Mannitol is a hypertonic dehydrating agent that can be used continuously for 5-7 days, but not for more than 2 weeks. Mannitol is a good dehydrating drug, which is fast-acting and can be used repeatedly. For more serious cases, such as acute cerebrovascular disease or brain tissue edema caused by traumatic brain injury, mannitol can be administered once every 6 hours, 4 times a day, for 5-7 days. For less severe cases, the drug can be administered once every 8 hours. During the application of mannitol for dehydration, the patient’s blood pressure, respiration, urine volume, blood biochemistry and renal function need to be continuously observed, and once abnormalities are found, the drug should be stopped or reduced immediately. If the patient’s vital signs are normal and cerebral edema persists, the drug can be continued, but not for more than 2 weeks. The application of mannitol must be carried out under the guidance of a doctor, and should not be used arbitrarily to avoid serious consequences such as water-electrolyte disorders.