Dexmedetomidine Versus Propofol for Sedation During Awake Endotracheal Intubation

Inclusion Criteria: 1. Age 18-65 Years old; 2. scheduled for elective surgery under general anesthesia with oral tracheal intubation; 3. The American Society of Anesthesiologists(ASA) grade is I or II, and the cardiac function is 1-2; 4. Body mass index (BMI) 18-30 kg/m2. Exclusion Criteria: 1. Patients have severe cardiac diseases (cardiac function grading greater than grade 3/arrhythmia including sick sinus syndrome, atrial fibrillation, atrial flutter, atrioventricular block, frequent ventricular premature, multiple ventricular premature, ventricular premature R on T, ventricular fibrillation and ventricular flutter/acute coronary syndrome) or respiratory failure or hepatic failure or renal failure; 2. body mass index (BMI) ≥30 kg/m2 or \<18 kg/m2; 3. Patients with poor blood pressure control (receive regular antihypertensive medical treatment but still have systolic blood pressure \> 150 mmHg and/or diastolic blood pressure \> 90 mmHg); 4. Patients with a higher risk of reflux and aspiration, such as full stomach, gastrointestinal obstruction, gastroparesis, and pregnant women; 5. Patients have schizophrenia, epilepsy, Parkinson's disease, intellectual disability, hearing impairment.; 6. Patients who take sedative and analgesic drugs for a long time; 7. Patients who are allergic to propofol, dexmedetomidine, midazolam or remifentanil 8. Patients who are expected to be difficult to intubate; 9. Patients who are participating in other clinical trials, or who refuse to sign informed consent.