatment groups were included in 111 studies (89%); in 103 (93%) of those studies, sweet solutions reduced behavioral responses, compared with placebo/ no treatment.

CONCLUSION

Clinical equipoise relating to analgesic effects of sweet solutions no longer exists for single episodes of procedures for healthy preterm and term newborn infants. Uncertainties include outcomes after prolonged use of sweet solutions, concomitant use of other analgesics, and effectiveness beyond the newborn period. Future research should focus on addressing these knowledge and research gaps.

Detection of 'EEG bursts' in the early preterm EEG: visual vs. automated detection

OBJECTIVE

To describe the characteristics of activity bursts in the early preterm EEG, to assess inter-rater agreement of burst detection by visual inspection, and to determine the performance of an automated burst detector that uses non-linear energy operator (NLEO).

METHODS

EEG recordings from extremely preterm (n=12) and very preterm (n=6) infants were analysed. Three neurophysiologists independently marked bursts in the EEG, the characteristics of bursts were analyzed and inter-rater agreement determined. Unanimous detections were used as the gold standard in estimating the performance of an automated burst detector. In addition, some details of this automated detector were revised in an attempt to improve performance.

RESULTS

Overall, inter-rater agreement was 86% for extremely preterm infants and 81% for very preterm infants. In visual markings, bursts had variable lengths (approximately 1-10s) and increased amplitudes (and power) throughout the frequency spectrum. Accuracy of the original detection algorithm was 87% and 79% and accuracy of the revised algorithm 93% and 87% for extremely preterm and very preterm babies, respectively.

CONCLUSION

Visual detection of bursts from the early preterm EEG is comparable albeit not identical between raters. The original automated detector underestimates the amount of burst occurrence, but can be readily improved to yield results comparable to visual detection. Further clinical studies are warranted to assess the optimal descriptors of burst detection for monitoring and prognostication.

SIGNIFICANCE

Validation of a burst detector offers an evidence-based platform for further development of brain monitors in very preterm babies.