The purpose of this study is to investigate the frequency and grade of gastrointestinal dysfunction in patients after thoracic cardiovascular surgery, and to search for biomarkers of gastrointestinal dysfunction. All adult patients undergoing elective cardiac surgery requiring cardiopulmonary bypass at Örebro University Hospital, Örebro, Sweden, are asked for participation in this study. All participating patients sign informed consent at the inclusion. The first three postoperative days the function of the gastrointestinal tract is scored according to a rating scale (grade 0-4), along with other clinical parameters. Plasma blood samples are collected from each patient preoperatively and the first three postoperative days. The plasma samples are stored in a biobank for later determination of plasma proteins. In the analysis, the patients are divided according to the gastrointestinal rating scale and the plasma protein expression, gastrointestinal complications and all-cause mortality are compared between the groups.