When mannitol is used in the usual doses for kidney function tests, diuresis to lower intracranial pressure or intraocular pressure, there are generally no serious side effects. When it is injected too quickly, there is a transient headache, blurred vision, dizziness, chills, and even confusion and convulsions. These may be the manifestation of central nervous system disease itself, or may be due to dehydration, induced by high osmolality symptoms, there may be subdural or subarachnoid hemorrhage, need to make a differentiation, plasma osmolality can be helpful. In larger doses, such as more than 200g in 8 hours, chest tightness, chest pain, arrhythmia or tachycardia, cough, rales or rales at the base of the lungs during respiration, jugular vein varicose and so on, these can be caused by cardiac insufficiency or injection of mannitol too fast, excessive dosage, poor renal excretion, so that the cardiac overload, and in severe cases, can lead to acute pulmonary oedema, eg, 400-440g of mannitol, and so on. In severe cases, acute pulmonary edema may result, e.g., with high doses of 400-440 g. Mannitol intravenous input may also have muscle weakness, immobility, numbness, tingling sensation or muscle spasm, etc. This may be due to the application of mannitol led to diuresis, dehydration, loss of sodium, thus causing water and electrolyte disorders, if the patient was originally water loss or blood volume, the symptoms are more likely to appear. The above disorders should be corrected while injecting mannitol. Continuous application of large doses of mannitol can also cause hyperosmolar nephropathy (also known as mannitol nephropathy), the patient's urine output is reduced or even reach the degree of oliguria (less than 400 ml of urine per day), there may be symptoms such as swelling, hyperosmolar coma and other symptoms, renal puncture biopsy can be found in the epithelial cells of the renal tubule is swollen, it should be immediately discontinued, and given dextrose injection or dextrose sodium chloride injection, in order to reduce plasma osmolality