Hess W
Institut für Anaesthesiologie des Universitätsklinikums der Gesamthochschule Essen.
Anaesthesist. 1987 Sep;36(9):455-67.
Hemoglobin as a vehicle for oxygen carries roughly 65 times the volume of oxygen that would otherwise be transported by simple solution in plasma. Conformational shifts of the molecule induce a cooperative oxygen-hemoglobin affinity. This property is reflected in the sigmoidal shape of the oxygen-hemoglobin dissociation curve. The affinity of hemoglobin is affected by temperature, hydrogen ions, carbon dioxide, and intraerythrocytic 2,3-DPG, with all these factors mutually influencing each other. Physiologic conditions associated with shifts in hemoglobin-oxygen affinity are oxygen uptake in the lung, oxygen delivery in the capillaries, and particularly oxygen delivery in working muscle, diaplacental oxygen transfer, and the regulation of erythropoesis. Hemoglobin-oxygen affinity attains pathological significance for oxygen supply during respiratory or metabolic alkalosis when the hemodynamic and tissue responses of the individual are limited: the increased affinity can critically lower capillary oxygen tension. Methemoglobin and carbon monoxide shift the oxygen dissociation curve to the left, so that intoxication with both substances reduces both total oxygen capacity and oxygen delivery of the remaining hemoglobin able to bind oxygen. This effect of methemoglobin and carbon monoxide must be considered in intensive care of intoxicated victims. Transfusions of large volumes of stored red cells, whose hemoglobin shows high affinity, can force the capillary oxygen tension down, especially in patients with impaired cardiac performance. The lowered oxygen affinity of patients with chronic renal disease and anemia must be preserved by avoiding an increase in the acidotic plasma pH. In the neonate, hemoglobin possesses a high affinity for oxygen physiologically; the hemodynamic reserve of the neonate is limited. Therefore, the hemoglobin content plays a crucial role in oxygen transport capacity during the initial months of extrauterine life. Consequently, red cell transfusion must be started much earlier in neonatal surgery than in adults. The red cells must be fresh, or at best "rejuvenated". Normally, oxygen affinity is not relevant for oxygen supply, but the position of the oxygen-hemoglobin dissociation curve may be a critical factor in the situations described above, particularly when blood flow is additionally restricted.
血红蛋白作为氧气的载体，携带的氧气量大约是血浆中单纯溶解运输氧气量的65倍。分子的构象变化会诱导氧气与血红蛋白的协同亲和力。这一特性反映在氧合血红蛋白解离曲线的S形上。血红蛋白的亲和力受温度、氢离子、二氧化碳和红细胞内2,3 -二磷酸甘油酸（2,3-DPG）的影响，所有这些因素相互影响。与血红蛋白 - 氧气亲和力变化相关的生理状况包括肺部的氧气摄取、毛细血管中的氧气输送，尤其是工作肌肉中的氧气输送、胎盘氧转运以及红细胞生成的调节。当个体的血流动力学和组织反应受到限制时，血红蛋白 - 氧气亲和力在呼吸性或代谢性碱中毒期间对氧气供应具有病理意义：亲和力增加会严重降低毛细血管氧张力。高铁血红蛋白和一氧化碳会使氧解离曲线向左移动，因此这两种物质中毒会降低总氧容量以及剩余能够结合氧气的血红蛋白的氧气输送能力。在对中毒受害者进行重症监护时，必须考虑高铁血红蛋白和一氧化碳的这种影响。大量输注储存红细胞（其血红蛋白显示出高亲和力）会使毛细血管氧张力降低，尤其是在心脏功能受损的患者中。慢性肾病和贫血患者降低的氧气亲和力必须通过避免酸性血浆pH值升高来维持。在新生儿中，血红蛋白在生理上对氧气具有高亲和力；新生儿的血流动力学储备有限。因此，在宫外生活的最初几个月里，血红蛋白含量在氧气运输能力中起着关键作用。因此，新生儿手术中的红细胞输血必须比成人手术更早开始。红细胞必须是新鲜的，或者最好是“恢复活力的 ”。通常情况下，氧气亲和力与氧气供应无关，但氧合血红蛋白解离曲线的位置在上述情况下可能是一个关键因素，特别是当血流进一步受限的时候。
