Influence Of Brain-located Mild Hypothermia On Brain Edema And Permeability Of Blood Brain Barrier After Experimental Intracerebral Hemorrhage In Rabbits

Intracerebral hemorrhage (ICH) is a serious disease that has high mortality and often leads to deformity on survivals .At present, there is still no effective therapeutic ways. It is well known that the most important reason of death is herniation induced by brain edema after ICH. Therefore how to inhibit the formation of brain edema became the focus problem in the therapy of ICH. Clinic study has proved that brain-located mild hypothermia can reduce brain edema after ICH. But studies of the mechanism are very little. In this experiment, we investigate the influence of brain-located mild hypothermia on brain edema and blood-brain barrier (BBB) after experimental intracerebral hemorrhage in rabbits. Discuss the possible mechanism of the neuroprotective effects of the brain-located mild hypothermia. A total of 49 rabbits were divided into 3 groups: the sham-operation group (n=15), the normothermia group (n=17), the mild hypothermia group (n=17). Each group was divided into 3 subgroups: 1d,3d, 5 d after operation. The normothermia group and the mild hypothermia group received an injection of 0.2ml of autologous blood into the basal ganglia. The sham-operation group underwent the same operation but didn't receive injection of blood. Took two rabbits from both normothermia 1d group and mild hypothermia 1d group for the observation of histopathological change and ultrastructure change. An head cooling therapeutic instrument was used to induce and maintain mild hypothermia in the rabbits of mild hypothermia group. The ice bag of the instrument was placed on the operated side of the rabbits'head. The temperature was modulated at 10℃-13℃ and the continuous treatment lasted 24 hours. Evan's blue was used as a passive permeability marker of blood-brain barrier. 2%Evan's blue was injected through auricular vein two hours before killing the rabbits and Evan's blue levels and water content in cerebral tissue around the hematoma were determined. The data were analyzed by one-way analysis of variance.In mild hypothermia 1d and 3d groups, the percentage of brain water content were much lower than those in normothermia 1d and 3d groups, but higher than those in sham-operation 1d and 3d groups. The difference was significant. There was no significant difference of water content between mild hypothermia 5d group and normothermia 5d group. In mild hypothermia 1d group, Evan's blue content in cerebral tissue was much lower than those in normothermia 1d group, but higher than those in sham-operation 1d group. The difference was significant. There was no significant difference of Evan's blue content between mild hypothermia 3d and 5d groups and normothermia 3d and 5d groups. Ultrastructure in mild hypothermia 1d group is less injury than that of normothermia group.Animal model was made by autologous blood injection into the basal ganglia of rabbits. The model is similar to the clinical ICH , and mimic the natural events and pathologies that occur with ICH in humans. This study indicated that brain-located mild hypothermia significantly reduced brain edema formation after intracerebral hemorrhage in rabbits, especially in 1d group and 3d group. The effect had no significant difference in 5d groups. The study also indicated that brain-located mild hypothermia helped to relieve the impairment on BBB and had a protective effect on BBB in mild hypothermia 1d group. But the protective effect had no significant difference in 3d and 5d groups. Despite the protective affect on BBB, there are still some else mechanism of the inhibition of brain edema formation. Therefore further study is important.The mechanism of brain edema formation after intracerebral hemorrhage is very complex. It is impossible for simple brain-located mild hypothermia to inhibit brain edema absolutely. But the study indicated that it reduced brain edema formation and had protective affect on BBB, this lends a support to the use of brain-located in the treatment of ICH.From the study we can conclude that Brain-located mild...