Effect of esketamine on the EC50 of remifentanil for blunting cardiovascular responses to endotracheal intubation in female patients under general anesthesia: a sequential allocation dose-finding study.

Abstract

This study aimed to investigate the effect of esketamine on the dose-effect relationship between remifentanil and the cardiovascular response to endotracheal intubation during target-controlled infusion (TCI) of propofol. Patients underwent elective gynecological laparoscopic surgery under general anesthesia with endotracheal intubation, aged 18-65years, American Society of Anesthesiologists class I or II, 18kg/m2 ≤ body mass index ≤ 30kg/m2, were randomly divided into the control (group C) and esketamine groups (group E). Before anesthesia induction, group E received an intravenous injection of 0.3mg/kg of esketamine, while group C received an equal dose of physiological saline. TCI of propofol to the effect-site concentration (EC) of 3.0μg/mL, and then TCI of remifentanil to the effect room and intravenous injection of rocuronium 0.6mg/kg after MOAA/S was 0. Endotracheal intubation was performed after 2min. Dixon's modified sequential method was used, and the initial EC of remifentanil was 3.0ng/mL. The EC of remifentanil was determined according to the intubation response of the previous patient, with an adjacent concentration gradient of 0.3ng/mL. The EC50 and EC95 values and their 95% confidence intervals (CIs) were determined using probit regression analysis. The EC50 for cardiovascular response inhibition to endotracheal intubation using remifentanil was 3.91ng/mL (95% CI: 3.59-4.33ng/mL) and EC95 was 4.66ng/mL (95% CI: 4.27-6.23ng/mL) with TCI of propofol 3.0μg/mL. After intravenous administration of 0.3mg/kg of esketamine, the EC50 of remifentanil was 3.56ng/mL (95% CI: 3.22-3.99ng/mL) and EC95 was 4.31ng/mL (95% CI: 3.91-5.88ng/mL). Combined with TCI of propofol 3.0μg/mL for anesthesia induction, esketamine significantly reduced the EC50 and EC95 of remifentanil to inhibit the cardiovascular response to endotracheal intubation. The trial was registered in the Chinese Clinical Trials Registry ( www.chictr.org.cn ; registration number: ChiCTR2200064932; date of registration:24/10/2022).