延迟亚低温联合硫酸镁促进心肺复苏后神经功能恢复及其机制的研究

Mild therapeutic hypothermia is the only treatment demonstrated to improve survival and neurological outcome of patients that regain spontaneous circulation after cardiac arrest. However, even with therapeutic hypothermia, approximately 1/2 of post-cardiac arrest patients still die or have an unfavorable neurologic outcome. A fundamental gap in our current knowledge is what, if any, therapeutic interventions provide additional neuroprotection when combined with therapeutic hypothermia after cardiac arrest. A continued lack of understanding in the area will prevent the optimization of post-cardiac arrest care and limit the number of patients who return to normal function after being resuscitated from cardiac arrest..Magnesium modulates the activity of the NMDA receptor, creating a voltage-dependent block which inhibits Ca2+ influx. Ischemia-reperfusion injury results in widespread neuronal depolarization,thereby relieving the magnesium block of NMDA receptors. Supplementation with Mg2+ would be expected to partially preserve the blockade of the NMDA receptor, while a deficiency in available Mg2+ could exacerbate calcium influx after injury. Consistent with this hypothesis，postinjury Mg2+ treatment reduced calpain activation in the neuron of brain-injured rats, and also attenuated neurologic function damage，our overall goal is to improve the neurologic outcome of patents resuscitated from cardiac arrest. The overall objective of this application is to determine if intravenous magnesium sulfate (MgSO4) provides added therapeutic benefit when combined with hypothermia after cardiac arrest. Our central hypothesis is that post-cardiac arrest intravenous MgSO4 combined with mild therapeutic hypothermia reduces neurodegeneration and improves neurologic function when compared to hypothermia alone. This hypothesis is supported by our own in vitro data demonstrating synergistic neuroprotection with combined MgSO4 and hypothermia in primary hippocampal neuron culture after NMDA exposure. In addition we have generated preliminary in vivo data that suggests enhanced neuroprotection when intravenous MgSO4 is combined with therapeutic hypothermia after cardiac arrest in rats. Our own preliminary data is supported by the work of Zhu et al who reported enhanced neuroprotection when intravenous MgSO4 was combined with mild therapeutic hypothermia after transient forebrain ischemia in rats. More recently, Chang et al reported that intravenous MgSO4 (without hypothermia) improved cerebral blood flow and survival in a rat cardiac arrest model. The rationale for this project is to provide proof-of-principle data in a cardiac arrest model that is needed to justify and guide further testing of this combination therapy in large animal models and eventually clinical trials.

亚低温治疗是目前唯一在临床上被证实的在心跳骤停恢复自主循环后能有效提高生存率和改善神经系统预后的治疗方式，但即使经过亚低温治疗，仍有约二分之一恢复心跳的患者最终死亡或神经功能不良。我们前期研究发现，亚低温治疗即使延迟4小时进行仍能够有效改善患者预后，但延持8小时则无效；在体外和动物实验中发现，亚低温联合硫酸镁比单纯亚低温能进一步保护缺血再灌注后的神经元。本申请项目拟采取延迟的亚低温联合静输硫酸镁治疗心肺复苏后的全脑缺血再灌注损伤，以获得比单纯亚低温治疗更好的疗效，并将亚低温的治疗时间窗扩大。本项目还将利用体外和动物模型研究亚低温和（或）硫酸镁对脑缺血再灌注后Calpain调控调控肌醇三磷酸/钙信号通路的影响。本研究不仅能够明确亚低温联合硫酸镁治疗心肺复苏后脑缺血再灌注的最佳方案，而且能够发掘脑Calpain调控肌醇三磷酸/钙信号通路的机制，为脑缺血再灌注损伤的治疗提供新途径。

亚低温治疗是目前唯一在临床上被证实的在心跳骤停恢复自主循环后能有效提高生存率和改善神经系统预后的治疗方式，而且即使延迟4小时的亚低温治疗仍能够有效改善患者预后。而在体外实验和局灶性脑缺血的动物实验中发现，亚低温联合硫酸镁比单纯亚低温能.进一步保护缺血再灌注后的神经元。.本研究项目旨在摸索静脉输入不同浓度的硫酸镁与延迟的亚低温治疗相结合进一步提高心脏停跳复苏所造成全脑缺血再灌注后的大鼠的生存率、神经功能及神经元存活率。.应用延迟4小时的亚低温结合静脉输注高（240mg/kg/h x 1小时+30mg/kg/h x 27小时）、中（120mg/kg/h x 1小时+20mg/kg/h x 27小时）、低(60mg/kg/h x 1小时+10mg/kg/h x 27小时)浓度硫酸镁的联合方案对心脏停跳复苏所造成的全脑缺血再灌注损伤进行治疗。相对于单纯亚低温治疗组（29%），高、中、低浓度硫酸镁联合治疗方案的7日生存率分别为13%，29%和33%,除了亚低温结合静脉输入高浓度硫酸镁的治疗方案显著降低了生存率外（P=0.001），其余各组生存率没有统计学差异（P=0.93）；对于神经功能保护，相对于单纯亚低温治疗组（17%），高、中、低浓度硫酸镁联合治疗方案的优良神经功能（GNS≥450）比例分别为0%，13%和17%,各组之间没有统计学差异（P>0.05）; 在神经元保护方面，相对于单纯亚低温治疗组（47.5%），高、中、低浓度硫酸镁联合治疗方案的海马神经元存活率分别为55.1%，58.5%和57.9%,各组之间没有统计学差异（P>0.05）。亚低温结合高浓度硫酸镁静脉输入联合治疗方案与单纯亚低温治疗相比降低了生存率，而亚低温结合静脉输入中等浓度或低浓度硫酸镁的联合治疗方案与单纯亚低温治疗相比，在改善生存率和神经功能方面没有统计学差异。对于神经元保护，亚低温结合高、中、低浓度硫酸镁联合治疗方案和单纯亚低温治疗四组之间均没有统计学差异。.对于窒息法心脏停跳大鼠模型，亚低温结合静脉输入硫酸镁的联合治疗方案相对于单纯的亚低温治疗没有改善全脑缺血再灌注后的生存率、神经功能和神经元存活率。这项研究提示对于心脏停跳患者的救治，除了常规的心肺复苏和高级生命支持，应以体温控制性治疗为主，而无须积极地静脉输入硫酸镁。