Hypothermia versus ethanol: neurologic outcome after incomplete cerebral ischemia in midazolam-anesthetized rats

We examined neurologic outcome after incomplete cerebral ischemia in rats treated with hypothermia versus ethanol, two techniques that decrease brain metabolism. All animals, including control rats, received a baseline midazolam anesthetic. Ischemia was produced by right carotid artery occlusion combined with hemorrhagic hypotension to a mean arterial pressure of 30 mm Hg for 30 min. Neurologic outcome was evaluated for 3 days after ischemia using a 5-point scale. In separate studies, cerebral blood flow (CBF) was measured using radioactive microspheres, and cortical oxygen consumption (CMRO2) was calculated from the blood flow data and the arteriovenous oxygen difference. Hypothermia to 31 degrees C decreased CBF 50% and CMRO2 52% compared with control rats, and significantly improved outcome. Although ethanol decreased CBF 35% and CMRO2 22%, it did not improve outcome from stroke compared with control rats. These results suggest that hypothermia protects the brain from ischemia and that ethanol does not, despite a decrease in CMRO2.