What Is Delirium and How Should It Be Managed?


Introduction and Scope of the Problem

The word delirium is derived from the Latin term meaning “off track.” Delirium has many descriptors, including acute confusion, altered mental status, sundowning, intensive care unit (ICU) psychosis, organic psychosis, acute brain failure, toxic metabolic state, cerebral insufficiency, and encephalopathy. All of these terms are used to describe an acute cognitive impairment associated with medical illness, which can be labeled as delirium. The American Psychiatry Association Diagnostic and Statistical Manual of Mental Disorders , Fifth Edition (DSM-V), provides the most widely recognized and used definition ( Table 28.1 ). Briefly, delirium is a transient, often reversible cause of cerebral dysfunction that can manifest clinically with a wide range of neuropsychiatric abnormalities. The clinical hallmarks of delirium are decreased attention span and waxing and waning confusion.

Table 28.1
Diagnostic Criteria for Delirium
From: American Psychiatric Association . Diagnostic and Statistical Manual of Mental Disorders . 5th ed. Washington, DC: American Psychiatric Association; ©2013:596
A. Disturbance in attention (i.e., reduced ability to direct, focus, sustain, and shift attention) and awareness (reduced orientation to the environment).
B. The disturbance develops over a short period of time (usually hours to a few days), represents an acute change from baseline attention and awareness, and tends to fluctuate in severity during the course of a day.
C. An additional disturbance in cognition (e.g., memory deficit, disorientation, language, visuospatial ability, or perception).
D. The disturbances in Criteria A and C are not better explained by a preexisting, established, or evolving neurocognitive disorder and do not occur in the context of a severely reduced level of arousal such as coma.
E. There is evidence from the history, physical examination, or laboratory findings that the disturbance is a direct physiological consequence of another medical condition, substance intoxication, or withdrawal (i.e., due to a drug of abuse or to a medication), or exposure to a toxin, or is due to multiple etiologies.

Although delirium is a transient global disorder of cognition, affect and behavior are often involved. The increased morbidity and mortality rates associated with delirium make it a medical emergency. Therefore early diagnosis and resolution of symptoms are correlated with the best outcomes. Unfortunately, delirium is often unrecognized or misdiagnosed. It is commonly mistaken for dementia or depression, attributed to hospitalization, or considered a consequence of old age (older patients are expected to become confused in the hospital). For people with dementia in particular, delirium may be the only presentation of a severe medical illness. The tendency of delirium to be mistaken for other psychiatric illnesses makes recognition and timely treatment difficult. This chapter will provide an overview of the prevalence, features, and effects of delirium and describe evidence-based strategies for screening and management.

Prevalence

The prevalence of delirium depends on the population being studied. Certain subsets of patients have higher incidences of delirium, including hospitalized older adults (29% to 64%), hospitalized cancer patients (25% to 50%), patients on palliative care units (28% to 42%), orthopedic patients (5% to 61%), patients in ICUs (80%), and patients at the end of life (88%). Delirium is present in 10% to 22% of older adults at the time of inpatient hospital admission, with an additional 10% to 30% of cases developing after admission. Delirium is also common among nursing home residents, with patients commonly developing delirium superimposed on dementia (22% to 89%). No prospective studies have evaluated delirium prevalence in patients receiving home hospice care, although in one study, hospice nurses reported that 50% of their patients were confused during the previous week. Delirium is often underrecognized and underdiagnosed, as the condition is rarely included in the list of a patient’s medical diagnoses.

Morbidity and Mortality

Delirium is associated with numerous negative outcomes, including increased risk of mortality, longer hospital stays, and decreased ability to care for self, which increases both caregiver burden and nursing home placement. Additionally, patients with delirium are frequently not capable of accurately reporting physical symptoms, which can affect treatment (e.g., pain management) and can lead to higher hospitalization cost. In specific studies looking at older patients and patients during the postoperative period, delirium resulted in prolonged hospital stays, increased complications, increased cost, increased long-term disability, and worsening cognitive function. Patients who recover from delirium also report recalling the experience with distress and are more likely to experience lasting psychological sequelae, including depression and posttraumatic stress disorder (PTSD). Perhaps the most striking complication of delirium is the increase in mortality. The risk of 12-month mortality for hospitalized patients with delirium is roughly double that of people without delirium.

Unfortunately, the impact of delirium often extends beyond the patient to affect others involved in the care of the patient, including families and both professional and unpaid family caregivers. Nurses report that it can be more challenging to provide care for delirious patients. Previous studies have also shown a correlation between the level of caregiver distress and dose of antipsychotic used to help mitigate symptoms. Family members also report distress when a loved one experiences delirium. This distress can have long-lasting consequences for the family caregiver, including decreased quality of life and increased risk for developing anxiety disorders. Additionally, delirium is the most common reason cited for palliative sedation requests, emphasizing how distressing delirium can be to both the patient and observers.

Relevant Pathophysiology

Delirium results from a wide variety of both physiological and structural insults, and its overall mechanism is still not fully understood. The main hypothesis involves reversible impairment of cerebral oxidative metabolism and multiple neurotransmitter abnormalities, specifically high dopaminergic tone and low cholinergic tone. Dopamine increase in mesolimbic and mesocortical tracts may cause agitation and delusions, whereas acetylcholine decrease in hippocampal and basal forebrain regions may lead to disorientation, hallucinations, and memory impairment. Clinically this hypothesis is supported by the tendency for anticholinergic medications to cause acute confusional states, especially in patients with impaired cholinergic transmission, such as in Alzheimer’s disease, and in patients with postoperative delirium who have increased serum anticholinergic activity. Additional support for this hypothesis is provided by the fact that symptomatic relief can be seen with the administration of neuroleptics, such as haloperidol, which are dopamine blockers. Other neurotransmitters (serotonin, γ-aminobutyric acid, cortisol, melatonin) are also believed to play a role in delirium, but their role is less clearly defined. No specific neuronal pathways causing delirium have been identified; however, imaging studies of metabolic (e.g., hepatic encephalopathy) and structural (e.g., traumatic brain injury, stroke) factors support the hypothesis that certain anatomical pathways may play a more important role than others. Additionally, disruptions in the blood–brain barrier can allow neurotoxic agents and inflammatory cytokines to enter the brain, which may contribute.

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