Effect of Midazolam Premedication on Opioid-induced Mask Ventilation Difficulty

. Patients of the midazolam group will be treated with midazolam premedication (3 cc mixture of 0.035 mg/kg midazolam and normal saline; maximum midazolam dose, 3 mg) intravenously a waiting area 3 minutes before transportation to an operating room

Control group patients are treated with 3 cc normal saline in a waiting area 3 minutes before transportation to an operating room