A Biased Coin Design Sequential Method for Determining the 95% Effective Dose of Ciprofol for Adjunctive Sedation Undergoing Knee Arthroplasty in Elderly People

Select the patients who will receive knee arthroplasty in the Second Hospital of Shanxi Medical University. The patients will receive a loading dosage of 0.05mg/kg of ciprofol to begin sedation following the completion of intravertebral anesthesia, and the maintenance dose is calculated using a biased coin design up-and-down sequential method. Based on the relevant literature and pilot study, 0.2 mg·kg-1·h-1 is selected as initial test dose with a dose gradient of 0.02 mg·kg-1·h-1. The Modified Alertness Sedation Score (MOAA/S ) scores and the bispectral index (BIS) were recorded for patients before administration (T0), 5 min after administration (T1), 10 min after administration (T2), 20 min after administration (T3), 30 min after administration (T4), 45 min after administration (T5), and 60min after administration (T6). If the first patient had ≥ 4 time points with MOAA/A score ≤3 from T0-T6, the sedation was regarded as satisfactory, the dose of next patient is randomly assigned to the next lower dose with 5% probability, or to the same dose with 95% probability; If the previous patient was not satisfactorily sedated, the next patient's infusion dose was increased by 0.02 mg·kg-1·h-1. When the number of satisfied cases of sedation reaches 45, the trial is terminated. At the same time, the change of vital signs and adverse reactions before and after administration were recorded