There is a significant burden that is associated with this condition. Compared with people who do not develop delirium, people who develop ICU delirium may:
- need to stay longer in hospital or in critical care
- have an increased incidence of dementia
- have more hospital-acquired complications, such as falls and pressure sores
- be more likely to need to be admitted to long-term care if they are in hospital
- be more likely to die
According to Ely et al as much as 83% of ICU patients on mechanical ventilation develop delirium. This figure is significant as ICU delirium is associated with negative patient and healthcare outcomes. These outcomes include increased time on mechanical ventilation, longer ICU and hospital length of stay,  elevated health care costs, increased cognitive dysfunction and increased risk of death.
Delirium can be divided into 3 subtypes: hyperactive, hypoactive, and mixed. The table below matches each subtype with common clinical manifestations.
|Hyperactive||Agitation, restlessness, emotional lability, hallucinations|
|Hypoactive||Lethargy, decreased responsiveness, slowed motor skills|
|Mixed||Fluctuation between hyper- and hypo- active symptoms|
[Source: Meagher D. Motor subtypes of delirium: past, present and future. Int Rev Psychiatry. 2009 Feb;21(1):59-73]
In critically ill patients, mixed delirium is the most common subtype (54.9%). Hypoactive delirium is second (43.5%), followed by a small percentage of patients who display purely hyperactive symptoms (1.6%) . ICU patients aged 65 and older are particularly susceptible to hypoactive delirium.
Causes and Risk Factors
Delirium develops as a result of multiple causes and risk factors. Old age, dementia, depression, smoking, and alcohol use are among the personal factors that increase patient susceptibility. In addition, another 20+ risk factors related to medical status have been identified by the literature. Below is a common mnemonic used to help clinicians identify causes related to illness and treatment:
|Illness and Treatment-Related Causes of Delirium|
|E||Eyes, ears, and other sensory deficits|
|L||Low O2 states (e.g. heart attack, stroke, and pulmonary embolism)|
|R||Retention (of urine or stool)|
|M||Metabolic causes (DM, Post-operative state, sodium abnormalities)|
[Adapted from: Saint Louis University Geriatrics Evaluation Mnemonics Screening Tools (SLU GEMS). Developed or compiled by: Faculty from Saint Louis University Geriatrics Division and St. Louis Veterans Affairs GRECC.]
Other risk factors common to the hospital setting include the absence of daylight, lack of visitors, sleep deprivation, immobility, and hospital lines.
The pathophysiology of delirium is not well understood. Theories related to its development and progression cite anatomical changes in the brain and neurotransmitter imbalances (ex. abnormal levels of serotonin, decreased acetylcholine, excess dopamine) as possible physiologic mechanisms.
Given the unknown pathophysiology, there is no imaging or laboratory tests that can diagnose delirium. As a result, delirium is a diagnosis of exclusion that requires careful clinical testing and observation.
Assessment and Monitoring
Guidelines for treating Pain, Agitation, and Delirium (PAD) recommend two tests for the assessment of delirium in adult ICU patients:
- The Intensive Care Delirium Screening Checklist (ICDSC)
- The Confusion Assessment Method for the ICU (CAM-ICU)
The following video demonstrates how to perform the CAM-ICU.
Prevention and Treatment
In 2010, Vasilevskis et al. proposed the ABCDE model to screen and prevent delirium among ICU patients. The updated version is expanded to include family engagement. The concepts corresponding to each letter of the mnemonic are as follows:
|Evidenced-Based Prevention and Treatment Strategies for ICU Delirium|
|A||Assess, prevent and manage pain|
|B||Both Spontaneous Awakening Trials (SAT) and Spontaneous Breathing Trials (SBT)|
|C||Choice of analgesia and sedation|
|D||Delirium: assess, prevent and manage|
|E||Early mobility and exercise|
|F||Family engagement and empowerment|
In addition to ABCDEF bundle, Brummel et al. advocate identifying and correcting for individualized causal factors of delirium (ex. minimizing unnecessary noise during rest hours to reduce sleep deprivation).
Implications for Physical Therapy Practice
Physical therapists have an important role in preventing and managing ICU delirium. Perhaps the most important measure is engaging patients in early mobilization in conjunction with nurses, occupational therapists, and physicians. Early mobilization in the ICU has been shown to reduce the number of days on mechanical ventilation, decrease ICU and hospital length of stay and is the only intervention to date proven to decrease the number of days of delirium. Frequent patient orientation, use of a patient's customary vision and hearing aids, and family training and education are additional interventions that can be integrated into therapy sessions. The CAM-ICU is a quick and easy tool for physical therapists to assess and monitor the course of a patient's delirium over time.
The multifactorial nature of delirium can make it easy to mistake for other brain dysfunctions. Below is a non-exhaustive list of conditions that should be considered in the differential diagnosis of ICU delirium:
- Psychiatric Disorders (ex. schizophrenia)
- Traumatic Head Injury
- Myocardial Infarction
NICE Guidelines on Delirium have been updated in March 2019. They recommend an initial risk factor assessment on admission. The interventions recommended to prevent delirium include; ensuring people who are at risk are not moved within and between wards or rooms unless absolutely necessary, provision of a multicomponent intervention tailored to the person's individual needs and care settings. Initial management should include identifying and managing the underlying cause or combination of causes. Ensure effective communication and reorientation and provide reassurance for people diagnosed with delirium. 
If a person with delirium is distressed or considered a risk to themselves or others and verbal and non-verbal de-escalation techniques are ineffective or not appropriate, consider giving short-term haloperidol starting at the lowest clinically appropriate dose. 
A systematic review and meta-analysis in 2015 reported that almost a third of patients who are admitted to an intensive care unit develop delirium, and these patients are at increased risk of dying during admission, longer stays in hospital, and cognitive impairment after discharge.
For further reading, the ICU Delirium and Cognitive Impairment Study Group is a great resource for learning and staying up to date on best practices for the prevention and management of ICU delirium.
For up to date research and developments in the assessment. prevention and management of delirium in ICU :https://www.icudelirium.org/
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