Demedetomidine infusion (2mcg/ml); loading 0.5 mcg/kg for 30 min (BW/2 ml/h for 30 min), then 0.5 mcg/kg (BW/4 ml/h) until 30 minutes before finish the operation.

NSS loading BW/2 ml/h for 30 min, then BW/4 ml/h until 30 minutes before finish the operation.

Demedetomidine infusion (2mcg/ml); loading 0.5 mcg/kg for 30 min (BW/2 ml/h for 30 min), then 0.5 mcg/kg (BW/4 ml/h) until 30 minutes before finish the operation.

After finish the operation, Desflurane will be stopped. All patients will be received the neuromuscular reversal drugs and TOF ratio > 0.9. All patients will be evaluated by Riker sedation agitation score before extubation and re-evaluated again at 15 minutes after extubation.

Riker sedation agitation scores

1. Dangerous agitation: trying to get out of bed, pulling out tube, thrashing
2. Very agitated: may require physical restraint, unable to calm with verbal instructions.
3. Agitated: mild agitation and anxiety but calm down with verbal instructions.
4. Calm and cooperative: aroused easily and follows commands
5. Sedated: difficult to aroused, but does arouse to verbal or physical stimuli, able to follow simple commands
6. Very sedated: does not follow commands but arouses to physical stimulation
7. Unarousable: little or no response to noxious stimuli

After finish the operation, the total of fentanyl consumption during the operation will be recorded.