Corresponding author: Keun-Man Shin, M.D., Ph.D., Department of Anesthesiology and Pain Medicine, Kangdong Sacred Heart Hospital, Hallym University Medical Center, 445, Gil-dong, Gangdong-gu, Seoul 134-701, Korea. Tel: 82-2-2224-2659, Fax: 82-2-474-0956, E-mail: paintx@ naver.com This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial Licens...