输液的目的不仅仅是补充细胞外液,而且还同时纠正其成分和理化性质的异常,并补充营养。因此必须准确地掌握患者异常的体液状态、造成体液异常的原因及其病理生理过程。正常体液可分为细胞外液和细胞内液。细胞外液构成全部机体细胞的生活环境,它是进行细胞生存所必需的生化反应和合成蛋白质的液态场所。而细胞内液的适宜条件依赖于细胞外液的正常和稳定。细胞外液又可分为血管内的血浆和血管外的组织间液(简称为组织液), The purpose of infusion is not only to supplement the extracellular fluid, but also to correct its composition and physical and chemical properties of abnormalities, and nutritional supplements. Therefore, we must accurately grasp the patient’s abnormal fluid state, resulting in abnormal fluid causes and pathophysiological processes. Normal body fluids can be divided into extracellular fluid and intracellular fluid. Extracellular fluid constitutes the living environment of all living cells and is a liquid site for the biochemical reactions and the synthesis of proteins necessary for cell survival. The appropriate conditions of intracellular fluid depends on the normal and stable extracellular fluid. Extracellular fluid can be divided into intravascular blood plasma and extravascular tissue fluid (referred to as tissue fluid),