Delirium is a specific type of disorder of consciousness in which the patient shows decreased cognitive function and response to the surrounding environment, impaired attention, orientation, and memory at the same time, and slowed thinking, and often hallucinations, delusions, and sometimes nervousness, excitement or irritability. There are many causes of delirium, and some of them are as follows: 1) organic brain diseases, such as meningitis, encephalitis, subarachnoid hemorrhage, seizures or traumatic brain injury, etc. 2) drug intoxication or drug withdrawal, commonly used drugs such as cimetidine, anti-Parkinson’s disease drugs, anti-hypertensive drugs and steroids, etc., may induce delirium after overdose or withdrawal. 3) poisoning, such as 4. other systemic diseases, such as hepatic encephalopathy, pulmonary encephalopathy, uremic encephalopathy, severe heart failure, hypertensive encephalopathy, severe electrolyte disorders due to various causes, and severe hypothyroidism, all may induce delirium.