1. Department of Anesthesiology and Pain Medicine, Juntendo University Faculty of Medicine, 1-3 Hongo 3-chome, Bunkyo-ku 113-8431, Japan
2. Department of Anesthesia and Pain Medicine, Hachinohe Heiwa Hospital, 4-6 Minatotakadai 2-chome, Hachinohe 031-8545, Japan
3. Department of Pain Medicine, Sata Hospital, 4-28 Watanabedori 2-chome, Chuo-ku 810-0004, Japan