1. Department of Anesthesiology; Hospital Universitari de Bellvitge; University of Barcelona Health Campus; Idibell; Barcelona Spain
2. Department of Anesthesiology; Hospital Universitario de Cruces; Bilbao Spain
3. Department of Anesthesiology; Hospital Clinic Universitari; University of Barcelona Health Campus; Idibaps; Barcelona Spain
4. Department of Anesthesiology; Hospital Universitario Virgen del Rocio; Sevilla Spain
5. Department of Anesthesiology; Hospital Universitario Virgen de la Arrixaca; Murcia Spain
6. Medical Statistics Core Facility; IDIBAPS; Hospital Clinic Barcelona; Spain. Biostatistics Unit; Faculty of Medicine; Universitat Autònoma de Barcelona; Barcelona Spain