title: Effects of mild hypothermia on blood-brain barrier disruption during isoflurane or pentobarbital anesthesia.
abstract: BACKGROUND
  This study was performed to determine whether mild hypothermia (32 degrees C) could attenuate the degree of blood-brain barrier (BBB) disruption caused by a hyperosmolar solution and whether the degree of disruption would vary depending on anesthetic agents.
  
  
  METHODS
  Rats were assigned to one of four groups: normothermic isoflurane, normothermic pentobarbital, hypothermic isoflurane, and hypothermic pentobarbital. During isoflurane (1.4%; normothermic or hypothermic) or pentobarbital (50 mg/kg administered intraperitoneally; normothermic or hypothermic) anesthesia, the external carotid artery and the femoral artery and vein were catheterized. Body temperature was maintained at 37 and 32 degrees C for the normothermic and hypothermic groups, respectively. To open the BBB, 25% mannitol was infused through the right carotid artery at the rate of 0.25 ml x kg(-1) x s(-1) for 30 s. The transfer coefficient of 14C-alpha-aminoisobutyric acid was determined.
  
  
  RESULTS
  Blood pressure was similar among the four groups of animals. The degree of the BBB disruption by hyperosmolar mannitol was less with isoflurane than pentobarbital anesthesia in the normothermic groups (transfer coefficient: 29.9 +/- 17.1 and 50.4 +/- 17.5 microl x g(-1) x min(-1) for normothermic isoflurane and pentobarbital, respectively; P < 0.05). Mild hypothermia decreased the BBB disruption during anesthesia with both anesthetic agents (hypothermic isoflurane: 9.8 +/- 8.3 microl x g(-1) x min(-1), P < 0.05 vs. normothermic isoflurane; hypothermic pentobarbital: 30.2 +/- 13.9 microl x g(-1) x min(-1), P < 0.05 vs. normothermic pentobarbital), but the disruption was less during isoflurane anesthesia (hypothermic isoflurane vs. hypothermic pentobarbital, P < 0.005). In the contralateral cortex, there were no significant differences among these four experimental groups.
  
  
  CONCLUSIONS
  The data demonstrated that hypothermia was effective in attenuating BBB disruption by hyperosmolar mannitol during isoflurane as well as pentobarbital anesthesia. The degree of disruption appeared smaller during isoflurane than during pentobarbital anesthesia in both the normothermic as well as the hypothermic groups.
authors.affiliation: Department of Anesthesia, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, New Brunswick 08901-1977, USA. chi@umdnj.edu
authors.forename: O Z
authors.initials: OZ
authors.lastname: Chi
authors.forename: X
authors.initials: X
authors.lastname: Liu
authors.forename: H R
authors.initials: HR
authors.lastname: Weiss
mesh_terms: D000465:Algorithms; D000621:Aminoisobutyric Acids / Q000493:pharmacokinetics; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001784:Blood Gas Analysis; D001812:Blood-Brain Barrier / Q000187:drug effects*; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism; D004234:Diuretics, Osmotic / Q000494:pharmacology; D006439:Hemodynamics / Q000187:drug effects; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D007036:Hypothermia, Induced; D007530:Isoflurane / Q000494:pharmacology*; D008353:Mannitol / Q000494:pharmacology; D010424:Pentobarbital / Q000494:pharmacology*; D051381:Rats
chemical_list: D000621:Aminoisobutyric Acids; D018685:Anesthetics, Inhalation; D004234:Diuretics, Osmotic; D006993:Hypnotics and Sedatives; D008353:Mannitol; D007530:Isoflurane; D010424:Pentobarbital