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

<h4>Background</h4>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.<h4>Methods</h4>Patients underwent elective gynecological laparoscopic surgery under general anesthesia with endotracheal intubation, aged 18-65 years, American Society of Anesthesiologists class I or II, 18 kg/m² ≤ body mass index ≤ 30 kg/m², were randomly divided into the control (group C) and esketamine groups (group E). Before anesthesia induction, group E received an intravenous injection of 0.3 mg/kg of esketamine, while group C received an equal dose of physiological saline. TCI of propofol to the effect-site concentration (EC) of 3.0 μg/mL, and then TCI of remifentanil to the effect room and intravenous injection of rocuronium 0.6 mg/kg after MOAA/S was 0. Endotracheal intubation was performed after 2 min. Dixon's modified sequential method was used, and the initial EC of remifentanil was 3.0 ng/mL. The EC of remifentanil was determined according to the intubation response of the previous patient, with an adjacent concentration gradient of 0.3 ng/mL. The EC₅₀ and EC₉₅ values and their 95% confidence intervals (CIs) were determined using probit regression analysis.<h4>Results</h4>The EC₅₀ for cardiovascular response inhibition to endotracheal intubation using remifentanil was 3.91 ng/mL (95% CI: 3.59-4.33 ng/mL) and EC₉₅ was 4.66 ng/mL (95% CI: 4.27-6.23 ng/mL) with TCI of propofol 3.0 μg/mL. After intravenous administration of 0.3 mg/kg of esketamine, the EC₅₀ of remifentanil was 3.56 ng/mL (95% CI: 3.22-3.99 ng/mL) and EC₉₅ was 4.31 ng/mL (95% CI: 3.91-5.88 ng/mL).<h4>Conclusions</h4>Combined with TCI of propofol 3.0 μg/mL for anesthesia induction, esketamine significantly reduced the EC₅₀ and EC₉₅ of remifentanil to inhibit the cardiovascular response to endotracheal intubation.<h4>Trial registration</h4>The trial was registered in the Chinese Clinical Trials Registry ( www.chictr.org.cn ; registration number: ChiCTR2200064932; date of registration:24/10/2022).

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