Fospropofol Disodium ED95 for Elderly Spinal Anesthesia Sedation

Inclusion Criteria: * Age ≥65 years, no gender restriction * Scheduled for elective lower extremity surgery with spinal anesthesia * ASA physical status classification Ⅰ-Ⅲ * BMI 18.5-28.0 * Written informed consent obtained from patients or their guardians Exclusion Criteria: * Age \<65 years； * Non-lower extremity surgery or conversion to general anesthesia； * ASA physical status classification Ⅳ or above； * BMI \<18.5 or \>28.0； * History of drug abuse or alcohol dependence； * Preoperative use of sedative or analgesic drugs； * Refusal to participate or inability to sign informed consent； * Severe arrhythmia or myocardial infarction within 3 months； * Severe liver or kidney dysfunction； * Severe respiratory diseases； * Coagulopathy； * Uncorrected severe electrolyte disturbance； * History of mental illness or cognitive impairment.