Tomonori Takazawa1, Takao Kato2, Shigeru Saito3. 1. Intensive Care Unit, Gunma University Hospital, 3-39-15 Showa-machi, Maebashi, Gunma, 371-8511, Japan. takazawt@gunma-u.ac.jp. 2. Department of Anesthesiology, Saitama Medical Center, Saitama Medical University, 1981 Kamoda, Kawagoe, 350-8550, Saitama, Japan. 3. Department of Anesthesiology, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, 371-8511, Gunma, Japan.