1. Department of Thoracic and Cardiovascular Surgery, University Hospital Tübingen, 72076 Tübingen, Germany
2. Department of Cardiovascular Surgery, University Heart Center Freiburg-Bad Krozingen, 79106 Freiburg, Germany
3. Medical Faculty, Albert-Ludwigs-University Freiburg, 79106 Freiburg, Germany
4. Department of Anesthesiology and Critical Care Medicine, University Hospital Tübingen, 72076 Tübingen, Germany
5. Department of Heart Surgery, Cardiovascular Center, Inselspital, 3010 Bern, Switzerland