*2.6. Statistics*

Baseline characteristics were analyzed using of Wilcoxon Rank Sum test for continuous variables and Fisher's exact test for binary variables. Associations between *MIF* polymorphisms and outcome parameters were analyzed using univariate logistic regression and results are presented together with odds ratios and 95% confidence intervals.

Multivariable logistic regression analysis was performed to analyze the influence of relevant baseline variables. Model selection was based on the postoperative complication (dependent variable) and the genotype (independent variable). Further variables were selected on the basis of univariate analyses and significant di fferences. Model selection was accomplished by a backward elimination or a stepwise procedure.

Serum MIF levels at individual time points were compared usingWilcoxon Rank Sum test according to the *MIF* genotype. Analyses were calculated with SAS 9.4 (SAS Institute Inc., Cary, NC, USA) and SPSS (IBM SPSS, version 21.0, Armonk, NY, USA). All *p*-Values refer to two-sided tests, and *p* < 0.05 was considered statistically significant.

#### *2.7. Study Approval*

Each patient provided written informed consent prior to inclusion in the study.
