深低温停循环下兔脑内兴奋性氨基酸的早期变化与脑损伤研究

目的　探讨体外循环(CPB)和深低温停循环(DHCA)下脑内兴奋性氨基酸(EAA )早期变化规律,及其“兴奋毒性”作用在脑损伤中的作用。方法　建立应用脑微透析技术的兔CPB和DHCA模型。利用高效液相的电化学检测方法,测定兔脑海马CA1区脑细胞间液中EAA的连续性变化。术后利用透射电子显微镜给予组织学损伤评分。结果　谷氨酸在CPB组各阶段变化差异无统计学意义(P >0 .0 5 ) ;DHCA组在恢复循环早期明显升高(P <0 .0 5 ) ,升高程度DHCA组明显高于CPB组(P <0 .0 1)。天冬氨酸在DHCA组恢复灌注3 0～60min阶段明显升高(P <0 .0 1) ,但与CPB组的组间对照差异无统计学意义(P >0 .0 5 )。透射电镜发现两组脑细胞超微结构均明显损伤,DHCA组损伤重于C组(P <0 .0 5 )。结论　“兴奋毒性”作用与中低温CPB造成的脑损伤无关。DHCA可使再灌注早期兴奋性氨基酸升高,并导致脑损伤加重

Relationship between cerebral injury and early changes of excitatory amino acids in rabbit brain due to deep hypothermic circulatory arrest

Objective To monitor and compare the early changes of excitatory amino acids (Glu and Asp) in the brain after CPB and deep hypothermic circulatory arrest (DHCA).The role of excitotoxicity of excitatory amino acids in cerebral injuries due to CPB and DHCA was determined.Methods The rabbit model of CPB and DHCA was established by using in vivo cerebral microdialysis.High performance liquid chromatography was employed to monitor the continuous changes of Glu and Asp in the hippocampus CA1 region.Histological examination by transmission microscopy was carried out postoperatively.Results There was no notable changes of Glu in CPB group in all phases,while there was a remarkable increase of Glu in DHCA group after circulation restoration ( P < 0.05). The escalation was higher in DHCA group than CPB group ( P < 0.01). Asp was increased significantly in DHCA group in 30 to 60 min after circulation restoration ( P < 0.01), while there was no statistical difference between two groups.Distinct cerebral untrastructural injuries were seen in both groups under transmission microscopy and statistics showed that injury in DHCA group was more severe than in CPB group ( P < 0.05). Conclusion Excitotoxicity by increased excitatory amino acids is irrelevant to cerebral injury due to mild to deep hypothermic CPB.DHCA might increase the excitatory amino acids in the early phases of circulatory restoration,which may be related to exacerbation of cerebral injuries.