The overall hypothesis for this programme of work is that liberal use of RBCs to correct anaemia (HB transfusion trigger ≤90g/L; target Hb range 91-110 g/L) improves clinical outcomes compared with a restrictive transfusion trigger (Hb transfusion trigger ≤70g/L; target Hb range 71-90 g/L) in anaemic critically ill patients requiring prolonged ICU stay (≥4 days).