Saline, also known as 0.9% sodium chloride injection, has the same osmotic pressure as the crystal osmolarity in the body, so direct input of saline can play a role in replenishing the fluid volume in the body. When shock is caused by traumatic infection and other factors, saline can be directly and quickly replenished, which can achieve the effect of rapid volume expansion and thus correct the symptoms of shock. Saline can also be used as a solvent for drugs, and many drugs can be added to saline for infusion into the body, and must be equipped with attention to the contraindications, such as vitamin C is not recommended to use saline to prepare. Saline can also be used for external washing, when the body surface appears contaminated trauma, you can carry out trauma flushing.