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

This is a single-center, prospective sequential study using a biased coin up-and-down allocation approach to determine the 90% effective infusion time (ET90) of sufentanil during the induction phase of general anesthesia to prevent sufentanil-induced cough (SIC). The study evaluates two age groups separately: younger adults (<65 years) and older adults (≥65 years).

Sufentanil will be administered intravenously via a infusion pump. Within each age cohort, the total sufentanil dose is predetermined, while the infusion time (rate) is adjusted based on the previous participant's outcome according to the biased coin up-and-down rule.

The primary success criterion is the absence of SIC during a prespecified observation period that starts at sufentanil infusion initiation and ends shortly after infusion completion during the induction phase. The primary outcome is the ET90, estimated for each age cohort with an appropriate statistical model using the observed infusion times and SIC outcomes.

Participants are screened before surgery based on age and general anesthesia requirements, and key comorbidities and contraindications are considered to reduce confounding. Safety is monitored throughout the induction phase and perioperative period, with attention to potential adverse events including hemodynamic instability and respiratory depression.

Approximately 120 patients are planned for enrollment to obtain sufficient evaluable participants in each cohort for ET90 estimation.

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.