Haller M, Forst H
Institute of Anaesthesiology, Ludwig-Maximilians-University, Klinikum Grosshadern, München, Germany.
Transfus Sci. 1997 Sep;18(3):459-77. doi: 10.1016/S0955-3886(97)00044-1.
According to our own experience and published reports the frequency of red cell transfusion in intensive care units is in the range of 0.2 to 0.4 units per patient per day and is dependent upon the local strategy, the patients involved and the kind of surgery performed. The rationale for red cell transfusion is to maintain or restore the oxygen carrying capacity of the blood to avoid tissue hypoxia which occurs when oxygen delivery drops below a certain critical value. Besides bleeding, phlebotomy is also a significant source of blood loss in critically ill patients. According to several recent reviews and consensus articles there is no basis for a fixed indicator for transfusion, such as a haemoglobin concentration of < 100 gL-1. The decision to transfuse has to be made according to the patients individual status. The major adaptive mechanism in response to acute anaemia is an increase in cardiac output and hence blood flow to tissues. As a consequence even moderate degrees of acute anaemia may not be tolerated by patients with cardiac disease, whilst marked anaemia carries a considerable risk of ischaemia in patients with brain lesions or cerebral arterial stenoses. In critically ill patients it has been postulated that supply dependency of oxygen consumption occurs over a wide range of oxygen delivery, far above the critical values of oxygen delivery seen under normal conditions. Maximising oxygen delivery was therefore formulated as a goal in these patients. However, whether pathological supply dependency of oxygen delivery really exists in critically ill patients is still under discussion and recent studies found no benefit in maximising oxygen delivery to this patient group. However, individualised triggers for red blood cell transfusion are adequate for critically ill patients considering their co-morbidities and severity of disease. Finally, the decision to transfuse must also take into account the potential risks (infectious and non-infectious), as well as benefits for the individual patient. In the future, the level of transfusions may be reduced by using blood sparing techniques such as blood withdrawal in closed systems, bedside microchemistry, intravascular monitors, or autotransfusion of drainage blood in intensive care units.
根据我们自己的经验以及已发表的报告，重症监护病房中红细胞输注的频率为每位患者每天0.2至0.4单位，这取决于当地的策略、所涉及的患者以及所进行的手术类型。红细胞输注的基本原理是维持或恢复血液的携氧能力，以避免当氧输送降至某个临界值以下时发生的组织缺氧。除了出血外，放血也是重症患者失血的一个重要来源。根据最近的几项综述和共识文章，不存在诸如血红蛋白浓度<100 g/L这样的固定输血指标依据。输血的决定必须根据患者的个体状况做出。应对急性贫血的主要适应性机制是心输出量增加，从而增加组织的血流量。因此，心脏病患者可能无法耐受即使是中度的急性贫血，而对于患有脑损伤或脑动脉狭窄的患者，明显贫血会带来相当大的缺血风险。在重症患者中，有人推测在广泛的氧输送范围内会出现氧消耗的供应依赖性，远远高于正常情况下所见的氧输送临界值。因此，将最大化氧输送作为这些患者的一个目标。然而，重症患者中氧输送的病理性供应依赖性是否真的存在仍在讨论中，最近的研究发现对该患者群体最大化氧输送并无益处。然而，考虑到重症患者的合并症和疾病严重程度，个体化的红细胞输血触发因素是合适的。最后，输血的决定还必须考虑潜在风险（感染性和非感染性）以及对个体患者的益处。未来，通过使用诸如密闭系统采血、床边微量化学检测、血管内监测器或重症监护病房引流血自体输血等血液保护技术，输血水平可能会降低。
