Motonobu Kimizuka1, Michiaki Yamakage2. 1. Department of Anesthesiology, Sapporo Medical University School of Medicine, South-1, West-16, Chuo-ku, Sapporo, Hokkaido, 060-8543, Japan. 2. Department of Anesthesiology, Sapporo Medical University School of Medicine, South-1, West-16, Chuo-ku, Sapporo, Hokkaido, 060-8543, Japan. yamakage@sapmed.ac.jp.