Patients with subarachnoid hemorrhage often have very high intracranial pressure. The main reason for the rise in intracranial pressure is that after the hemorrhage, the bloody cerebrospinal fluid usually stimulates nerves and blood vessels within the brain, which can lead to edema, such as vascular edema and neural edema, thereby gradually increasing the intracranial pressure. Sometimes, and relatively infrequently, the increase in cranial pressure is not significant. However, if the volume of subarachnoid hemorrhage is very large, the intracranial pressure can rise substantially, leading to symptoms like severe nausea, vomiting, and headache, and in severe cases, there can be significant disturbances in consciousness. Additionally, patients with subarachnoid hemorrhage may sometimes experience obstructive or communicating hydrocephalus, which can also lead to increased cranial pressure.