左旋精氨酸对复苏犬缺血缺氧性脑损害的影响

Influence of L-arginine on hypoxia-ischemia brain injury in dogs after circulatory arrest and resuscitation

目的利用犬停循环(CA)复苏模型,研究深低温及NO前体-左旋精氨酸(L-arg)对复苏犬脑氧代谢及超微结构的影响。方法健康成年杂种犬10只,随机分为L-arg预处理组和对照组,每组5只。按临床方法建立体外循环转流降温至鼻咽温18℃停循环,90min后恢复体外循环复苏。分别于CA前30min、CA0min、CA45min、CA90min、复苏后60min抽取颈静脉、颈动脉血测算颈静脉血氧饱和度(SjvO2)。取脑皮质透射电镜观察脑超微结构改变。处死后测脑皮质含水量。结果停循环后SjvO2逐步降低,至CA90min达最低值,复苏后回升。停循环期L-arg预处理组SjvO2高于对照组(P<0.001)。复苏后L-arg预处理组脑皮质超微结构改变轻于对照组,脑组织含水量亦低于对照组(P<0.05)。结论深低温可改善停循环后脑氧供需平衡,对缺血缺氧性脑损害有保护作用,L-arg预处理有利于停循环后脑复苏治疗。

Objective To study the effects of deep hypothermia and L-arginine（NO precursor） pretreatment on cerebral protection after circulatory arrest and resuscitation in a canine model. Methods Ten healthy adult dogs of both sexes, weighing 14.45±2.3k, g, were randomly divided into two groups（n=5）： sham treatment group and L-arginine pretreatment group. Extracorporeal circulation was established routinely,circulatory arrest was induced when the nasopharyngeal temperature was reduced to 18℃, then the animals were resuscitated 90rain later with extracorporeal circulation. SjvO2 was measured at 30rnin before circulatory arrest, Orain, 45rain, 90rain after circulato- ry arrest and at 60minutes after resuscitation. The ultrastructure changes in cerabral cortex were observed with transmission electron microscope （HITACHI 7500）. The brain water content was also determined after the dogs were sacrificed. Results SjvO2 had decreased obviously after circulatory arrest, attaining the lowest level in CA 90rain. After resuscitation it increased again in both groups. The levels of SjvO2 in dogs of L-arginine pretreatment group were markedly higher than that of control group at 45rain and 90rain after circulatory arrest （P〈0. 001）. The brain water content in pretreatment group was lower than that of control group （P=0. 044）. The ultrastructure changes in the brain were also milder in L-arginine pretreatment group. Conclusions Deep hypothermia can suppress cerebral oxygen metabolism and keep brain tissae viable after prolonged circulatory arrest for about 45rain. L-arginine had protective effects on the brain, and could improve cerebral oxygen metabolism after circulatory arrest and resuscitation.