title: Effect of mannitol on cerebral blood volume in patients with head injury.
abstract: BACKGROUND
  Mannitol has traditionally been the mainstay of medical therapy for intracranial hypertension in patients with head injury. We previously demonstrated that mannitol reduces brain volume in patients with cerebral edema, although whether this occurs because of a reduction in brain water, blood volume, or both remains poorly understood.
  
  
  OBJECTIVE
  To test the hypothesis that mannitol acts by lowering blood viscosity leading to reflex vasoconstriction and a fall in cerebral blood volume (CBV).
  
  
  METHODS
  We used O positron emission tomography to study 6 patients with traumatic brain injuries requiring treatment for intracranial hypertension. Cerebral blood flow (CBF), CBV, and cerebral metabolic rate for oxygen (CMRO2) were measured before and 1 hour after administration of 1.0 g/kg 20% mannitol.
  
  
  RESULTS
  CBV rose from 4.1 ± 0.4 to 4.2 ± 0.2 mL/100 g (P = .3), while intracranial pressure fell from 21.5 ± 4.9 to 13.7 ± 5.1 mm Hg (P < .003) after mannitol. Blood pressure, PaCO2, oxygen content, CBF, and CMRO2 did not change.
  
  
  CONCLUSIONS
  A single bolus of 1 g/kg of 20% mannitol does not acutely lower CBV. Another mechanism, such as a reduction in brain water, may better explain mannitol's ability to lower intracranial pressure and reduce mass effect.
authors.affiliation: Department of Neurology, Neurology/Neurosurgery Intensive Care Unit, Washington University School of Medicine, St. Louis, Missouri 63110, USA. diringerm@wustl.edu
authors.forename: Michael N
authors.initials: MN
authors.lastname: Diringer
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: Rajat
authors.initials: R
authors.lastname: Dhar
authors.forename: William J
authors.initials: WJ
authors.lastname: Powers
mesh_terms: D000328:Adult; D001809:Blood Viscosity / Q000187:drug effects; D001810:Blood Volume / Q000187:drug effects*; D006259:Craniocerebral Trauma / Q000150:complications / Q000188:drug therapy* / Q000503:physiopathology*; D004234:Diuretics, Osmotic / Q000008:administration & dosage; D006801:Humans; D019586:Intracranial Hypertension / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D008353:Mannitol / Q000008:administration & dosage*; D016896:Treatment Outcome; D014661:Vasoconstriction / Q000187:drug effects
chemical_list: D004234:Diuretics, Osmotic; D008353:Mannitol
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