1. Department of Anesthesiology and Pain Medicine, Kwangju Christian Hospital, Gwangju, Korea
2. Department of Anesthesiology and Pain Medicine, Chonnam National University Medical School and Hospital, Gwangju, Korea
3. Department of Anesthesiology and Pain Medicine, Brain Korea 21 Project, Center for Creative Biomedical Scientists at Chonnam National University, Gwangju, Korea