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The effects of regional cerebral blood flow during hyperventilation

过度通气时局部脑血流量的影响

基本信息

批准号：
15592147
负责人：
MOMOTA Yoshihiro
金额：
$ 1.41万
依托单位：
Osaka Dental College
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

项目摘要

An experimental study using the non-radioactive colored microsphere method was conducted to evaluate changes in regional cerebral blood flow associated with hyperventilation in rabbits. Rabbits underwent controlled ventilation using a mixture of nitrous oxide (67%) and oxygen (33%), and were subjected to the following procedures : (1)PaCO_2 of 30-40 mmHg was obtained by adjusting ventilation frequency and tidal volume and yellow microspheres were then injected into the left atrium (normocapnia group) ; and (2)hyperventilation was induced by increasing ventilation frequency and tidal volume to achieve a PaCO_2 of 25-30 mmHg and blue microspheres were then injected into the left atrium (hypocapnia group). Rabbits were randomly allocated to two groups, one undergoing first the hypocapnia and then the normocapnia procedure and the other undergoing first the normocapnia and then the hypocapnia procedure. Following the procedures, the brain was isolated and microspheres were retrieved from tissue samples from the pons, thalamus, cerebellum, hippocampus, and cerebral cortex as well as blood samples for reference. Blood flow in each sample was calculated on the basis of absorption of microspheres, and comparison of blood flow between normocapnic and hypocapnic procedures was performed. Regional cerebral blood flow in the state of hypocapnia was significantly lower in the cerebral cortex and cerebellum than in the state of normocapnia, but the magnitude of hypocapnia-associated decrease in blood flow was small in the hippocampus, pons, and thalamus. These findings indicate that the decrease in cerebral blood flow due to hyperventilation is especially significant in areas such as the cerebral cortex and cerebellum that require abundant supply of oxygen and to which delivery of blood from cerebral vessels is especially large.

本实验采用非放射性彩色微球法观察了过度通气时家兔局部脑血流的变化。家兔采用氧化亚氮（67%）和氧气（33%）混合气体进行控制性通气，（1）调节通气频率和潮气量使PaCO_2维持在30-40 mmHg，然后向左心房注射黄色微球（正常碳酸血症组）;（2）增加通气频率和潮气量，使PaCO_2达到25-30 mmHg，诱导过度通气，然后向左心房注射蓝色微球低碳酸血症组。将家兔随机分为两组，一组先进行低碳酸血症，然后进行正常碳酸血症程序，另一组先进行正常碳酸血症，然后进行低碳酸血症程序。在程序之后，分离脑，并从来自脑桥、丘脑、小脑、海马和大脑皮层的组织样品以及血液样品中取出微球以供参考。根据微球的吸收计算每个样品中的血流量，并比较正常碳酸血症和低碳酸血症程序之间的血流量。低碳酸血症状态下大脑皮质和小脑的局部脑血流量显著低于正常碳酸血症状态，但海马、脑桥和丘脑的低碳酸血症相关血流量减少幅度较小。这些发现表明，由于过度通气导致的脑血流量减少在需要充足氧气供应的区域如大脑皮层和小脑中特别显著，并且来自脑血管的血液输送到这些区域特别大。