Statistical analysis
INTRAOPERATIVE BLEEDING
Categorical variables are reported as the number (proportion) of patients, normally distributed data are presented as the mean and standard deviation (SD), and nonnormally distributed data are presented as the median (IQR [range]). The Kolmogorov–Smirnov test was used to assess the normality of the distribution. For baseline characteristics between groups, the standardized mean difference(SMD) with 95% confidence intervals (95% CIs) was calculated. Two-tailed unpaired Student’s t test was conducted to compare continuous variables between two groups. The Mann–Whitney U test was conducted to assess the differences between groups for nonnormally distributed data (age, BMI, ventilation duration, intraoperative fluid input, intraoperative bleeding and intraoperative urine). The chi-square test or Fisher’s exact test was used to compare two or more proportions (PPC with 3 days). Two-way ANOVA was conducted to evaluate the effects of group, time, and the interaction on GI, LUSs, respiratory mechanics, PaO