Statistical analysis
POCD
In a preliminary study, we found that the rate of POCD was 48% in the control group and 26% under intravenous lidocaine. The required sample size for each group was 73 when the significance was set at 0.05, and the power was set at 90%. Considering a 10% loss of follow-up rate, we ended up including 80 patients in each group, for a total of 160 patients in both groups. All data were statistically analysed using SPSS 23.0. The numerical variables were evaluated by the Shapiro‒Wilk normal test and analysed by Student’s t test when the distribution was normal; otherwise, the Wilcoxon-Mann‒Whitney U test was used. The classification variables were analysed by the chi-squared test for independence or Fisher’s exact test. Between-group differences were adjusted using Bonferroni correction. 