Primary Outcome Measures:
- EC50 of remifentanil for preventing persistent cough and defensive movement using Dixon's up-and-down method
After topical airway anesthesia with 10 % lidocaine in nostril and oropharyx, 1.5~2.0 mg of IV midazolam is injected. Awake nasotracheal fiberoptic intubation is performed with target-controlled infusion of remifentanil. Initial effect site concentration is 3.0 ng/ml. Smooth intubation is defined as absence of persistent cough with head elevation and defensive movement of extremities. In case of smooth intubation, effect site concentration is decreased by 0.5 ng/ml for the subsequent case. If intubation is not smooth, effect site concentration is increased by 0.5 ng/ml for the subsequent case. EC50 of remifentanil is determined using Dixon's up-and-down method.