1. 4th Department of Surgery, Attikon University Hospital, National and Kapodistrian University of Athens, 12462 Athens, Greece
2. Medical School, National and Kapodistrian University of Athens, Athens 11527, Greece
3. Department of Hygiene, Epidemiology and Medical Statistics, Medical School, National and Kapodistrian University of Athens, Athens 11527, Greece
4. 3rd Department of Surgery, Attikon University Hospital, National and Kapodistrian University of Athens, Athens 12462, Greece
5. 2nd Department of Anesthesiology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens 12462, Greece