1. Patient Blood Management Research Group, Hospital La Paz Institute for Health Research, 28040 Madrid, Spain
2. Department of Statistics, Charles III University of Madrid, 28903 Getafe, Spain
3. Department of Public Health & Maternal and Child Health, Faculty of Medicine, Complutense University of Madrid, 28040 Madrid, Spain
4. Intensive Care Unit, Hospital Germans Trias i Pujol, 08916 Badalona, Spain
5. Intensive Care Unit, La Paz University Hospital, 28040 Madrid, Spain
6. Intensive Care Unit, Clinic University Hospital of Valencia, 46010 Valencia, Spain
7. Intensive Care Unit, University Hospital of Guadalajara, 19002 Guadalajara, Spain