title: The effects of sustained hyperventilation on regional cerebral blood volume in thiopental-anesthetized rats.
abstract: Sustained hyperventilation has a time-limited effect on cerebrovascular dynamics. We investigated whether this effect was similar among brain regions by measuring regional cerebral blood volume (CBV) with steady-state susceptibility contrast magnetic resonance imaging during 3 h of hyperventilation. Regional CBV was determined in nine thiopental-anesthetized, mechanically-ventilated rats every 30 min in the dorsoparietal neocortex, the corpus striatum, and the cerebellum. The corpus striatum was the only brain region showing a stable reduction in CBV during the hypocapnic episode (PaCO(2), 24 +/- 3 mm Hg). In contrast, neocortex and, to a lesser extent, cerebellum exhibited a progressive return toward normal values despite continued hypocapnia. No evidence of a rebound in CBV was found on return to normal ventilation in the three brain regions. We conclude that sustained hyperventilation can lead to an uneven change in the reduction of CBV, possibly because of differences of brain vessels in their sensitivity to extracellular pH. Our results in neocortex confirm the transient effect of sustained hyperventilation on cerebral hemodynamics.
  
  
  CONCLUSIONS
  Sustained hyperventilation has a transient effect in decreasing cerebral blood volume (CBV). Using susceptibility contrast magnetic resonance imaging in thiopental-anesthetized rats, we found differences between brain regions in their transient CBV response to sustained hyperventilation.
authors.affiliation: Department of Anesthesiology, The University of Grenoble School of Medicine, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Broux
authors.forename: Irène
authors.initials: I
authors.lastname: Tropres
authors.forename: Olivier
authors.initials: O
authors.lastname: Montigon
authors.forename: Cécile
authors.initials: C
authors.lastname: Julien
authors.forename: Michel
authors.initials: M
authors.lastname: Decorps
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Payen
mesh_terms: D000758:Anesthesia; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D000818:Animals; D001810:Blood Volume; D002560:Cerebrovascular Circulation; D003287:Contrast Media / Q000493:pharmacokinetics; D005260:Female; D006863:Hydrogen-Ion Concentration; D006985:Hyperventilation / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013874:Thiopental / Q000494:pharmacology*
chemical_list: D018686:Anesthetics, Intravenous; D003287:Contrast Media; D013874:Thiopental