The Effects Of Selective Cerebral Ultra-profound Hypothermia On Brain Stem And Hippocampus In Monkeys After Occlusion Of Cerebral Blood Flow Under Different Time Limits

[Objective] To study the possibility of resuscitation ,function of brain stem,morphology changes of brain stem and hippocampus in experimental monkeys with occluding bilateral internal carotid arteries for 60 min under selective cerebral ultra-profound hypothermia after occlusion of cerebral blood flow under different time limits (0, 10,15 and 20min), determine the limit time of monkey brain ischemia resuscitation under common temperature.[Methods] 15 healthy adult rhesus monkeys , male, randomly divided into 4groups: resuscitation of Omin of bilateral internal carotid arteries blockage group(n=4) , resuscitation of 10min of bilateral internal carotid arteries blockage group(n=4) , resuscitation of 15min of bilateral internal carotid arteries blockage group(n=4), resuscitation of 20min of bilateral internal carotid arteries blockage group(n=3) . A catheter was inserted into right internal carotid artery ( ICA) to infuse 4℃cooling Ringer's liquid, two catheters were distally and proximally inserted intointernal jugular vein ( IJV ) to extract the hypothermic diluted blood forultrafiltration and then perfuse the warm blood into the right venae cava inferior afterrewarming. Then left ICA and IJV was clamped, 4℃cooling Ringer's liquid wasperfused into the right ICA after ischemia at common temperature to induce the brainto cool less 16℃. After 60 minutes, Perfusion was stopped. MRI scans were obtainedduring preoperative and postoperative course. During operative and postoperativecourse , observed heart rate,mean arterial pressure,pupil,reflex,consciousness to determine the function change of brain stem. The monkeys' brain was immediately removed soon after death in operation, and so did it in Long-term survival monkeys after we executed the monkeys 4 weeks after operation, the histopathological examination of brain stem and hippocampus was performed .[Results] All of the monkeys in resuscitation of 0min,10min of bilateral internal carotid arteries blockage group (n=8) lived up till they were executed. Pre and post blood occlusion brain stem function was stable. MRI scans were normal after operation. The histopathological examination of brain stem and hippocampus had no obvious abnormalities. 2 long-term surviving, 1 severe disable, 1 died in 15min of bilateral carotid artery blockage group (n=4) ,the function of the brain stem was effected in some degree during and after the operation; MRI scans of the 3 survival monkeys showed no brainstem ischemia. The histopathological examination of brain stem and hippocampus showed powder nerve cell necrosis. All monkeys of 20 min hypothermia group were not resuscitation after perfusion and died. The function of brain stem was obviously affected, 1 died in 15min hypothermia group, the histopathological examination of these monkeys' brain stem and hippocampus showed more nerve cell necrosis.[Conclusions] (1) Selective brain ultra-profound hypothermia (14.3-16℃) may achieved by half internal carotid artery cold irritating in rhesus monkey. (2) It is safe for resuscitation in 0min,10 min brain ischemia. The function change of brain stem, the histopathologic examination of brain stem and hippocampus are normal. Ultra-profound hypothermia has obvious neuroprotection. (3) It is possible for resuscitation in 15 min brain ischemia ,but result in high death and disability, some effect on the brain stem, the necrosis of dispersed nerve cell in the organizational structure of brain stem and hippocampus. (4) Resuscitation of 20min of bilateralcarotid artery blockage was invalid due to irreversibility brain-damage. (5) The goldtime of resuscitation for brain ischemia is probably in 10min. Life can be saved in15min hypothermia group , but may result in different degree neurological deficits and high disability and death rate, so resuscitation is at comparative stake .