| Objective :Deep hypothermic circulatory arrest (DHCA) can reduce the injury of cerebral nervous systerm from steping down the cerebral metabolism rate. Intermittent cerebroplegia perfusion can reduce or avoid aggregation of hemocyte in the micro-capillary of the brain tissue, can decrease the production of oxygen-derived free radicals during DHCA and reperfusion. Ginkgo biloba extract (GBE) has inartificial antioxidation character, can improve cerebral ischemia and hypoxia manifestly. This experiment is to study cerebral protective effect and mechanism of intermittent antegrade cerebroplegia perfution which contains GBE on brain of rabbits during DHCA.Methods :Thirty New Zealand rabbits were divided into three groups randomly (ten rabbits each group). To establish a model of closed chest cardiopulmonary bypass (CPB) via right common carotid artery and vein cannulation, and stop the circulation when the nasopharyngeal temperature was reduced to 18℃. Re-circulated and rewarmed for 30 minites after DHCA 90min. Group A did nothing during DHCA. Group B received intermittent antigrade cerebroplegia perfusion, which contained the same quantity crystal liquid and blood from CPB. Group C received cerebroplegia perfusion which joined the GBE into the fluid that group B received at the radio 1 to 10. To determine partial pressure of oxygen and carbon dioxide of the internal carotid artery and jugular vein blood at the begining of DHCA,DHCA 30min,60min,90min and re-circulatated 30min, and to caculate the cerebral extraction of oxygen (CEO2). To determine the lactic acid content of the internal jugular vein blood using the Lactic Acid Kit and spectrophotometric method. To observe ultrastructure changes of cerebral tissue using transmission electron microscope. To calculate the water content of brain tissue after recirculatating for 30 minites.Results :The CEO2 are declined rapidly in group A. But it increased obiviously after perfusioning cerebroplegia in group B and C. There was significantly difference among the three groups at DHCA 60min and 90min (P<0.05). With the lasting of time, the lactic acid content steped up significantly in group A and slowly in group B, but it steped up slightly and kept lower level in group C. The difference was significant among the three groups after perfusioning cerebroplegia. The water content of brain tissue was significantly different among the three groups (P<0.05). With the lasting of DHCA, destruction of ultrastructure changes of cerebral tissue was gradually manifest. It was normal at the begining of DHCA. The neuron swelled slightly, but organelles was integrity at DHCA 30min. The neuron swelled moderately and organelles dispersed, and the change of vacuolation was severe in number and degree at DHCA 60min. The neuron swelled obviously and organelles broke into pieces,and cristae of the mitochondria fragmentated obviously at DHCA 90min. The neuron swelled even more severely than bofore. Most mitochondria vacuolated severely, cristae disappeared mostly, and double-membrane was destroyed severely at re-circulatated 30min. The ultrastructure changes of cerebral tissue in group B lesioned manifestly than group A after intermittent cerebroplegia perfution at the same phase. And the changes was much less in group C than in group B. The ultrastructure structure was not much changed at DHCA 60min in group B. The ultrastructure structure kept no much change at DHCA 90min in group C.Conclusion :Intermittent cerebroplegia perfusion during DHCA can offer more oxygen, reduce the lactic acid content in internal jugular vein blood, reduce water content of the brain tissue and the destruction in ultrastructure structure of cerebral tissue. Perfusioning after joining EGB into cerebroplegia can profit cerebral metabolism more;reduce the injury of DHCA for longer time;and prolong the security time for circulatory arrest. |
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