Historically, neurocritical care textbooks have favored a more liberal PRBC transfusion strategy, as the brain is very sensitive to decreases in oxygen delivery.
Despite these recommendations, limited studies have failed to show a mortality benefit to PRBC transfusion in critically ill patients with neurologic illness.
Postulated reasons for the lack of morbidity or mortality benefit center around the injured brain's response to attempts to increase oxygen delivery through transfusion.
TBI: PET studies have shown an overall lower level of metabolic activity along with a lower oxygen extraction and loss of autoregulation
SAH: transfusion may increase the risk of vasospasm in SAH and worsen flow
Although the evidence is not overwhelming, current recommendations from SCCM-Eastern Society for the Surgery of Trauma recommend a restrictive PRBC transfusion threshold (Hgb < 7 gm/dL) even in neurocritical care patients.
References
Netzer G, Hess JR, Shanholtz C. Use of blood products in the intensive care unit: Concepts and controversies. Contemporary Critical Care June 2010;8(1):1-12
