Delirium

Delirium is the body’s way of responding to critical illness, and the expression of delirium is mainly through behavioural and cognitive change. Delirium on ICU can be caused by multiple factors, including increasing illness severity, the medication used to treat a patient on ICU, fewer day and night cues, intubation and ventilation, and metabolic disturbances. 

Many people with delirium experience vivid, often distressing visual hallucinations (such as distorted faces, animals in the bed space, scenes of fire and crime, kidnapping, being harmed), and may have very accurate memories of the hallucinations. Some people also experience auditory hallucinations and may perceive conspiracies on the unit, and people whispering about them. Some people’s behaviour can change drastically, and they may become aggressive, shout, and present with agitation and restlessness. Conversely, some people may become mute, very withdrawn and appear low in mood, and have little or no interest in their environment. 

Most people recover fully from delirium, but the speed of recovery varies for each person. Many patients will continue to experience symptoms of delirium on the ward or at home following discharge from ICU. It can take weeks, and sometimes, months, to fully recover from delirium. 

For many patients, being able to understand delirium can help to make sense of the experience, but some patients may require additional therapeutic support after discharge from ICU. 

It is important for both patients and families to understand that delirium is not a mental illness. Many patients worry about disclosing their experience of hallucinations due to concerns that they have developed a mental health condition. Delirium is a medical condition, and is directly linked to critical illness. Understanding the causes and signs and symptoms of delirium can often be reassuring for patients.