title: Normobaric hyperoxia reduces MRI diffusion abnormalities and infarct size in experimental stroke.
abstract: BACKGROUND
  Hyperbaric oxygen therapy is considered an important stroke treatment strategy.
  
  
  BACKGROUND
  To determine whether normobaric oxygen is neuroprotective, and, if so, what the therapeutic time window is.
  
  
  METHODS
  Experiment 1-Serial diffusion- and perfusion-weighted MRI (DWI and PWI) was performed after middle cerebral artery filament occlusion (MCAO) in rats randomized to FiO(2) 30% (normoxia) or FiO(2) 100% (hyperoxia). Experiment 2-48-hour lesion volumes were analyzed in rats subjected to 2-hour MCAO and randomized to normoxia or hyperoxia starting 15, 30, or 45 minutes after MCAO and ending 15 minutes after reperfusion.
  
  
  RESULTS
  Experiment 1-Lesion apparent diffusion coefficient (ADC) values were persistently low in normoxic animals. In hyperoxia-treated rats, ADC values in cortical border zones showed progressive recovery from 66 +/- 3% of contralateral before hyperoxia, to 104 +/- 20% at approximately 2 hours. Striatal ADC values showed early but ill-sustained improvement. ADC lesion volumes increased progressively in the normoxia group. In the hyperoxia group, ADC lesion volumes tended to decrease after starting hyperoxia; however, lesions later increased in size, and 2-hour lesion volumes were not significantly different from baseline. PWI showed stable right MCA hypoperfusion in all animals. Experiment 2-Hyperoxia within 30 minutes significantly reduced total and cortical lesion volumes at 48 hours after stroke. Striatal lesion volumes were significantly reduced in the hyperoxia-15 group.
  
  
  CONCLUSIONS
  In rats subjected to transient stroke, 100% oxygen administered within 30 minutes salvages ischemic brain tissue, especially in the cerebral cortex. Reducing the time to treatment enhances the degree of neuroprotection.
authors.affiliation: Neuroprotection Research Laboratory, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA. asinghal@partners.org
authors.forename: Aneesh B
authors.initials: AB
authors.lastname: Singhal
authors.forename: Rick M
authors.initials: RM
authors.lastname: Dijkhuizen
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Rosen
authors.forename: Eng H
authors.initials: EH
authors.lastname: Lo
mesh_terms: D000818:Animals; D002545:Brain Ischemia / Q000473:pathology / Q000503:physiopathology / Q000628:therapy*; D002540:Cerebral Cortex / Q000098:blood supply / Q000473:pathology / Q000503:physiopathology; D003342:Corpus Striatum / Q000098:blood supply / Q000473:pathology / Q000503:physiopathology; D018496:Hyperoxia / Q000473:pathology*; D020244:Infarction, Middle Cerebral Artery / Q000473:pathology / Q000503:physiopathology / Q000628:therapy*; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data; D008297:Male; D010102:Oxygen Inhalation Therapy / Q000379:methods / Q000706:statistics & numerical data; D051381:Rats; D017207:Rats, Sprague-Dawley