Investigation of Cerebral Motor Activity Modulations Following Median Nerve Stimulation During General Anaesthesia

Study of Modulations of Motor Brain Activity Following Stimulation of the Median Nerve During General Anesthesia

Accidental Awareness during General Anesthesia (AAGA) occurs in 1-2% of high-risk practice patients and is a cause of severe psychological trauma, termed post-traumatic stress disorder (PTSD). Actually, no monitoring techniques can accurately predict or detect an AAGA. Since the first reflex for a patient during an AAGA is to move, a brain-computer interface (BCI) based on the detection of an intention of movement would be conceivable to alert the anesthetist. The investigators previously showed that median nerve stimulation (MNS) could be the keystone of a BCI specialized in the detection of movement intention. Indeed, based on these previous results, the investigators can envisage a routine system where the patient would be stimulated at the median nerve position, while a BCI device would analyze the event-related desynchronization (ERD) and event-related synchronization (ERS) modulations in the motor cortex to check whether the patient is intending to move or not. According to the investigator's knowledge, no published studies have investigated the detection of EEG patterns in relation to peripheral nerve stimulation over the sensorimotor cortex during general anesthesia. The main objective of this study is to describe the changes in terms of ERD and ERS modulations, in the EEG signal over the motor cortex, during general anesthesia with propofol, while a median nerve stimulation is performed.

STIM-MOTANA is an interventional and prospective study conducted in patients scheduled for surgery under general anesthesia, involving EEG measurements and median nerve stimulation. In this study, 30 patients will undergo surgery under total intravenous anesthesia using a propofol target-controlled infusion pump. The rest of the anesthetic protocol will be at the discretion of the anesthesiologist in charge. Changes in ERD and ERS during median nerve stimulation according to the various propofol concentrations will be continuously monitored by an EEG amplifier. Pre- and post-injection comparisons of propofol will be performed by paired series tests. After surgery, patients will have a gradual decrease of propofol at different effect-site concentrations (from 4.0 μg/ml to 2.0 μg/ml, in increments of 0.5 μg/ml).

Inclusion Criteria:

• Patients >18 years and <81 years
• Right-handed
• Programmed for surgery with the use of an intravenous anesthesia with a propofol concentration objective

Exclusion Criteria:

• Allergy to propofol, soy or peanuts
• BMI<20 or >30
• Pregnant or breastfeeding women
• Adult unable to give consent
• Medical or surgical history that may interfere with median nerve stimulation or the obtention of the EEG signal (for example: diabetes, polyneuropathy, central neurodegenerative disease, epilepsy, brain surgery)
• History of right median nerve injury
• Amputation of the upper right limb
• Impossibility of affixing an EEG helmet
• Addiction