Statistical analysis
The predefined primary endpoint was the cerebral oxygenation during laparoscopic hepatectomy under LCVP achieved by anesthetic intervention. In a previous study of patients undergoing major surgery, the mean (standard deviation [SD]) percentage change in rSOIBM SPSS statistical software, version 20 (IBM, Chicago, IL, US) was used for the statistical analysis. The distribution normality of continuous variables was measured using the Shapiro–Wilk test. Normally distributed continuous data were compared using the Student’s t-test, while non-normally distributed continuous data were compared using the Mann–Whitney U test. Continuous data are presented as the mean (SD) or median (interquartile range). The repeated-measures analysis of variance was used for within-group comparisons of the different time points. Categorical data were compared using the chi square test and are presented as number (percentage). A 