The purpose of this study is to assess efficacy and safety of dexmedetomidine at the time of extubation and after extubation, in patients requiring postoperative sedation in the ICU.

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 with serious disturbance of the central nervous system (disturbance of consciousness).
• Patient has undergone or requires intracranial surgery during current hospitalization
• Patient requires muscle relaxant drugs after admission to the ICU (except when an endotracheal tube is reinserted).
• Patient requires epidural or intrathecal administration of analgesia/anesthesia after surgery and during their ICU stay.
• Patients for whom propofol or opioids are contraindicated.
• Patient has known or suspected allergies to any medication that might be administered during the course of the study.
• Patient is obese (body mass index >35)
• Patient was recently hospitalized for drug overdose
• Patient for whom alpha-2 antagonists or alpha-2 agonists are contraindicated
• Patient is currently or previously treated, within 30 days before the start of the study, with an alpha-2 antagonist or alpha-2 receptor agonist.
• Patient has participated in another clinical study within 30 days prior to admission to the ICU and patient is currently participating in another clinical study.
• Patient was diagnosed with severe symptoms and judged likely to die within 24 hours.
• Patient is considered unable to undergo all procedures required by the protocol.
• Patient with excessive bleeding that is likely require reoperation.
• Patient with an ejection fraction of < 30%.
• Patient, in the opinion of the investigator or subinvestigator in the post-marketing clinical study, that has symptoms or factors that may increase his/her risk as a result of the clinical study, or that may not provide sufficient study data.