EEG Dynamics in Children Before, During and After General Anesthesia.

EEG Dynamics in Children Before, During and After General Anesthesia.

Paediatric anaesthesia

Submitted June 2026 by Dr Barney Rathnayaka Mudiyanselage

Review summary

This is a single-centre study from Berlin with the goal of further understanding the perioperative EEG of the paediatric population throughout key phases of anaesthesia and how it may vary with age.

A total of 147 frontal EEGs from children ranging from 1 month to 8 years of age presenting for elective surgery were recorded prospectively during the awake state, induction, maintenance, and return of consciousness phases of anaesthesia.

The patients were divided into four groups by age:

• 0–5 months
• 6–11 months
• 12–23 months
• Over 24 months.

EEG data were acquired using the Narcotrend monitor. The raw EEG and frequency bands were subsequently compared between the groups.

Key findings

There was signification variation in EEG activity across all four measured phases of anaesthesia with increasing age. In particular, there was a clear difference in EEG frequency bands and their changes when comparing the 0–6 month group with the three older age groups.

The findings are visually displayed in the article using four box-and-whisker graphs which summarise the following findings:

When comparing the raw EEG response between age groups:

• All age groups had predominantly delta activity.
• Overall EEG power increased with age.
• Total EEG activity for all groups followed the same pattern: an increase from baseline at induction, a decline during maintenance, followed by a return to baseline or slightly below during the return to consciousness.

When comparing frequency bands between age groups:

Delta activity: Showed a consistent trend during each phase of anaesthesia across all groups. The signal in variation between phases was more pronounced in older children and reached statistical significance, it failed to do so in the youngest age bracket

• Induction: All age groups showed a step increase in delta activity

• Maintenance: All age groups had a reduction in delta activity from their baseline measure

• Emergence: Delta activity returned to baseline or slightly lower, with increasing age at return of consciousness.

Alpha activity: Was discernibly different in the 0–6 month age group compared with the three older groups. Children under 6 months had no significant variation in alpha frequency over the four measured phases.

In contrast, children over 6 months showed an increase in alpha activity during induction and maintenance, with older groups demonstrating a progressively greater and statistically significant increase in alpha frequency from induction to maintenance with age.

At return of consciousness both alpha beta activity returns to baseline.

Beta activity : Remained similar across groups but when displayed graphically the pattern appeared to be follow that of alpha activity as age increased.

Strengths

Like most research in paediatric anaesthesia, the study was pragmatic in its approach at all steps of the study to accomodate real life limitations.

This is one of the few studies at present which follows the paediatric EEG through four key phases of anaesthesia with a large enough cohort to produce a statistical difference between age groups.

The selection criteria was appropriate and clear to achieve its specific goal: to provide further information for the construction of the foundation of basic paediatric EEG use in anaesthesia. Exclusion criteria included patients with neurological and psychiatric pathology excluding procedures shorter than 15 minutes.

The mode of measurement is generalisable as frontal EEG monitoring is currently the most commonplace approach to depth of anaesthesia EEG monitoring in Australasia. Attempts were made to record periods of the procedure with minimal interference; incomplete data sets were excluded.

All groups had enough patients and points of data to provide statistically significant results for the primary outcome with statistical analysis taking into consideration many confounding factors for example duration of surgery and end tidal volatile concentration. This was also supplemented with the older age groups being powered well enough to provide significant findings in the study’s secondary outcomes ( the change in alpha power through each phase).

Limitations

An interesting point of difference between groups was the practice of premedication prior to baseline measurement. Children under 6 months were not pre-medicated whilst 94% of the other participant groups received a dose of midazolam prior to baseline measurement. These results may therefore be more generalisable to a paediatric anaesthesia practice with a high rate of midazolam premedication.

The anaesthesia regimen for induction and maintenance was also not controlled for the study; intravenous anaesthesia techniques were used more frequently in older children.

Return of consciousness was also challenging to measure - clinical endpoints are subjective and variable, they also change with age, which may impact on the precision of reporting.

Finally, a potentially useful signal within the youngest age bracket was the variation in delta activity with each phase of anaesthesia. The group was not powered to show statistical significance for this variation; a subsequent, better-powered study might provide a useful reference for assessing depth in this vulnerable demographic.

Bottom line

The findings of this study indicate that the EEG varies with a child’s age, with alpha activity beginning to appear under general anaesthesia at over six months of age during induction and maintenance with alpha activity being a useful measure to assess depth in children over six months of age.

Children under six months of age pose greater difficulty due to their lack of the typical frequency bands described above. Instead, this paper suggests that the clinician might to depend on the patients baseline delta activity and its stepwise change throughout anaesthesia to assess adequacy. This trend itself was a secondary outcome and did not reach statistical significance within this study.

The difference in EEG activity at baseline between adults and children indicate that the interpretation of a raw EEG differs sufficiently from adult practice to require an alternative approach.

Further reading and clinical context

As a clinician who uses processed EEG monitoring in my work as an anaesthetist, I thought it would be interesting to speak with a colleague who is highly published in the field of paediatric EEG in anaesthesia for further context.

We discussed the current state of knowledge in this area:

• That the EEG changes from birth to maturation, and that alpha activity develops from around 6 months of age

• That Density Spectral Array (DSA) is a helpful parameter for monitoring depth of anaesthesia in the paediatric population

• That the DSA is not helpful for lightening the plane of anaesthesia

• That alpha activity is a supplementary marker for depth of anaesthesia, and cannot replace vigilant assessment of clinical response and an understanding of the pharmacokinetics of the anaesthetic agent being used

My use of routine EEG monitoring is purely for total intravenous anaesthesia when using paralysis, or in the high risk patient to avoid burst suppression. My preference is for a monitor that can report a DSA.

The spectrogram provides an simple to interpret additional marker when assessing the depth of anaesthesia with propofol TIVA, with the presence of an alpha band marking adequacy of depth, and loss of this band as an excess in depth - a sign which is known precede burst suppression. Separation between the alpha and delta bands indicates lightening of anaesthesia with propofol.

The spectrogram shows a very different pattern with propofol and sevoflurane, with no separation of the alpha and delta bands on spectrogram under general anaesthesia.

Other monitors may only provide an EEG waveform, from which it is possible to detect slow-wave anaesthesia, burst suppression, or high frequency activity consistent with the awake state. Dimensionless indices such as the BIS value may be more limited by their lower granularity.

Despite its limitations, the study gives serves as a primer for the clinician looking to translate their knowledge of depth-of-anaesthesia monitoring to the paediatric population - in particular, the differences between < 6 month-olds and older children.

References

1. L. Cornelissen, S. E. Kim, P. L. Purdon, E. N. Brown, and C. B. Berde, “Age-Dependent Electroencephalogram (EEG) Patterns During Sevoflurane General Anesthesia in Infants,” eLife 4 (2015): e06513.

2. M. Markus, H. Nagelsmann, M. Schneider, L. Rupp, C. Spies, and S. Koch, “Peri- and Intraoperative EEG Signatures in Newborns and Infants,” Clinical Neurophysiology 132, no. 12 (2021): 2959–2964.

3. D. Beekoo, K. Yuan, S. Dai, et al., “Analyzing Electroencephalography (EEG) Waves Provides a Reliable Tool to Assess the Depth of Sevoflurane Anesthesia in Pediatric Patients,” Medical Science Monitor 25 (2019): 4035–4040.

4. M. H. Y. Long, E. H. L. Lim, G. A. Balanza, J. C. Allen, Jr., P. L. Purdon, and C. L. Bong, “Sevoflurane Requirements During Electroencephalogram (EEG)-Guided vs Standard Anesthesia Care in Children: A Randomized Controlled Trial,” Journal of Clinical Anesthesia 81 (2022): 110913.

5. C. A. Sullivan, C. Egbuta, R. S. Park, K. Lukovits, D. Cavanaugh, and K. P. Mason, “The Use of Bispectral Index Monitoring Does Not Change Intraoperative Exposure to Volatile Anesthetics in Children,” Journal of Clinical Medicine 9, no. 8 (2020): 2437.

6. J. Tokuwaka, T. Satsumae, T. Mizutani, K. Yamada, S. Inomata, and M. Tanaka, “The Relationship Between Age and Minimum Alveolar Concentration of Sevoflurane for Maintaining Bispectral Index Below 50 in Children,” Anaesthesia 70, no. 3 (2015): 318–322.

7. L. Cornelissen, S. E. Kim, J. M. Lee, E. N. Brown, P. L. Purdon, and C. B. Berde, “Electroencephalographic Markers of Brain Development During Sevoflurane Anaesthesia in Children up to 3 Years Old,” British Journal of Anaesthesia 120, no. 6 (2018): 1274–1286.

8. J. Y. Chao, R. Gutierrez, A. D. Legatt, et al., “Decreased Electroencephalographic Alpha Power During Anesthesia Induction Is Associated With EEG Discontinuity in Human 

9. L. Seltzer, M. F. Swartz, J. Kwon, et al., “Neurodevelopmental Outcomes After Neonatal Cardiac Surgery: Role of Cortical Isoelectric Activity,” Journal of Thoracic and Cardiovascular Surgery 151, no. 4 (2016): 1137–1142.Infants,” Anesthesia and Analgesia 135, no. 6 (2022): 1207–1216.

10. Power & Kam Chapter 11 - Consciousness, EEG, Sleep and Emotions

11. Miller’s Chapter 40 - Monitoring the State of the Brain

12. Rampil, I. A Primer for EEG Signal Processing in Anesthesia. Anesthesiology 1998; 89:980-1002

13. Viertio-Oja, H. Description of the Entropy algorithm as applied in the Datex-Ohmeda S/5 Entropy Module. Acta Anaesthesiol Scand 2004; 48: 154–161

14. Medtronic. Monitoring Consciousness. Using the Bispectral Index (BIS) brain monitoring system.