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,
- increased likelihood of being discharged to a long-term care facility
- 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 hypoactive 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.]
In hospitals, other common risk factors 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.
There are no imaging or laboratory tests to diagnose delirium. Delirium is a diagnosis of exclusion that requires careful clinical testing and observation.
Assessment and Monitoring
ICU Pain, Agitation, and Delirium (PAD) guidelines 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
Delirium prevention should be multicomponent intervention tailored to patient needs. The ABCDEF bundle provides a framework to screen and prevent delirium in ICU patients. 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 the aforementioned strategies, patient management should include measures to prevention infection, dehydration, constipation, and hypoxia. If possible, movement of patients within and between rooms or wards should be avoided. Other simple, yet vital preventative measures include frequent patient reorientation, use of patients' customary vision and hearing aids, and promotion of good sleep hygiene.
If prevention is unsuccessful, treatment of delirium should focus on identifying and managing the underlying causes. The care team should also 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, short-term haloperidol, a medication often prescribed for acute psychosis, should be considered, starting at the lowest clinically appropriate dose. 
Implications for Physical Therapy Practice
Physical therapists play 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. Family training, patient reorientation, delirium assessment, use of appropriate vision and hearing aids, and pain management can readily be integrated into therapy sessions. The CAM-ICU is a quick and easy tool that allows 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
For up to date research and developments on the assessment, prevention, and management of ICU delirium visit the ICU Delirium and Cognitive Impairment Study Group.
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