Ilker Ince1, Alper Kilicaslan2, Esra Kutlu3, Ali Aydin4. 1. Department of Anesthesiology and Reanimation, School of Medicine, Ataturk University, Erzurum, Turkey; Anesthesiology Clinical Research Office, Ataturk University, Erzurum, Turkey; Outcomes Research Consortium, Cleveland Clinic, OH, USA. Electronic address: ilkerince1983@yahoo.com. 2. Department of Anesthesiology and Reanimation, School of Meram Medicine, Necmettin Erbakan University, Konya, Turkey. 3. Outcomes Research Consortium, Cleveland Clinic, OH, USA. 4. Department of Orthopedics and Traumatology, School of Medicine, Ataturk University, Erzurum, Turkey.