Investigators investigates the effect of perioperative dexmedetomidine 0.5 ug/kg/hr followed by a postoperative continuous infusion fentanyl-based PCA(Patient-Controlled Analgesia) drug mixed with dexmedetomidine 0.2ug/kg/hr for two days on reducing postoperative delirium and postoperative rescue analgesics in elderly patients who undergo hip surgery. The other half of patients received fentanyl-based PCA only.

Elderly patients are susceptible to postoperative delirium. Delirium occurs in 10~60% and is associated with longer hospital stays, increased costs, and morbidity. Postoperative delirium usually occurs 2~3 days after surgery. Intraoperative infusion of dexmedetomidine lacks preventing postoperative delirium in elderly noncardiac major surgery.

We hypothesized postoperative dexmedetomidine for two days as a mixture drug of fentanyl-based PCA could reduce the incidence of postoperative delirium. We compared this effect with other control group who received fentanyl-based PCA only.

We also investigate EEG patterns of patients during emergence and compared the EEG patterns who developed delirium postoperatively in PACU(Postanesthesia care unit) or general ward. Dexmedetomidine has analgesic effect. We expected postoperative dexmedetomidine has benefits of opioid sparing effects.

Inclusion Criteria: over 65 yrs old elderly patient who undergo elective hip surgery and ASA(The American Society of Anesthesiologists) physical status I-III

Exclusion Criteria:

history of dementia, drug abuser, hypersensitivity to dexmedetomidine, fentanyl, propofol, disable to speech, reject the clinical study, hemodynamic instability during surgery, an illiterate, pregnancy