Electroencephalogram dynamics during unconsciousness mediated by GABAergic-anesthetics

Abstract

This dataset of electroencephalogram (EEG) activity was collected from subjects undergoing general anesthesia using GABAergic agents. The typical EEG of subjects during unconsciousness mediated by GABAergic anesthetics shows slow-delta oscillations (0.3 - 4Hz) and alpha oscillations (8 – 14Hz). At higher doses, these oscillations devolve into burst suppression, a state of profound brain inactivation. This data was used to investigate the transition between these states of unconsciousness. It was collected as part of a larger study to investigate the changes in brain activity during unconsciousness mediated by GABAergic anesthetics. All data collection and experimental protocols were approved by the Mass General Brigham Human Research Committee.

Background

The typical electroencephalogram (EEG) of patients during unconsciousness mediated by GABAergic anesthetics shows slow-delta oscillations (0.3 - 4Hz) and alpha oscillations (8 – 14Hz). At higher doses, these oscillations devolve into burst suppression, a state of profound brain inactivation. In [1], we report a physiological modulation of brain activity that characterizes the transition between these states of unconsciousness. We find that the modulation is present in the alpha band and in the slow-delta band. Using this modulation, we can track the level of unconsciousness of patients under GABAergic general anesthesia. In this dataset, we are sharing the EEG of subjects under GABAergic-anesthetic mediated unconsciousness to allow other researchers to explore and understand this modulation.

Methods

We share EEG data from four different groups of patients. Each group received either propofol or sevoflurane as the primary anesthetic to maintain unconsciousness. All data were recorded under human studies protocols approved by the Massachusetts General Hospital Human Research Committee. These patients are: a young healthy volunteer (age between 18-35 years old) who received increasing followed by decreasing doses of propofol through computer-controlled infusions; a surgical patient (44 year old) administered propofol by manual titration; a surgical patient administered propofol by manual titration whose EEG showed dissipating alpha waves (70 years old); and a surgical patient (54 years old) administered sevoflurane by manual titration. EEG acquisition was completed as follows:

• Volunteer subject administered propofol: Whole head EEG data were recorded using a 64-channel BrainVision MRI Plus system (Brain Products) with a sampling rate of 5,000 Hz, bandwidth 0.016-1000 Hz, and resolution 0.5 µV least significant bit. The Fp1 channel was selected for the analysis. Subjects were instructed to close their eyes throughout the experiment to avoid eye-blink artifacts in the EEG.
• Surgical patients administered propofol: Frontal EEG data were recorded using the SedLine brain function monitor (Masimo Corporation, Irvine, CA, USA) with a sampling frequency of 178 Hz. The Fp2 channel was selected for the analysis.
• Surgical patient administered sevoflurane: Frontal EEG data were recorded using the SedLine brain function monitor (Masimo Corporation, Irvine, CA, USA) with a pre-amplifier bandwidth of 0.5-92 Hz, sampling rate of 250 Hz, and with 16-bit, 29 nV resolution. The Fp2 channel was selected for the analysis.

Spectrograms of the EEG data were produced using standard multi-taper spectral analysis methods. The slow and the alpha band were extracted by bandpass filtering with a 2nd order Butterworth filter, between 0.3-4Hz and 8-14Hz, respectively. Further details on methods are provided in [1].

Data Description

The data for four subjects are shared. The data for each subject is in a separate folder. The folders are:

• Propofol_Volunteer
• Propofol_OR_strongAlpha
• Propofol_OR_weakAlpha
• Sevoflurane_OR

and each contains:

• the time vector (1d-array; x-axis) of the spectrogram in s: t_spec_*.csv
• the frequency vector (1d-array; y-axis) of the spectrogram in Hz: f_spec_*.csv
• the values (2d array) of the spectrogram in dB: val_spec_*.csv
• the EEG alpha wave (1d-array) in uV: alphaWave_*.csv
• the EEG slow wave (1d-array) in uV: slowWave_*.csv

In addition:

• The folder Propofol_Volunteer contains the effect-site concentration of propofol in propofolConcentration_*.csv where column 1 is time in s and column 2 is concentration in ug/mL.
• The folders Propofol_OR_strongAlpha and Propofol_OR_weakAlpha contain the infusion scheme of propofol in propofolInfusionRate_*.csv where column 1 is time in s, column 2 is continuous infusion rate in mg/min and column 3 is bolus infusion amount in mg (represented as mg/min over 1 min).
• The folder Sevoflurane_OR contains the end-tidal sevoflurane concentration in SevofluraneConcentration_*.csv where column 1 is time in s and column 2 is end-tidal concentration in %. It also contains the infusion scheme of propofol in propofolInfusionRate_*.csv where column 1 is time in s and column 2 is the bolus infusion amount in mg (represented as mg/min over 1 min).

All files are in csv format. The sampling frequency for the alpha and slow wave is either 250Hz or 178Hz as described in the Methods section. This data covers the subjects in Figures 3, 4, 5 and 6 of [1].

The EEG alpha and slow bands that are shared were used to derive the alpha modulation index and the slow modulation index, respectively [1]. Details on how the computation of these indices was executed is provided in [1]. The alpha and slow bands are truncated to be in the range where the modulation indices were computed, specifically where alpha and slow oscillations are expressed and modulated.

• The time points where the alpha waves and slow waves start and end with respect to the spectrogram are provided in the second and third entry of duration_start_end_*.csv in each folder.

The spectrograms cover the full general anesthesia session, and extend beyond the regime where alpha and slow oscillations are expressed. For instance, the spectrograms also comprise periods where the subjects are awake and periods of induction and emergence from unconsciousness.

• The total duration of the session is provided in the first entry of duration_start_end_*.csv in each folder.

Usage Notes

The EEG alpha and slow bands that are shared were used to derive the alpha modulation index and the slow modulation index, respectively [1]. Details on how the computation of these indices was executed is provided in [1]. This data can be used to gain a better understanding of the modulation at the level of the slow waves and the alpha waves that occurs during unconsiousness mediated by GABAergic anesthetics. It also opens the possibility to refine approaches for characterizing and computing the modulation. The user should be aware that in surgical sessions, multiple drugs (e.g., analgesics) are administered that can alter the effectiveness of the primary anesthetics and alter dynamics. Momentary alterations in the EEG could be a result of surgical manipulations. As csv files, the shared EEG and drug infusion signals can be accessed on any platform and processed in any desired manner.

Release Notes

This is the first release of this dataset.

Ethics

All data collection and experimental protocols were approved by the Mass General Brigham Human Research Committee (Institutional Review Board). For the propofol volunteer study, all subjects provided informed consent. For the surgical patient studies, there was no data collection specific consent as the EEG recordings, physiological data and anesthetic administration data were collected as part of standard care and de-identified.

Acknowledgements

This work was generously supported by the JPB Foundation; the Picower Institute for Learning and Memory; George J Elbaum (MIT ’59, SM ’63, PhD ’67), Mimi Jensen, Diane B. Greene (MIT, SM ’78), Mendel Rosenblum, Bill Swanson, annual donors to the Anesthesia Initiative Fund; and the NIH Awards P01 GM118269 and R01 NS123120 (to E.N.B.).

Conflicts of Interest

Patent pending.

References

1. Adam, E., Kwon, O., Montejo, K. A. & Brown, E. N. (2023) Modulatory dynamics mark the transition between anesthetic states of unconsciousness. Proceedings of the National Academy of Sciences. 120(30), e2300058120.