1. Department of Anaesthesia and Critical Care, Infanta Leonor University Hospital, Madrid, Spain
2. Universidad Complutense de Madrid, Madrid, Spain
3. Spanish Perioperative Audit and Research Network, Zaragoza, Spain
4. Grupo Español de Rehabilitación Multimodal. Enhanced Recovery After Surgery Spain Chapter, Zaragoza, Spain
5. Department of General Surgery, Lozano Blesa University Hospital, Zaragoza, Spain
6. Department of Anaesthesia and Perioperative Medicine. Lozano Blesa University Hospital, Zaragoza, Spain
7. Department of Anaesthesia and Perioperative Medicine, Río Hortega University Hospital, Valladolid, Spain
8. Department of Anaesthesia and Perioperative Medicine, Alava University Hospital, Alava, Spain
9. Blood and Tissue Bank of Navarra, Servicio Navarro de Salud-Osasunbidea, Pamplona, Navarra, Spain
10. Anemia Working Group Spain, Barcelona, Spain
11. Department of Anaesthesia and Critical Care, Vall d´Hebrón University Hospital, Barcelona, Spain
12. Department of Anaesthesia and Perioperative Medicine, Hospital Clínic Universitat de Barcelona, Barcelona, Spain
13. Department of Anaesthesia and Critical Care, La Paz University Hospital, Madrid, Spain
14. Department of Anaesthesia and Critical Care, Hospital Universitario Central de Asturias, Oviedo, Spain
15. Department of Anaesthesia and Perioperative Medicine, Hospital de Sant Joan Despí Moisès Broggi, Consorci Sanitari Integral, Barcelona, Spain
16. Department of Anaesthesia and Critical Care, Complejo Asistencial Universitario de Salamanca, Salamanca, Spain