title: Effect of osmotic agents on regional cerebral blood flow in traumatic brain injury.
abstract: OBJECTIVE
  Cerebral blood flow (CBF) is reduced after severe traumatic brain injury (TBI) with considerable regional variation. Osmotic agents are used to reduce elevated intracranial pressure (ICP), improve cerebral perfusion pressure, and presumably improve CBF. Yet, osmotic agents have other physiologic effects that can influence CBF. We sought to determine the regional effect of osmotic agents on CBF when administered to treat intracranial hypertension.
  
  
  METHODS
  In 8 patients with acute TBI, we measured regional CBF with positron emission tomography before and 1 hour after administration of equi-osmolar 20% mannitol (1 g/kg) or 23.4% hypertonic saline (0.686 mL/kg) in regions with focal injury and baseline hypoperfusion (CBF <25 mL per 100 g/min).
  
  
  RESULTS
  The ICP fell (22.4 ± 5.1 to 15.7 ± 7.2 mm Hg, P = .007), and cerebral perfusion pressure rose (75.7 ± 5.9 to 81.9 ± 10.3 mm Hg, P = .03). Global CBF tended to rise (30.9 ± 3.7 to 33.1 ± 4.2 mL per 100 g/min, P = .07). In regions with focal injury, baseline flow was 25.7 ± 9.1 mL per 100 g/min and was unchanged; in hypoperfused regions (15% of regions), flow rose from 18.6 ± 5.0 to 22.4 ± 6.4 mL per 100 g/min (P < .001). Osmotic therapy reduced the number of hypoperfused brain regions by 40% (P < .001).
  
  
  CONCLUSIONS
  Osmotic agents, in addition to lowering ICP, improve CBF to hypoperfused brain regions in patients with intracranial hypertension after TBI.
authors.affiliation: Department of Neurology, Washington University School of Medicine, St Louis, MO 63110, USA.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Scalfani
authors.forename: Rajat
authors.initials: R
authors.lastname: Dhar
authors.forename: Allyson R
authors.initials: AR
authors.lastname: Zazulia
authors.forename: Tom O
authors.initials: TO
authors.lastname: Videen
authors.forename: Michael N
authors.initials: MN
authors.lastname: Diringer
mesh_terms: D000328:Adult; D001930:Brain Injuries / Q000188:drug therapy*; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D004234:Diuretics, Osmotic / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007427:Intracranial Pressure / Q000187:drug effects*; D008297:Male; D008353:Mannitol / Q000627:therapeutic use*; D008875:Middle Aged; D049268:Positron-Emission Tomography; D012462:Saline Solution, Hypertonic / Q000627:therapeutic use*
chemical_list: D004234:Diuretics, Osmotic; D012462:Saline Solution, Hypertonic; D008353:Mannitol