1. Department of Anesthesiology and Pain Medicine, Konkuk University Medical Center, Konkuk University School of Medicine, Neungdong-ro 120-1, Kwangjin-gu, Seoul 05030, Republic of Korea
2. Department of Anesthesiology and Pain Medicine, Wondang OK Pain Clinic, 783 Hoguk-ro, Deogyang-gu, Goyang-si, Gyeonggi-do 10461, Republic of Korea