Statistical analysis
It was reported that anesthesia researches using the up-and-down
methodology typically need 20-40 patients per group [9,16,17]. We
have also considered a dropout rate of 10%. Therefore, the estimated
sample size will be 30 patients per group, and a total of 90 patients
will be randomized.
Data were expressed as mean (standard deviation, SD) for continuous
variables, median (Min, Max) for continuous variables with skewed
distribution, or number (n) for categorical variables. First, all data
are tested for normality by shapiro.test. For data that does not conform
to the normal distribution, we use the Kruskal-Wallis rank sum test to
check the differences between groups; for the data whose variance
conforms to the normal distribution, we use the Bartlett test of
homogeneity of variances to test whether the variances are homogeneous.
Subsequently, we used ANOVA’s Tukey method or Kramer Nemenyi test to
test the differences between groups, as appropriate. The modified
Dixon’s up-and-down method was used for determining the
ED50 of propofol with different doses of esketamine. We
use Dixon method to test either the minimum or maximum value is an
outlier. Using log-logistic dose-response model test was used to test
the differences of EC50 between groups. We defineP value < 0.05 as a significant difference between
groups.