Delayed cerebral ischemia after subarachnoid hemorrhage (SAH) may be affected by a number of factors, including cerebral blood flow and oxygen delivery. Anemia affects about half of patients with SAH and is associated with worse outcome. Anemia also may contribute to the development of or exacerbate delayed cerebral ischemia. This review was designed to examine the prevalence and impact of
anemia in patients with SAH and to evaluate the effects of transfusion. A literature search was made to identify original research on anemia and transfusion in SAH patients. A total of 27 articles were identified that addressed the effects of red blood cell transfusion (RBCT) on brain physiology, anemia in SAH, and clinical management with RBCT or erythropoietin. Most studies provided retrospectively analyzed data of very low-quality according to the GRADE criteria. While RBCT can have beneficial effects on brain physiology, RBCT may be associated with medical complications, infection, vasospasm, and poor outcome after SAH. The effects may vary with disease severity or the presence of vasospasm, but it remains unclear whether RBCTs are a marker of disease severity or a cause of worse outcome. Erythropoietin data are limited. The literature review further suggests that the results of the Transfusion Requirements in Critical Care Trial and subsequent observational studies on RBCT in general critical care do not apply to SAH patients and that randomized trials to address the role of RBCT in SAH are required.