Data analysis
Continuous data with normal distribution were expressed as the mean (SD) and analyzed using independent samples t test, whereas data without normal distribution were expressed as median (interquartile range, IQR) and compared by Mann–Whitney Primary outcome was analyzed in intention-to-treat and per protocol populations respectively. RCSQ score was presented as median (IQR) and compared by Mann–Whitney BIS value was recorded at 1-min interval from initial administration of trial drug to end of surgery. Time-weighted average (TWA) BIS was calculated as the summation of BIS values multiplied by the referred time, and divided by the specified recording duration.All tests were two tailed and 