The EC90 of remifentanil for inhibiting endotracheal intubation responses under anesthesia induction with ciprofol: study protocol for a dose-finding trial with the biased-coin design.

Background: Tracheal intubation may cause significant hemodynamic responses. Many drugs have been shown to be effective in modifying these cardiovascular responses, including remifentanil, fentanyl, sufentanil, and alfentanil. However, the 90% effect-site concentration (EC90) of remifentanil required to control cardiovascular responses to tracheal intubation when combined with ciprofol remains unclear. The purpose of this study was to determine the EC90 of remifentanil inhibiting cardiovascular responses to tracheal intubation during anesthesia induction with ciprofol using biased-coin design up-and-down sequential method (BC-UDM).

Methods: This is a prospective sequential allocation dose-finding study. American Society of Anesthesiologists physical status (ASA) I-II elective surgical patients receiving target-controlled infusion (TCI) of remifentanil effect-site concentration (Ce), followed by ciprofol and rocuronium for anesthesia, were enrolled. The cardiovascular response to tracheal intubation was defined as positive when mean arterial pressure (MAP) or heart rate (HR) is 15% higher than the baseline value. Using the BC-UDM, the Ce of remifentanil was determined based on the cardiovascular response to tracheal intubation of the previous patient. The EC90 and 90% confidence intervals (90% CIs) were estimated by R-Foundation centered isotonic regression and the pooled adjacent violators algorithm with bootstrapping.

Discussion: The results of this study sought to demonstrate EC90 of remifentanil blunting sympathetic responses to tracheal intubation during anesthesia index (Ai)-guided ciprofol anesthesia using BCD-UDM. It may help to minimize the cardiovascular responses to tracheal intubation.

Trial registration: Chinese Clinical Trial Registry ChiCTR2300078275. Registered on December 3, 2023.