Assessment of delirium

Overview 
Theory 
Emergencies 
Diagnosis 
Resources 

Last reviewed: 21 Nov 2024

Last updated: 13 Apr 2023

Introduction

Delirium is an acute, fluctuating change in mental status, with inattention, disorganised thinking, and altered levels of consciousness.[1] It is a potentially life-threatening disorder characterised by high morbidity and mortality. Guidelines address recognition, risk factors, and treatment for delirium.[2][3]

Adverse sequelae

Mortality for those diagnosed with delirium in hospital is twice that of patients with similar medical conditions without delirium and rises as high as 14% within 1 month of diagnosis.[4] Delirium occurs in 20% to 25% of hospitalisations annually and is the most common hospital-related complication in the US.[5][6] Delirium is common in the intensive care unit especially among mechanically ventilated patients. In critically ill patients, it is associated with an increased length of stay and increased mortality.[7] Studies have demonstrated a 12% prevalence of delirium in older emergency department patients.[8] Despite its frequency, delirium is frequently under-recognised given the fluctuating nature of symptoms and an overall under-appreciation of its significance by healthcare providers. Moreover, delirium has also been associated with elevated risks for functional and cognitive decline, poor rehabilitation potential, institutionalisation, and re-hospitalisation.[1][9][10][11][12] While delirium is generally considered reversible, studies suggest that delirium symptoms can last for weeks to months following onset.[13] Persistent delirium has been found to be frequent in older hospitalised patients, and associated with adverse outcomes.[14]

Classification

The Diagnostic and Statistical Manual of Mental Disorders (DSM-5-TR) notes that in order to be diagnosed with delirium, a patient must show all 4 of the following features.[15]

A disturbance in attention (i.e., reduced clarity of awareness of the environment) is evident, with reduced ability to focus, sustain, or shift attention. This disturbance in consciousness might be subtle, initially presenting solely as lethargy or distractibility, and might be frequently dismissed by clinicians and/or family members as being related to the primary illness.
A change in cognition (such as memory deficit, disorientation, language disturbance) or the development of a perceptual disturbance not better accounted for by a pre-existing or evolving dementia.
The disturbance develops over a short period of time (usually hours to days), represents an acute change from baseline, and tends to fluctuate during the course of the day.
There is evidence from the history, physical examination, or laboratory findings that the disturbance is caused by the direct physiological consequences of a general medical condition, substance intoxication, or substance withdrawal. The changes in attention and cognition must not occur in the context of a severely reduced level of arousal, such as coma.

Three clinical subtypes of delirium have been identified.[16][17][18] These include:

Hyperactive delirium - a condition where a patient might have heightened arousal, with restlessness, agitation, hallucinations, and inappropriate behaviour
Hypoactive delirium - a condition where a patient might display lethargy, reduced motor activity, incoherent speech, and lack of interest
Mixed delirium - a combination of hyperactive and hypoactive signs and symptoms.

The term sub-syndromal delirium has also been used to define partially resolved or incomplete forms of delirium.

Epidemiology

The prevalence of delirium in the community is believed to be 1% to 2%, a figure that increases to 14% for patients aged >85 years.[13]

Prevalence of delirium ranges from 10% to 40% in older hospitalised patients.[5]

Delirium affects up to 30% of people on medical wards.[3] Prevalence ranges from 14% to 24% in the emergency department, 15% to 53% for postoperative patients, and 70% to 87% for intensive care patients.[19][20][21]

Pathophysiology

The pathophysiology of delirium remains relatively unclear. In general, neuroimaging studies reveal disruptions in higher cortical functioning in multiple disparate areas of the brain, including the prefrontal cortex, subcortical structures, thalamus, basal ganglia, lingual gyri, and frontal, fusiform, and temporoparietal cortex.[22][23]
Electroencephalographic (EEG) studies also show diffuse slowing of cortical activity.
Theories on the pathogenesis of delirium point to the role of neurotransmitters, inflammation, and chronic stress on the brain. For example, the role of cholinergic deficiency in inducing delirium is strengthened by the clear association of anticholinergic drug use with increased incidence.[24] Studies in surgical patients have demonstrated a dysfunctional interaction between the cholinergic and immune systems in patients who developed postoperative delirium.[25]
Dopaminergic excess is also believed to contribute. Evidence does not appear to support the use of antipsychotic medications (dopamine antagonists) for the prevention or treatment of delirium, but is not entirely consistent.[26][27][28][29][30][31][32][33]
Other neurotransmitters implicated in the pathophysiology of delirium include noradrenaline, serotonin, gamma-aminobutyric acid, glutamate, and melatonin.
Evidence also points to the role of cytokines such as interleukins 1 and 2 and TNF-alpha and interferon in contributing to delirium.[34]
Finally, chronic hypercortisolism, as induced by chronic stress secondary to illness or trauma, may also contribute to delirium initiation.[35]

Differentials

Common

Dementia
Pain
Stroke and transient ischaemic attack
Myocardial infarction
Acute systemic infection
Hypoglycaemia
Hyperglycaemia
Hypoxia
Hypercapnia
Acute urinary obstruction
Medication- or illicit drug-related
Alcoholic ketoacidosis
Hepatic encephalopathy
Renal failure
Hypernatraemia
Hyponatraemia
Hypercalcaemia
Meningitis/encephalitis
Brain tumour
Post-ictal state
Dehydration (volume depletion)
Constipation

Full details

Uncommon

Traumatic head injury
Adrenal crisis
Thyrotoxicosis
Myxoedema coma
Brain abscess
Neurosyphilis
Wernicke's encephalopathy

Full details

Contributors

Authors

Margaret Pisani, MD, MPH

Associate Professor

Yale University School of Medicine

New Haven

Disclosures

MP declares that she has no competing interests.

Acknowledgements

Dr Margaret Pisani would like to gratefully acknowledge David M. Dosa, a previous contributor to this topic.

Disclosures

DMD declares that he has no competing interests.

Peer reviewers

Marquis Foreman, PhD, RN, FAAN

Professor and Associate Dean for Nursing Science Studies

College of Nursing

University of Illinois at Chicago

Disclosures

MF declares that he has no competing interests.

Andrew Parfitt, MBBS, FFAEM

Clinical Director

Acute Medicine

Associate Medical Director

Consultant Emergency Medicine

Guy's and St Thomas' NHS Foundation Trust

Clinical Lead and Consultant

Accident Emergency Medicine

St Thomas' Hospital

London

Disclosures

AP declares that he has no competing interests.

Guidelines
- Delirium: prevention, diagnosis and management in hospital and long-term care
- Risk reduction and management of delirium: a national clinical guideline
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Assessment of delirium

Summary

Introduction

Adverse sequelae

Classification

Epidemiology

Pathophysiology

Differentials

Common

Uncommon

Contributors

Authors

Margaret Pisani, MD, MPH

Disclosures

Acknowledgements

Disclosures

Peer reviewers

Marquis Foreman, PhD, RN, FAAN

Disclosures

Andrew Parfitt, MBBS, FFAEM

Disclosures

Guidelines

Videos

Log in or subscribe to access all of BMJ Best Practice

Log in or subscribe to access all of BMJ Best Practice

Log in to access all of BMJ Best Practice