Sample size calculation
Using a 5% significance level, a sample size of 64 for each group was calculated to ensure a power of 90% and to detect a difference of 1 day in postoperative LOS between the two groups. Taking a 20% drop-out rate into account, we ultimately determined 72 cases per arm of our study. Intention-to-treat analysis was conducted for all of the included patients after randomization. The per-protocol analysis was also performed.
Statistical analysis
Quantitative data were described as means ± 1 standard deviation or as medians and interquartile ranges (IQR), where appropriate. Normally distributed quantitative data were analyzed using the Student’s t -test; otherwise we used a Mann–Whitney U test. We presented qualitative data as numbers (percentages) and analyzed them by χ2 test or Fisher’s exact-probability test. Multivariate logistic regression analysis was used to assess the effect of the full ERAS-program elements both on primary and secondary outcomes. A two-sided P value < .05 was considered to be statistically significant. All of the analyses were performed using SPSS for Windows version 16.0 (SPSS Inc., Chicago, IL, USA).