陆兆辉 王伟 徐志伟 朱德明
上海交通大学医学院附属上海儿童医学中心 心脏外科,上海 200127
基金资助:上海市高校选拔培养优秀青年教师科研专项基金(JDY06045)
作者简介:(1978-02),男,住院医师,博士;通讯作者:朱德明
目的:深低温停循环(deep hypothermia circulatory arrest,DHCA)后应用梯度灌注复温,调整脑组织血流-温度-代谢平衡,籍以优化体外循环复温过程中的神经保护策略。
方法:实验对象为3-4周龄的上海白猪(n=12),雌雄不拘,体重9.775±0.93Kg;将实验动物随机分为两组,建立微创的乳猪DHCA灌注模型(肛温18℃);A组为实验组(n=6),DHCA停循环90分钟,术后复温策略为梯度灌注复温,肛温每升高5℃,维持平台温度15分钟;B组为对照组(n=6),DHCA停循环90分钟,按照常规复温。以肛温33℃为目标恢复温度。两组均采用pH稳态方法管理血气。于术中监测试验动物的肛温、心率、心电图、血气分析、颈动脉血流量、颈静脉谷氨酸/天冬氨酸浓度,术后1小时取出试验动物脑组织,应用免疫组化方法对脑组织内的损伤敏感因子,NFB组分p50 蛋白的表达进行测定。
结果:实验组的复温时间为67.3±7.8min,对照组的复温时间为41.8±3.6min(P<0.05);分别于体外循环开始后10分钟、复温开始后15分钟、30分钟、45分钟进行采样。结果表明,实验组和对照组的脑血流量在复温后15分钟时无明显区别,而升温30分钟和45分钟时实验组的脑血流量显著低于对照组(P<0.05);升温30分钟和45分钟时实验组的BE值明显低于实验组(P<0.05);高压液相色谱(HPLC)分析表明升温30分钟和45分钟时对照组颈静脉谷氨酸浓度高于实验组,而仅在升温45分钟时,对照组的颈静脉天冬氨酸的浓度高于实验组。免疫组化分析表明两组之间没有明显差异。
结论:梯度灌注复温能够在深低温停循环后复温过程中起到一定的神经保护作用。其神经保护效应可能与保持复温阶段脑部血流-代谢-温度平衡有关。
关键词:深低温;停循环;再灌注;复温;
Neuoprotective Effect of Gradient Perfusion-rewarming after Deep Hypothermia Circulatory Arrest
Objective: To evaluate the neuroprotective effect of gradient perfusion-rewarming after deep hypothermia circulatory arrest (DHCA) in piglets.
Methods: 12 Shanghai piglets (3-4 weeks old) were randomly divided into two groups of A (experiment group) and B (control group), average weight 9.775±0.93Kg. Animal CPB model is completed with microinvasive technique. DHCA duration is 90 min in two groups. During the rewarming period, group A was rewarmed with gradient perfusion strategy, maintain the temperature for 15 min every 5 ℃ elevation of the core temperature. Group B was rewarmed according normal consistent rewarming strategy. PH-stat management is adopt in both groups. Blood gas analysis, rectal temperature, heart rate, ECG, blood flow rate of carotid artery, glumatic acid/ aspartate level of jugular vein and protein NFB of brain tissue are monitored during and/or after the cardiopulmonary bypass (CPB).
Results: Duration of rewarming in group A is 67.3±7.8min, and 41.8±3.6min in group B (P<0.05). Sample collected at the beginning of CPB, 15 min of rewarming, 30 min of rewarming and 45 min of rewarming show that there is no difference between the blood flow rate at 15 min of rewarming; difference are shown at the 30 min and 45 min of rewarming (p<0.5). High performance liquid chromatography (HPLC) analysis show the obvious difference of glumatic acid level of jugular vein at 30 min of rewarming and 45 min of rewarming (p<0.5), this kind of difference of aspartate can only be seen at the 45 min of rewarming. Immunohistochemistry analysis show there is no difference of brain damage in two groups.
Conclusion: Controlled gradient perfusion-rewarming strategy can improve the neuroprotective effect during DHCA, keeping the balance of the blood flow, cerebral local temperature and brain metabolism might be the mechanism.
Key Words:Deep Hypothermia; Circulatory Arrest; Perfusion; Rewarming
近十年来,婴幼儿先天性心脏病的纠治技术进展迅速,围手术期并发症及死亡率显著下降,但体外循环手术后脑部并发症-脑功能紊乱发生率仍比较高[1],据统计体外循环手术后60%的病人有不同程度的脑功能紊乱,症状轻重不等,可呈轻微的行为改变、暂时性记忆丧失,严重的可出现昏迷、抽搐、偏瘫、截瘫等,虽然多数程度较轻,且呈一过性,神经系统症状迅速恢复而无后遗症,但少数病人属严重脑缺血缺氧,可因而致残甚至死亡。对于婴幼儿来说,优化先天性心脏病围手术期的神经保护策略对于患儿的生存率和远期生存质量起着至关重要的作用。
深低温停循环技术(Deep Hypothermia Circulatory Arrest, DHCA)在新生儿和小婴儿复杂先心病的外科救治中有无可替代的作用,是心血管手术发展史上的里程碑,近年来的研究发现,DHCA时应用pH-stat可获得较Alpha-stat更好的脑保护效果[2],尤其在小婴儿深低温体外循环下,不会产生脑组织奢灌和颅内压增高。但是对于DHCA复温过程的控制,在学界还有存在一定的争论[3]。本研究拟应用梯度灌注复温技术,并对其神经保护效应进行探讨。
表1 组间不同时间点脑血流量对比
Tab 1 Blood flow in groups at different time
组别 |
基础值 |
升温15分钟 |
升温30分钟 |
升温45分钟 |
实验组(ml/min) |
118.33±14.57 |
38.13±16.84 |
57.19±12.32 |
94.76±19.80 |
对照组(ml/min) |
121.17±15.11 |
42.12±11.36 |
78.10±21.51 |
111.43±21.18 |
统计分析 |
p>0.05 |
P>0.05 |
P<0.05 |
P<0.05 |
2.4实验组中升温15min与升温30min时天冬氨酸浓度无明显差异(p>0.05),升温45min时比升温30min、升温15min天冬氨酸浓度高(p<0.01)。对照组中天冬氨酸浓度变化与实验组中相同。两组间在升温15min时天冬氨酸浓度无明显差异(p>0.05),在升温30分钟时两组天冬氨酸浓度也无明显差异(p>0.05),升温45分钟时对照组天冬氨酸浓度则明显高于实验组(p<0.05)。
表2 不同时间点颈静脉谷氨酸含量(μmol/L)
Tab 2 Level of glumatic acid at different time
组别 |
升温15min(Ⅰ) |
升温30min(Ⅱ) |
升温45min(Ⅲ) |
Ⅰ*Ⅱ |
Ⅰ*Ⅲ |
Ⅱ*Ⅲ |
实验组 |
390±127 |
315±62 |
525±79 |
p>0.05 |
P<0.05 |
p>0.05 |
对照组 |
548±201 |
443±76 |
584±182 |
p>0.05 |
P<0.05 |
p>0.05 |
统计分析 |
p>0.05 |
P<0.01 |
P<0.01 |
|
|
|
表3 不同时间点颈静脉天冬氨酸含量(μmol/L)
Tab 3 Level of aspirate at different time
组别 |
升温15min(Ⅰ) |
降温30min(Ⅱ) |
升温45min(Ⅲ) |
Ⅰ*Ⅱ |
Ⅰ*Ⅲ |
Ⅱ*Ⅲ |
实验组 |
58±39 |
83±32 |
149±26 |
p>0.01 |
p<0.01 |
p<0.01 |
对照组 |
60±15 |
107±19 |
203±48 |
p>0.01 |
p<0.01 |
p<0.01 |
统计分析 |
p>0.05 |
p>0.05 |
p<0.05 |
|
|
|
值得提出的是,复温阶段颈静脉谷氨酸和天冬氨酸的浓度均明显高于刚开始转流时(P<0.01),因此未在上述数据中予以列出。这可能跟长时间深低温停循环(90min)有关。临床上DHCA的时程一般限制在45分钟以内。
表 4 海马区域NfkB表达阳性率(%)
Tab 4 expression of NfkB in hippocampus of piglet
组别 |
1 |
2 |
3 |
4 |
5 |
6 |
均值 |
8.77 |
7.65 |
15.88 |
10.78 |
7.05 |
11.36 |
10.24±3.24 | |
对照组 |
6.84 |
10.66 |
15.26 |
11.70 |
13.42 |
13.45 |
11.89±2.94 |
统计分析 |
P>0.05 | ||||||
图1:NFkb在小猪海马组织中的表达(×200)
Fig 1 expression of NfKB in CA1 and CA3 of hippocampus of piglet
A:小猪海马CA1区空白对照细胞未见明显棕黄色颗粒
B:小猪海马CA3区空白对照细胞未见明显棕黄色颗粒
C:小鼠海马在两组中CA1区可见细胞明显呈棕黄染色
D:小鼠海马在两组中CA3区可见细胞呈明显棕黄染色
体外循环中温度控制起着非常重要的作用[8],我们的动物实验表明DHCA后梯度灌注复温策略可以使脑部血流量上升更加平稳,减少兴奋性氨基酸的释放,实验组在复温阶段的脑血流量因为温度-压力控制而缓慢上升,可能与神经组织代谢之间达成一种平衡状态,从而起到一定的神经保护效应;但组织学检查并未检验出梯度再灌注有明显的神经保护效应。这可能跟DHCA的时程较长,脑组织损伤总体较为严重有关,也可能由于术后观察时间较短,未能对神经损伤进行长期动态的监测,因此今后应该倾向于对DHCA后长期神经功能监测方面的研究。
参考文献:
1: Greeley WJ, Kern FH, Meliones JN, Ungerleider RM. Effect of deep hypothermia and circulatory arrest on cerebral blood flow and metabolism. Ann Thorac Surg. 1993 Dec;56(6):1464-6.
2:Priestley MA, Golden JA, O’Hara IB, et al. Comparison of neurologic outcome after deep hypothermic circulatory arrest with alpha-stat and cardiopulmonary bypass in newborn pigs. J Thorac Cardiovasc Surg.2001,121(2):336-43
3: Tveita T. Rewarming from hypothermia. Newer aspects on the athophysiology of rewarming shock. Int J Circumpolar Health. 2000 Oct;59(3-4):260-6.
4. Nanri KC, Montecot V, Springhetti JS, et al. The selective inhibitor of neuronal nitric oxide synthase, 7-nitroindazole, reduces the delayed neuronal damage due to forebrain ischemia in rats. Stroke. 1998,29:1248–1253
5. 朱德明, 王伟. 我国小儿体外循环发展五年的调查[J]. 中国体外循环杂志,2005,3(4): 195-198
6. Greeley WJ, Kern FH, Ungerleider RM, Boyd JL 3rd, Quill T, Smith LR, BaldwinB, Reves JG. The effect of hypothermic cardiopulmonary bypass and total circulatory arrest on cerebral metabolism in neonates, infants, and children. J Thorac Cardiovasc Surg. 1991 May;101(5):783-94.
7. Croughwell N, Smith LR, Quill T, Newman M, Greeley W, Kern F, Lu J, Reves JG. The effect of temperature on cerebral metabolism and blood flow in adults during cardiopulmonary bypass. J Thorac Cardiovasc Surg. 1992 Mar;103(3):549-54.
8. 朱德明,王伟,黄继红等. 体外循环中温度对小儿神经系统的影响[J]. 中国体外循环杂志, 2008, 6(4): 201-203
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