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 (\<65 years) and older adults (≥65 years). The trial does not test superiority or between-group differences as the primary objective.

All participants receive sufentanil via a peripheral intravenous pump. The total sufentanil dose is fixed within each age cohort (young: 0.40 μg/kg; elderly: 0.30 μg/kg), while the pump injection time is adjusted using the biased coin up-and-down allocation method. SIC success is defined as no audible cough within a prespecified observation window from the start of the infusion until 2 minutes after infusion ends.

The primary outcome is the ET90 of sufentanil and its 95% confidence interval for each age cohort, estimated using centered isotonic regression with bootstrap confidence intervals. Approximately 120 patients will be screened to obtain at least 54 evaluable participants per cohort.