Gordana Kristek1, Ivan Radoš1, Dalibor Kristek2, Leonardo Kapural3, Nenad Nešković1, Sonja Škiljić1, Vesna Horvat4, Sanja Mandić5, Ivana Haršanji-Drenjančević1. 1. Department of Anaesthesiology, Josip Juraj Strossmayer University of Osijek, University Hospital Osijek, Reanimatology and Intensive Care, Osijek, Croatia. 2. Department of Surgery, Josip Juraj Strossmayer University of Osijek, University Hospital Osijek, Osijek, Croatia. 3. Carolinas Pain Institute, Winston-Salem, North Carolina, USA lkapuralmd@gmail.com. 4. Carolinas Pain Institute, Winston-Salem, North Carolina, USA. 5. Department of Clinical Laboratory Diagnostics, Josip Juraj Strossmayer University of Osijek, University Hospital Osijek, Osijek, Croatia.