Saline mainly refers to 0.9% sodium chloride, which is a sterile aqueous solution of sodium chloride; other concentrations of sodium chloride are not saline. Saline has a wide range of clinical uses, can be used to rinse burns, abrasions, surgical incisions and other wounds, play a role in cleaning. It can also be used as a solvent for intravenous or intramuscular infusion of various drugs. Because of its osmotic pressure value and normal human plasma, tissue fluid are roughly the same, so it can be used as a rehydration solution to replenish body fluids, correct the water electrolyte acid-base balance disorder. The concentration of sodium ions contained in saline is basically equal to that of the human body, so hypernatremia or hyponatremia will not occur after infusion. In addition, because its osmotic pressure is equal to that of the human body, there will be no excessive water loss or water absorption by the cells, so that the cells of the human body can be maintained in a stable form. Saline is only one type of sodium chloride solution, which is widely used in clinical practice.