Todd M M, Weeks J B, Warner D S
Department of Anesthesiology, University of Iowa, College of Medicine, Iowa City 52242.
Am J Physiol. 1992 Jul;263(1 Pt 2):H75-82. doi: 10.1152/ajpheart.1992.263.1.H75.
The influence of isovolemic hemodilution with 6% hetastarch [hematocrits (Hct) ranging from 43 to 20%] on cerebral blood flow (CBF), cerebral red blood cell and plasma volumes, total cerebral blood volume (CBV), and cerebral Hct was examined in normothermic, normocarbic, halothane-anesthetized Sprague-Dawley rats. CBF was measured via the indicator-fractionation method ([3H]nicotine), red blood cell volume was measured using 99mTc-labeled red blood cells, while plasma volume was measured using [14C]dextran. Brain tissue was fixed in situ by microwave irradiation. All data plots (e.g., CBF vs. Hct) were fitted by linear regression methods. Hemodilution was associated with a progressive increase in forebrain CBF (from a fitted value of 78 ml.100 g-1.min-1 at Hct = 43%, to 171 ml.100 g-1.min-1 at 20%). Cerebral plasma volume also rose, while red blood cell volume decreased. Total CBV (i.e., the sum of red blood cell and plasma volumes) increased in parallel with CBF (from 2.51 ml/100 g at Hct = 43 to 4.94 ml/100 g at Hct = 20%). This increase is larger than can be explained by a simple increase in the diameter of arterial/arteriolar resistance vessels and may be due to either capillary recruitment or to an increase in the volume of postarteriolar structures. Calculated cerebral tissue hematocrit decreased. The magnitude of this decrease was larger than the reduction in arterial Hct; the ratio of cerebral to arterial Hct decreased from 0.780 at an arterial Hct equaling 43% to 0.458 at Hct equaling 20%.(ABSTRACT TRUNCATED AT 250 WORDS)
在正常体温、正常碳酸血症、氟烷麻醉的斯普拉格 - 道利大鼠中，研究了用6%羟乙基淀粉进行等容血液稀释（血细胞比容从43%降至20%）对脑血流量（CBF）、脑红细胞和血浆容量、总脑血容量（CBV）以及脑血细胞比容的影响。通过指示剂分离法（[³H]尼古丁）测量CBF，用⁹⁹ᵐTc标记的红细胞测量红细胞容量，用[¹⁴C]右旋糖酐测量血浆容量。通过微波辐射原位固定脑组织。所有数据图（如CBF与血细胞比容的关系图）采用线性回归方法拟合。血液稀释与前脑CBF的逐渐增加相关（血细胞比容为43%时拟合值为78 ml·100 g⁻¹·min⁻¹，血细胞比容为20%时为171 ml·100 g⁻¹·min⁻¹）。脑血浆容量也增加，而红细胞容量减少。总CBV（即红细胞和血浆容量之和）与CBF平行增加（血细胞比容为43%时为2.51 ml/100 g，血细胞比容为20%时为4.94 ml/100 g）。这种增加幅度大于仅由动脉/小动脉阻力血管直径简单增加所能解释的，可能是由于毛细血管募集或后小动脉结构体积增加。计算得出的脑组织血细胞比容降低。这种降低幅度大于动脉血细胞比容的降低幅度；脑与动脉血细胞比容的比值从动脉血细胞比容为43%时的0.780降至血细胞比容为20%时的0.458。（摘要截取自250字）
