The purpose of this study is to determine whether reducing a patient's body temperature (mild hypothermia of 33 degrees Centigrade) will significantly reduce the risk of brain injury (notably reperfusion injury and hemorrhagic conversion) in patients who have suffered a significant interruption of blood flow to an area of brain (occlusion of large proximal cerebral artery) and have undergone successful removal of that interruption (revascularization).This will be achieved by comparing patients who have undergone hypothermia to those who have not.