GSTM1 and anemia (phenotype): Our primary research question is to determine whether a “liberal” strategy of maintaining Hb concentrations at 9 g/dL or higher would result in a different neurological outcome when compared to a “restrictive” approach to RBC transfusion maintaining Hb concentrations at 7 g/dL or higher in critically ill patients with anemia (Hb ≤ 9 g/dL) and acute brain injury.