Chao C R, Hohimer A R, Bissonnette J M
Department of Obstetrics and Gynecology, Columbia University, New York, New York 10032.
J Cereb Blood Flow Metab. 1991 May;11(3):416-23. doi: 10.1038/jcbfm.1991.82.
The early time period following ischemia may be of pathogenetic importance in hypoxic-ischemic brain injury. Global cerebral oligemia was induced in ten late gestation fetal sheep by inflation of a balloon occluder around the brachiocephalic artery. Cerebral blood flow, oxygen, glucose, and lactate net flux, and oxygen delivery were measured by the Fick principle following 1 h of oligemia and at 5, 30, and 60 min of postoligemic reperfusion. During oligemia, cerebral blood flow decreased by 74 +/- 10% (mean +/- SD) and oxygen consumption decreased by 34 +/- 24%. The glucose:oxygen quotient was elevated throughout the oligemic period. In the early (5 min) reperfusion period, blood flow and oxygen delivery were not different from control but oxygen consumption was persistently depressed by 27 +/- 32%; fractional extraction of oxygen was 0.38 +/- 0.10 during control and 0.24 +/- 0.09 during early reperfusion. The venous oxygen tension increased modestly from 15.2 +/- 2.4 to 18.0 +/- 1.7 mm Hg; the postoligemic venous pO2 was limited by the lack of reactive hyperemia combined with the low arterial pO2 of the intrauterine environment. Postoligemic carbohydrate fluxes could not be differentiated from control possibly due to blood-brain barrier limitations. These factors may be related to the relative resistance of the fetal brain to hypoxic-ischemic injury.
缺血后的早期阶段在缺氧缺血性脑损伤的发病机制中可能具有重要意义。通过在头臂动脉周围放置球囊封堵器充气，对10只妊娠晚期胎羊造成全脑低灌注。在低灌注1小时后以及低灌注后再灌注5分钟、30分钟和60分钟时，根据菲克原理测量脑血流量、氧、葡萄糖和乳酸净通量以及氧输送量。在低灌注期间，脑血流量减少了74±10%（平均值±标准差），氧消耗减少了34±24%。在整个低灌注期间，葡萄糖：氧商升高。在早期（5分钟）再灌注期，血流量和氧输送量与对照组无差异，但氧消耗持续降低27±32%；对照期间氧的分数提取率为0.38±0.10，早期再灌注期间为0.24±0.09。静脉血氧分压从15.2±2.4毫米汞柱适度升高至18.0±1.7毫米汞柱；低灌注后静脉血氧分压受到缺乏反应性充血以及子宫内环境动脉血氧分压较低的限制。低灌注后碳水化合物通量与对照组无差异，可能是由于血脑屏障的限制。这些因素可能与胎儿脑对缺氧缺血性损伤的相对抵抗力有关。
