A majority of the elderly patients undergo surgery for malignant tumors. For these patients,
postoperative tumor recurrence and metastasis are main factors that worsen long-term
outcomes. The investigators hypothesize that dexmedetomidine supplemented analgesia in
elderly patients after cancer surgery may help to maintain immune function and improve
long-term outcomes, possibly by relieving stress and inflammatory response, improving
analgesic efficacy and sleep quality, and reducing delirium incidence.