The Subjects fasted for 6 h before study drug administration. An 18-gauge angiocatheter was placed in a vein of the antecubital area. A second angiocatheter was placed in the contralateral radial artery for frequent blood sampling. Subjects were monitored with electrocardiography, pulse oximetry, end-tidal carbon dioxide concentration, and invasive blood pressure measurement (Datex-Ohmeda S/5;Planar Systems, Inc., Beaverton, OR) and Bispectral Index (BIS) (Aspect 2000; Aspect Medical Systems, Inc., Newton,MA). In addition, the electroencephalographic activity of seven monopolar channels (Fp1, Fp2, F3, F4, Cz, P3, and P4, referenced by A2) was recorded by QEEG-8 (LXE3208, Laxtha Inc., Daejeon, Korea).