摘要目的 探讨右美托咪定后处理对猪心脏骤停复苏后脑损伤的影响.方法 国产健康雄性白猪28头,体质量(36±2) kg.采用随机数字表法分为4组(n=7):假手术组(S组)、心肺复苏组(CPR组)、低剂量右美托咪定后处理组(LDP组)与高剂量右美托咪定后处理组(HDP组).S组仅进行动物准备,其他三组采用电刺激诱发室颤8 min、心肺复苏5 min的方法制备猪心脏骤停复苏模型.于复苏后5 min时,LDP组经静脉输注右美托咪定负荷剂量0.25μg/kg后以0.25μg/ (kg.h)维持6h,HDP组经静脉输注右美托咪定负荷剂量0.5 μg/kg后以0.5 μg/(kg.h)维持6h,另两组给予等容量生理盐水.于复苏后1、3、6和24 h时,采集静脉血样检测神经元特异性烯醇化酶(NSE)和S100B蛋白的血清水平.于复苏后24 h时,应用神经功能缺损评分(NDS)评估神经功能状态.然后,动物实施安乐死,获取大脑皮层组织,检测肿瘤坏死因子-o(TNF-α)、白细胞介素-6(IL-6)、丙二醛(MDA)的含量和超氧化物歧化酶(SOD)的活性,以及检测细胞凋亡程度与半胱氨酸天冬氨酸蛋白酶-3(caspase-3)的表达水平.结果 与S组相比,其他三组动物在复苏后均出现神经功能障碍与脑损伤,表现为NDS评分升高、血清NSE和S100B水平增加(均P＜0.05).与CPR组相比,LDP组和HDP组动物在复苏后24 h时的NDS评分降低、在复苏后6h与24 h时的血清NSE和S100B水平减少NDS:24 h为194±26、103±16和278±23;NSE (ng/mL):6 h为32.4±1.8、28.6±3.7和36.2±2.8,24h为39.9±4.2、35.1±1.5和45.1±3.0;S100B(pg/mL):6 h为2 534±207、2 382±170和2 825±113,24 h为3 719±164、3 246±176和4 085±161,均P＜0.05].与LDP组相比,HDP组动物在复苏后24 h时的神经功能障碍与脑损伤程度进一步减轻(均P＜0.05).组织病理分析显示,CPR组、LDP组和HDP组动物在复苏后出现脑组织炎症反应、氧化应激与细胞凋亡.但与CPR组相比,LDP组和HDP组动物在复苏后的脑组织TNF-α、IL-6与MDA含量减少,SOD活性升高,细胞凋亡指数与caspase-3蛋白表达降低(均P＜0.05).与LDP组相比,HDP组动物脑组织病理损伤程度进一步减轻(均P＜0.05).结论 右美托咪定后处理能呈剂量依赖性地减轻复苏后脑损伤程度,其保护机制可能与减轻组织炎症反应、氧化应激及细胞凋亡等有关.

abstractsObjective To investigate the effects of dexmedetomidine postconditioning on brain injury after cardiac arrest and resuscitation in a swine model.Methods Twenty-eight healthy male domestic pigs,weighing 36±2 kg,were randomized (random number) into 4 groups (n=7 each group):sham operation group (S group),cardiopulmonary resuscitation group (CPR group),low-dose dexmedetomidine postconditioning group (LDP group),and high-dose dexmedetomidine postconditioning group (HDP group).Animals in the S group only underwent the surgical preparation.In the other three groups,the experimental model was established by 8 mins of electrically induced ventricular fibrillation and then 5 mins of cardiopulmonary resuscitation.At 5 min after resuscitation,a loading dose of dexmedetomidine of 0.25 μg/kg was intravenously infused followed by continuous infusion at a rate of 0.25 μg/(kg·h) for 6 h in the LDP group,and a loading dose of dexmedetomidine of 0.5 μ.g/kg was infused followed by continuous infusion at a rate of 0.5 μg/(kg·h) for 6 h in the HDP group.The same amount of normal saline was administered in the S and CPR groups.At 1 h,3 h,6 h and 24 h after resuscitation,the levels of serum neuron specific enolase (NSE) and S100B protein were measured.At 24 h after resuscitation,neurologic deficit score (NSD) was evaluated.After that,the animals were euthanized and cerebral cortex was obtained for the determination of tumor necrosis factor-α (TNF-α),interleukin-6 (IL-6)and malondialdehyde (MDA) contents,superoxide dismutase (SOD) activity,cell apoptosis and caspase-3 expression.Results Compared with the S group,post-resuscitation neurologic dysfunction and brain injury were observed in the other three groups,which were indicated by significantly higher NDS and markedly greater levels of serum NSE and S 100B (all P＜0.05).Compared with the CPR group,the score of NDS at 24 h post-resuscitation were significantly lower and the levels of serum NSE and S100B at 6 h and 24 h post-resuscitation were significantly less in the LDP and HDP groups [NDS:194±26,103±16 vs 278±23 at 24 h;NSE (ng/mL):32.4±1.8,28.6±3.7 vs 36.2±2.8 at 6 h,39.9±4.2,35.1±1.5 vs 45.1±3.0 at 24 h;S100B (pg/mL):2 534±207,2 382±170 vs 2 825±113 at 6 h,3 719±164,3 246±176 vs 4 085±161 at 24 h,all P＜0.05].Compared with the LDP group,neurologic dysfunction and brain injury at 24 h postresuscitation were further significantly alleviated in the HDP group (all P＜0.05).Pathological analysis indicated that brain inflammation,oxidative stress and cell apoptosis were observed after resuscitation in the CPR,LDP and HDP groups.However,the contents of TNF-α,IL-6 and MDA were significantly lower while the activity of SOD was significantly higher,and cell apoptosis and caspase-3 expression were significantly reduced in the brain after resuscitation in the LDP and HDP groups compared with the CPR group (all P＜0.05).In addition,those pathological injuries mentioned above were further significantly alleviated in the brain after resuscitation in the HDP group compared to the LDP group (all P＜0.05).Conclusions Dexmedetomidine postconditioning significantly alleviated the severity of postresuscitation brain injury in a dose-dependent manner,in which the protection was produced possibly through reducing tissue inflammation,oxidative stress and cell apoptosis.