Richardson B S, Carmichael L, Homan J, Patrick J E
Department of Obstetrics and Gynaecology, St. Joseph's Health Centre, Lawson Research Institute, University of Western Ontario, London, Canada.
J Dev Physiol. 1993 Feb;19(2):77-83.
Cerebral oxidative metabolism and associated circulatory responses were determined in 14 unanesthetized fetal sheep near term, during a normoxic control period and subsequently, during four days of prolonged and graded hypoxemia induced by progressively lowering maternal inspired oxygen concentration with 1-2% CO2 added; first day 18%, second day 16%, third day 12-14%, fourth day 10-12%. Preductal arterial and sagittal vein blood samples were analyzed for oxygen content, blood gas tensions and pH. Regional blood flow was measured with a microsphere technique. Cerebral blood flow increased in a stepwise manner with the graded reduction in fetal arterial O2 saturation and continued to be well predicted by blood gas and metabolic alterations, with no adaptive change evident. Cerebral oxidative metabolism remained little changed with chronically induced hypoxemia until arterial O2 saturation was less than 30% and with fetal acidemia evident when decreased to 70% of normoxic control values. Whether the decrease in oxidative metabolism by the brain at this time represents an adaptive response whereby growth and functional alterations lead to a decrease in nonessential energy utilization or rather a pathological change, remains to be determined.
在14只近足月未麻醉的胎羊中，测定了脑氧化代谢及相关循环反应，包括一个常氧对照期，随后通过逐渐降低母体吸入氧浓度并添加1-2%二氧化碳诱导进行为期四天的持续且分级的低氧血症；第一天18%，第二天16%，第三天12-14%，第四天10-12%。分析了导管前动脉和矢状静脉血样的氧含量、血气张力和pH值。用微球技术测量区域血流量。随着胎儿动脉血氧饱和度的分级降低，脑血流量呈逐步增加，并且仍然可以通过血气和代谢改变得到很好的预测，未观察到明显的适应性变化。在慢性诱导的低氧血症情况下，脑氧化代谢变化不大，直到动脉血氧饱和度低于30%，且当降至常氧对照值的70%时出现胎儿酸血症。此时大脑氧化代谢的降低是代表一种适应性反应，即生长和功能改变导致非必需能量利用减少，还是代表一种病理变化，仍有待确定。
