The faster the titration rate of mannitol, the higher the plasma osmolality, the stronger the dehydration effect and the better the efficacy will be. However, it is important to pay attention to the underlying disease of the patient. In patients with cardiac or renal insufficiency, too fast a titration rate may lead to fatal disease. Short-term elevation of blood volume may cause acute cardiac insufficiency; too much diuresis can lead to insufficient effective blood volume, which can cause increased blood viscosity and can cause acute myocardial infarction and cerebral infarction. Too fast drip rate may have a damaging effect on renal function. It is generally required to be titrated within 20 min. It depends on the situation of each patient. The duration of mannitol application is generally 7±3d, and 14±3d in individual severe cases. Longer duration of mannitol application (>3d) leads to a gradual decrease in its dehydrating effect. Adverse effects of mannitol Internal environmental disturbances, water-electrolyte imbalance. Acute renal failure, mostly complicated by hematuria, can be reversed after timely detection and discontinuation of the drug. Vascular irritation during infusion, pain and redness in the infusion vein, and other changes, complicating phlebitis, should be promptly treated with hot compresses, magnesium sulfate wet compresses, etc. Mannitol warming input method, can control the symptoms of phlebitis. Leakage during infusion can cause local skin necrosis in severe cases. Once leakage occurs, need to deal with timely, can take 50% magnesium sulfate local wet compress, 0.01% phentolamine solution wet gauze wet compress, scalding cream topical measures, can improve microcirculation, eliminate edema, to prevent tissue necrosis. If the extravasation is accompanied by local bruising, local closed injection of procaine can reduce the fragility of local blood vessels, thus reducing or preventing the extravasation of fluid and pain reaction, relieving vasospasm, improving the ischemic-hypoxic state, facilitating the absorption of exudate and reducing local injury. If the treatment is not timely, more than 24h can not be recovered. For local ischemia has occurred, the use of hot compresses is strictly prohibited, because hot compresses can make the local tissue temperature rise, accelerated metabolism, increased oxygen consumption, and aggravate tissue necrosis. Allergic reactions: allergic reactions are rare, occasionally seen in asthma, rash, and even death. It is necessary to stop the drug in time and treat with anti-allergic symptomatic drugs. When administered too fast, some patients may experience headache, dizziness, arrhythmia, chills, blurred vision and acute pulmonary edema, and heart failure may occur in patients with cardiac insufficiency. Complications of mannitol application aggravate cerebral edema: mannitol dehydration to lower cranial pressure depends on the integrity of BBB, mannitol can only remove water from normal brain tissues, but not only has no dehydrating effect on diseased brain tissues, but also due to the destruction of blood-brain barrier, mannitol can enter the brain tissues in the focal area through the ruptured blood vessels, causing the formation of cerebral edema in the focal area to accelerate and aggravate. In patients with cerebral ischemia, due to the increased permeability of the blood vessels in the ischemic area, mannitol molecules can easily enter the cellular interstices of the ischemic area from within the blood vessels, and at the same time, because mannitol cannot be metabolized, excessive accumulation leads to reverse osmosis, thus aggravating the edema in the ischemic area. Clinical animal tests have also confirmed the effect of lowering brain pressure and reducing cerebral edema before 5 doses, but after 5-7 doses, edema increases. Significant intracranial pressure rebound: When mannitol in the blood is rapidly excreted by the kidneys, the osmotic pressure of the blood decreases significantly, thus causing water to move from the blood to the brain tissue intracranial pressure rises again. Intracranial rebleeding aggravation: The previous view was that intracerebral hemorrhage was a transient process of about 30-40 minutes, which stopped with the appearance of blood clots; however, with the continuous development of imaging and the application of CT and MRI in clinical practice, it was found that the hematoma in about 38% of patients with cerebral hemorrhage continued to expand within 24 hours after the onset, especially within 6 hours whose expansion was about 33%. In addition to factors related to the organism itself, it is mainly related to the inappropriate use of mannitol. The main reasons for rehemorrhage caused by mannitol are (1) the dehydration of brain tissue outside the hematoma by mannitol can cause the pressure gradient between the hematoma and brain tissue to increase rapidly and the support of brain tissue to decrease, thus causing the early hematoma to expand; (2) on the other hand, as mannitol rapidly absorbs brain tissue fluid into the bloodstream, a short period of hypervolemia occurs, which further increases blood pressure and aggravates active cerebral hemorrhage.