Bundled postconditioning therapies improve hemodynamics and neurologic recovery after 17 min of untreated cardiac arrest

ObjectiveIschemic postconditioning (stutter CPR) and sevoflurane have been shown to mitigate the effects of reperfusion injury in cardiac tissue after 15 min of ventricular fibrillation (VF) cardiac arrest. Poloxamer 188 (P188) has also proven beneficial to neuronal and cardiac tissue during reperfusion injury in human and animal models. We hypothesized that the use of stutter CPR, sevoflurane, and P188 combined with standard advanced life support would improve post-resuscitation cardiac and neurologic function after prolonged VF arrest.MethodsFollowing 17 min of untreated VF, 20 pigs were randomized to Control treatment with active compression/decompression (ACD) CPR and impedance threshold device (ITD) (n = 8) or Bundle therapy with stutter ACD CPR + ITD + sevoflurane + P188 (n = 12). Epinephrine and post-resuscitation hypothermia were given in both groups per standard protocol. Animals that achieved return of spontaneous circulation (ROSC) were evaluated with echocardiography, biomarkers, and a blinded neurologic assessment with a cerebral performance category score.ResultsBundle therapy improved hemodynamics during resuscitation, reduced need for epinephrine and repeated defibrillation, reduced biomarkers of cardiac injury and end-organ dysfunction, and increased left ventricular ejection fraction compared to Controls. Bundle therapy also improved rates of ROSC (100% vs. 50%), freedom from major adverse events (50% vs. 0% at 48 h), and neurologic function (42% with mild or no neurologic deficit and 17% achieving normal function at 48 h).ConclusionsBundle therapy with a combination of stutter ACD CPR, ITD, sevoflurane, and P188 improved cardiac and neurologic function after 17 min of untreated cardiac arrest in pigs.All studies were performed with approval from the Institutional Animal Care Committee of the Minneapolis Medical Research Foundation (protocol #12-11).     

Optimized postconditioning algorithm protects liver graft after liver transplantation in rats

Background: Ischemia reperfusion injury(IRI) causes postoperative complications and influences the outcome of the patients undergoing liver surgery and transplantation. Postconditioning(Post C) is a known manual conditioning to decrease the hepatic IRI. Here we aimed to optimize the applicable Post C protocols and investigate the potential protective mechanism.Methods: Thirty Sprague–Dawley rats were randomly divided into 3 groups: the sham group(n = 5),standard orthotopic liver transplantation group(OLT, n = 5), Post C group(OLT followed by clamping and re-opening the portal vein for different time intervals, n = 20). Post C group was then subdivided into 4 groups according to the different time intervals:(10 s × 3, 10 s × 6, 30 s × 3, 60 s × 3, n = 5 in each subgroup). Liver function, histopathology, malondialdehyde(MDA), myeloperoxidase(MPO), expressions of p-Akt and endoplasmic reticulum stress(ERS) related genes were evaluated.Results: Compared to the OLT group, the grafts subjected to Post C algorithm(without significant prolonging the total ischemic time) especially with short stimulus and more cycles(10 s × 6) showed significant alleviation of morphological damage and graft function. Besides, the production of reactive oxidative agents(MDA) and neutrophil infiltration(MPO) were significantly depressed by Post C algorithm. Most of ERS related genes were down-regulated by Post C(10 s × 6), especially ATF4, Casp12, hspa4, ATF6 and ELF2, while p-Akt was up-regulated.Conclusions: Post C algorithm, especially 10 s × 6 algorithm, showed to be effective against rat liver graft IRI. These protective effects may be associated with its antioxidant, inhibition of ERS and activation of p-Akt expression of reperfusion injury salvage kinase pathway.     

缺血后适应减轻树鼩缺血性脑水肿及脑梗死的机制

目的 观察缺血后适应对树鼩血栓性脑缺血时大脑皮层脑水含量、局部脑血流、梗塞面积及神经元超微结构的影响,探讨其对树鼩脑缺血时神经保护的可能机制。 方法 将88只健康成年树鼩随机分为对照组、脑缺血4 h组、脑缺血24 h组、后适应4 h组及后适应24 h组（每组n=8）,另取8只动物做HE染色（n=3）及电子显微镜观察（n=5）。本实验采用光化学反应诱导树鼩血栓性脑缺血而建立脑缺血动物模型,在脑缺血模型建成后4 h夹闭缺血侧颈总动脉5 min,再灌注5 min,如此交替进行3个循环以建立缺血后适应模型。测定大脑皮层局部脑血流,脑组织含水量,脑梗死范围,并观察皮层及海马CA1区神经元超微结构改变。 结果 脑缺血时神经元固缩,线粒体肿胀,嵴溶解或形成空泡,内质网肿胀,内质网池形成。缺血后适应能使海马CA1区神经元固缩减少,线粒体和内质网的病理改变减轻,细胞水肿改善。随着缺血时间的延长,缺血24h组脑水含量明显增加86.81%±1.08%,此时脑梗塞面积明显扩大33.00%±3.03%,局部脑血流明显降低（134.27±28.75）ml/min。缺血后适应24h组脑组织含水量明显减少（81.04%±1.04%,P＜0.01）;脑梗塞面积缩小（16.79%±1.29%,P＜0.01）;而局部脑血流明显增加［（195.25±21.18）ml/min,P＜0.01］。 结论 缺血后适应可缓解树鼩缺血性脑水肿并缩小梗死范围,其机制可能与改善局部脑血流有关。     

七氟醚后处理对体外循环犬肺保护的作用

目的探讨七氟醚后处理对体外循环(CPB)犬肺组织缺血-再灌注损伤(LIRI)的保护作用.方法 健康成年杂种犬12只 ,随机分为两组(n=6) ,左肺缺血再灌注组(C组)、七氟醚后处理组(Y组).两组犬麻醉后行双腔气管插管机械通气 ,股动、静脉穿刺置管测平均动脉压(MAP)及中心静脉压(CVP) ,开胸并建立犬CPB.C组犬左肺行缺血再灌注 ,Y组左肺缺血再灌注后行七氟醚后处理.分别于CPB前(T1)、开放左肺动脉时(T2)及停机后2h(T3)取肺组织 HE染色观察形态学变化并进行病理评分 ,取股动脉血行动脉血气分析并计算氧合指数(OI)、呼吸指数(RI)和动态肺顺应性(Cd).结果 (1)光镜观察 :两组犬肺组织破坏程度随时间推移而增加 ,两组T1、T2 时点肺组织无明显差异 ;T3 时点C组肺组织破坏最为严重 ,Y组肺组织破坏程度明显低于C组 ;(2)病理学评分 :两组T3 时点病理学评分明显高于T1、T2 时间点 ,Y组病理评分明显低于C组(P<0 .05);(3)呼吸参数变化 :随时间推移两组OI和Cd明显降低而RI明显升高 ,T3 时间点Cd和OI ,Y组明显高于C组(P<0.05) ,而RI ,Y组明显低于C组(P<0.05).结论七氟醚后处理可提高体外循环犬的OI、Cd ,降低犬RI ,对犬体外循环导致的肺损伤有一定的保护作用.     

缺血后适应对糖尿病大鼠再灌注心肌的保护作用及其与P-Akt的关系

目的 探讨缺血后适应对糖尿病大鼠离体心脏缺血再灌注损伤的影响及其信号机制.方法 2周龄健康SD大鼠60只,雌雄不拘,体重250～300 g,随机分为6组:空白对照组(N组);缺血再灌注组(IR组);缺血后适应组(Post组);糖尿病大鼠后适应组(Dpost组);糖尿病大鼠缺血再灌注组(DIR组);糖尿病大鼠空白组(DN组).将链脲酶素(STZ,美围Sigma公司)按65 mg/kg经大鼠腹腔注射,48 h后断尾法连续两次测血糖≥16.65 mmol/L,并出现多饮、多食、多尿、体重减轻,脱毛等表现确定糖尿病模型成功.糖尿病模型制作成功后建立离体心脏Langendorff灌注模型,观测心脏冠状动脉灌流量、心肌梗死范围,免疫印迹(western blot)对P-Akt测定、电镜下观察心肌和线粒体改变.结果 糖尿病大鼠血糖浓度平均为(23.15±2.16)mmol/L,非糖尿病大鼠为(4.16±0.31)mmol/L.两组大鼠血糖浓度差异有统计学意义(P<0.01).缺血后适应组(Post组、DPost组)较缺血再灌注组(IR组、DIR组)冠状动脉流量(ml/min)明显增加(6.5±1.2、5.6±1.0对3.4±1.0、2.0±1.3),心肌梗死范围(%)明显减少(25.2±2.1、34.2±3.6对47.5±3.5、65.2±4.5),P-Akt的表达明显增强,心肌纤维和线粒体的完整程度明显较好.结论 缺血后适应在糖尿病大鼠离体心脏具有显著的保护作用,这一作用可能与Akt激活有关.     

mKATP对七氟醚后处理大鼠心肌细胞超微结构的影响

目的观察线粒体依赖ATP敏感钾通道（mKATP）的开放对七氟醚后处理大鼠心肌的保护作用。方法健康成年雄性SD大鼠32只,体重220～280g,将其随机分为4组（n=8）：假手术组（S组）、缺血再灌注组（IR组）、七氟醚后处理组（S-Post组）、七氟醚后处理＋拈抗剂组（S-Post＋5一HD组）。采用结扎冠状动脉左前降支法制备大鼠心肌缺血再灌注模型。观察各组心肌细胞超微结构变化,并计算梗死面积。结果与S组心肌梗死面积（7±1．7）％相比,其余各组显著增高（P〈0.05）;与IR组心肌梗死面积（50±2．8）％相比,S-Post组心肌梗死面积（36±2．2）％显著降低（P〈0．05）,心肌细胞损伤轻;S-Post＋5-HD组心肌梗死面积（48±2．5）％与IR组差异无统计学意义（P〉0．05）。结论七氟醚后处理对大鼠缺血再灌注心肌具有保护作用,而这种保护作用与mKATP通道的开放有关。     

Reperfusion injury: does it exist?

It is well established that reperfusion of the heart is the optimal method of salvaging previously ischemic myocardium. However, the idea of reperfusion injury, i.e. injury caused by the process of reperfusion per se, still remains a controversial issue. In this review, we present mounting evidence supporting the concept that reperfusion injury exists, based on work conducted with adenosine and opioid receptor ligands, and the discovery of two new concepts regarding reperfusion injury: 'postconditioning' (POC) and the reperfusion injury salvage kinase (RISK) signaling pathway.     

The cardioprotective and inotropic components of the postconditioning effects of GLP-1 and GLP-1(9–36)a in an isolated rat heart

GLP-1 and its metabolite GLP-1(9–36)a have been shown to exert cardiotropic effects, and were demonstrated to be cardioprotective agents in isolated, postischemic rat or mouse hearts. An agent's total effect on myocardial performance in a postconditioning paradigm is a sum of its myocyte-preserving (cardioprotective) and contractility-affecting (negative or positive inotropic) action components. These components may not always be explicitly separated by the experimental protocol. We propose an analytical approach to identify and quantify the cardioprotective and inotropic components in a postconditioning protocol, as exemplified by use of GLP-1 and GLP-1(9–36)a following a global ischemia in isolated rat hearts. Peptides were administered during the first 15 min of 120 min reperfusion. GLP-1 0.3 nM reduced infarct size from 23.2 ± 2.4% to 14.1 ± 2.3% of area-at-risk (n = 15, P = 0.0223), an effect abolished by the GLP-1 receptor antagonist, exendin(9–39) 5 nM. GLP-1 showed only a small, non-significant tendency to increase mechanical performance (increase of LVDP by 26.7%, P = 0.1621; RPP 33.5%, P = 0.0858; dP/dt_max 28.5%, P = 0.1609). This could be accounted for by the cardioprotective component of GLP-1 action, rather than any true inotropic effect. In contrast, GLP-1(9–36)a did not reduce infarct size significantly, but acted as a strong negative inotrope in postischemic hearts, causing a contractility deficit (LVDP 58.8%, P = 0.0004; RPP 58.2%, P = 0.0007; dP/dt_max = 58.2%, P = 0.0012), quantifiable by an analysis of infarct size-mechanical performance plots. These results help resolve certain apparent discrepancies between some of the published effects of GLP-1 and GLP-1(9–36)a.     

Myocardial protection in man—from research concept to clinical practice

Myocardial protection aims at preventing myocardial tissue loss: (a) In the acute stage, i.e., during primary angioplasty in acute myocardial infarction. In this setup, the attenuation of reperfusion injury is the main target. As a “mechanical” means, post-conditioning has already been tried in man with encouraging results. Pharmacologic interventions that could be of promise are statins, insulin, peptide hormones, including erythropoietin, fibroblast growth factor, and many others. (b) The patient with chronic coronary artery disease offers another paradigm, with the target of avoidance of further myocyte loss through apoptosis and inflammation. Various pharmacologic agents may prove useful in this context, together with exercise and “mechanical” improvement of cardiac function with attenuation of myocardial stretch, which by itself is a noxious influence. A continuous effort toward acute and chronically preserving myocardial integrity is a concept concerning both the researcher and the clinician.     

尼可地尔后处理对急性缺血诱导的大鼠心肌细胞凋亡的影响

目的 探讨尼可地尔后处理对大鼠心肌缺血再灌注损伤的保护作用及机制.方法 SD大鼠随机分为6组:假手术组、缺血再灌注组、缺血后处理组、尼可地尔后处理2、5和10 mg/kg剂量组.采用左冠状动脉前降支结扎30 min、再灌注120 min建立大鼠心肌缺血再灌注模型.缺血后处理组在缺血后再灌注前实施5次10 s再灌注-10 s再阻断循环.尼可地尔后处理组在缺血后再灌注前分别给予三个剂量10 min.检测血清肌酸激酶和丙二醛含量,及超氧化物歧化酶活性;检测心肌细胞的凋亡率和Caspase-3蛋白的表达.结果 尼可地尔后处理能使肌酸激酶、丙二醛含量降低,超氧化物歧化酶活性增高,心肌细胞凋亡率降低, Caspase-3蛋白表达减少.结论 尼可地尔后处理对缺血再灌注损伤的心肌具有保护作用,其机制可能与提高超氧化物歧化酶活性,增强心肌抗氧化能力,减轻氧自由基损伤,稳定细胞膜,抑制细胞凋亡有关.