Surgical Critical Care

ICU Delirium

Delirium is a derangement of attention and awareness that occurs over a short period of time in the intensive care setting. Disorientation, memory loss, and disturbance of perception are additional disturbances associated with delirium. It is the most common mental dysfunction in the ICU. 

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There are 3 main types of delirium: 

• Hyperactive

• Hypoactive (can be severe and is commonly missed in ICU)

• Mixed

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Delirium is very common in the ICU. Some investigations report up to 80% of patients on mechanical ventilation will have some degree of delirium. Diagnosing delirium means ruling out other neuro-cognitive disorders that cause hyperactivity, confusion or reduced level of arousal. Disorders that can mimic ICU delirium include: 

• Intoxication

• Withdrawal states

• Meningitis

• Encephalitis

• Stroke

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Three fourths of the delirium in the ICU is either hypoactive or mixed. Hyperactive delirium occurs in only 23% of cases. Common symptoms of hyperactive delirium include: 

• restlessness

• emotional lability

• agitation

• hallucinations

• illusions

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Conversely, symptoms of hypoactive delirium include:

• confusion

• sedation

• apathy

• decreased responsiveness

• withdrawn affect

• slowed motor function

• drowsiness

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It is notable that patients with hypoactive delirium are thought to have increased mortality. 

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Mixed delirium is seen most frequently in the ICU, both symptoms seen in hyperactive and hypoactive delirium are present.

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History and Physical

Deficits in attention and awareness with at least one alteration in cognition will be noted. Onset is usually over a short period and symptoms may wax and wane. Simple orientation to person place and situation will not adequately assess for delirium. Symptoms can last days or longer. 

For initial diagnosis of delirium a thorough neurological and physical exam should be performed to look for clues to determine the source of delirium. For example, the presence of fever could  and may reveal clues suggesting the cause of delirium. The presence of a fever, for example, could reveal an infectious etiology, whereas focal neurological deficits may indicate a neurological or vascular cause of the delirium. A history of alcohol / substance disuse could reveal intoxication, withdrawal, Wernicke's encephalopathy or other relevant vitamin deficiency.

Additional workup for Delirium

Laboratory and radiographic testing should be done in the light of the patient's history and physical exam, with the following investigations providing a partial list of what should be considered:

• Routine lab monitoring

• Investigation of possible/likely infectious causes (urinary tract infection, meningitis, etc.)

• Investigation of possible/likely metabolic disturbances (hypoglycemia, electrolytes, ammonia, etc.)

• Investigation of possible/likely intoxication or withdrawal (urine drug screen)

• Investigation of possible/likely neurological or vascular insults (imaging)

• Investigation of vitamin deficiencies

• Investigation of endocrinopathies

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Prevention

Target modifiable risk factors. Interventions that improve cognitive function, facilitate sleep hygiene, increase mobility, vision and hearing. 

Besides, strategies for preventing infection, dehydration, constipation, and hypoxia are mandatory. Currently, no pharmacological agents have enough evidence to recommend their use in preventing delirium. In the ICU setting, mechanically ventilated adult patients at risk of developing delirium may benefit from dexmedetomidine infusions (e.g., 0.1 μg/kg per hour) over BDZs infusions in regards to decreasing the prevalence of delirium. Melatonin is probably useful for ICU delirium, but further studies are needed. There is also evidence that early mobilization of the adult ICU patient population may reduce the duration and incidence of delirium.

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A mnemonic ABCDEF bundle was proposed for assessing and preventing the complication.[35] 

• A=Assess, prevent and manage pain

• B=Both Spontaneous Breathing Trials and Spontaneous Awakening Trials

• C=Choice of sedation and analgesia

• D=Delirium: assess, prevent and manage

• E=Early mobility and exercise

• F=Family engagement and empowerment

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Differential 

Delirium is a diagnosis of exclusion and requires accurate clinical testing and observation. Several conditions must be considered for the differential diagnoses.

• Neurocognitive disorders

• Psychotic disorders such as brief psychotic disorder, schizophrenia, schizophreniform disorder, among others

• Mood disorders with psychotic features including bipolar and depressive episodes

• Acute stress disorder

• Malingering and factitious disorder

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Sequela of Delirium in the ICU

• Longer duration of mechanical ventilation

• Longer ICU length of stays

• More ICU readmissions

• Higher incidence of device dislodgement

• Prolonged hospital stays

• Lower 6 month survival when compared to patients with similar dx and no delirium

• Long term cognitive impairment after critical illness​​

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For more information on delirium, check out: icudelirium.org