Jan K M, Chien S
Am J Physiol. 1977 Jul;233(1):H106-13. doi: 10.1152/ajpheart.1977.233.1.H106.
Twenty-five closed-chest pentobarbitalized dogs were used for studying coronary flow dynamics and myocardial oxygen utilization following variations of hematocrit (Hct) by isovolumetric exchange of blood with plasma or packed red cells. Coronary blood flow (133Xe washout) and cardiac output varied inversely with Hct. Coronary systemic, and pulmonary flow resistances varied in the same direction with Hct. Blood viscosity played a significant role in determining the flow resistances in these three regions. Analysis of vascular hindrance (vascular resistance/blood viscosity) suggested that coronary vasodilation occurred following Hct changes beyond the range of 20-60%. In systemic and pulmonary circulations, however, there was vasoconstriction following hemodilution. The range of optimum Hct for maximum O2 transport (blood flow X arterial O2 content) was much wider in coronary (20-60% Hct) than in systemic circulation (40-60% Hct). The O2 consumptions in total body and in myocardium were essentially constant over a wide range of Hct (20-60%). The maintenance of total body O2 consumption over the Hct range of 20-40% was attributable to an increase in A-V O2 extraction. The O2 extraction ratio in the coronary circulation was constant over the entire range of Hct studied, suggesting that the myocardial O2 consumption was primarily determined by the coronary O2 transport.
选用25只戊巴比妥麻醉的开胸犬，通过用血浆或红细胞压积等容置换血液来改变血细胞比容（Hct），研究冠脉血流动力学和心肌氧利用情况。冠脉血流量（133Xe洗脱法）和心输出量与Hct呈反比。冠脉、体循环和肺循环的血流阻力与Hct呈同向变化。血液粘度在决定这三个区域的血流阻力方面起重要作用。血管阻力分析（血管阻力/血液粘度）表明，Hct变化超出20%-60%范围后冠脉血管舒张。然而，在体循环和肺循环中，血液稀释后会出现血管收缩。最大氧输送（血流量×动脉血氧含量）的最佳Hct范围在冠脉循环中（20%-60% Hct）比体循环中（40%-60% Hct）宽得多。在较宽的Hct范围（20%-60%）内，全身和心肌的氧消耗基本恒定。在20%-40%的Hct范围内全身氧消耗的维持归因于动静脉氧摄取增加。在所研究的整个Hct范围内，冠脉循环中的氧摄取率恒定，表明心肌氧消耗主要由冠脉氧输送决定。
