Kiel J W, Riedel G L, Shepherd A P
Department of Physiology, University of Texas Health Science Center, San Antonio 78284.
Am J Physiol. 1989 Jan;256(1 Pt 2):H171-8. doi: 10.1152/ajpheart.1989.256.1.H171.
To determine the effects of hemodilution on gastric and intestinal oxygenation, isolated segments of canine stomach and small bowel were perfused by a pressurized reservoir with blood at hematocrits of 40 and 20%. Arteriovenous O2 difference, blood flow, and arterial and venous pressures were monitored continuously as perfusion pressure was reduced in 30-mmHg steps from 180 to 30 mmHg. O2 consumption was calculated as the product of the steady-state arteriovenous O2 difference and blood flow at each perfusion pressure. Gastric and intestinal O2 uptake were relatively well maintained over most of the pressure range when the hematocrit was set at 40%. After hemodilution, gastric O2 uptake decreased significantly only at 90 and 60 mmHg, but intestinal O2 uptake was significantly reduced except at 30 mmHg. When gastric and intestinal O2 uptake were plotted as a function of blood flow, the O2 uptake vs. blood flow relationship were shifted down and to the right by hemodilution. Hemodilution also linearized the O2 uptake vs. blood flow relationship in the intestine. However, when O2 uptake was plotted as function of O2 delivery, the gastric O2 uptake vs. delivery curves at the two hematocrits were superimposed on each other, but the O2 uptake vs. delivery curves for the intestine diverged except at low rates of O2 delivery. We conclude that by reducing the O2-carrying capacity of the blood, hemodilution adversely affects gastric and intestinal oxygenation. Our results also indicate that hemodilution lowers gastric O2 uptake by reducing O2 delivery; however, hemodilution lowers intestinal O2 uptake not only by reducing O2 delivery but also by impairing O2 extraction.
为了确定血液稀释对胃和肠道氧合的影响，用加压储液器以血细胞比容分别为40%和20%的血液灌注犬胃和小肠的离体节段。当灌注压力从180 mmHg以30 mmHg的步长降至30 mmHg时，连续监测动静脉氧分压差、血流量以及动脉和静脉压力。氧耗量计算为每个灌注压力下稳态动静脉氧分压差与血流量的乘积。当血细胞比容设定为40%时，在大多数压力范围内，胃和肠道的氧摄取相对保持良好。血液稀释后，仅在90 mmHg和60 mmHg时胃氧摄取显著降低，但除30 mmHg外，肠道氧摄取显著减少。当将胃和肠道的氧摄取绘制为血流量的函数时，血液稀释使氧摄取与血流量的关系向下和向右移动。血液稀释还使肠道中氧摄取与血流量的关系线性化。然而，当将氧摄取绘制为氧输送的函数时，两个血细胞比容下的胃氧摄取与输送曲线相互叠加，但除低氧输送速率外，肠道的氧摄取与输送曲线不同。我们得出结论，通过降低血液的携氧能力，血液稀释对胃和肠道氧合产生不利影响。我们的结果还表明，血液稀释通过减少氧输送来降低胃氧摄取；然而，血液稀释不仅通过减少氧输送，还通过损害氧提取来降低肠道氧摄取。
