Aneurysmal Subarachnoid Hemorrhage: Red Blood Cell Transfusion and Outcome

Inclusion Criteria: 1. Age ≥18 years old at time of presentation 2. First ever episode aneurysmal SAH 3. Confirmed aneurysmal SAH diagnosis: as confirmed by treating Neurosurgeon or Neuro-interventionalist and supported by blood in subarachnoid space (demonstrated on cranial imaging or cerebrospinal fluid positive for xanthochromia) that is the result of a ruptured saccular aneurysm (confirmed by cranial imaging - cranial topography or magnetic resonance imaging angiography or catheter angiogram) 4. Incident hemoglobin ≤100g/L within 14 days following SAH (defined by first day of hospital presentation) Exclusion Criteria: 1. Physician and or family decision to withdraw/withhold critical care at time of enrolment 2. Active bleeding with hemodynamic instability at time of enrolment 3. Patients with contra-indication or known objection to blood transfusions 4. SAH due to causes other than saccular aneurysm rupture including mycotic, traumatic and dissecting aneurysms, and aneurysms associated with arteriovenous malformations.