Due to severe dehydration of the body, some non-formative fractions in the blood infiltrate into the tissues, causing a concentration of formative fractions in the blood. The following is a detailed description of the etiology. Dehydration refers to a condition in which the body consumes a large amount of water due to a lesion that cannot be replenished immediately, resulting in metabolic disorders that can be severe enough to cause deficiency and even life-threatening, requiring reliance on fluid infusion to replenish body fluids. According to the change of blood sodium or osmolality, dehydration is divided into hypotonic dehydration, which is a combination of reduced extracellular fluid and low blood sodium; hypertonic dehydration, which is a combination of reduced extracellular fluid and high blood sodium; and isotonic dehydration, which is a combination of reduced extracellular fluid and normal blood sodium. Specifically, it refers to a group of clinical syndromes caused by a decrease in extracellular fluid. Depending on the accompanying changes in blood sodium or osmolality, dehydration is subdivided into hypotonic dehydration, which is a decrease in extracellular fluid combined with low blood sodium; hypertonic dehydration, which is a decrease in extracellular fluid combined with high blood sodium; and isotonic dehydration, which is a decrease in extracellular fluid with normal blood sodium.