• Percent of patients who maintain a Richmond Agitation-Sedation score = 0, -1, -2, continuously from 1 hour before extubation or end of propofol infusion before extubation, whichever is later, to 1 hour after extubation
  

• The variations in vital signs (blood pressure and heart rate) in patients from 10 minutes before extubation to 10 minutes after extubation
  

The study is to conduct as a phase IV post-marketing clinical study in accordance with the approval condition of dexmedetomidine hydrochloride in Japan. The study will compare the use of dexmedetomidine in patient management at the time of extubation with other sedative/ analgesic management, Comparison is made in the use of dexmedetomidine in patient management between a group in which management is performed with dexmedetomidine and a group in which standard management is performed with propofol in patients requiring postoperative sedation in the ICU The usefulness of dexmedetomidine during postextubation period is also evaluated.

Inclusion Criteria:

• Patient or legally acceptable representative (if acceptable by Institutional Review Board/Ethics Committee) has signed and dated the Informed Consent after the study has been fully explained
• Patient is male or female; at least 20 years of age
• Patient who is in condition of American Society of Anesthesiology (ASA) I to III Class preoperatively
• Patient is orally intubated and anticipated to require sedation for mechanical ventilation for a minimum period of 4 hours following open-heart surgery, coronary artery bypass grafting (CABG), or major vascular surgery
• If patient is female with child bearing potential, she is to be non-pregnant, and not lactating

Exclusion Criteria:

• Patient has serious central nervous system (CNS) trauma
• Patient has undergone or requires intracranial surgery during current hospitalization
• Patient requires the use of neuromuscular blocking agents after admission to ICU, except for the insertion of the endotracheal tube
• Patient requires epidural or spinal analgesia/anesthesia after the end of surgery and during his/her ICU stay
• Patient in whom propofol or opioids are contraindicated
• Patient has known or suspected allergy to any medication that might be administered during the course of the study
• Patient is grossly obese (i.e., body mass index > 35)
• Patient is currently hospitalized for drug overdose
• Patient in whom alpha-2 antagonists or alpha-2 agonists are contraindicated
• Patient is currently being treated or has been treated within the last 30 days with alpha-2 agonist or antagonist
• Patient has participated in a trial with any experimental drug within 30 days prior to admission to the ICU
• Terminally ill patient, whose life duration expectancy is no more or around 24 hours
• Patient is considered unable to undergo any procedure required by the protocol
• Patient with excessive bleeding which will likely require resurgery
• Patient has an ejection fraction of < 30%
• In the Investigator's opinion, patient has any symptom or factor, which might increase risk to the patient or preclude obtaining satisfactory study data