Dick W, Baur C, Reiff K
Klinik für Anästhesiologie, Johannes Gutenberg-Universität Mainz.
Anaesthesist. 1992 Jan;41(1):1-14.
The question as to what extent the hematocrit (Hct) is a strong indicator for or against the need for transfusion of whole blood or blood products is still controversial. In order to enable the clinician to make a definite decision, a number of aspects have to be taken into consideration. The human organism has only limited oxygen reserves, and these are even more limited under pathological conditions. Oxygen flux - the amount of oxygen transported by the blood in 1 min - is a critical factor in the oxygenation of the human body. Another critical factor is oxygen consumption, which is highly variable depending on the presence of conditions such as rest, shivering, seizures, hypothermia, etc. Furthermore, different organ systems have different oxygen consumption rates. The ratio of oxygen consumption to oxygen flux is referred to as the oxygen extraction rate or oxygen utilization. Under normal conditions oxygen uptake is independent of oxygen flux, and thus independent of blood flow. Under conditions of organ dysfunction, however, oxygen deficiency may be present without being recognized on standard clinical diagnostic parameters. The normal human organism has a number of possibilities to compensate for acute or chronic anemia, i.e., increases in cardiac output, organ perfusion, 2,3-DPG content, a shift in the oxygen dissociation curve, etc. These compensatory mechanisms may, however, be restricted or cease to function under conditions of acute or chronic disease. Arterial and mixed-venous PO2 and oxygen content are some of the parameters used to assess the oxygen reserves available to the organism even under critical conditions. Although oxygen content is the most significant of these parameters, accurate measurement of this parameter remains a problem of laboratory medicine. PVO2 is of only limited importance under conditions of anemia. Minimum oxygen content or minimum oxygen flux values should under no conditions be approximated during anesthesia or intensive care. The critical Hct as an indicator for or against transfusion of blood or blood products is considerably modified by restricted organ function, anesthesia, intensive care treatment, resuscitation, etc.(ABSTRACT TRUNCATED AT 400 WORDS)
血细胞比容（Hct）在多大程度上是支持或反对输注全血或血液制品的有力指标，这一问题仍存在争议。为了使临床医生能够做出明确的决定，必须考虑多个方面。人体的氧储备有限，在病理条件下这些储备甚至更加有限。氧通量——血液在1分钟内输送的氧量——是人体氧合的关键因素。另一个关键因素是氧消耗，它因休息、颤抖、癫痫发作、体温过低等情况的存在而有很大差异。此外，不同的器官系统有不同的氧消耗率。氧消耗与氧通量的比值称为氧摄取率或氧利用率。在正常情况下，氧摄取与氧通量无关，因此与血流无关。然而，在器官功能障碍的情况下，可能存在氧缺乏，但在标准临床诊断参数上未被识别。正常人体有多种补偿急性或慢性贫血的可能性，即心输出量增加、器官灌注增加、2,3-二磷酸甘油酸（2,3-DPG）含量增加、氧解离曲线移位等。然而，在急性或慢性疾病的情况下，这些补偿机制可能会受到限制或停止发挥作用。动脉血氧分压（PO2）和混合静脉血氧分压以及氧含量是用于评估即使在危急情况下机体可用氧储备的一些参数。尽管氧含量是这些参数中最重要的，但准确测量该参数仍然是检验医学中的一个问题。在贫血情况下，混合静脉血氧分压的重要性有限。在麻醉或重症监护期间，绝不应接近最低氧含量或最低氧通量值。血细胞比容作为支持或反对输血或血液制品的指标，会因器官功能受限、麻醉、重症监护治疗、复苏等因素而发生很大变化。（摘要截选至400字）
