Delirium is a common complication in elderly inpatients, characterized mainly by acute changes in cognition and attention, with a 20% incidence of delirium in those >65 years of age and a 1O%-30% incidence of delirium in elderly patients admitted by the emergency department. Delirium is also a major symptom of potentially life-threatening medical problems (e.g., drug overdose, poisoning, hypoglycemia, etc.). Compared to matched patients without delirium, patients with delirium have an average of 8 d more days in the hospital, and the mortality rate of patients hospitalized with delirium compared to age-matched controls is 22%-76%, with a 1-year mortality rate of 35%-40%. Physical and cognitive recovery at 6 and 12 months is much worse in delirium patients. Delirium (the so-called “acute clouded state of consciousness”) is primarily a disorder of consciousness, attention, cognitive function (memory impairment, disorientation, and language impairment), psychomotor behavior, and affect, often with an acute onset, can be a precursor to serious illness and death, and occurs within a short period of time (usually from hours to days). The condition tends to fluctuate over a 24-h period. Delirium typing: Delirium can be divided into overactive and underactive types. The patient’s threshold of wakefulness is increased, and he is very sensitive to his surroundings, so he can have many hallucinations and delusions. As a result, patients become emotionally tense and fearful, with avoidance, escape or aggressive behavior and uncoordinated psychomotor excitement. The patient’s language can increase, incoherent thinking, sometimes shouting, not easy for others to understand, self-awareness and awareness of the surrounding environment are impaired, this state is mostly day light and night heavy, lasting from a few hours to several days. However, the patient’s brainstem reflexes such as corneal, pupil, head and eye, as well as deep and superficial reflexes are normal. It is commonly seen in acute encephalopathy syndrome, hyperthermic delirium, and symptomatic psychosis. In many patients, delirium does not manifest clinically as typical hyperactivity and hallucinations, but indifference and hypoactivity are also common. 2. The reduced activity type manifests as expressionlessness, motor retardation, slow speech, unresponsiveness, confusion, and depression, and is common in the elderly. The rate of departments where delirium appears delirium is mostly seen in comprehensive medical institutions, 11% to 16% in patients with medical diseases, 28% to 44% in postoperative patients, and 80% in patients with advanced diseases. Treatment of delirium 1. General treatment Early identification of the cause of delirium and correction of risk factors. Diagnosis and treatment of hyperglycemia, hypoxia or hypoxemia, hyperthermia, hypertension, vitamin B, deficiency, withdrawal status, and anticholinergic (or other drug)-induced delirium should be given priority. The patient’s vital signs should be closely monitored, and fluid intake and output and oxygen application should be noted. Non-essential medications should be discontinued and the dose of essential medications should be minimized. Environmental interventions include: opening windows in the intensive care unit (ICU) and changing the lighting in other rooms to suggest the change of day and night; trying to reduce the noise in the ICU; giving regular and moderate stimulation; restoring patients to the use of glasses or hearing aids; ensuring that clocks and calendars are available for easy orientation; providing a more familiar environment and reducing the sense of unfamiliarity. 2. Medication The most commonly used highly effective antipsychotic is haloperidol, which has an initial dose of 1-2 mg/2 to 4 h and a smaller initial dose for elderly patients (i.e., 0.25-0.5 mg/2 to 4 h), while patients with persistent agitation require high doses of intravenous infusions. Cardiac monitoring should be performed in patients with delirium treated with antipsychotics. Atypical antipsychotics, such as risperidone (0.5 mg twice/d), olanzapine (2.5 to 5.0 mg once/d), and quetiapine (2.5 to 5.2 mg once/d), have similar efficacy to haloperidol, but with fewer adverse effects. Benzodiazepines can exacerbate delirium and are ineffective when used alone to treat common delirium, but can be used for certain specific types of delirium, such as those most commonly used to treat delirium caused by alcohol or benzodiazepine withdrawal. The anxiolytic, sedative, and drowsy effects of such drugs are enhanced with increasing doses when treated with them.