Focal perfusion of circulating cooled blood reduces the infarction volume and improves neurological outcome in middle cerebral artery occlusion

Objective: The neuroprotective effect of hypothermia has been well established. The use of hypothermia for the treatment of stroke by systemic hypothermia is limited by the cooling rate and has severe complications. The goal of this study was to determine if local cerebral cooling via infusion could reduce infarction volume and improve the neurological outcome in a rat model of middle cerebral artery (MCA) occlusion. Methods: A hollow filament was used to block the MCA for 2 hours, and then the ischemic territory was locally infused with autocirculating cold arterial blood (13-15 degrees C). This cold blood infusion (< 0.6 ml/min) significantly reduced the temperature of the MCA supplied territory to 32-34 degrees C in 5-10 minutes. This hypothermic procedure was maintained for 30 minutes. After evaluating the neurological score at 2 days and 28 days, all animals were euthanized and their brains were sectioned and stained with hematoxylin and eosin (H&E). Their infarct volumes were calculated. Results: Local mild hypothermia in the brain was induced by autocirculation with a cold blood infusion, whereas the rectal temperature was maintained within the normal range. The infarction volume was significantly reduced and the neurological outcome was significantly improved (p < 0.05) after MCA occlusion in Group 2 (hypothermia) compared with Group 1 (MCA occlusion) and Group 3 (normothermia). Conclusion: Local brain hypothermia induced by autocirculating cold arterial blood infused into ischemic tissue has neuroprotective effects. [Neurol Res 2009; 31: 340-345]