Marcus M L, Heistad D D, Ehrhardt J C, Abboud F M
J Appl Physiol. 1976 Apr;40(4):501-7. doi: 10.1152/jappl.1976.40.4.501.
Cerebral arteriovenous shunting of 7-10-, 15-, 25-, and 50-mum labeled microspheres was studied in 12 anesthetized dogs. Approximately 8% of the 7-10-mum spheres were shunted to cerebral venous blood, whereas less than 2% of the 15-, 25-, and 50-mum spheres were shunted. Cerebral vascular dilatation induced by hypoxia or hypercapnia did not alter the shunting. The calculated total cerebral flow was 10-15% lower with 7-10-mum microspheres as compared with simultaneous flows measured with the larger microspheres which also suggests that 7-10-mu spheres were shunted through the brain. The calculated distribution of cerebral flow was similar with 7-10- and 15-mum spheres but markedly altered when 50-mum spheres were used. Repeated injections of 15-mum spheres were used. Repeated injections of 15-mum microspheres given under stable conditions yielded total cerebral blood flows which averaged +/- 6% of their respective mean and the regional distribution of flow was highly reproducible. These data suggest that, in dogs, 15-mum spheres are an appropriate size to use to measure cerebral blood flows, since shunting is minimal, the distribution is not artifactually distorted, and the measurements are reproducible.
在12只麻醉犬身上研究了7-10微米、15微米、25微米和50微米标记微球的脑动静脉分流情况。7-10微米的微球中约8%分流至脑静脉血，而15微米、25微米和50微米的微球分流比例不到2%。缺氧或高碳酸血症诱导的脑血管扩张并未改变分流情况。与用较大微球同时测量的血流相比，使用7-10微米微球时计算出的总脑血流量低10%-15%，这也表明7-10微米的微球经脑分流。7-10微米和15微米微球计算出的脑血流分布相似，但使用50微米微球时则明显改变。采用重复注射15微米微球。在稳定条件下重复注射15微米微球得出的总脑血流量平均为各自平均值的±6%，且血流的区域分布具有高度可重复性。这些数据表明，在犬类中，15微米的微球是用于测量脑血流量的合适大小，因为分流极少，分布不会被人为扭曲，且测量结果具有可重复性。
