1. Outcomes Research Department, Anesthesiology Institute, Cleveland Clinic Ohio, USA
2. Department of Orthopaedic and Trauma Surgery, Hospital Interzonal General de Agudos Eva Perón, San Martín, Buenos Aires, Argentina
3. Department of Orthopaedic Surgery, Cleveland Clinic, Cleveland, Ohio, USA
4. Department of Anesthesiology, Cleveland Clinic, Cleveland, Ohio, USA