Delirium in the ICU
Delirium in the ICU is a disturbance in consciousness characterized by an acute onset of impaired cognitive function with a fluctuating course. The pathophysiology is poorly understood but thought to be related to an imbalance of neurotransmitters. Delirium affects up to 50% of patients in an intensive care unit (ICU). It is particularly common among those requiring mechanical ventilation, affecting up to 80%. In spite of this, ICU delirium is frequently unrecognized.
|TIPS FOR PREVENTING AND TREATING ICU DELIRIUM|
Delirium in the ICU
Delirium can present with agitation and unruly behavior, and hallucinations may occur. Frequently, however, signs of delirium are more subtle, including sleepiness, changes in sleep-wake cycle, or inability to focus or shift attention.
Providers in the ICU rarely know the baseline status of their patients. Underdiagnosis commonly occurs when delirium signs and symptoms are misattributed to advanced age, dementia, or psychiatric disease. In addition, clinicians may be unaware that older adults with delirium are often hypoactive, demonstrating sleepiness or obtundation, and the diagnosis is missed because delirium is not recognized.
ICU delirium is associated with a number of adverse outcomes, including prolonged ICU and hospital stay. Delirium may continue following hospital discharge, and lead to long-term cognitive impairment. Delirium is independently associated with an increased risk of death, both during hospitalization and in long-term follow-up.
Numerous risk factors for delirium have been identified (Table 1). Among ICU patients, key risk factors that independently predict delirium include dementia, hypertension, alcoholism, coma, severity of illness, and mechanical ventilation. Benzodiazepines have also been associated with an increased risk of delirium. There is conflicting data about the risk of delirium in patients receiving opioids, and there are insufficient data regarding the risk of delirium in patients treated with propofol.
|Table 1. Risk Factors for Delirium|
Diagnosis of delirium
The diagnosis of delirium is based on the following clinical features:
- acute change in mental status from baseline that fluctuates throughout the day,
- inattention, and
- the presence of disorganized thinking and/or altered level of consciousness (see Figure below).
The Society of Critical Care Medicine recommends routine screening for delirium in ICU patients. Without screening, delirium is missed in up to 75% of cases. Screening should be performed using a well-validated tool such as the Confusion Assessment Method in the ICU (CAM-ICU), which is described in Table 2.
|Table 2. Confusion Assessment Method in the ICU (CAM-ICU)|
|Assessment Feature||Assessment Method||Diagnose Delirium if|
|1. Acute onset of mental status changes with fluctuating course||Assess clinically for acute change in mental status with fluctuation, or use serial Glasgow Coma Scores or sedation ratings within 24-hour periods.|
|2. Inattention||Read patient a short list of random letters and ask patient to squeeze your hand whenever the letter “A” is heard.|
|3. Disorganized thinking||Hold up a certain number of fingers on your hand and ask patient to do the same.|
|4. Altered level of consciousness||Rate level of consciousness. Score positive for anything other than “calm and alert.”|
More information about the CAM-ICU
The CAM-ICU takes about 2 minutes, has excellent psychometric properties, and was designed specifically for use in critically ill patients, including those receiving mechanical ventilation.
Special attention to sedation employed in ICU patients may reduce the risk of delirium. In particular, consider use of an “analgesia-first” sedation strategy, thereby limiting exposure to benzodiazepines and other sedatives. Moreover, the use of bolus or “prn” sedation administration is preferred to continuous infusion of a sedative drug. It is also recommended that clinicians target a light level of sedation and institute daily interruption of sedation to minimize sedative exposure.
The Society of Critical Care Medicine recommends the use of dexmedetomidine rather than benzodiazepines when continuous intravenous sedative infusions are necessary in ICU patients. Dexmedetomidine has been shown to reduce delirium duration compared with benzodiazepines in adult ICU patients who have delirium unrelated to benzodiazepine or alcohol withdrawal. However, it is unclear if this is because benzodiazepines increase delirium risk or dexmedetomidine reduces delirium risk.
Orientation and Sleep
ICU patients should be routinely reoriented to their surroundings by clinicians, friends, and family. Environmental interventions to promote sleep including clustering patient care activities to avoid frequent interruptions, exposure to natural light in the daytime and avoidance of light during sleeping hours, and control of sound to maintain usual day/night sleep cycles (e.g., ear plugs), may also help prevent delirium. For patients with eyeglasses or hearing aids, these should be used during the ICU stay to minimize sensory impairment.
Early mobilization of critically ill patients has been shown to reduce the rate of ICU delirium. Therefore, admission orders to encourage “activity as tolerated” should be used instead of “strict bed rest” whenever appropriate, and early physical therapy consultation is advised.
There is currently no evidence to support the use of pharmacotherapy for prevention of ICU delirium.
The same non-pharmacologic strategies that are employed to prevent ICU delirium are also useful for treatment. Most notably, early mobilization has been shown to reduce the duration of delirium.
If non-pharmacologic strategies alone are ineffective in treating ICU delirium, clinicians may consider adjunctive pharmacotherapy. While low-dose haloperidol is the gold standard, limited data indicate that the newer antipsychotics, such as quetiapine, may reduce duration of delirium in critically ill adults, though large placebo-controlled trials are needed to establish whether these drugs are truly beneficial. If used, these agents should be discontinued upon resolution of delirium to minimize the risk that patients are discharged from the hospital on these medications that were intended only for short-term use.