Effects of Normobaric Hyperoxia in a Rat Model of Transient Focal Cerebral Ischemia and Reperfusion

Abstract

3 Background: The role of therapeutic oxygen in treatment of acute stroke is controversial. Oxygen improves cellular aerobic metabolism and can salvage ischemic tissue. However, oxygen free radicals can increase blood brain barrier (BBB) damage, and oxygen can induce vasoconstriction, which could worsen stroke outcome. We studied the effects of normobaric oxygen in cerebral ischemia and reperfusion. Methods: Rats were subjected to normobaric hyperoxia (FiO2 100%) or normoxia (FiO2 30%) during two hour filament occlusion and one hour reperfusion of the middle cerebral artery. Twenty-four hour infarct volumes, regional cerebral blood flow (rCBF) using laser Doppler flowmetry, and severity of BBB damage (assessed by quantifying Evan’s Blue dye (EB) leakage after one hour of reperfusion) were compared between groups. Results: Physiological parameters were similar in hyperoxic and control groups, except for paO2, which was expectedly higher in the hyperoxic group (pO2 484 mm Hg) as compared to controls (pO2 118 mm Hg). Mean rCBF dropped to 25% after onset of ischemia and recovered to 75–90% after arterial unocclusion, indicating successful reperfusion. Mean total (right hemispheric) infarct volume was 65 mm 3 in the hyperoxia group and 209 mm 3 in controls, p 3 in hyperoxic rats and 129 mm 3 in controls (p 3 in hyperoxic rats and 80 mm 3 in controls (p Conclusion: Total and cortical infarct volumes can be significantly reduced with normobaric hyperoxia during transient cerebral ischemia and reperfusion. Hyperoxia does not decrease blood flow to ischemic brain, and its benefit in reducing infarct volume may outweigh any potential damage from BBB damage.