Tan I K, Lim J M
Intensive Care Unit, Pamela Youde Nethersole Eastern Hospital, 3 Lok Man Road, Chai Wan, Hong Kong SAR, People's Republic of China.
Ann Acad Med Singap. 2001 May;30(3):293-9.
The optimal haematocrit for the critically ill patient is undetermined.
This review focuses on clinical and experimental papers regarding the aetiology and management of anaemia from the Medline database. Data from our intensive care unit (ICU) were also included.
Anaemia may result from frequent blood sampling, gastrointestinal bleeding, surgical blood loss, impaired erythropoeitic response, and nutritional deficiencies of iron, vitamin B12 and folate. Available data on the minimum tolerated Hct are conflicting. There has been emphasis that transfusions should not be based on a single "trigger". Recent data suggest a linear relationship between Hct and cerebral oxygen delivery (DO2). There is evidence that anaemia increases the mortality, and the risk is higher in patients with cardiovascular disease. Conversely, transfusions are not without risks, which include transmission of infections, incompatibility reactions and immunomodulation. Restricting blood transfusion has been shown to result in lower 30-day mortality in certain patient groups. Minimising blood loss and nutritional support are important. Alternative strategies to transfusion include erythropoeitin and blood substitutes like cell-free haemoglobin, perfluorocarbon emulsions and liposome-encapsulated Hb. Hyperbaric oxygen has also been tried.
Oxygen consumption requires oxygen delivery. Haematocrit delivers oxygen. However, if oxygen delivery is not limited by haematocrit or is achieved by other means, then the concept of the optimal haematocrit is irrelevant. There are currently no guidelines for the management of anaemia in the critically ill.
危重症患者的最佳血细胞比容尚未确定。
本综述聚焦于来自Medline数据库中有关贫血病因及管理的临床和实验性论文。我们重症监护病房（ICU）的数据也被纳入其中。
贫血可能由频繁采血、胃肠道出血、手术失血、红细胞生成反应受损以及铁、维生素B12和叶酸的营养缺乏所致。关于最低可耐受血细胞比容的现有数据相互矛盾。一直强调输血不应基于单一“触发因素”。近期数据表明血细胞比容与脑氧输送（DO2）之间存在线性关系。有证据表明贫血会增加死亡率，且在心血管疾病患者中风险更高。相反，输血并非没有风险，包括感染传播、不相容反应和免疫调节。在某些患者群体中，限制输血已被证明可降低30天死亡率。尽量减少失血和营养支持很重要。输血的替代策略包括促红细胞生成素和血液替代品，如无细胞血红蛋白、全氟碳乳液和脂质体包裹的血红蛋白。高压氧也已被尝试。
氧消耗需要氧输送。血细胞比容输送氧气。然而，如果氧输送不受血细胞比容限制或通过其他方式实现，那么最佳血细胞比容的概念就无关紧要了。目前尚无针对危重症患者贫血管理的指南。
