1 Department of Anesthesiology, Hirosaki University Graduate School of Medicine, Zaifu-cho 5, Hirosaki 036-8562, Japan. Electronic address: h18gm124@hirosaki-u.ac.jp.
2 Department of Anesthesiology, Hirosaki University Graduate School of Medicine, Zaifu-cho 5, Hirosaki 036-8562, Japan. Electronic address: saitoj@hirosaki-u.ac.jp.
3 Department of Anesthesiology, Hirosaki University Graduate School of Medicine, Zaifu-cho 5, Hirosaki 036-8562, Japan.
4 Department of Anesthesiology, Hirosaki University Graduate School of Medicine, Zaifu-cho 5, Hirosaki 036-8562, Japan. Electronic address: kitasan@hirosaki-u.ac.jp.
5 Department of Anesthesiology, Hirosaki University Graduate School of Medicine, Zaifu-cho 5, Hirosaki 036-8562, Japan. Electronic address: hirotak@hirosaki-u.ac.jp.