Abstract<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> Objective:To study whether hypoxic preconditioning can improve outcome after severe hypoxia in rats. Methods:72 male Wistar rats, 260~290g in body weight, were randomly allocated to sham, control (H0)and hypoxic preconditioning groups, H1, H2, H3 and H4, with 12 rats in each group. The rats were anesthetized, paralyzed and mechanically ventilated. The hypoxic preconditioning was accomplished by disconnecting the ventilator for 1 min, followed by re-ventilation for 5 min. H1, H2, H3 and H4 group received hypoxic preconditioning for 1, 2, 3 and 4 times, respectively, before disconnecting the ventilator. Rats in H0 group underwent hypoxia without hypoxic preconditioning. Acute hypoxia was induced by disconnecting the tracheal tube from the ventilator for 4 min. Cardiopulmonary resuscitation began after the acute hypoxia. Rats in the sham group received anesthesia, controlled ventilation but without acute hypoxia. Blood pressure, heart rate, mortality rate, time of cardiac arrest (TCA),return of spontaneous circulation (TROSC)and low-flow time (TLFT) were recorded. Neural deficit scores (NDS) were evaluated at 24, 48 and 72hafter resuscitation, respectively. CA1 region of left hippocampus were removed 3 days later for electron microscope examination. Results:The mortality in H0, H1, H2, H3 and H4 group was 33.3%, 25.0% ,16.7%,16.7% and 8.3% respectively; CA was significantly longer in H1, H2, H3 and H4 group than H0 group(p<0.05) by 11.1%, 19.8%, 20.7% and 29.3% respectively;TROSC was evidently shorter 37.1% and 40.8% in H3 and H4 group than H0 group(p<0.05); TLFT was greatly shorter in H1, H2, H3 , H4 group than in H0 group(p<0.05); NDS improved significantly in H4 group than H0, H1, H2 and H3 group(p<0.05),and H4 group has no significantly changed than the sham group. Electron microscope examination of hippocampus CA1 region showed less injury of neuron, blood brain barrier, astrocyte and organelle after hypoxic preconditioning. Conclusions:Hypoxic preconditioning plays a positive role in improving the outcome after severe hypoxia in rats. Key words:hypoxia; hypoxic preconditioning; mortality; neural function Corresponding auther: Bao-guo Wang,MD:E-mail address:wbgttyy@sina.com 缺氧预处理(hypoxia preconditioning,HPC)即用短暂的缺氧刺激启动机体的防御和保护体系使组织细胞在后续的长期缺氧(或缺血)中损伤减少。本实验对全麻无自主呼吸的大鼠施以缺氧预处理,探讨缺氧预处理的合适方式、脑保护作用,为后期临床研究提供实验室依据。 |