Transient Hypothermia Reduces Focal Ischemic Brain Injury in the Rat

Abstract

The effect of transient hypothermia on focal cerebral ischemia was evaluated using a rat model of permanent middle cerebral artery (MCA) occlusion. MCA occlusion was performed on 10 rats at a temporalis muscle temperature of 24°C (hypothermic group) and on 10 rats at 36°C (normothermic group). Rats in the hypothermic group were maintained at 24°C for 1 hour after MCA occlusion and then allowed to rewarm to 36°C over the next 2 hours. Animals in both groups were killed 24 hours after MCA occlusion. Cerebral infarcts were visualized by staining of coronal brain sections with 2,3,5-triphenyltetrazolium chloride. Normothermic rats displayed an average infarct volume of 233.1 ± 13.2 mm3 (standard error of the mean), whereas hypothermic rats had an average infarct volume of 166.2 ± 22.8 mm3 (P < 0.01). Expressed as a percentage of the volume of the right hemisphere, the normothermic group had an infarct volume of 22.1 ± 1.5% and the hypothermic group an infarct volume of 16.0 ± 2.2% (P < 0.05). These results demonstrate that transient hypothermia to a temporalis muscle temperature of 24°C significantly reduces subsequent infarct size in an experimental model of permanent arterial occlusion. (Neurosurgery 29:369-373, 1991)