Elective Surgery Requiring Laryngeal Mask Airway General Anesthesia

This is a prospective two-group dose-finding trial using biased-coin sequential up-and-down design. We plan to enroll 108 patients who need general anesthesia with laryngeal mask airway placement, divided into young group (18-65 years old) and elderly group (65 years old and older). All patients will receive tegileridine combined with fixed-dose propofol for anesthesia induction. The main goal is to find the 90% effective dose (ED90) of tegileridine that can fully block body movement, cough, tearing and unstable blood pressure/heart rate during laryngeal mask insertion. We will also record cough rate, hemodynamic changes, sedation depth and all perioperative adverse reactions to provide safe dosing reference for different age patients in clinical anesthesia.