1. Staff Anesthesiologist, University of Santiago de Compostela. Department of Anesthesiology, Hospital Clínico Universitario de Santiago, Santiago de Compostela, Spain.
2. Professor of Anesthesiology.
3. Associate Professor of Anesthesiology, University of Santiago de Compostela, Department of Anesthesiology, Hospital Clínico Universitario de Santiago, Spain.
4. Staff of Clinical Epidemiology Unit, Hospital Clínico Universitario de Santiago, Santiago de Compostela, Spain.
5. Associate Professor of Anesthesiology, Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut.