1 Department of Cardiovascular Surgery, University Medical Center Freiburg, Faculty of Medicine Freiburg, Germany.
2 Department of Anaesthesiology, Surgical Intensive Care, Emergency Medicine and Pain Therapy, Klinikum Frankfurt Hoechst, Germany; Academic Teaching Hospital of the University of Frankfurt, Germany.
3 FOM University of Economy & Management, Department of Health & Social, Franklinstr. 52, Frankfurt Campus, D-60486 Frankfurt am Main, Germany.