Effect of pretreatment with low-dose Esketamine on the Propofol requirements and the onset time of cisatracurium during the induction of general anesthesia: a prospective, randomized, double-blinded trial

Background: Esketamine has been increasingly used as an adjuvant for propofol-based induction. However, the effective esketamine dose for this indication remains unclear. The authors investigated the effect of different intravenous bolus low doses of esketamine pretreatment on the propofol requirements and the onset time of cisatracurium during anesthesia induction. Methods: 140 patients undergoing elective surgery under general anesthesia were randomly allocated into four groups: pretreatment with saline (Group C), pretreatment with 0.1 mg/kg esketamine (Group K0.1), pretreatment with 0.3 mg/kg esketamine (Group K0.3), and pretreatment with 0.5 mg/kg esketamine (Group K0.5). The propofol dosage was recorded when the eyelash reflex disappeared and the Index of Consciousness (IoC) value reached 60 during the infusion. The onset time for cisatracurium was recorded. Results: The total dose of propofol at the point of eyelash reflex loss was significantly lower in group K0.5 than in groups K0.3 (P = 0.019), K0.1 (P < 0.001) and C (P < 0.001). The dose of propofol at the point of the loss of eyelash reflex was lower in group K0.3 than in groups K0.1 (P = 0.006) and C (P < 0.001). The total dose of propofol at an IoC value of 60 was significantly higher in group K0.5 than in groups K0.1 (P < 0.001) and C (P < 0.001). The dose of propofol at an IoC value of 60 was higher in group K0.3 than in groups K0.1 (P = 0.009) and C (P < 0.001). The onset time of cisatracurium during induction was not significantly different among the groups. Conclusion: Esketamine decreases the dose of propofol in a dose-dependent manner at the point of the loss of eyelash reflex, while 0.5 mg/kg esketamine and 0.3 mg/kg esketamine pretreatment before induction significantly increase the dose of propofol at the targeted IoC value of 60. Esketamine does not affect the onset time of cisatracurium when it is combined with propofol during IoC-guided induction of anesthesia. Clinical trial number: Clinical trial number and registry URL: ChiCTR2000041041, registration date: December 16, 2020 http://www.chictr.org.cn. © The Author(s) 2025.