Dexmedetomidine Supplemented Analgesia and Long-term Survival After Cancer Surgery

Inclusion Criteria: * Age \>= 65 years, \< 90 years; * Scheduled to undergo curative resection for primary solid organ cancer under general anesthesia, with an expected duration of surgery \>=2 hours; * Planned to use patient-controlled intravenous analgesia after surgery; * Provide written informed consent. Exclusion Criteria: * Preoperative history of schizophrenia, epilepsy, parkinsonism or myasthenia gravis; * Preoperative radio- or chemotherapy; * Inability to communicate in the preoperative period because of coma, profound dementia or language barrier; * Preoperative obstructive sleep apnea (previously diagnosed as obstructive sleep apnea, or a STOP-Bang score \>= 3 and serum HCO3- \>= 28 mmol/L); * Brain trauma or neurosurgery; * Preoperative left ventricular ejection fraction \< 30%, sick sinus syndrome, severe sinus bradycardia (\< 50 beats per minute), or second-degree or above atrioventricular block without pacemaker; * Severe hepatic dysfunction (Child-Pugh class C) or severe renal dysfunction (requirement of renal replacement therapy before surgery); * ASA classification \>= IV.