90% Effective Infusion Time of Sufentanil to Prevent Induction Cough: A Biased Coin Sequential Study

This single-center, prospective biased coin up-and-down sequential study aims to determine the 90% effective infusion time (ET90) of sufentanil to prevent sufentanil-induced cough (SIC) during the induction phase of general anesthesia in adults undergoing endotracheal intubation. Two age cohorts are studied separately: younger adults (\

Inclusion Criteria: * American Society of Anesthesiologists (ASA) physical status I-III * Aged ≥18 ears old * Scheduled for elective surgery requiring general anesthesia with tracheal intubation Exclusion Criteria: * Resting vital signs upon operating-room arrival: systolic blood pressure ≥160 mmHg, or diastolic blood pressure ≥100 mmHg, or heart rate ≥110 beats per minute. * Anticipated difficult airway, requirement for rapid-sequence induction, or emergency surgery. * Chronic cough, asthma, chronic obstructive pulmonary disease (COPD), bronchiectasis, active pulmonary disease, or upper respiratory tract infection within the preceding 2 weeks. * Regular opioid use for more than 2 weeks within 6 months before surgery; or recent use of antitussive agents or other medications that may alter the cough reflex. * Known history of allergy to study drug (sufentanil citrate). * Pregnancy, lactation, psychiatric disorders, or individuals unable to communicate appropriately.