Frontal EEG Dynamics During Anesthesia in Patients With Obesity and Normal Weight

This prospective observational study aims to compare frontal electroencephalographic (EEG) spectral dynamics between patients with obesity and normal weight undergoing general anesthesia. The primary objective is to evaluate whether changes in frontal alpha power around propofol-induced loss of consciousness differ between the two BMI groups. Secondary objectives include comparing changes in delta power, the alpha/delta power ratio, and frontal alpha asymmetry around loss of consciousness, as well as evaluating EEG spectral dynamics throughout the intraoperative period. Anesthetic management will be determined by the attending anesthesiologist according to routine clinical practice, without intervention by the study investigators.

Inclusion Criteria: * Adults aged 18-65 years * Scheduled for elective surgery under general anesthesia * American Society of Anesthesiologists (ASA) physical status I-III * General anesthesia induction performed with propofol * Availability of continuous frontal EEG monitoring (SedLine) during anesthesia * BMI 18.5-24.9 kg/m² for the normal-weight group or BMI ≥30 kg/m² for the obesity group * Ability to provide written informed consent Exclusion Criteria: * \- BMI 25.0-29.9 kg/m² * History of epilepsy or seizure disorder * Known major neurological disease that may affect EEG activity * Altered level of consciousness before anesthesia * Regular use of antiepileptic medications or other drugs known to substantially affect EEG activity * Emergency surgery * Pregnancy * Skin lesions, infection, or other conditions of the forehead preventing appropriate placement of the EEG sensor * Inability to obtain an adequate-quality EEG recording because of technical failure or excessive artifacts * Requirement for substantial deviation from the planned routine anesthetic management that prevents standardized EEG assessment * Refusal to participate or inability to provide written informed consent