Difficult tracheal intubation is a cause of severe patient damage and death. There is not a good method to predict it. The McGrath Series 5 video laryngoscope can improve visualization of the glottic structures one to two grades. Moreover unlike a classical laryngoscope with a Macintosh blade, the McGrath provides a view of the glottis without requiring alignment of the oral, pharyngeal and laryngeal axes. In this study, the investigators will use it to compare the Cormack-Lehane score in sedation and anesthesia condition. It helps to know the role of videolaryngoscope in predicting difficult intubation.

• The enrolled patients were given a bolus of sufentanil 0.3-0.5μg/kg to achieve Ramsay sedation score 2-3. The Cormack-Lehane score in sedation was evaluated by McGrath videolaryngoscope.
• Then the patients were induced with propofol. A bolus of rocuronium was given to facilitate intubation. The Cormack-Lehane score in anesthesia was recorded when intubated by McGrath videolaryngoscope.
• BMI, mouth opening, thyromental distance, intubation duration and ramsay sedation score were also recorded.
• To compare the Cormack-Lehane score in sedate and anesthesia condition

Inclusion Criteria:

• patients scheduled for general surgery under general anesthesia
• ASA classification 1-3

Exclusion Criteria:

• emergent operation, aspiration risk
• a history of difficult airway
• expected difficult airway
• incooperative patients with mental diseases, hearing disorders