深低温停循环后梯度灌注复温的脑保护作用

Neuoprotective effect of gradient perfusion-rewarming after deep hypothermia crculatory arrest

目的探讨深低温停循环（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3-4周龄上海白猪12只，雌雄不拘，体质量（9．78±0．93）kg。通过简单随机分为实验组和对照组，每组6只，建立微创的乳猪DHCA灌注模型（肛温18℃）。实验组DHCA停循环90min，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15min；对照组DHCA停循环90min后常规复温。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，分别于转流开始后10min，复温开始后15、30和45min采样，监测肛温、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1h取实验动物脑组织，对海马CA1区进行组织学评估，并应用免疫组化方法测定脑组织内的损伤敏感因子、NF-κB组分p50蛋白的表达。结果实验组的复温时间为（67．3±7．8）min，对照组的复温时间为（41．8±3．6）min（P＜0．05）。复温后15min时，实验组和对照组脑血流量的差异无统计学意义。升温30min和45min时，实验组的脑血流量显著低于对照组（P＜0．05）。高压液相色谱（HPLC）分析显示，升温30min和45min时对照组颈静脉谷氨酸浓度高于实验组，仅在升温45min时，对照组的颈静脉天冬氨酸的浓度高于实验组。组织学评估显示梯度复温组海马CA1区椎体细胞层损失较少，免疫组化分析示实验组和对照组NF-κB的表达差异无统计学意义。结论深低温停循环后，梯度灌注复温有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。

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 （9.78±0.93 ）kg. 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 eardiopulmonary bypass （CPB）. Results Duration of rewarming in group A is （67.3 ± 7. 8） min, and （41.8 ± 3.6） min 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 rain of rewarming （ P〈0.5 ） , this kind of difference of aspartate can only be seen at the 45 rain of rewarming. Histologic evaluation shows gradient rewarming has a better effect on preservation of CA1 area neuron in hippocampus, however, Immunohistochemistry doesn＇t find the same effect. 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.