1 Department of Anesthesiology, Fukushima Medical University School of Medicine, 1, Hikariga-Oka, Fukushima, Fukushima, 960-1295, Japan.
2 Department of Anesthesiology, Fukushima Medical University School of Medicine, 1, Hikariga-Oka, Fukushima, Fukushima, 960-1295, Japan. kei-y7of@fmu.ac.jp.