Optimal dose of ciprofol combined with remifentanil for laryngeal mask placement without muscle relaxant: a biased-coin up-and-down sequential allocation trial

OBJECTIVE: To determine the effective dose of ciprofol in combination with remifentanil for successful laryngeal mask airway (LMA) placement without the use of muscle relaxants. DESIGN: A two-phase, biased-coin, up-and-down sequential allocation trial. SETTING: Single tertiary hospital; general anesthesia induction. PATIENTS: 106 American Society of Anesthesiologists (ASA) physical status I-II adult patients (aged 18-75 years) scheduled for elective surgery under LMA anesthesia. INTERVENTIONS: • Phase 1: Ciprofol was fixed at 0.4 mg/kg, while remifentanil doses were adjusted using a biased-coin design to estimate the median effective dose (ED₅₀) and 95% effective dose (ED₉₅). • Phase 2: Remifentanil was fixed at the ED₅₀ determined in Phase 1, and ciprofol doses were similarly titrated to determine its effective dose. MEASUREMENTS: Successful LMA placement was defined as the absence of coughing or gagging, along with an effective seal (air leak pressure > 20 cmH₂O). Secondary outcomes included hemodynamic fluctuations (ΔMAP > 20%), apnea, and injection pain. RESULTS: The ED₅₀ of remifentanil was 0.7 μg/kg when combined with ciprofol 0.34 mg/kg. Adverse events included hypotension (12.7%) and bradycardia (9.5%). CONCLUSIONS: The combination of ciprofol 0.34 mg/kg and remifentanil 0.7 μg/kg provides effective conditions for LMA placement without muscle relaxants. This regimen reduces opioid requirements and may promote faster recovery. TRIAL REGISTRATION: Chinese Clinical Trial Registry ChiCTR2200062686; registered on August 15, 2022 (retrospectively registered).