Electrode challenges in amplitude-integrated electroencephalography (aEEG): research application of a novel noninvasive measure of brain function in preterm infants

Neonatal Electroencephalogram Electrode-Related Pressure Injury Prevention Quality Improvement Study

OBJECTIVE

To lengthen the days between electroencephalogram electrode-related pressure injury (EERPI) to 100 EERPI-free days in 6 months of study implementation with a goal to maintain 200 EERPI-free days thereafter (≤1 EERPI event/year).

METHODS

This quality improvement study took place in a level IV neonatal ICU over three epochs spanning 2 years: epoch 1 or baseline (January-June 2019), epoch 2 or implementation of intervention (July-December 2019), and epoch 3 or sustainment (January-December 2020). A daily electroencephalogram (EEG) skin assessment tool, introduction in practice of a flexible hydrogel EEG electrode, and successive rapid-cycle staff-education sessions were key interventions of the study.

RESULTS

Seventy-six infants were monitored for 214 continuous EEG (cEEG) days, of which six (13.2%) developed EERPI in epoch 1. Eighty infants were monitored for 193 cEEG days, of which two (2.5%) developed EERPI in epoch 2. One hundred thirty-nine infants were monitored for 338 cEEG days, and none developed EERPI in epoch 3. There was no statistical difference with respect to the median cEEG days among study epochs. A G-chart of EERPI-free days showed an increase in EERPI-free days from an average of 34 days in epoch 1 to 182 days in epoch 2 and 365 days (or zero harm) in epoch 3. Skin erythema from EEG electrodes was noted during the study.

CONCLUSIONS

The structured study interventions eliminated EERPI events in infants monitored with cEEG. Preventive intervention at the cEEG-electrode level coupled with skin assessment successfully reduced EERPIs in neonates.

Neuromonitoring in neonatal critical care part II: extremely premature infants and critically ill neonates

Neonatal intensive care has expanded from cardiorespiratory care to a holistic approach emphasizing brain health. To best understand and monitor brain function and physiology in the neonatal intensive care unit (NICU), the most commonly used tools are amplitude-integrated EEG, full multichannel continuous EEG, and near-infrared spectroscopy. Each of these modalities has unique characteristics and functions. While some of these tools have been the subject of expert consensus statements or guidelines, there is no overarching agreement on the optimal approach to neuromonitoring in the NICU. This work reviews current evidence to assist decision making for the best utilization of these neuromonitoring tools to promote neuroprotective care in extremely premature infants and in critically ill neonates. Neuromonitoring approaches in neonatal encephalopathy and neonates with possible seizures are discussed separately in the companion paper. IMPACT: For extremely premature infants, NIRS monitoring has a potential role in individualized brain-oriented care, and selective use of aEEG and cEEG can assist in seizure detection and prognostication. For critically ill neonates, NIRS can monitor cerebral perfusion, oxygen delivery, and extraction associated with disease processes as well as respiratory and hypodynamic management. Selective use of aEEG and cEEG is important in those with a high risk of seizures and brain injury. Continuous multimodal monitoring as well as monitoring of sleep, sleep-wake cycling, and autonomic nervous system have a promising role in neonatal neurocritical care.

Evaluation of the suitability and clinical applicability of different electrodes for aEEG/cEEG monitoring in the extremely premature infant

INTRODUCTION

Monitoring of brain function using continuous electroencephalography (aEEG/cEEG) is an essential tool in the standard care of the term infant, and its use is growing in the premature infant as a biomarker of lesion and brain maturity. However, the placing of the electrodes is a great challenge, particularly in the extremely premature infant, which often discourages neuromonitoring. The aim of this study is to assess the different electrodes available, to select the one that best suits the peculiarities of the extremely premature infant, and evaluate its applicability in clinical practice.

POPULATION AND METHODS

With the aim of designing a neuromonitoring study protocol using aEEG/cEEG in <28 weeks premature infants, an analysis was made of our experience with the type of electrodes available. The electrode that was considered most suitable for this population was chosen by assessing: the need of preparing the scalp, speed in positioning the electrodes, if the application was invasive or not, the possibility of repositioning, risk of skin injuries, sterility of the technique, and durability. The electrode chosen was used for continuous electroencephalographic monitoring started in the first 24 h of life, and maintained until at least 72 h of life.

RESULTS

The electrodes evaluated were: subdermal needles, silver cups, and 2 types of self-adhesive electrodes (solid hydrogel and wet gel). The wet gel electrodes were chosen. They were used on 41 neonates with a mean gestational age of 25.8 ± 1.1 weeks. Good stable impedance was rapidly obtained, without the need of excessive manipulations, and no skin injuries were observed. The satisfaction of the staff involved in positioning them was very high.

CONCLUSION

The self-adhesive disposable electrodes with wet gel and integrated cable enabled the electrodes to be positioned rapidly and provided continuous non-invasive and good quality aEEG/cEEG monitoring in the extremely premature infant.

[Evaluation of the suitability and clinical applicability of different electrodes for aEEG/cEEG monitoring in the extremely premature infant]

INTRODUCTION

Monitoring of brain function using continuous electroencephalography (aEEG/cEEG) is an essential tool in the standard care of the term infant, and its use is growing in the premature infant as a biomarker of lesion and brain maturity. However, the placing of the electrodes is a great challenge, particularly in the extremely premature infant, which often discourages neuromonitoring. The aim of this study is to assess the different electrodes available, to select the one that best suits the peculiarities of the extremely premature infant, and evaluate its applicability in clinical practice.

POPULATION AND METHODS

With the aim of designing a neuromonitoring study protocol using aEEG/cEEG in<28 weeks premature infants, an analysis was made of our experience with the type of electrodes available. The electrode that was considered most suitable for this population was chosen by assessing: the need of preparing the scalp, speed in positioning the electrodes, if the application was invasive or not, the possibility of repositioning, risk of skin injuries, sterility of the technique, and durability. The electrode chosen was used for continuous electroencephalographic monitoring started in the first 24h of life, and maintained until at least 72h of life.

RESULTS

The electrodes evaluated were: subdermal needles, silver cups, and 2 types of self-adhesive electrodes (solid hydrogel and wet gel). The wet gel electrodes were chosen. They were used on 41 neonates with a mean gestational age of 25.8±1.1 weeks. Good stable impedance was rapidly obtained, without the need of excessive manipulations, and no skin injuries were observed. The satisfaction of the staff involved in positioning them was very high.

CONCLUSION

The self-adhesive disposable electrodes with wet gel and integrated cable enabled the electrodes to be positioned rapidly and provided continuous non-invasive and good quality aEEG/cEEG monitoring in the extremely premature infant.

Perinatal factors associated with amplitude-integrated electroencephalography abnormalities in preterm infants on the first day of life

OBJECTIVE

Evaluate the association between perinatal factors and amplitude-integrated electroencephalogram abnormalities in preterm infants on the first day of life.

METHODS

This was a cross-sectional study of 60 infants with gestational age between 23 and 32 weeks, without malformations. Infants were continuously monitored by amplitude-integrated electroencephalogram on the first day of life, for at least 3h. The tracings were recorded and analyzed in each column for the following: burst-suppression pattern, sleep-wake cycle, and amplitude of the lower margin (<3μV or <5μV). The association of maternal complications, mode of delivery, birth weight, gestational age, neonatal sex, resuscitation procedures, hypothermia on admission, and the Score for Neonatal Acute Physiology, Perinatal Extension, Version II [SNAPPE-II]) with amplitude-integrated electroencephalogram alterations was assessed by multiple logistic regression.

RESULTS

A discontinuous pattern occurred in 65% of infants, and a continuous pattern occurred in 23%. The burst-suppression pattern was associated with vaginal delivery (OR: 7.6; 95% CI: 1.1-53.1) and SNAPPE-II≥40 (OR: 13.1; 95% CI: 1.8-95.1). A lower margin of the amplitude-integrated electroencephalogram of <3μV was also associated with SNAPPE-II≥40 (OR: 10.6, 95% CI: 2.3-49.2), while a value <5μV was associated with lower GA (OR: 0.51, 95% CI: 0.34-0.76). There were no associations between the perinatal variables and the absence of a sleep-wake cycle in amplitude-integrated electroencephalogram recordings on the first day of life.

CONCLUSION

Biological variables and clinical severity are associated with electroencephalographic characteristics of preterm infants on the first day of life and should be considered in clinical practice when amplitude-integrated electroencephalogram is performed.

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.

Long term electroencephalography in preterm neonates: Safety and quality of electrode types

OBJECTIVES

The objective of this study was to compare gold cup and hydrogel electrodes for frequency of electrode replacement, longevity of the original electrodes after initial placement, recording quality, and skin safety issues in long-term EEG studies in preterm neonates.

METHODS

We performed a prospective trial with newborns born at ≥23 weeks and ≤30 weeks of gestational age (GA). Two mirror image EEG electrode arrays were utilized on consecutive subjects, where gold cup electrodes alternated with hydrogel electrodes.

RESULTS

Our sample included 50 neonates with mean GA of 27 (±1) weeks. The mean recording time was 84 (±15) hours. No difference was present in the frequency of replacement of either type across the total recording time (p = 0.8). We collected the time at which electrodes were first replaced, and found that hydrogel electrodes showed a longer uninterrupted recording time of 28(±2) hours vs. 20(±2) hours for gold cup electrodes (p = 0.01). Recording quality was similar in either type (p = 0.2). None of the patients experienced significant skin irritation from a discrete electrode.

CONCLUSION

Long-term EEG studies can be performed with either gold cup or hydrogel electrodes, validating the safety and quality of both electrode types.

SIGNIFICANCE

Hydrogel electrodes are a reasonable alternative for use in long-term EEG studies in preterm neonates.

Fabrication of chitosan/Au-TiO2 nanotube-based dry electrodes for electroencephalography recording

In this paper, we describe a method for fabricating dry electrodes for use in recording electroencephalograms (EEGs), which are based on the use of chitosan (Ch), gold (Au) particles, and titanium dioxide (TiO₂) nanotube arrays deposited on titanium (Ti) thin sheets. The samples were characterized by scanning electron microscopy, X-ray diffraction, electrochemical impedance spectroscopy, and EEG signal collection. The TiO₂ nanotube arrays were grown on the Ti thin sheet by an electrochemical anodic oxidation method. The Au particles were deposited on the bottom and surface layers of the TiO₂ nanotube array using an electrochemistry-based multi-potential step technology. The fabricated dry Ch/Au-TiO₂ electrodes have an efficient conversion interface for ion current/electron current, a high biocompatible contact surface, and a fast electron transfer channel. To confirm that the Ch/Au-TiO₂ layer can be used in dry EEG electrodes, the impedance spectra of the electrodes in solution and skin were analyzed. The mean impedance values for skin were found to be approximately 169±33.0kΩ at 2.15Hz and 67.4±8.9kΩ at 100Hz. In addition, EEG signals from the forehead and sites with hair were collected using both the dry Ch/Au-TiO₂ electrode and a wet Ag/AgCl electrode for comparison purposes. It was found that high quality EEG signal recordings could be obtained using the dry electrodes. The fact that electrolytes are not required means that the electrodes are suitable for use in long-term bio-potential testing.

Newborns' sleep-wake cycle development on amplitude integrated electroencephalography

BACKGROUND

To observe the development of neonatal sleep among healthy infants of different conceptional age (CA) by analyzing the amplitude-integrated electroencephalography (aEEG) of their sleep-wake cycles (SWC).

METHODS

Bedside aEEG monitoring was carried out for healthy newborns from 32 to 46 weeks CA between September 1, 2011 and August 30, 2012. For each aEEG tracing, mean duration of every complete SWC, number of SWC repetition within 12 hours, mean duration of each narrow and broadband of SWC, mean voltage of the upper edge and lower edge of SWC, mean bandwidth of SWC were counted and calculated. Analysis of the correlations between voltages or bandwidth of SWC and CA was performed to assess the developmental changes of central nervous system of newborns with different CA.

RESULTS

The SWC of different CA on aEEG showed clearly identifiable trend after 32 weeks of CA. The occurrence of SWC gradually increases from preterm to post-term infants; term infants had longer SWC duration. The voltage of upper edge of the broadband decreased at 39 weeks, while the lower edge voltage increases and the bandwidth of broadband declined along with the growing CA. The upper edge of the narrowband dropped while the lower edge rised gradually, especially in preterm stage. The width of the narrowband narrowed down while CA increased.

CONCLUSIONS

The SWC on aEEG of 32-46 weeks infants showed a continuous, dynamic and developmental progress. The appearance of SWC and the narrowing bandwidth of narrowband is the main indicator to identify the CA-dependent SWC from the preterm to the late preterm period. The lower edge of the broadband identifies the term to post-term period.

Serial aEEG recordings in a cohort of extremely preterm infants: feasibility and safety

OBJECTIVE

Amplitude-integrated electroencephalography (aEEG) monitoring is increasing in the neonatal population, but the safety and feasibility of performing aEEG in extremely preterm infants have not been systematically evaluated.

STUDY DESIGN

Inborn infants 23(0/7) to 28(6/7) weeks gestation or birth weight 401 to 1000 g were eligible. Serial, 6-h aEEG recordings were obtained from first week of life until 36 weeks postmenstrual age. Adverse events were documented, and surveys evaluated the impact of the aEEGs on routine care. Success of performing aEEGs according to protocol and aEEG quality were assessed.

RESULT

A total of 102 infants were enrolled, with 755 recordings performed. 83% of recordings were performed according to schedule, and 96% were without adverse event. Bedside nurses reported no interference with routine care for 89% of recordings. 92% of recordings had acceptable signal quality.

CONCLUSION

Serial aEEG monitoring is safe in preterm infants, with few adverse events and general acceptance by nursing staff.

Quantification of neonatal amplitude-integrated EEG patterns

BACKGROUND

Amplitude-integrated EEG (aEEG) is increasingly used in research with premature infants; however, comprehensive interpretation is limited by the lack of simple approaches for reliably quantifying and summarizing the data.

AIM

Explore operational measures for quantifying continuity and discontinuity, measured by aEEG as components of infant brain function.

STUDY DESIGN

An exploratory naturalistic study of neonates while in the Neonatal Intensive Care Unit (NICU). One single channel aEEG recording per infant was obtained without disruption of nursing care practices.

SUBJECTS

24 infants with mean postmenstrual age (PMA) of 33.11 weeks (SD 3.49), average age of 2.62 weeks (SD 1.35) and mean birth weights of 1.39 kg (SD 0.73).

OUTCOME MEASURES

Quantification of continuity and discontinuity included bandwidth and lower border of aEEG, calculated proportion of time with signal amplitude below 10 μV, and peak counts. Variance of bandwidth and lower border denoted cycling.

RESULTS

Group mean bandwidth was 52.98 μV (SD 27.62). Median peak count in 60 second epochs averaged 3.63 (SD 1.74), while median proportion < 10 μV was 22% (SD 0.20). The group mean of lower border within-subject aggregated medians was 6.20 μV (SD 2.13). Group mean lower border standard deviation was 3.96 μV. Proportion < 10 μV showed a strong negative correlation with the natural log of the lower border median (r = -0.906, p < .0001) after controlling for PMA.

CONCLUSIONS

This study introduces a novel quantification process by counting peaks and proportion of time < 10 μV. Expanded definitions and analytic techniques will serve to strengthen the application of existing scoring systems for use in naturalistic research settings and clinical practice.

Changes of amplitude integration electroencephalogram (aEEG) in different maturity preterm infant

BACKGROUND

With the improvement of perinatal care and neonatal intensive care technology in recent years, a preterm infant, especially with small gestational age and very low birth weight, survives more and more. At the same time, adverse neurodevelopmental prognosis caused by brain damage in preterm infant also increased significantly. Preterm infant brain injury has become the most important factor for early death and neurodevelopment of preterm infant.

METHODS

Amplitude integration electroencephalogram (aEEG) has an important clinical value in the assessment of brain development in the maturity of preterm infant. With the application of a neonatal brain function monitor, we value the aEEG graphic continuity, periodicity, narrowband lower margin amplitude, and bandwidth score and analyze wide- and narrowband on the lower bounds of voltage and bandwidth.

RESULTS

The graphics of preterm infant aEEG become mature with the growth of the gestational age (1). With the growth of corrected gestational age, the aEEG graphics of preterm infant has the following feature: lower bound voltage of narrowband rising and width narrowing of narrowband (2). Extrauterine life can speed up the maturation of aEEG graphics (3).

CONCLUSIONS

The aEEG technology is a noninvasive, operable, and simple analysis and suitable for application in the newborn intensive care unit.