This clinical trial is designed to observe the effect of dexmedetomidine nasal spray on the incidence of postoperative delirium in elderly patients undergoing thoracoscopic lung resection. Eligible elderly patients scheduled for thoracoscopic lung resection will be randomly divided into two groups: the dexmedetomidine group will receive dexmedetomidine hydrochloride nasal spray, while the placebo group will be administered an equivalent volume of placebo nasal spray. The primary outcome is the incidence of postoperative delirium within 3 days after surgery. Secondary outcomes include the severity and duration of delirium, as well as postoperative pain, subjective sleep quality, and the incidence of adverse events, which will be compared between the two groups to evaluate the safety and efficacy of dexmedetomidine nasal spray.

Inclusion Criteria:

• American Society of Anesthesiologists (ASA) physical status II-III.
• Age ≥ 65 years, with no gender restriction.
• Patients scheduled for elective thoracoscopic lung resection under general anesthesia, with an expected operative duration of 1-4 hours.
• Body mass index (BMI) between 18 kg/m² and 30 kg/m².

Exclusion Criteria:

• Known hypersensitivity to dexmedetomidine hydrochloride or any of the excipients in the investigational product.
• Pre-existing nasal conditions, nasal surgery, or nasal allergies that may significantly impair nasal drug absorption (e.g., chronic nasal congestion, rhinorrhea, epistaxis, nasal anatomical abnormalities, or mucosal pathology affecting absorption).
• History of cranial trauma.
• Pre-existing diagnosis or clinical suspicion of neurocognitive impairment, defined as a Mini-Mental State Examination (MMSE) score < 24.
• History of schizophrenia, epilepsy, Parkinson's disease, or myasthenia gravis.
• History of alcohol or substance abuse/dependence.
• Left ventricular ejection fraction < 30%; sick sinus syndrome; severe sinus bradycardia (< 50 bpm); or second- or higher-degree atrioventricular block without permanent pacemaker implantation.
• History of myocardial infarction, unstable angina, severe cardiac arrhythmia, or decompensated cardiac insufficiency.
• Asthma, emphysema, chronic bronchitis, or chronic obstructive pulmonary disease (COPD) considered inappropriate for study participation by the investigator.
• Severe hepatic impairment (Child-Pugh Class C).
• Severe renal dysfunction requiring preoperative dialysis.
• Inability to provide valid informed consent due to cultural background, language barrier, or cognitive impairment.
• Refusal to sign the informed consent form.
• Other conditions deemed inappropriate for study participation by the investigator.