title: Comparison of induced hypertension, fluid bolus, and blood transfusion to augment cerebral oxygen delivery after subarachnoid hemorrhage.
abstract: OBJECTIVE
  Critical reductions in oxygen delivery (DO(2)) underlie the development of delayed cerebral ischemia (DCI) after subarachnoid hemorrhage (SAH). If DO(2) is not promptly restored, then irreversible injury (that is, cerebral infarction) may result. Hemodynamic therapies for DCI (that is, induced hypertension [IH] and hypervolemia) aim to improve DO(2) by raising cerebral blood flow (CBF). Red blood cell (RBC) transfusion may be an alternate strategy that augments DO(2) by improving arterial O(2) content. The authors compared the relative ability of these 3 interventions to improve cerebral DO(2), specifically their ability to restore DO(2) to regions where it is impaired.
  
  
  METHODS
  The authors compared 3 prospective physiological studies in which PET imaging was used to measure global and regional CBF and DO(2) before and after the following treatments: 1) fluid bolus of 15 ml/kg normal saline (9 patients); 2) raising mean arterial pressure 25% (12 patients); and 3) transfusing 1 U of RBCs (17 patients) in 38 individuals with aneurysmal SAH at risk for DCI. Response between groups in regions with low DO(2) (< 4.5 ml/100 g/min) was compared using repeated-measures ANOVA.
  
  
  RESULTS
  Groups were similar except that the fluid bolus cohort had more patients with symptoms of DCI and lower baseline CBF. Global CBF or DO(2) did not rise significantly after any of the interventions, except after transfusion in patients with hemoglobin levels < 9 g/dl. All 3 treatments improved CBF and DO(2) to regions with impaired baseline DO(2), with a greater improvement after transfusion (23%) than hypertension (14%) or volume loading (10%); p < 0.001. Transfusion also resulted in a nonsignificantly greater (47%) reduction in the number of brain regions with low DO(2) when compared with fluid bolus (7%) and hypertension (12%) (p = 0.33).
  
  
  CONCLUSIONS
  The IH, fluid bolus, and blood transfusion interventions all improve DO(2) to vulnerable brain regions at risk for ischemia after SAH. Transfusion appeared to provide a physiological benefit at least comparable to IH, especially among patients with anemia, but transfusion is associated with risks. The clinical significance of these findings remains to be established in controlled clinical trials.
authors.affiliation: Department of Neurology, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8111, St. Louis, Missouri 63110, USA. dharr@neuro.wustl.edu
authors.forename: Rajat
authors.initials: R
authors.lastname: Dhar
authors.forename: Michael T
authors.initials: MT
authors.lastname: Scalfani
authors.forename: Allyson R
authors.initials: AR
authors.lastname: Zazulia
authors.forename: Tom O
authors.initials: TO
authors.lastname: Videen
authors.forename: Colin P
authors.initials: CP
authors.lastname: Derdeyn
authors.forename: Michael N
authors.initials: MN
authors.lastname: Diringer
mesh_terms: D000368:Aged; D002545:Brain Ischemia / Q000150:complications / Q000209:etiology; D002544:Cerebral Infarction / Q000209:etiology / Q000517:prevention & control*; D002560:Cerebrovascular Circulation / Q000502:physiology; D015331:Cohort Studies; D017707:Erythrocyte Transfusion / Q000009:adverse effects / Q000379:methods*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000139:chemically induced*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D049268:Positron-Emission Tomography; D011446:Prospective Studies; D012965:Sodium Chloride / Q000008:administration & dosage*; D013345:Subarachnoid Hemorrhage / Q000150:complications* / Q000503:physiopathology
chemical_list: D012965:Sodium Chloride; D010100:Oxygen
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