心脏骤停及脑损伤
心脏骤停
心脏骤停后脑损伤
Post-cardiac arrest brain injury (PCABI) is the main cause of death in patients resuscitated from cardiac arrest, and the main cause of long-term disability in those who survive the acute phase.
HIBI临床影像学表现
HIBI临床病理生理学
原发性
脑损伤
脑氧输送依赖于脑血流(CBF),心脏骤停导致所有重要器官的血流灌注和氧供停止。大脑由于缺乏固有的能量储存。很快产生神经元缺血和细胞死亡。
头高位CPR和REBOA
主动脉球囊阻断技术(REBOA)常被用于严重失血性休克和创伤性心脏骤停患者的治疗,大量动物研究显示REBOA可使冠状动脉灌注、脑灌注及自主循环恢复率升高,需大规模临床试验来证明其可行性及能否改善心脏骤停患者的预后。
CPR新技术-ECPR
继发性
脑损伤
自主循环(ROSC)恢复后,脑血流也随之恢复,但缺血的脑血管床再灌注将导致继发性脑损伤,主要以脑氧输送(CDO2)与氧消耗不平衡为特征。
继发性脑损伤干预
这张图表比较好,提高氧输送、降低氧消耗来改善脑氧的输送,包括几个方面。第一个是动脉的血氧含量,第二个是脑的灌注压,第三个是脑血管的反应性等等一些情况来提高氧输送,提高氧输送的同时,还要注意降低氧的消耗,通过比如说目标体温的管理,一些药物,镇静镇痛等等。
脑氧供及氧耗的决定因素
壹
提高动脉血氧含量——增加氧供
CaCO2(ml/100 ml blood)=1.34×Hb×SaO2)+(PaO2×0.003)
Hb水平与预后的关系
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PaO2与预后的关系
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PaO2的调节
在缺乏确凿证据的情况下,目标应该是常氧(氧分压为10-12kPa)。
目前欧洲复苏委员会(ERC)和欧洲重症监护医学学会(ESICM)共同发布的复苏后治疗指南建议同时避免缺氧和高氧,将SpO2保持在94%~98%的“安全范围”内。
贰
增加脑血管反应性——增加氧供
脑血管反应性取决于血二氧化碳分压(PaCO2)
PaCO2的作用
动脉血二氧化碳分压(PaCO2)通过对血管平滑肌的影响调节脑血管阻力和脑血流,当20mmHg<PaCO2<80mmHg时,PaCO2↑脑血管舒张,PaCO2↓脑血管收缩。PaCO2介导的脑血管反应性原理可用于优化脑血流和脑氧合。
低碳酸血症(PaCO2<35mmHg)引起血管收缩,减少CBF,从而导致缺血。
高碳酸血症(PaCO2>45mmHg)导致脑血管扩张充血,增加颅内压而降低脑灌注压,CBF减少。
PaCO2与预后的关系
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轻度高碳酸血症与预后的关系
叁
增加脑灌注压——增加氧供
CPP=MAP-ICP
MAP-个体化灌注目标
MAP与预后的关系
最佳MAP的监测方法
近红外光谱监测(NIRS)可通过分析MAP与局部氧饱和度(rSO2)的关系来确定最佳MAP,评估HIBI后脑自动调节功能。
NIRS在额叶最外层2cm处测量氧合与非氧合血红蛋白比值,即局部氧饱和度(rSO2)。整合MAP和rSO2之间的波动,得出相关性参数COx。正COx值表示自动调节功能障碍,Cox为负或近零表示自动调节功能完整。
MAP目标
目前对于脑损伤中个体化血压目标的最佳控制范围尚未达成共识。ERC-ESICM发布的复苏后护理指南没有建议任何特定的血压目标,但建议避免低血压(MAP<65mmHg)和靶向控制MAP以达到足够的尿量(>0.5ml/kg/h)、维持乳酸的正常或降低。
肆
降低脑氧代谢率——降低氧耗
脑氧代谢率(CMRO2)依赖于细胞活性,发热、癫痫发作、拟交感神经药物使用时增加,镇静、低体温时降低。
TTM改善预后
目标温度管理(TTM)是目前唯一被证实可以有效改善CA患者神经功能预后的措施,它的有效性已经被多项随机对照试验及Meta分析证实。可以降低脑代谢率和耗氧量,减少自由基的生成、减轻脑水肿等。
TTM与预后的关系
TTM最佳深度
TTM持续时间
脑氧监测方法
SUMMARY
心脏骤停后脑损伤是致死致残的主要原因。 管理重点是通过优化脑氧输送和氧消耗之间平衡限制继发性损伤。 优化策略可能有提升Hb、同时避免高氧和低氧、轻度高碳酸血症、个体化MAP、目标温度管理等。 能有效改善心脏骤停复苏后脑氧输送的策略,还需要大规模临床试验去论证。 | 小 结 |
参考文献
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