1. Department of Anesthesiology, Faculty of Medicine, University of Niš, Niš, Serbia.
2. Clinic for Anesthesiology, Clinical Centre Niš, Niš, Serbia.
3. Department of Pathology, Faculty of Medicine, University of Niš, Niš, Serbia.
4. Department of Biochemistry, Faculty of Medicine, University of Niš, Zorana Ðinđića 81, 18000 Niš, Serbia.