Median Effective Dose of Esketamine Combined with Remifentanil for Anesthesia Induction in Painless Colonoscopy

This study aimed to determine the median effective dose (ED₅₀) of esketamine in combination with remifentanil for anesthesia induction during painless colonoscopy, utilizing the sequential dosing method.

This study adopted a sequential design.Patients scheduled for painless colonoscopy at the Endoscopy Center of Northern Jiangsu People's Hospital in April 2023 were screened for inclusion in this study. The inclusion criteria encompassed male and female participants aged 18 to 60 years, with a body mass index (BMI) between 18 and 30 kg/m² and classified as American Society of Anesthesiologists (ASA) physical status I or II. Participants undergoing colonoscopy as the sole procedure, without severe communication barriers, were included. Exclusion criteria included patients undergoing additional diagnostic or therapeutic procedures besides colonoscopy and those with a history of oral sedative or analgesic use exceeding one month. Data were analyzed using SPSS 20.0. Normally and non-normally distributed data were expressed as mean ± standard deviation and median (interquartile range), respectively. ED50, ED95 and 95% CI were determined by Probit regression. Correlation and logistic regression analyses were performed, and the sample size was verified by power analysis (α=0.05).For anesthesia induction, the remifentanil dose was fixed at 0.3 μg/kg, while the esketamine dose was adjusted sequentially. The initial dose of esketamine was 0.1 mg/kg and was incrementally increased by a ratio of 1:1.2 for each subsequent dose administered. Successful induction of anesthesia was defined as a positive response, while unsuccessful induction was classified as a negative response. An "inflection point" was defined as the dose transition from a negative response (unsuccessful anesthesia induction) to a positive response (successful anesthesia induction) within the sequential dosing framework. The sample size was determined by identifying at least seven such inflection points, where each inflection point involved two consecutive participants: one demonstrating a negative response at a given dose, immediately followed by another demonstrating a positive response at the next dose. Data from these inflection points were aggregated for the final analysis.

A total of 23 study participants were included in this study, with the following distribution: 13 males and 10 females. 13 participants were classified as Grade I, and 10 were classified as Grade II. The ED₅₀ of esketamine combined with remifentanil for anesthesia induction in painless colonoscopy was 0.209 mg/kg, with a 95% confidence interval (CI) of 0.178 to 0.248 mg/kg. The dose required for 95% efficacy (ED₉₅) was 0.259 mg/kg, with a 95% CI of 0.231 to 0.478 mg/kg.

The ED₅₀ and ED₉₅ of esketamine combined with remifentanil for anesthesia induction in painless colonoscopy were 0.209 mg/kg (95% CI: 0.178-0.248 mg/kg) and 0.259 mg/kg (95% CI: 0.231-0.478 mg/kg), respectively. This anesthetic regimen shows promising safety and efficacy profiles and may serve as a viable option for clinical application in painless colonoscopy procedures.