Inclusion criteria:  Enrolment in one of the parent trials (HEMOTION or SAHaRA trials) HEMOTION trial (acute moderate of severe blunt traumatic brain injury (Glasgow Coma Score18 [GCS] ≤ 12)) SAHaRA trial (acute subarachnoid hemorrhage as confirmed by treating neurosurgeon or neuro-interventionist and supported by blood in subarachnoid space resulting from a ruptured aneurysm) Adult patients (age ≥18 years old) Patients suffering from anemia (Hb ≤100 g/L)  Exclusion criteria:  Contraindications or known objections to blood transfusions Active bleeding with hemodynamic instability at the time of enrollment Decision to withdraw or withhold life-sustaining therapies made NIRS monitoring not reliable