中度低温对急性胰腺炎大鼠核转录因子-κB表达的影响

目的观察急性出血坏死性胰腺炎（AHNP）后不同时间点胰腺和肺组织中核转录因子-κB（NF-κB）的DNA结合活性动态变化，以及胰腺炎后应用中度低温对NF-κB活性的影响。方法第一部分实验采用牛磺胆酸钠逆行注射造成大鼠AHNP模型。大鼠随机分为正常对照组以及AHNP常温2、5和12h组，用电泳迁移率改变法（EMSA）测定各组大鼠胰腺和肺组织中NF-κB的活性。第二部分实验将大鼠随机分为假手术组、AHNP常温组和低温组，诱导AHNP后2h和5h测定各组胰腺和肺组织中NF-κB的活性。结果急性胰腺炎后大鼠胰腺和肺组织NF-κB活性均持续增强，且各时间点胰腺组织NF-κB活性显著强于肺组织（P均〈0．01）。与AHNP常温组相比，低温组AHNP后2h和5h肺组织NF-κB活性均显著降低（P均〈0．01），而胰腺组织NF-κB活性与常温组差异不明显。结论急性胰腺炎伴有胰腺和肺组织NF-κB活性的显著增强。中度低温对急性胰腺炎后肺组织NF-κB的激活有抑制作用。     

胰头夹闭法致大鼠急性坏死性胰腺炎动物模型的建立

目的通过暂时夹闭胰头部的方法建立一种新型大鼠急性坏死性胰腺炎(ANP)的动物模型。方法将健康雄性SD大鼠180只随机分为:对照组、假手术组、ANP模型组,每组60只。ANP模型组开腹后钝性分离胰腺周围韧带直至胰头部,无创血管钳夹闭胰头2 h后松开。在造模完成后分别于0 h、4 h、12 h、24 h、48 h、72 h各时间点随机取10只大鼠检测血淀粉酶、脂肪酶,取胰腺组织标本检测湿/干重比,行病理组织学观察。结果 ANP模型组大鼠血淀粉酶、血清脂肪酶与对照组和假手术组比较,差异显著(P﹤0.05)。病理组织学观察可见造模后随时间进程胰腺炎呈加重表现(P<0.05)。结论通过夹闭胰头部的方法建立了一种新型大鼠急性坏死性胰腺炎动物模型,为急性坏死性胰腺炎的发病机制及药物干预研究提供了一种较为理想的动物模型。     

重症急性胰腺炎大鼠模型的改良

目的：探讨5％牛磺胆酸钠逆行胆胰管注射诱导重症急性胰腺炎大鼠模型的相关技术的改良。方法：将36只健康雄性SD大鼠随机分为模型组（n=18）和假手术组（n=18），应用经胆胰管近十二指肠开口端逆行刺入注射5％牛磺胆酸钠诱导重症急性胰腺炎动物模型；两组均在模型诱导后3、6、12h检测血淀粉酶、胰腺组织含水量，观察胰腺组织形态变化．光镜下进行胰腺病变程度Kusske评分。结果：模型组在模型诱导后3、6、12h血淀粉酶、胰腺组织含水量、胰腺大体病理的Hughes评分和胰腺组织学Kusske评分比假手术组明显升高（P〈0．05，P〈0．01）。结论：此大鼠模型是SAP大鼠模型诱导方法的有效改进，具有创伤小，操作简便，存活时间长、模型诱导成功率高的特点，是较为理想的SAP动物模型。     

海风藤酮对重症急性胰腺炎大鼠腹腔器官血流的干预效应

背景:海风藤酮具有显著的抗氧化作用和钙离子拮抗样效应,能有效清除氧自由基,抑制钙离子内流,还能降低胰腺酶活性,减轻胰腺组织自我消化。目的:研究海风藤酮对重症急性胰腺炎大鼠腹腔器官血流,特别是胰腺血流的影响及其作用机制。设计:对比观察的动物实验。单位:解放军第四军医大学唐都医院普外科实验室和中心实验室。材料:选用Sprague-Dawiey(SD)雄性大鼠40只,清洁级,体质量200～280g。海风藤酮(共150mg)(北京大学药学院,批号:20050347);牛磺胆酸钠(Sigma公司,批号:86339);淀粉酶试剂(Roche公司,批号:irp170505)按说明书用。Imexlab9100多普勒超声诊断仪(美国Imex公司);多普勒超声诊断仪专用的8mHz探头(产品号X1-M008)(美国Imex公司)。方法:实验于2006-04/10在解放军第四军医大学唐都医院普外科实验室完成。应用随机数字表法选取8只大鼠作为假手术组,其余大鼠禁食12h后制作重症急性胰腺炎模型。造模后的重症急性胰腺炎大鼠采用随机数字表法分为2组:海风藤酮组(n=16)和模型组(n=16),两组又分别分为术后12和24h2个时间点进行观察,每个时间点8只。假手术组大鼠不进行任何手术操作。海风藤酮组大鼠术后3h经空肠造瘘管给药,剂量为海风藤酮10mg/kg,1次/6h,1～2次。配置时,药物溶于25g/L二甲基亚砜中,即刻应用。模型组大鼠经空肠造瘘管给予等量的二甲基亚砜。假手术组动物仅作开腹手术。假手术组于术后12h,模型组和海风藤酮组分别于重症急性胰腺炎术后12,24h测定血淀粉,同时运用多普勒超声测定胰腺局部动脉(相当于胰头、体交界处)、门静脉血流、脾动脉及肠系膜上动脉血流。主要观察指标:各组不同时间血浆淀粉酶和血流量变化情况。结果:纳入SD大鼠40只全部进入结果分析。①血浆淀粉酶测定结果:模型组和海风藤酮组血浆淀粉酶在各时点与假手术组相比均明显升高(P<0.01);模型组随时间延长,血浆淀粉酶继续升高,与术后12h比较,差异明显(P<0.05)。②胰腺局部动脉血流情况:在术后12和24h时,海风藤酮组和模型组胰腺局部动脉血流量明显低于假手术组(P<0.01);在海风藤酮组,随胰腺炎病程进展,胰腺局部血流量进一步下降(P<0.05),但各时点局部动脉血流量明显高于模型组(P<0.01)。③肠系膜上动脉根部、门静脉及脾动脉血流情况:海风藤酮组和模型组在术后12和24h时肠系膜上动脉血流量明显低于假手术组(P<0.01)。海风藤酮组各时点血流量与模型组比较,明显升高(P<0.01)。结论:海风藤酮能促使重症急性胰腺炎大鼠胰腺血流量增加,减轻胰腺的病理损害。     

微波对急性胰腺炎大鼠氧自由基代谢功能的影响

目的 从大鼠氧自由基代谢水平探讨微波对急性胰腺炎大鼠模型的治疗作用。方法 将30只SD大鼠随机分为3组，即假手术组、模型组及实验组一假手术组、模型组术后均无特殊处理。实验组大鼠分别于造模后3h、9h及23h行上腹部微波辐射治疗。各组大鼠均于术后24h经内眦采血检测血清淀粉酶(AMY)、超氧化物歧化酶(SOD)及丙二醛(MDA)的含量变化并同时观察胰腺组织病理学改变。结果 实验组大鼠血清淀粉酶含量升高幅度低于模型组(P＜0．05)；实验组血清SOD含量明显高于模型组(P＜0．01)；实验组血清MDA含量明显低于模型组(P＜0.05)；光镜观察发现实验组大鼠胰腺病理改变程度明显轻于模型组。结论 急性胰腺炎大鼠存在脂质过氧化损伤，光镜下可见其胰腺组织发生严重病理改变。微波治疗可降低急性胰腺炎大鼠模型的AMY，MDA含量，提高SOD含量，减轻胰腺组织病理改变，对急性胰腺炎大鼠模型具有一定的治疗作用。     

一种新型L-精氨酸诱导的大鼠急性坏死性胰腺炎动物模型的建立

目的通过对大鼠胰腺注射L-精氨酸的方法建立一种新型大鼠急性坏死性胰腺炎(ANP)动物模型。方法将健康雄性SD大鼠150只随机分为:对照组、假手术组、ANP模型组,每组50只。ANP模型组在胰体尾部被膜下及实质内多点均匀注射L-精氨酸。在造模完成后分别于4h、12h、24h、48h、72h各时间点每组随机取10只大鼠做CT观察胰腺变化情况,并通过内眦静脉采血检测血淀粉酶、脂肪酶,取胰腺组织行病理组织学观察。结果腹部CT可见胰腺病变随时间进程呈加重表现;ANP模型组大鼠造模后血淀粉酶[4h(1500.2±328.5)U/L、12h(2264.3±366.2)U/L、24h(2836.0±505.2)U/L、48h(3741.2±551.8)U/L、72h(2614.3±361.5)U/L]和血清脂肪酶[4h(343.2±44.1)U/L、12h(379.0±39.1)U/L、24h(432.3±53.0)U/L、48h(456.5±64.9)U/L、72h(451.1±39.6)U/L]与对照组及假手术组比较显著升高,差异有统计学意义(P均<0.05)。病理组织学观察可见造模后随时间进程胰腺炎呈加重表现。结论实验通过对大鼠胰腺注射L-精氨酸的方法成功地建立了一种典型、稳定、可重复的大鼠ANP动物模型,用于其发病机制及药物干预后的效果评价。     

亚低温对急性脊髓损伤后肿瘤坏死因子-α表达及运动功能恢复的影响

目的 观察大鼠脊髓损伤(SCI)后亚低温对肿瘤坏死因子-α (TNF-α)mRNA表达及运动功能恢复的影响,探讨其可能的作用机制.方法 72只SD大鼠随机分为对照组(n=24)、常温组(n=24)和亚低温组(n=24),每组再分为六个亚组,每亚组4只,参照改良Allen法建立大鼠脊髓(T9)中度损伤模型,亚低温组给予亚低温治疗5 h,而对照组不做亚低温处理.分别于损伤后6 h、12 h、24 h、72 h、1周和4周,利用 Tarlov评分检测亚低温对大鼠SCI后运动功能恢复的影响;然后将大鼠处死,利用半定量 RT-PCR方法观察损伤段脊髓组织中TNF-α mRNA表达的变化.结果 亚低温组TNF-α mRNA表达SCI后6~72 h明显少于常温组(P<0.05),而运动功能评分每个时间点都明显高于常温组(P<0.05).结论 亚低温可明显抑制SCI后TNF-α的表达,具有良好的恢复运动功能的作用.     

病变侧亚低温对大鼠局灶性脑缺血再灌注后凋亡相关蛋白变化的影响

目的:观察病变侧亚低温对大鼠局灶性脑缺血再灌注后生长抑制和DNA损伤诱导基因45(Gadd45)和Bcl-2蛋白变化的影响。方法:实验于2004-11/2005-07在哈尔滨医科大学病理教研室实验室完成。将雄性Wistar大鼠48只随机分为4组:①常温缺血组(n=20):采用改良线栓法建立大鼠大脑中动脉缺血2h再灌注模型,再灌3,12,24,48和72h分别处死,每个时间点4只。②亚低温缺血组(n=20):造模和处死时间同常温缺血组,并于栓塞后30min实施病灶侧亚低温(设定制冷器温度为6～8℃,脑内缺血区温度为32℃左右)并持续4h。③假手术组(n=4):手术,但不栓塞,术后24h处死。④正常组(n=4):不干预。各组大鼠处死前进行神经功能缺陷评分(0～4分,评分越高,神经功能缺陷越重);苏木精-伊红染色观察组织病理变化;采用免疫组化的方法检测Gadd45和Bcl-2蛋白的表达。结果:48只进入结果分析。①神经功能缺陷评分:亚低温缺血组大鼠各时间点均明显低于常温缺血组(P<0.05)。②Gadd45表达:在再灌注3h表达增强,且随再灌注时间的延长而逐渐增强(P<0.05),至48h达高峰,其后又随之下降。亚低温缺血组各时间点表达明显少于常温缺血组(P<0.05)。③Bcl-2表达:再灌注3h增多,随再灌注时间的延长,其表达逐渐增多(P<0.05),至24h达高峰,其后又随之下降,亚低温缺血组各时间点表达明显高于常温缺血组(P<0.05)。结论:Gadd45在脑缺血再灌注损伤过程中,早期能修复受损的DNA,损伤加重时则促进细胞凋亡;Bcl-2在脑缺血再灌注损伤过程中主要起抑制细胞凋亡的作用。亚低温能减少Gadd45的表达,增加Bcl-2的表达;能明显减轻缺血所致的损伤,并能明显抑制细胞调亡;对大鼠缺血后神经功能的恢复有确切的疗效。     

亚低温对脑缺血性损伤后基因修复蛋白和增殖性抗原表达的影响

目的观察脑缺血再灌注后核苷酸切除修复交叉互补基因蛋白p80和增殖性细胞核抗原表达的时空变化及趋势,判断亚低温在缺血性脑损伤中是否具有作用。方法实验于2004-10/2005-05在哈尔滨医科大学病理教研室实验室完成。①取44只大鼠随机分为3组:假手术组(n=4),常温组和亚低温组(n=20),后两组根据再灌注时间分为再灌注3,12,24,48和72h5个亚组,每亚组4只。②用线栓法建立局部脑缺血模型,假手术组不插入栓线。③亚低温组于缺血30min时实施病灶侧脑部亚低温,脑温控制在32～35℃,持续4h,其他两组脑温保持在37℃左右。④各组在相应时间点断头处死大鼠取脑,用免疫组织化学方法检测p80和增殖性细胞核抗原的表达。结果44只大鼠进入结果分析。①p80表达:在假手术组极少,主要见于细胞质中;常温组p80的表达随再灌注时间延长而升高,48h达到峰值,72h时有下降的趋势;亚低温组的表达与常温组趋势一致,且均高于同一时间点的常温组。②增殖性细胞核抗原表达:假手术组有广泛表达,主要见于细胞核中;与假手术组相比,常温组在再灌3h表达即明显下降,随着再灌注时间的延长,表达逐渐升高,24h达到高峰,随后逐渐下降;亚低温组的表达在缺血再灌注后持续升高,且高于相应的常温组。结论亚低温能显著抑制或延迟p80和增殖性细胞核抗原在脑缺血再灌注损伤后表达的下降,提高DNA的修复能力,进而减轻缺血再灌后神经细胞的损伤。     

重症急性胰腺炎大鼠IL-8 IL-10及NF-κB的表达

目的 通过观察重症急性胰腺炎（SAP）大鼠白介素-8（IL-8）、白介素-10（IL-10）及胰腺NF-κB的表达，探讨重症急性胰腺炎的发生发展机制。方法将40只大鼠随机分为正常对照组（假手术组）、模型组（重症急性胰腺炎组），每组20只，造模后24h测定血淀粉酶、IL-8及IL-10，切取相同部位的胰腺组织观察组织病理学改变，进行NF—κB的免疫组织化学染色。结果模型组大鼠血清淀粉酶、IL-8及IL-10的浓度均显著高于对照组，模型组NF-κB免疫组化染色较对照组显著增强。结论IL-8、IL-10及NF—κB在重症急性胰腺炎的发生发展中起重要作用，重症急性胰腺炎的早期即有胰腺组织NF—κB的活化。     

Long-term mild hypothermia with extracorporeal lung and heart assist improves survival from prolonged cardiac arrest in dogs.

BACKGROUND AND PURPOSE: although normothermic extracorporeal lung and heart assist (ECLHA) improves cardiac outcomes, patients can not benefit from hypothermia-mediated brain protection. The present study evaluated the effects of long-term ECLHA with mild to moderate hypothermia (33 degrees C) in a canine model of prolonged cardiac arrest. METHODS: 15 dogs were assigned to either the hypothermic (seven dogs, 33 degrees C) or normothermic group (eight dogs, 37.5 degrees C). All dogs were induced to normothermic ventricular fibrillation (VF) for 15 min, followed by 24 h of ECLHA and 72 h of intensive care. The hypothermia group maintained core (pulmonary artery) temperature at 33 degrees C for 20 h starting from resuscitation, then were rewarmed by 28 h. Outcome evaluations included: (1) mortality; (2) catecholamine dose; (3) time to extubation; (4) necrotic myocardial mass (g); and (5) neurological deficits score (NDS). RESULTS: in the normothermic group five dogs died of cardiogenic shock and one dog succumbed to poor oxygenation. The two surviving dogs remained comatose (NDS 60.5 +/- 4.9%) with necrotic myocardial mass of 14.5 +/- 3.5 g. In the hypothermic group, one dog died from pulmonary dysfunction, the other six dogs survived. The surviving dogs showed brain damage (29.8 +/- 2.5%), but there was evidence of some brain-protective effect. The mass of necrotic myocardium was 4.2 +/- 1.3 g in the hypothermic group or 3.4 times smaller than in the normothermic group. The survival rate was significantly higher in the hypothermic than in the normothermic group (P < 0.05). The catecholamine requirement was also lower in the hypothermic than in the normothermic dogs (P < 0.05). CONCLUSIONS: Long-term mild to moderate hypothermia with ECLHA induced immediately after cardiac arrest improved survival as well as cerebral and cardiac outcomes.     

Delayed platelet dysfunction in prolonged induced canine hypothermia.

Mild to moderate hypothermia (33-32 degrees C) is recognized as beneficial for brain protection after brain trauma. However, there are few experimental reports on hemostatic changes during prolonged hypothermia. We compared hemostatic changes during 72 h of mild to moderate hypothermia with data in normothermic dogs. METHOD: Mongolian dogs in a hypothermic group (N=7, 33 degrees C core temperature) and normothermic group (N=6, 37.5 degrees C core temperature) were anesthetized and instrumented to control temperatures and record hemodynamic changes continuously. Hypothermia or normothermia was maintained for 72 h. Platelet count, platelet aggregation, and thromboelastograms (TEG) were measured in each group. RESULTS: Heart rate, blood pressure, pulmonary pressure and blood gas were not significantly different between the two groups. Platelet counts, compared to baseline values, were significantly decreased in both groups (P<0.01). Platelet aggregation was significantly decreased in the hypothermic group after 24 h (P<0.04). CONCLUSION: Long-term hypothermia induced platelet dysfunction, leading to decreased platelet aggregation and prolonged coagulation time (R and K times of TEG).     

一氧化氮对急性出血坏死性胰腺炎肝脏中Toll样受体2/4 mRNA表达的影响

目的探讨一氧化氮(NO)对于急性出血坏死性胰腺炎(AHNP)时肝脏中T o ll样受体2/4(TLR 2/4)mRNA表达的影响。方法采用牛磺胆酸钠(TAC)逆行胰胆管注射制备AHNP肺损伤大鼠模型。动物分为假手术组、胰腺炎组和L精氨酸(L A rg)治疗组。假手术组于术后6 h,胰腺炎组和L A rg组分别于术后3、6、12 h取静脉血和肝组织,测定血清丙氨酸转氨酶(ALT)、天冬氨酸转氨酶(A ST)、淀粉酶和肝组织NO,逆转录聚合酶链反应(RT PCR)方法检测不同时间点肝组织肿瘤坏死因子α(TNFα)、TLR 2/4mRNA表达变化。结果与假手术组比较,胰腺炎组大鼠3 h肝组织TLR 2/4 mRNA表达开始增高〔(1.970±0.362)×10-3,(175.000±0.111)×1-0 3比(1.150±0.725)×10-6,(11.450±1.724)×10-4,〕12 h表达达峰值〔(2.940±0.316)×1-0 3,(2 673.000±88.380)×1-0 3,P均<0.01〕;血清淀粉酶ALT、A ST 3 h后即升高,肝损伤加重,肝组织TNFαmRNA表达升高,NO浓度逐渐降低(P<0.05或P<0.01);给予L A rg治疗后,NO浓度升高(P<0.05),TLR 2/4 mRNA表达降低〔3 h:(0.351±0.153)×1-0 3,(135.000±22.310)×1-0 3;6 h:(2.100±0.535)×10-3,(187.000±26.850)×1-0 3;12 h:(2.620±0.208)×1-0 3,(1 959.000±270.000)×10-3;P<0.05或P<0.01〕,血清淀粉酶、ALT、A ST均降低,肝损伤减轻,肝组织TNFαmRNA降低(P<0.05或P<0.01)。结论AHNP时,肝组织内TLR 2/4 mRNA表达上调,肝组织损伤加重;NO可以明显抑制AHNP肝组织TLR 2/4 mRNA的表达。     

Moderate hypothermia may be detrimental after traumatic brain injury in fentanyl-anesthetized rats

OBJECTIVES: To determine whether transient, moderate hypothermia is beneficial after traumatic brain injury in fentanyl-anesthetized rats. DESIGN: Prospective, randomized study. SETTING: University-based animal research facility. SUBJECTS: Adult male Sprague-Dawley rats. INTERVENTIONS: All rats were intubated, mechanically ventilated, and anesthetized with fentanyl (10 microg/kg intravenous bolus and then 50 microg.kg(-1).hr(-1) infusion). Controlled cortical impact was performed to the left parietal cortex, followed immediately by 1 hr of either normothermia (brain temperature 37 +/- 0.5 degrees C) or hypothermia (brain temperature 32 +/- 0.5 degrees C). Hypothermic rats were rewarmed gradually over 1 hr. Fentanyl anesthesia and mechanical ventilation were continued in both groups until the end of rewarming (2 hrs after traumatic brain injury). MEASUREMENTS AND MAIN RESULTS: Histologic assessment performed 72 hrs after traumatic brain injury was the primary outcome variable. Secondary outcome variables were physiologic variables monitored during the first 2 hrs after traumatic brain injury and plasma catecholamine and serum fentanyl concentrations measured at the end of both hypothermia and rewarming (1 and 2 hrs after traumatic brain injury). Contusion volume was larger in hypothermic vs. normothermic rats (44.3 +/- 4.2 vs. 28.6 +/- 4.0 mm, p <.05), but hippocampal neuronal survival did not differ between groups. Physiologic variables did not differ between groups. Plasma dopamine and norepinephrine concentrations were increased at the end of hypothermia in hypothermic (vs. normothermic) rats (p <.05), indicating that hypothermia augmented the systemic stress response. Similarly, serum fentanyl concentrations were higher in hypothermic (vs. normothermic) rats at the end of both hypothermia and rewarming (p <.05), demonstrating that hypothermia reduced the clearance and/or metabolism of fentanyl. CONCLUSIONS: Moderate hypothermia was detrimental after experimental traumatic brain injury in fentanyl-anesthetized rats. Since treatment with hypothermia has provided reliable benefit in experimental traumatic brain injury with inhalational anesthetics, these results indicate that the choice of anesthesia/analgesia after traumatic brain injury may dramatically influence response to other therapeutic interventions, such as hypothermia. Given that narcotics commonly are administered to patients after severe traumatic brain injury, this study may have clinical implications.     

Rapid induction of hypothermia with a small volume aortic flush during cardiac arrest in pigs

Purpose

The induction of deep cerebral hypothermia (15°C) via large-volume cold (4°C) saline aortic flush during cardiac arrest and resuscitation with cardiopulmonary bypass improves neurologic outcome in pigs. We hypothesized that induction of mild cerebral hypothermia (33°C) via smaller volume and resuscitation without bypass will improve survival and neurologic outcome after 15 minutes of cardiac arrest as compared with conventional resuscitation attempts.

Basic Procedures

Twenty-four pigs (29-38 kg) underwent ventricular fibrillation cardiac arrest for 15 minutes. Conventional resuscitation (n = 8) was compared with hypothermic (4°C, n = 8) and normothermic (38.5°C, n = 8) aortic flush (30 mL/kg) at the beginning of resuscitation efforts, with defibrillation attempts 2 minutes later. Outcomes after 9 days were compared.

Main Findings

In the hypothermic flush group, brain temperature decreased from 38.3°C ± 0.5°C to 33°C ± 0.5°C within 277 ± 112 seconds. We observed considerably higher mean coronary perfusion pressures in the normothermic and hypothermic flush groups (hypothermic vs conventional, P = .023; normothermic vs conventional, P = .041). Three animals of each flush group, compared with none of the conventional group, achieved restoration of spontaneous circulation (P = .2); and 3 pigs of the hypothermic flush group and 2 pigs of the normothermic flush group survived to 9 days without differences in neurologic outcome.

Principal Conclusion

A smaller volume, cold saline aortic flush during prolonged cardiac arrest rapidly induces mild cerebral hypothermia to 33°C and improves coronary perfusion pressure but does not result in a significant improvement in outcome as compared with conventional resuscitation attempts.     

Cerebral Cortical Aquaporin-4 Expression in Brain Edema following Cardiac Arrest in Rats

OBJECTIVES: Brain edema occurs following clinical as well as experimental cardiac arrest (CA) and predicts a poor neurologic outcome. The objective of this study was to determine the expression of cerebral cortex aquaporin (AQP)-4, a member of a family of membrane water-channel proteins, in brain edema formation following normothermic or hypothermic CA. METHODS: Twenty-four rats were subjected to time-matched normothermic (N-Sham, 37.5 degrees C +/- 0.5 degrees C, n = 6) or hypothermic (H-Sham, 34 degrees C +/- 0.5 degrees C, n = 6) sham experiments and normothermic (N-CA, n = 6) or hypothermic (H-CA, n = 6) CA induced by asphyxiation for 8 minutes. Hypothermia was induced before CA. The animals were resuscitated with cardiopulmonary resuscitation, ventilation, and epinephrine administration. Brain edema was determined by brain wet-to-dry weight ratio at one hour of resuscitation. AQP4 immunoactivity in the cerebral cortex was determined using immunohistochemical staining and was semiquantified as an intensity of staining with an automated cell imaging system. RESULTS: Mild hypothermia in the sham experiments did not alter cerebral cortex AQP4 immunoactivity (mean +/- SD) (55.0 +/- 3.7 in H-Sham vs. 53.3 +/- 1.7 in N-Sham, p > 0.05). N-CA resulted in a significant increase in AQP4 immunoactivity (61.8 +/- 4.5) compared with N-Sham (p = 0.01) and H-Sham (p = 0.03). H-CA attenuated AQP4 compared with N-CA (53.4 +/- 1.3, p = 0.01). Brain wet-to-dry weight ratios were 4.41 +/- 0.07 in N-Sham, 4.40 +/- 0.08 in H-Sham (p > 0.05 vs. N-Sham), 4.55 +/- 0.04 in N-CA (p = 0.004 vs. N-Sham; p = 0.005 vs. H-Sham), and 4.43 +/- 0.09 in H-CA (p = 0.02 vs. N-CA; p > 0.05 vs. N-Sham and H-Sham). CONCLUSIONS: Cerebral cortical AQP4 expression is up-regulated after normothermic CA, which is attenuated by hypothermia induced before CA.     

Post-cardiac arrest temperature manipulation alters early EEG bursting in rats

OBJECTIVES: Hypothermia improves outcomes after cardiac arrest (CA), while hyperthermia worsens injury. EEG recovers through periodic bursting from isoelectricity after CA, the duration of which is associated with outcome in normothermia. We quantified burst frequency to study the effect of temperature on early EEG recovery after CA. METHODS: Twenty-four rats were divided into three groups, based on 6h of hypothermia (T=33 degrees C), normothermia (T=37 degrees C), or hyperthermia (T=39 degrees C) immediately post-resuscitation from 7-min asphyxial CA. Temperature was maintained using surface cooling and re-warming. Neurological recovery was defined by 72-h neurological deficit score (NDS). RESULTS: Burst frequency was higher during the first 90min in rats treated with hypothermia (25.6+/-12.2min(-1)) and hyperthermia (22.6+/-8.3min(-1)) compared to normothermia (16.9+/-8.5min(-1)) (p<0.001). Burst frequency correlated strongly with 72-h NDS in normothermic rats (p<0.05) but not in hypothermic or hyperthermic rats. The 72-h NDS of the hypothermia group (74, 61-74; median, 25-75th percentile) was significantly higher than the normothermia (49, 47-61) and hyperthermia (43, 0-50) groups (p<0.001). CONCLUSIONS: In normothermic rats resuscitated from CA, early EEG burst frequency is strongly associated with neurological recovery. Increased bursting followed by earlier restitution of continuous EEG activity with hypothermia may represent enhanced recovery, while heightened metabolic rate and worsening secondary injury is likely in the hyperthermia group. These factors may confound use of early burst frequency for outcome prediction.     

Mild Hypothermia Induced before Cardiac Arrest Reduces Brain Edema Formation in Rats

OBJECTIVES: The mechanisms by which hypothermia improves cardiac arrest (CA)-induced brain damage are unclear. The authors hypothesized that mild hypothermia induced before CA attenuates brain edema formation by preventing neutrophil-mediated dysfunction of the endothelial cell junction proteins. METHODS: Eighteen rats were randomized to normal control surgery (group 1, n = 6), normothermic (37.5 degrees C) CA (group 2, n = 6), or hypothermic (34 degrees C) CA (group 3, n = 6). Hypothermia was induced with external cooling before CA in group 3. Cardiac arrest was induced by 8 minutes of asphyxiation. Brain edema was determined by wet-to-dry weight ratio and cerebral spinal fluid pressure (CSFP). Brain neutrophil content was determined by myeloperoxidase (MPO) activity, and occludin degradation was assessed by western blotting. RESULTS: Normothermic CA significantly increased brain wet-to-dry weight ratio from 4.52 +/- 0.04 in group 1 to 4.80 +/- 0.04 in group 2 (p = 0.0003) and CSFP from 3.6 +/- 0.9 in group 1 to 8.9 +/- 0.9 mm Hg in group 2 (p = 0.004). Mild hypothermia before CA in group 3 significantly reduced brain wet-to-dry weight ratio (4.68 +/- 0.03, p = 0.008 vs. group 2) and CSFP (3.8 +/- 0.5 mm Hg, p = 0.004 vs. group 2). Cardiac arrest increased brain MPO from 0.07 +/- 0.025 in group 1 to 0.16 +/- 0.02 units/gram brain weight in group 2 (p = 0.006) that was not decreased by hypothermia before CA (0.12 +/- 0.02 in group 3 (p = 0.07 vs. group 2). There was no occludin proteolysis in any group. CONCLUSIONS: Mild hypothermia before CA decreases CA-induced brain edema. The hypothermia-elicited reduction in brain edema does not appear to be neutrophil-dependent and the early brain edema formation may not involve the proteolysis of occludin.     

Posttraumatic hypothermia is neuroprotective in a model of traumatic brain injury complicated by a secondary hypoxic insult.

OBJECTIVE: Human traumatic brain injury frequently results in secondary complications, including hypoxia. In previous studies, we have reported that posttraumatic hypothermia is neuroprotective and that secondary hypoxia exacerbates histopathologic outcome after fluid-percussion brain injury. The purpose of this study was to assess the therapeutic effects of mild (33 degrees C) hypothermia after fluid-percussion injury combined with secondary hypoxia. In addition, the importance of the rewarming period on histopathologic outcome was investigated. DESIGN: Prospective experimental study in rats. SETTING: Experimental laboratory in a university teaching hospital. INTERVENTION: Intubated, anesthetized rats underwent normothermic parasagittal fluid-percussion brain injury (1.8-2.1 atmospheres) followed by either 30 mins of normoxia (n = 6) or hypoxic (n = 6) gas levels and by 4 hrs of normothermia (37 degrees C). In hypothermic rats, brain temperature was reduced immediately after the 30-min hypoxic insult and maintained for 4 hrs. After hypothermia, brain temperature was either rapidly (n = 6) or slowly (n = 5) increased to normothermic levels. Rats were killed 3 days after traumatic brain injury, and contusion volumes were quantitatively assessed. MEASUREMENTS AND MAIN RESULTS: As previously shown, posttraumatic hypoxia significantly increased contusion volume compared with traumatic brain injury-normoxic animals (p <.02). Importantly, although posttraumatic hypothermia followed by rapid rewarming (15 mins) failed to decrease contusion volume, those animals undergoing a slow rewarming period (120 mins) demonstrated significantly (p <.03) reduced contusion volumes, compared with hypoxic normothermic rats. CONCLUSIONS: These data emphasize the beneficial effects of posttraumatic hypothermia in a traumatic brain injury model complicated by secondary hypoxia and stress the importance of the rewarming period in this therapeutic intervention.