Effect of Continuous Intraoperative Esketamine Infusion on Perioperative Negative Emotions in Breast Cancer Surgery Patients With Mild-to-Severe Depression

Inclusion Criteria: 1. Age ≥ 18 years. 2. Scheduled to undergo elective breast cancer resection surgery. 3. American Society of Anesthesiologists (ASA) physical status classification of I-III. 4. Clearly understand and voluntarily agree to participate in the study, and sign the informed consent form. 5. Female patients with mild to severe depressive symptoms (defined as a Hospital Anxiety and Depression Scale-Depression subscale score of ≥8) 6. Anticipated anesthesia duration greater than 90 minutes. Exclusion Criteria: 1. Patients with significant preoperative abnormalities in cardiac, pulmonary, hepatic, or renal function, or coagulation disorders . 2. Patients taking antipsychotics, antidepressants, or glucocorticoids, or with a history of alcohol abuse or illicit drug use . 3. Patients with an MMSE score \<18, dementia, intellectual disability, or those unable to communicate (e.g., coma, severe dementia, hearing or language impairment) . 4. Patients with a history of psychiatric or neurological disorders (e.g., schizophrenia, epilepsy, Parkinson's disease, or severe myasthenia gravis) . 5. Patients with poorly controlled or untreated hypertension (≥180/110 mmHg) . 6. Patients with elevated intracranial or intraocular pressure. 7. Patients with untreated or inadequately treated hyperthyroidism . 8. Patients with a known allergy to the drugs involved in this study . 9. Patients unable to complete the assessment scales required by this study. 10. Patients who are currently participating in other clinical trials