Mariko H Tsuji1, Shigehito Sato2, Hiroshi Naito2. 1. Department of Anesthesiology, University Hospital of Tsukuba, 2-1-1 Amakubo, 305, Tsukuba, Ibaraki, Japan. 2. Department of Anesthesiology, Institute of Clinical Medicine, University of Tsukuba, 1-1-1 Tennoudai, 305, Tsukuba, Ibaraki, Japan.