Saline, also known as sodium chloride injection, has a sodium chloride concentration of 0.9% in physiological saline, 0.45% in hypotonic saline, and can reach 3%-5% in hypertonic saline. Hypertonic saline can be used to correct hypotonic dehydration, including oral or intravenous infusion. In addition, nasal irrigation with hypertonic saline also helps to constrict the nasal vessels, which can lead to a reduction in nasal secretions. Hypertonic saline is used topically and has some antibacterial as well as antiseptic effects. Hypertonic saline is used in patients with increased intracranial pressure and hydrocephalus, and it can be used in combination with mannitol to effectively relieve intracranial hypertension and reduce hydrocephalus.