title: Computational modeling of HHH therapy and impact of blood pressure and hematocrit.
abstract: BACKGROUND
  After an aneurysmal subarachnoid hemorrhage, cerebral microcirculatory changes occur as a result cerebral vasospasm. The objective of this study is to investigate, with a computational model, how various degrees of vasospasm are influenced by increasing the mean blood pressure and decreasing the blood viscosity.
  
  
  METHODS
  Using ANSYS CFX software, a computational model was constructed to simulate steady-state fully developed laminar blood flow through a rigid wall system consisting of the internal carotid artery (ICA), anterior cerebral artery, posterior cerebral artery, and middle cerebral artery (MCA). The MCA was selected for the site of a single acute vasospasm. Five severities of vasospasm were studied: 3 mm (normal), 2.5, 2, 1.5, and 1 mm. The ICA was assumed to have a constant inlet flow rate of 315 mL/min. The anterior cerebral artery and posterior cerebral artery were assumed to have constant outlet flow rates of 105 mL/min and 30 mL/min, respectively. The MCA was assumed to have a constant outlet pressure of 92 mL/min. Two different hematocrits, 45% and 32%, were simulated using the models.
  
  
  RESULTS
  For a hematocrit of 45, the mean ICA inlet pressure required to pump blood through the system was 104 mm Hg for the 3-mm diameter MCA and 105, 108, 116, and 158 mm Hg for vasospasm diameters of 2.5, 2, 1.5, and 1 mm, respectively. For a hematocrit of 32, the mean ICA inlet pressure required was 102, 103, 105, 113, and 152 mm Hg, respectively.
  
  
  CONCLUSIONS
  The MCA required a large increase in mean ICA inlet pressure for vasospasm diameters less than 1.5 mm, which suggests that for vasospasms more than 50% diameter reduction, the blood pressure must be increased dramatically. Decreasing the hematocrit had minimal impact on blood flow in a constricted vessel.
authors.affiliation: Medical Center of Central Georgia, Macon, Georgia, USA. mydoctoronline@gmail.com
authors.forename: Joe Sam
authors.initials: JS
authors.lastname: Robinson
authors.forename: M Sami
authors.initials: MS
authors.lastname: Walid
authors.forename: Sinjae
authors.initials: S
authors.lastname: Hyun
authors.forename: Robert
authors.initials: R
authors.lastname: O'Connell
authors.forename: Chris
authors.initials: C
authors.lastname: Menard
authors.forename: Brandi
authors.initials: B
authors.lastname: Bohleber
mesh_terms: D001794:Blood Pressure / Q000502:physiology*; D001809:Blood Viscosity; D002343:Carotid Artery, Internal / Q000473:pathology; D002560:Cerebrovascular Circulation; D003198:Computer Simulation; D005440:Fluid Therapy; D006400:Hematocrit; D006438:Hemodilution; D006801:Humans; D006973:Hypertension; D020768:Middle Cerebral Artery / Q000473:pathology; D008962:Models, Theoretical; D013345:Subarachnoid Hemorrhage / Q000097:blood / Q000150:complications / Q000628:therapy*; D020301:Vasospasm, Intracranial / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*