The ED95 of Ciprofol for Laryngeal Mask Airway Insertion With Fentanyl in Children: A Biased-Coin Dose-Finding Trial

This is a prospective, single-blind (participant and outcomes assessor-blinded), biased-coin design up-and-down sequential allocation trial. A total of 180 pediatric patients (ASA I-II) scheduled for elective surgery requiring LMA insertion will be enrolled and divided into three age groups: toddlers (1-3 years), preschoolers (4-6 years), and school-age children (7-12 years), with 60 patients per group.

All patients will receive a fixed dose of fentanyl (1 μg/kg) and a predetermined bolus dose of ciprofol, administered intravenously over 1 minute. The initial ciprofol dose is set at 0.35 mg/kg, with a dose step size of 0.1 mg/kg. The dose for each subsequent patient is determined by the biased-coin design: if the previous patient achieves successful LMA insertion (no movement), the next patient receives the same dose with a probability of 0.947 or a 0.1 mg/kg lower dose with a probability of 0.053. If the previous patient fails (movement occurs), the next patient receives a 0.1 mg/kg higher dose.

The study employs a single-blind design: the anesthesiologist who administers the study drug is aware of the ciprofol dose, whereas the anesthesiologist who performs the LMA insertion and the observer who evaluates the patient's response are both blinded to the dose assignment. LMA insertion will be attempted 90 seconds after drug administration. Successful insertion is defined as the absence of jaw tightness, gross purposeful movement, coughing, gagging, or laryngospasm during LMA insertion and cuff inflation. The primary outcome is the ED95 of ciprofol for successful LMA insertion in each age group, estimated using isotonic regression with bootstrap resampling.