Dual effect of HBO on cerebral infarction in MCAO rats

Various reports in the literature have shown that hyperbaric oxygen (HBO) r educes cerebral infarction both in animals and humans. After the initial is chemic insult, however, initiating HBO treatment at different intervals has yielded conflicting results. The present study was undertaken to determine the optimal therapeutic window in which to start HBO treatment for cerebra l infarction after transient focal ischemia. In this study, the operator oc cluded the middle cerebral artery (MCA) of anesthetized rats by introducing a blunted nylon filament into the proximal MCA from the dissected external carotid artery. When the operator removed the filament after 2 h, focal is chemia and reperfusion occurred. The operator then placed the rat in the HB O chamber and administered 3 atm absolute HBO for 1 h according to the prot ocol. The rat was killed 24 h after reperfusion, and the percentage of infa rction (infarct ratio) was calculated by dividing the infarction area by th e total area of the ipsilateral hemisphere. The results showed that the per centage of infarcted area decreased significantly (P< 0.05) both in the 3- (7.59%) and 6-h (5.35%) HBO-treatment groups compared with the control (no treatment) group (11.34%). However, the percentage of infarcted area increa sed significantly (P< 0.01 and P< 0.05, respectively) both in the 12- (23%) and 23-h (20%) treatment groups. The results of this study suggest that ap plying HBO within 6 h of ischemia-reperfusion injury could benefit the pati ent but that applying HBO 12 h or more after injury could harm the patient.