Case Studies Using the Electroencephalogram to Monitor Anesthesia-Induced Brain States in Children

Intraoperative pediatric electroencephalography monitoring: an updated review

Intraoperative electroencephalography (EEG) monitoring under pediatric anesthesia has begun to attract increasing interest, driven by the availability of pediatric-specific EEG monitors and the realization that traditional dosing methods based on patient movement or changes in hemodynamic response often lead to imprecise dosing, especially in younger infants who may experience adverse events (e.g., hypotension) due to excess anesthesia. EEG directly measures the effects of anesthetics on the brain, which is the target end-organ responsible for inducing loss of consciousness. Over the past ten years, research on anesthesia and computational neuroscience has improved our understanding of intraoperative pediatric EEG monitoring and expanded the utility of EEG in clinical practice. We now have better insights into neurodevelopmental changes in the developing pediatric brain, functional connectivity, the use of non-proprietary EEG parameters to guide anesthetic dosing, epileptiform EEG changes during induction, EEG changes from spinal/regional anesthesia, EEG discontinuity, and the use of EEG to improve clinical outcomes. This review article summarizes the recent literature on EEG monitoring in perioperative pediatric anesthesia, highlighting several of the topics mentioned above.

Effect of Repeated Exposure to Sevoflurane on Electroencephalographic Alpha Oscillation in Pediatric Patients Undergoing Radiation Therapy: A Prospective Observational Study

BACKGROUND

Pharmacological tolerance is defined as a decrease in the effect of a drug over time, or the need to increase the dose to achieve the same effect. It has not been established whether repeated exposure to sevoflurane induces tolerance in children.

METHODS

We conducted an observational study in children younger than 6 years of age scheduled for multiple radiotherapy sessions with sevoflurane anesthesia. To evaluate the development of sevoflurane tolerance, we analyzed changes in electroencephalographic spectral power at induction, across sessions. We fitted individual and group-level linear regression models to evaluate the correlation between the outcomes and sessions. In addition, a linear mixed-effect model was used to evaluate the association between radiotherapy sessions and outcomes.

RESULTS

Eighteen children were included and the median number of radiotherapy sessions per child was 28 (interquartile range: 10 to 33). There was no correlation between induction time and radiotherapy sessions. At the group level, the linear mixed-effect model showed, in a subgroup of patients, that alpha relative power and spectral edge frequency 95 were inversely correlated with the number of anesthesia sessions. Nonetheless, this subgroup did not differ from the other subjects in terms of age, sex, or the total number of radiotherapy sessions.

CONCLUSIONS

Our results suggest that children undergoing repeated anesthesia exposure for radiotherapy do not develop tolerance to sevoflurane. However, we found that a group of patients exhibited a reduction in the alpha relative power as a function of anesthetic exposure. These results may have implications that justify further studies.

A Narrative Review Illustrating the Clinical Utility of Electroencephalogram-Guided Anesthesia Care in Children

The major therapeutic end points of general anesthesia include hypnosis, amnesia, and immobility. There is a complex relationship between general anesthesia, responsiveness, hemodynamic stability, and reaction to noxious stimuli. This complexity is compounded in pediatric anesthesia, where clinicians manage children from a wide range of ages, developmental stages, and body sizes, with their concomitant differences in physiology and pharmacology. This renders anesthetic requirements difficult to predict based solely on a child's age, body weight, and vital signs. Electroencephalogram (EEG) monitoring provides a window into children's brain states and may be useful in guiding clinical anesthesia management. However, many clinicians are unfamiliar with EEG monitoring in children. Young children's EEGs differ substantially from those of older children and adults, and there is a lack of evidence-based guidance on how and when to use the EEG for anesthesia care in children. This narrative review begins by summarizing what is known about EEG monitoring in pediatric anesthesia care. A key knowledge gap in the literature relates to a lack of practical information illustrating the utility of the EEG in clinical management. To address this gap, this narrative review illustrates how the EEG spectrogram can be used to visualize, in real time, brain responses to anesthetic drugs in relation to hemodynamic stability, surgical stimulation, and other interventions such as cardiopulmonary bypass. This review discusses anesthetic management principles in a variety of clinical scenarios, including infants, children with altered conscious levels, children with atypical neurodevelopment, children with hemodynamic instability, children undergoing total intravenous anesthesia, and those undergoing cardiopulmonary bypass. Each scenario is accompanied by practical illustrations of how the EEG can be visualized to help titrate anesthetic dosage to avoid undersedation or oversedation when patients experience hypotension or other physiological challenges, when surgical stimulation increases, and when a child's anesthetic requirements are otherwise less predictable. Overall, this review illustrates how well-established clinical management principles in children can be significantly complemented by the addition of EEG monitoring, thus enabling personalized anesthesia care to enhance patient safety and experience.

Electroencephalographic delta and alpha oscillations reveal phase-amplitude coupling in paediatric patients undergoing sevoflurane-based general anaesthesia

BACKGROUND

Sevoflurane-induced anaesthesia generates frontal alpha oscillations as early as 6 months of age, whereas strong delta oscillations are present at birth. In adults, delta oscillations and alpha oscillations are coupled: the phase of delta waves modulates the amplitude of alpha oscillations in a phenomenon known as phase-amplitude coupling. We hypothesise that delta-alpha phase-amplitude coupling exists in young children and is a feature of sevoflurane-based general anaesthesia distinct from emergence after anaesthesia.

METHODS

Electroencephalographic data from 31 paediatric patients aged 10 months to 3 yr undergoing elective surgery with sevoflurane-based anaesthesia were analysed retrospectively. Delta-alpha phase-amplitude coupling was evaluated during maintenance of anaesthesia and during emergence.

RESULTS

Delta-alpha phase-amplitude coupling was observed in the study population. Strength of phase-amplitude coupling, represented by the delta-alpha mean amplitude vector, was greater during general anaesthesia than during emergence (Wilcoxon paired signed-rank test, Z=3.107, P=0.002). Frontal alpha amplitude during anaesthesia was not uniformly distributed across all delta phases. During general anaesthesia, alpha power was restricted to the positive phase of the delta wave (omnibus circular uniformity, general anaesthesia: P<0.001, mean phase: 114º; 99% confidence interval: 90º-139º; emergence: P=0.35, mean phase 181º, 99% confidence interval: 110º-253º).

CONCLUSIONS

Sevoflurane-based anaesthesia is associated with delta-alpha phase-amplitude coupling in paediatric patients. These findings improve our understanding of cortical dynamics in children undergoing general anaesthesia, which might improve paediatric intraoperative depth of anaesthesia monitoring techniques.

The impact of age and electrode position on amplitude-integrated EEGs in children from 1 month to 17 years of age

Aim

Amplitude-integrated electroencephalography (aEEG) is used to monitor electrocortical activity in critically ill children but age-specific reference values are lacking. We aimed to assess the impact of age and electrode position on aEEG amplitudes and derive normal values for pediatric aEEGs from neurologically healthy children.

Methods

Normal EEGs from awake children aged 1 month to 17 years (213 female, 237 male) without neurological disease or neuroactive medication were retrospectively converted into aEEGs. Two observers manually measured the upper and lower amplitude borders of the C3 – P3, C4 – P4, C3 – C4, P3 – P4, and Fp1 – Fp2 channels of the 10–20 system. Percentiles (10th, 25th, 50th, 75th, 90th) were calculated for each age group (&lt;1 year, 1 year, 2–5 years, 6–9 years, 10–13 years, 14–17 years).

Results

Amplitude heights and curves differed between channels without sex-specific differences. During the first 2 years of life, upper and lower amplitudes of all but the Fp1–Fp2 channel increased and then declined until 17 years. The decline of the upper Fp1–Fp2 amplitude began at 4 years, while the lower amplitude declined from the 1st year of life.

Conclusions

aEEG interpretation must account for age and electrode positions but not for sex in infants and children.

Sevoflurane requirements during electroencephalogram (EEG)-guided vs standard anesthesia Care in Children: A randomized controlled trial

STUDY OBJECTIVES

Intra-operative electroencephalographic (EEG) monitoring utilizing the spectrogram allows visualization of children's brain response during anesthesia and may complement routine cardiorespiratory monitoring to facilitate titration of anesthetic doses. We aimed to determine if EEG-guided anesthesia will result in lower sevoflurane requirements, lower incidence of burst suppression and improved emergence characteristics in children undergoing routine general anesthesia, compared to standard care.

DESIGN

Randomized controlled trial.

SETTING

Tertiary pediatric hospital.

PATIENTS

200 children aged 1 to 6 years, ASA 1 or 2, undergoing routine sevoflurane anesthesia for minor surgery lasting 30 to 240 min.

INTERVENTIONS

Children were randomized to either EEG-guided anesthesia (EEG-G) or standard care (SC). EEG-G group had sevoflurane titrated to maintain continuous slow/delta oscillations on the raw EEG and spectrogram, aiming to avoid burst suppression and, as far as possible, maintain a patient state index (PSI) between 25 and50. SC group received standard anesthesia care and the anesthesia teams were blinded to EEG waveforms.

MEASUREMENTS

The primary outcomes were the average end-tidal sevoflurane concentration during induction and maintenance of anesthesia. Secondary outcomes include incidence and duration of intra-operative burst suppression and Pediatric Anesthesia Emergence Delirium (PAED) scores.

RESULTS

The EEG-G group received lower end-tidal sevoflurane concentrations during induction [4.80% vs 5.67%, -0.88% (-1.45, -0.31) p = 0.003] and maintenance of anesthesia [2.23% vs 2.38%, -0.15% (-0.25, -0.05) p = 0.005], and had a lower incidence of burst suppression [3.1% vs 10.9%, p = 0.044] compared to the SC group. PAED scores were similar between groups. Children <2 years old required higher average end-tidal sevoflurane concentrations, regardless of group.

CONCLUSIONS

EEG-guided anesthesia care reduces sevoflurane requirements in children undergoing general anesthesia, possibly lowering the incidence of burst suppression, without altering emergence characteristics. EEG monitoring allows direct visualization of brain responses in real time and allows clearer appreciation of varying sevoflurane requirements in children of different ages.

Applications and Limitations of Neuro-Monitoring in Paediatric Anaesthesia and Intravenous Anaesthesia: A Narrative Review

Safe management of anaesthesia in children has been one of the top areas of research over the last decade. After the large volume of articles which focused on the putative neurotoxic effect of anaesthetic agents on the developing brain, the attention and research efforts shifted toward prevention and treatment of critical events and the importance of peri-anaesthetic haemodynamic stability to prevent negative neurological outcomes. Safetots.org is an international initiative aiming at raising the attention on the relevance of a high-quality anaesthesia in children undergoing surgical and non-surgical procedures to guarantee a favourable outcome. Children might experience hemodynamic instability for many reasons, and how the range of normality within brain autoregulation is maintained is still unknown. Neuro-monitoring can guide anaesthesia providers in delivering optimal anaesthetic drugs dosages and also correcting underling conditions that can negatively affect the neurological outcome. In particular, it is referred to EEG-based monitoring and monitoring for brain oxygenation.