Brain Protective Effects of Mild Hypothermia on the Reversible Cerebral Ischemia in the Rat

ABSTRACT

OBJECTIVE: The authors report a experimental research of brain protective effects of mild hypothermia on the reversible cerebral ischemia in the rat. METHODS: We divided the experimental objects into two groups;the control group of normal temperature(36.5degreesC) and the experimental group of hypothermia, and also the latter into three group;group I (33.5degreesC), group II(30.5degreesC), group III(27.5degreesC) depending on the body temperature of hypothermia. The hypothermia was maintained for two hours of middle cerebral artery occlusion and initial 30 minutes of reperfusion and again the temperature was elevated and maintained to 36.5degreesC. Then the cerebral infarct volume was measured at 12 hours after reperfusion of middle cerebral artery. RESULTS: The physiological parameters between the control and the each experimental group were insignificant except the depression of mean systemic arterial pressure in group II and III during hypothermia (p<0.05). As the temperature depression became deeper, the cerebral infarct volume was reduced; 0.99+/-0.26% in group I, 0.66+/-0.14% in group II, and 0.17+/-0.05% in group III. In each experimental group, compared with 2.13+/-0.53% in the control group the cerebral infarct volume was reduced so much that the result was significant statistically. In addition to that, the comparison of cerebral infarct volume between group I and III was proved to be significant statistically(p<0.05), but meaningless between group I and group II. CONCLUSION: It is suggested that mild hypothermia of 33.5degreesC for a short time(2.5hours) has the brain protective effect on reversible focal cerebral ischemia and reperfusion injury without the change of physiologic parameters.