During study period, patients undergoing elective cardiac surgery in Konkuk University Medical Center are randomly assigned to get remifentanil-based regimen consisting of remifentanil 0.75 mcg/kg/min and supplemental propofol for maintaining BIS 40-60 (Group R) or sevoflurane (end-tidal 1.2-2.8 vol%) and sufentanil (0.015 mcg/kg/min) balanced regimen in Group S.