RBC Transfusion Improves Cerebral Oxygen Delivery in Subarachnoid Hemorrhage.
OBJECTIVE
Impaired oxygen delivery due to reduced cerebral blood flow is the hallmark of delayed cerebral ischemia following subarachnoid hemorrhage. Since anemia reduces arterial oxygen content, it further threatens oxygen delivery increasing the risk of cerebral infarction. Thus, subarachnoid hemorrhage may constitute an important exception to current restrictive transfusion practices, wherein raising hemoglobin could reduce the risk of ischemia in a critically hypoperfused organ. In this physiologic proof-of-principle study, we determined whether transfusion could augment cerebral oxygen delivery, particularly in vulnerable brain regions, across a broad range of hemoglobin values.


METHODS
Prospective study measuring cerebral blood flow and oxygen extraction fraction using O-PET. Vulnerable brain regions were defined as those with baseline oxygen delivery less than 4.5 mL/100 g/min.


METHODS
PET facility located within the Neurology/Neurosurgery ICU.


METHODS
Fifty-two patients at risk for delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage with hemoglobin 7-13 g/dL.


METHODS
Transfusion of one unit of RBCs over 1 hour.


RESULTS
Baseline hemoglobin was 9.7 g/dL (range, 6.9-12.9), and cerebral blood flow was 43 ± 11 mL/100 g/min. After transfusion, hemoglobin rose from 9.6 ± 1.4 to 10.8 ± 1.4 g/dL (12%; p < 0.001) and oxygen delivery from 5.0 (interquartile range, 4.4-6.6) to 5.5 mL/100 g/min (interquartile range, 4.8-7.0) (10%; p = 0.001); the response was comparable across the range of hemoglobin values. In vulnerable brain regions, transfusion resulted in a greater (16%) rise in oxygen delivery associated with reduction in oxygen extraction fraction, independent of Hgb level (p = 0.002 vs normal regions).


CONCLUSIONS
This study demonstrates that RBC transfusion improves cerebral oxygen delivery globally and particularly to vulnerable regions in subarachnoid hemorrhage patients at risk for delayed cerebral ischemia across a wide range of hemoglobin values and suggests that restrictive transfusion practices may not be appropriate in this population. Large prospective trials are necessary to determine if these physiologic benefits translate into clinical improvement and outweigh the risk of transfusion.
1Department of Neurology, Washington University School of Medicine, St. Louis, MO.2Department of Radiology, Washington University School of Medicine, St. Louis, MO.3Department of Neurosurgery, Washington University School of Medicine, St. Louis, MO.
Rajat
R
Dhar
Allyson R
AR
Zazulia
Colin P
CP
Derdeyn
Michael N
MN
Diringer
D000368:Aged; D002544:Cerebral Infarction / Q000097:blood / Q000209:etiology / Q000517:prevention & control*; D002560:Cerebrovascular Circulation; D017707:Erythrocyte Transfusion; D005260:Female; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D049268:Positron-Emission Tomography; D011446:Prospective Studies; D013345:Subarachnoid Hemorrhage / Q000150:complications / Q000503:physiopathology* / Q000628:therapy*
D006454:Hemoglobins; D010100:Oxygen