Precautions for the use of 20% mannitol: 1. Because of the high concentration of mannitol, it may lead to phlebitis and extravasation. Therefore, during the infusion process, the first is to choose a thick and open blood vessel for intravenous infusion, and to use as little as possible or not to use the small veins on the back of the hands and feet. 2. If 20% mannitol is infused too fast, there may be a transient increase in intracranial pressure, headache, blurred vision, etc., so special attention should be paid to control the speed of mannitol input. 3. 20% mannitol is an osmotic diuretic and is mainly metabolized by the kidneys, so it may lead to acute renal failure, oliguria or anuria. Patients with poor kidneys, especially those with oliguria or anuria, should be wary of using it. 4. 20% mannitol may cause hypokalemia after heavy urination, so patients are advised to take appropriate potassium supplements. For patients with diabetes, it is recommended that 20% mannitol be used with caution or prohibited, while for pregnant women it needs to be prohibited.