1. Department of Anesthesiology, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan
2. Department of Oral and Maxillofacial Surgery, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan
3. Faculty of Medicine, Department of Anesthesiology, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan