Effective dose of propofol combined with intravenous esketamine for smooth flexible laryngeal mask airway insertion in two distinct age groups of preschool children.

"Declarations Ethics approval and consent to participateThis study was registered before patient enrollment at the Chinese Clinical Trial Registry Center (Registration Number: ChiCTR2100044317). This study was approved by the Ethics Committee of the Qilu Children’s Hospital of Shandong University (IRB: QLET-ITB/P-2,021,031). All methods were performed following the Declaration of Helsinki. Written informed consent was obtained from the parents or other legal guardians of all enrolled children participating in the trial. Consent for publicationNot applicable. Competing interestsThe authors declare no competing interests. Competing interests The authors declare no competing interests."

"Funding This study was funded by the Special Fund for Comfort Medical Research of the Shandong Medical Association."

"Trial registration Chinese Clinical Trial Registry Center (Registration Number: ChiCTR2100044317; Registration Date: 2021/03/16)"