As the survival of critically ill patients improves, the development of delirium in the ICU has become a growing public health issue. Delirium is defined as a rapid change in consciousness (hours to days) characterized by reduced environmental awareness, decreased attention and altered cognition. These clinical features can manifest themselves as memory deficits, disorientation, hallucinations, fluctuating levels of alertness, and motor abnormalities.
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. 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.]
Additional 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 provides a step by step demonstration of 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
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.
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