ED50 and ED95 of Remifentanil for Intubation Without NOL Variation

Inclusion Criteria: * ASA status I or II * Mallampati class I or II * Patients \> 18 years old and \<65 years (defining elderly patients) * Elective general, gynecological, orthopedic, plastic or urological surgery under general anesthesia * Type of surgery that usually necessitate endotracheal intubation and controlled ventilation Exclusion Criteria: * Patient refusal * History of psychiatric diseases or psychological problems (including mental retardation); inability to give consent; language barrier. * Anticipated difficult airway (Mallampati class III and IV, thyromental distance \< 6 cm, mouth opening \< 3 cm, neck extension \<80° and neck flexion \<35°, inability to prognath, meaning bringing lower mandibular before the upper maxilla) * Patient with history of neck rigidity or instability * BMI \> 30 kg/m2 * Anticipated difficult ventilation (patients with beard, obesity with BMI more than 30 kg/m2) * Patient with history of oropharyngeal or tracheal surgery (excluding adenoidectomy, tonsillectomy and teeth removal) * Severe coronary artery disease * Serious cardiac arrhythmias (including atrial fibrillation) * Use of β-blockers (all types) * History of opioid or illicit drug substance abuse * Chronic use of psychotropic and/or opioid drugs * Allergy to remifentanil or propofol * Pregnancy * Contraindications to mask ventilation (gastrointestinal tract obstruction, pregnancy, active not-treated gastroesophageal reflux disease, non-fasting patients) * Unexpected difficult airway requesting excessive, possibly painful airway manipulations * Requiring hemodynamic support with vasopressors or inotropes 2 min before laryngoscopy to 5 min after insertion of endotracheal tube