Timing of mannitol application: cerebral hemorrhage: the application of mannitol is dangerous during the period from the beginning of bleeding from a ruptured blood vessel until the formation of a clotting embolus no longer bleeds. In cases without impaired consciousness and progressive exacerbation, it is mostly used 6-8 h after the onset of the disease, but it cannot be generalized and depends on the specific case. Craniocerebral injury: mannitol application is contraindicated whenever the presence of active intracranial hemorrhage is considered. Of course, in patients with brain herniation or patients with impaired consciousness, infusion can be given before emergency surgery to properly reduce intracranial pressure and mitigate secondary damage to normal brain tissue. Brain tumors: pre- and post-operatively, the size of the patient’s tumor and its effects can be considered in terms of whether to apply or the dose to be applied. If cytotoxic edema is predominant, add hormone therapy as appropriate. U.S. guidelines for the diagnosis and treatment of severe craniocerebral injury: bulk studies have found that ICP 20mmHg as the threshold for increased ICP is the ideal threshold for determining the prognosis of patients with craniocerebral injury, and it has also been set at 25mmHg. When Icp is as high as 20-25mmHg, intracranial pressure should be lowered. The dose of mannitol application: The use of mannitol advocates a high dose of 1.0 g/kg. Wise et al. have considered a high dose of 1.0 g/kg as an effective dose, with an effective time of 4-6 hours. They believed that for patients with severe intracranial pressure elevation, if rapid and effective reduction of intracranial pressure is required, a dose of 1.0g/kg of mannitol is appropriate, and the dose should be repeated within 120 minutes. However, some people believe that the maximum dose of mannitol can only reach 1g/kg every 6 hours, and there is no need to increase the dose or shorten the dosing interval, as exceeding this dose cannot increase the effect of dehydration, but only increase the side effects. Some people advocate the use of small doses of mannitol (0.2 to 0.5g/kg). It is believed that the effect of low-dose mannitol in reducing intracranial pressure is similar to that of high-dose, and it can avoid severe dehydration, osmotic imbalance and extravasation of mannitol at high doses. Clinical observations have shown that the treatment of acute cerebrovascular disease with a small dose of 0.5 g/kg mannitol has similar efficacy to large doses, and no toxic side effects occur. The first dose of 0.75g/kg of mannitol, followed by 0.25g/kg every 2 hours or until the plasma osmolality exceeds 310mOsm/L, has been used regularly and frequently, and the intracranial pressure changes more smoothly. Most scholars now believe that patients with acute cerebrovascular disease are often combined with impairment of cardiac and renal function, and high-dose mannitol increases the cardiac and renal burden by constricting renal blood vessels. Small doses of mannitol dilate, diuretic, dilate renal blood vessels, and have a protective effect on the kidneys, and the effect of small doses of mannitol on lowering cranial pressure is similar to that of large doses. U.S. guidelines for the diagnosis and treatment of severe craniocerebral injury: mannitol is effective in controlling the increase of ICP, the effective dose is 0.25-1.Og/kg per time, intermittent 4-12h administration, can be used with the application of tachyphylaxis. High doses should not exceed 320 mOsm/L. If this limit is exceeded, there is a risk of acute renal failure (acute tubular necrosis). Jiang Jiyao in the Chinese Journal of Neurosurgery pointed out that the 24h mannitol dosage is 150-1800ml depending on the intracranial pressure, and also pointed out that the combined application of mannitol + tachyonuria + albumin has the best dehydration effect. Patients with cardiac or renal insufficiency or advanced age should use with caution or reduce the dosage or alternate with tachypnea. If necessary, replace with glycerol fructose or albumin. According to my clinical observation: for patients with cerebral hemorrhage and traumatic brain injury who have sudden deterioration of consciousness and abnormal pupil reaction during inpatient treatment and observation, rapid (pressurized injection) high-dose application of mannitol can sometimes temporarily reverse the condition, and in some cases it can take effect within 5 minutes, which can buy time to review CT and prepare (again) for surgery. After rapid infusion of the drug, the hypotensive effect appears in 1-5 min and peaks in 20-60 min. If urgent lowering of cranial pressure is needed, the first dose of 1g/kg is administered at 30 min; if long-term lowering of cranial pressure is desired, the time of administration is extended to 60 min and the dose is reduced, e.g. 0.25-0.5g/kg q6h.(from: Handbook of Neurosurgery Fifth Edition)