Electroencephalography (EEG) is routinely used to monitor general anesthesia (GA). Unanswered questions concern the possibility of using the EEG signal to classify patients as more or less sensitive to anesthetic drugs from the onset of anesthesia. We investigate here possible statistical correlation between different phases of general anesthesia. We test whether it could be possible to predict the speed of return to consciousness from the induction or the maintenance phases. For that goal, we tracked the maximum power of the α-band and follow its time course. Using an optimization procedure, we quantify the characteristic shift of the α-band during recovery and the associated duration. Interestingly, we found no correlation (Pearson coefficient) between these shifts and the amount of α-band or iso-electric suppressions (flat EEG epochs) present in the maintenance phase or induced by a propofol injection during induction. To quantify the instability of the α-band, we introduce the total variation the α-band that accounts for all possible deviation from a flat line. To conclude, the present analysis shows that it would not be possible to anticipate the duration of recovery of consciousness from previous phases of general anesthesia in children and adults. Possibly the involved neuronal mechanisms during the different phases are not comparable.

The authors have declared no competing interest.

D.H. research is supported by a grant ANR NEUC-0001 and the European Research Council 882673).

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

This prospective observational study included patients receiving a scheduled elective procedure requiring general anesthesia. The EEG data used in the study were recorded from Louis-Mourier Hospital (Colombes, France), collected between October 2019 and September 2021 and included 51 children and 35 adults. Age group and clinical information were also provided. For adult patients, general anesthesia was induced by intravenous administration of a opioid agent (remifentanil or sufentanil) and a hypnotic agent (propofol), the doses of which were defined according to the Minto and Schnider models. This study is followed by the Institutional Review Board of La Société de Réeanimation. In agreement with the ethics committee for this non-interventional study an information letter was given and an oral agreement was obtained from each patient before anesthesia. The protocol was approved by Louis-Mourier Hospital (Colombes, France) following the guideline of the ethics committee, and therefore, has been performed in accordance with the ethical standards laid down in 1964 declaration of Helsinki and its later amendments. \\ For children, the hypnotic agent (sevoflurane) was administrated by inhalation and followed by one or more bolus of propofol until the appearance of iso-electric suppressions for oro-tracheal intubation. The initial quantity of propofol was calibrated according to the children weight. Depending on the patient reaction and the anesthesia phase, the anesthesiologist can adjust the concentrations as long as standard of care is respected.

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All data produced in the present study are available upon reasonable request to the authors