There are two standards of mannitol 250ml drip rate as follows: first, if the increase in intracranial pressure, or the emergence of hypertensive emergencies, hypertensive encephalopathy, combined with optic papilledema accompanied by obvious dizziness, headache, nausea, vomiting or intracranial hemorrhage requires mannitol full speed and rapid static drip, that is, 120 drops per minute, through the rapid achievement of blood concentration, to play a rapid reduction of intracranial pressure The effect of mannitol is to rapidly lower the intracranial pressure by rapidly reaching the blood concentration. Secondly, if mannitol is used when blood pressure is not high and intracranial pressure is mildly elevated, or when mannitol is used to relieve neuropathic headache, the titration rate of mannitol is usually controlled at about 60-80 drops per minute, so that the vascular permeability will not be too fast, or the intracranial pressure and blood pressure will be lowered too fast or too violently, which will lead to secondary cerebrovascular diseases.