The Effect of Esketamine on Postoperative Cognitive Function in Elderly Patients Undergoing Oral and Maxillofacial Surgery

Inclusion Criteria: Age ≥ 60 years, either sex; Scheduled for elective oral and maxillofacial surgery under general anesthesia (including oral and maxillofacial tumor surgery, orthognathic surgery, and maxillofacial trauma repair surgery); American Society of Anesthesiologists (ASA) physical status I-III; Expected duration of anesthesia ≥ 2 hours; Willing and able to provide written informed consent. Exclusion Criteria: Pre-existing behavioral disorders or psychiatric diseases (e.g., Alzheimer's disease, Parkinson's disease), or current use of antipsychotic medications (e.g., clozapine, risperidone, olanzapine, haloperidol, chlorpromazine); Pre-existing severe organ dysfunction including: severe cardiovascular disease (life-threatening arrhythmias, severe uncontrolled hypertension, coronary artery disease, heart failure), severe respiratory disease (respiratory failure, severe chronic obstructive pulmonary disease), severe hepatic insufficiency (Child-Pugh Class C), or severe renal insufficiency (glomerular filtration rate \< 30 mL/min or creatinine \> 2.5 mg/dL); Known contraindications to esketamine including: hypersensitivity to the active substance or any excipients; severe risk of elevated blood pressure or intracranial pressure; uncontrolled or untreated hypertension (resting systolic/diastolic blood pressure \> 180/100 mmHg); preeclampsia or eclampsia; untreated or inadequately treated hyperthyroidism; conditions requiring uterine relaxation (e.g., uterine rupture, …