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

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. 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).

The right-hand median nerve will be stimulated in the same way as for measurement with a conduction velocity or for an evoked potential. Two stimulation electrodes will be placed on the right-hand wrist according to the standards.The stimulation is transcutaneous and painless using the specific Micromed device Sd Ltm Stim Energy (Micromed, Mˆacon, France). The stimulus intensity will range between 3 and 14 mA. The stimulation duration will be 100 ms with a frequency of 0.1 Hz.

Changes in ERD and ERS patterns during median nerve stimulation according to the various propofol concentrations will be continuously monitored by an EEG amplifier. EEG signals will be acquired using the OpenViBE platform with a Biosemi Active Two 64-channel EEG system, arranged in the Biosemi's ABC system covering the entire scalp at 2048 Hz. Among all recorded sites, some of the electrodes will be localized around the primary motor cortex, the motor cortex, the somatosensory cortex, and the occipital cortex.