【摘要】 目的 旨在探讨维持脑低温是否作为逆灌脑保护的主要作用机制。方法 15℃深低温停循环120min期间，15头猪被分为3组：A组(n=5)，停循环；B组(n=5)，23～29mmHg压力冷血逆行脑灌注；C组(n=5)，34～40mmHg压力冷血逆行脑灌注。然后，在37℃下转流60min。深低温停循环以脑皮层15℃为标准。连续监测脑、食管和灌注血液的温度。激光多普勒血流仪测定脑血流量，脑动、静脉血氧含量计算氧摄取率。结果 在降温和复温期间，脑温度的变化比食管温度要慢。不论停循环还是逆灌保护，脑组织都自然复温2℃～3℃，表明逆灌不能有效地维持停循环期间的脑低温，逆灌能维持躯体低温。逆灌期间，氧摄取率上升，提示逆灌可以提供营养血流到脑组织。结论 在猪的急性模型，逆灌产生的脑保护作用机制主要不是维持脑的低温，而是提供营养血流或氧到脑组织。

    【关键词】 逆行脑灌注；深低温停循环；脑温度；脑保护

    Study of brain protecting mechanism by retrograde cerebral perfusion during circulatory arrest

    LIN Zhi-jun,YIN Xiao-mei.

    Departments of Cardio-thoracic Surgery,Sir Run Run Shaw Hospital,Faculty of Medicine,Zhejiang University,Hangzhou 310016,China

    【Abstract】 Objective This study was to determine if retrograde cerebral perfusion (RCP) improves brain protection mainly as a result of its ability to maintain cerebral hypothermia in a pig model.Methods Fifteen pigs were subjected to 120 minutes of hypothermic circulatory arrest (HCA) alone (A group,n=5),HCA+RCP at perfusion pressures of 23～29mmHg(B group,n=5),or at perfusion pressures of 34～40 mm Hg(C group,n=5) at 15℃,followed by 60 minutes of normothermic cardiopulmonary bypass.After brain temperature reached 15℃,HCA was initiated with or without RCP.Temperatures in the brain,esophagus,and perfusate/blood were monitored continuously.Brain tissue blood flow was measured continuously using a laser flowmeter.Brain oxygen extraction was calculated from the oxygen contents in arterial and venous blood samples.Results The change in temperature was slower in the brain than in the esophagus during cooling and rewarming.A similar degree of spontaneous rewarming (from 15℃ to 17～18℃)occurred in the brain during both HCA and RCP,indicating RCP does not provide better maintenance of cerebral hypothermia during circulatory arrest relative to HCA alone.The esophageal temperature rose more slowly during RCP than during HCA alone,indicating that RCP maintains better hypothermia in the body.During RCP,oxygen was extracted continuously from the blood by the brain,indicating that RCP may provide nutrient flow to the brain.Conclusion In an acute pig model,cerebral hypothermia does not appear to be a principal mechanism by which RCP improves brain protection.Retrograde cerebral perfusion seems to provide nutrient flow/oxygen to brain tissue,leading to better brain protection. ......