Diagnosis and Treatment of Agitation and Delirium in the Intensive Care Unit Patient

Jason P. Caplan

I. GENERAL PRINCIPLES

A. Definition.

1. Agitation is a frequent behavioral aberration in severely ill patients, which carries significant risks for the safety of the patient and staff.

2. Agitation may be a symptom of delirium (a neuropsychiatric manifestation of a systemic disturbance), the most common cause of agitation in the intensive care unit (ICU). Delirium is defined as alterations in attention and cognition that develop over hours to days and wax and wane. The hallmark of delirium is inattention that can be gauged by simple bedside testing (e.g., attention to conversation, serial subtraction of 7 from 100, recitation of the months of the year backwards).

B. Epidemiology.

1. Delirium occurs in >30% of all patients in the ICU and in >80% of patients in the ICU who are intubated.

C. Risk factors.

1. Acute physiologic risk factors include metabolic disturbances, infection, shock, hypoxia, renal failure, hepatic failure, and intracranial processes.

2. Chronic physiologic risk factors include advanced age; malnutrition; alcohol or drug abuse; and prior diagnoses of depression, dementia, stroke, seizure, congestive heart failure, or human immunodeficiency virus infection.

3. Iatrogenic risk factors include medication side effects (most commonly those of anticholinergics, benzodiazepines, opioids, antihistamines, and steroids) and the presence of indwelling catheters.

II. ETIOLOGY AND PATHOGENESIS

A. The mnemonic “WWHHHHIMPS” aids recall of the life-threatening causes of delirium (Table 142-1).

B. The current leading hypothesis on the neural mechanism of delirium implicates hypocholinergic and hyperdopaminergic states.

C. Acetylcholine is the primary neurotransmitter of the reticular activating system, a network vital to both alertness and attention. Therefore, a relative cholinergic deficit is likely to disrupt these functions.

D. Impaired oxidative metabolism increases the release, and disrupts the reuptake and extracellular metabolism, of dopamine. Excess dopamine is associated with hallucinations, delusions, and other psychotic symptoms, and may facilitate the excitatory effects of glutamate, thereby producing agitation.

TABLE 142-1 WWHHHHIMPS: A Mnemonic for the Life-threatening Causes of Delirium

Withdrawal

Wernicke encephalopathy

Hypoxia or hypoperfusion of the brain

Hypertensive crisis

Hypoglycemia

Hyper- or hypothermia

Intracranial mass or hemorrhage

Meningitis or encephalitis

Poisons (including medications)

Status epilepticus

Adapted from Wise MG, Trzepacz PT. Delirium (confusional states). In: Rundell JR, Wise MD, eds. The American psychiatric press textbook of consultation-liaison psychiatry. Washington, DC: American Psychiatric Press, 1996:258-274.

III. DIFFERENTIAL DIAGNOSIS

A. Two delirium screening scales have been validated for use by nonpsychiatric personnel in the ICU: the Confusion Assessment Method for the ICU (CAM-ICU) and the Intensive Care Delirium Screening Checklist (ICDSC). Both are available at www.icudelirium.org.

B. Delirious patients may present with a hypoactive subtype that is commonly mistaken for depression. Hypoactive delirium is distressing to the patient, may progress to the agitated form, and requires appropriate treatment.

C. Patients with dementia are at risk for agitation and delirium in the ICU as a result of being in unfamiliar surroundings. Behavioral measures should be employed to help these patients maintain orientation to their milieu.

D. Patients with schizophrenia

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