STIM-MOTANA: an interventional and prospective study to detect motor cerebral activity after median nerve stimulation during general anesthesia (Preprint)
Authors: Sébastien Rimbert 
Published: December 2022

BACKGROUND

Accidental Awareness during General Anesthesia (AAGA) is defined by an unexpected awareness of the patient during general anesthesia. This phenomenon occurs in 1-2% of high-risk practice patients and can cause physical suffering and/or psychological after-effects called post-traumatic stress disorder (PTSD). Actually, no monitoring techniques are satisfactory enough to effectively prevent AAGA, therefore new alternatives are needed. Because the first reflex for a patient during an AAGA is to move, but can not do it because of the neuromuscular blockers, we believe that it is possible to design a brain-computer interface (BCI) based on the detection of movement intention to warn the anesthetist. To do this, we propose to describe and detect the changes in terms of motor cortex oscillations, during a general anesthesia with propofol, while a median nerve stimulation is performed. We believe that our results could enable the design of an BCI based on median nerve stimulation which could prevent AAGA.

OBJECTIVE

The first objective is to verify that ERD and ERS patterns induced by median nerve stimulation can be detected in the cortical motor EEG signal under various concentrations of propofol corresponding to the anesthetic doses required for general anesthesia.
The secondary objective is to characterize and to understand how the ERD and ERS generated after each median nerve stimulation will be altered according to each concentration of propofol at the effect site. These results will be discussed in relation to previous results obtained from a protocol investigating the effect of light propofol sedation on EEG signals in motor cortex.
The third objective is to analyze EEG signals offline and try and to detect median nerve stimulation under propofol with new machine learning algorithms. Complementary, the short and middle latency components of the somatosensory evoked potentials will be analyzed for the different propofol concentrations.
The long-term goal is to design a brain-computer interface that can detect intraoperative awareness during general anesthesia.

METHODS

STIM-MOTANA is an interventional and prospective study conducted in patients scheduled for surgery under general anesthesia, involving EEG measurements and median nerve stimulation at two different times: (i) when the patient is awake before surgery, (ii) and under general anesthesia. 30 patients will receive surgery under complete intravenous anesthesia with a target-controlled infusion pump of propofol. Changes in Event-Related Desynchronization (ERD) and Event-Related Synchronization (ERS) during median nerve stimulation according to the various propofol concentrations. In addition, we will apply 4 different offlines machine learning algorithms to detect the median nerve stimulation at the cerebral level.

RESULTS

We will compute the amplitude of ERD/ERS modulations before and after each median nerve stimulation during the different phases of anesthesia at two different times: when the patient is awake before surgery, and under general anesthesia.
The primary evaluation end-point will be the amplitude of the ERD. According to the Pfurtscheller's method. ERD/ERS modulations will be calculated using a baseline taken before each stimulation. Changes in ERD/ERS during median nerve stimulation according to the various propofol concentrations will be continuously monitored. To compare the motor EEG signal before and after injection of the anesthetic product, we will apply paired statistical tests (t-student).

CONCLUSIONS

STIM-MOTANA is an interventional study aimed at designing an innovative BCI-based EEG-motor brain activity, which would detect the intention to move of a patient during general anesthesia. STIM-MOTANA is the first study to investigate cerebral motor-activity modulations following peripheral nerve stimulation during general anesthesia.

CLINICALTRIAL

STIM-MOTANA has received the approval of Ethic committee of CHU Brugmann Hospital (CE2021/225). Results will be published in international peer-reviewed journals and summaries will be provided to the funders and patients.
Registration at EUDRACT (2021-006457-56) and ClinicalTrials.gov (NCT05272202).