Delirium is a state of acute temporary confusion, usually with an altered level of consciousness. Older, frail people are at risk of experiencing delirium with any medical or surgical disease. It is estimated that between 10-40% of older adults are admitted to hospital with diagnosed delirium. A further 20% of these patients will develop delirium during the hospitalization period. A nurse plays a vital role in recognizing patients experiencing delirium as many of these patients go diagnosed or misdiagnosed.

Delirium is not a disease but is a set of symptoms due to an underlying cause. It is a temporary, reversible syndrome.



Although delirium is a common condition, the pathophysiology of it is poorly understood and there are many proposed delirium pathways. What is known, is that it is a condition that arises from dysfunction to the reticular activating system in the central nervous system, affecting both cerebral hemispheres. Hshieh, Fong, Marcantonio,& Inouye (2010) attributes a deficit of acetylcholine to the development of delirium. They state that as a result of primary brain injuries such as stroke or trauma, ischaemia occurs. The direct damage caused to neurons, disrupts normal cellular metabolism leading to impaired cerebral metabolism. The resulting decrease in acetylcholine results in deficits in this neurotransmitter. Acetylcholine in the CNS controls motivation, attention and arousal (alertness). A deficit in acetylcholine can be responsible for the onset of delirium.

Another pathway affecting acetylcholine levels is secondary brain injury or primary non-CNS conditions such as dehydration, falls, malnutrition, or illness and infection. In this pathway, inflammation causes microglial activation resulting in the production of cytokines. These proteins alter the permeability of the blood brain barrier and increases the secretion of dopamine, serotonin, and noradrenaline within the brain. Increased activity of these neurotransmitters causes a decreased synthesis of acetylcholine, resulting in an acetylcholine deficit and ultimately, delirium.

Despite having clear pathways, delirium is rarely a caused by only one contributing factor. Increasing age, thiamine deficiency, hypoglycemia, heart or renal disease, substance abuse, hypoxia or sleep disruption can all be contributing factors to the development of delirium. Other causes can be a urinary tract infection, fecal impaction, and urinary retention.

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Clinical manifestations

Delirium usually has a sudden onset and has a short duration, lasting for hours to weeks. Manifestations of delirium can range from hypoactivity to hyperactivity. A patient may experience both hypo and hyper symptoms at different times in the same day.

Hypoactive symptoms include:

  • lethargic
  • confused
  • withdrawn
  • sedated
  • decreased attention
  • incoherent speech

Hyperactive symptoms include:

  • hallucinations
  • agitation
  • disorientation
  • paranoia
  • aggression
  • restless
  • delusions

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This short video depicts a patient whom is experinecng delirium

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Diagnosing delirium

There are mnemonics which help in delirium differential diagnosis


  • Infectious (encephalitis, meningitis, UTI, pneumonia)
  • Withdrawal (alcohol, barbiturates, benzodiazepines)
  • Acute metabolic disorder (electrolyte imbalance, hepatic or renal failure)
  • Trauma (head injury, postoperative)
  • CNS pathology (stroke, hemorrhage, tumour, seizure disorder, Parkinson’s)
  • Hypoxia (anemia, cardiac failure, pulmonary embolus)
  • Deficiencies (vitamin B 12 , folic acid, thiamine)
  • Endocrinopathies (thyroid, glucose, parathyroid, adrenal)
  • Acute vascular (shock, vasculitis, hypertensive encephalopathy)
  • Toxins, substance use, medication (alcohol, anesthetics, anticholinergics, narcotics)
  • Heavy metals (arsenic, lead, mercury)



  • C-Cognitive deficit
  • O-Organ dysfunction (lung, heart, liver, kidney)
  • N-Neuro (SZ, ICP)
  • F-Fever/infection, faecal impaction
  • U-Urinary retention/UTI
  • S-Sensory impairment (eyes/ears)
  • E-EtOH, endocrine, electrolytes
  • D-Drugs – narcotics, anti-cholinergics, anti-inflammatory etc.


The clinical criteria for diagnosing delirium includes the following:

  • Reduced clarity of awareness
  • impaired ability to focus
  • easily distracted
  • A change in cognition: language and memory impairment, disorientation
  • Short term memory is affected
  • perceptual disturbances: illusions, delusions, hallucinations


A mini-mental state examination is the most widely used tool for evaluating mental status of the patient:



Nursing management

The treatment of delirium focuses on treating the precipitating factors for example treating an underlying infection with antibiotics or addressing nutritional deficits.

  • promote a calm safe environment
  • use a single room if possible
  • re orientate to TPP
  • educate family on how to offer reassurance
  • complementary therapies to reduce anxiety
  • regularly monitor mental status
  • monitor food and fluid intake/output
  • offer reassurance to the patient and family




A comprehensive list of nursing interventions in the treatment of delirium can be found here

A delirium management pathway can be found here: delirium-management-pathway

An information sheet for family and visitors on delirium: delirium-info-for-relatives-visitors



Johnston, A. (2015). Structure and function of the neurological system. In J. Craft & C. Gordon (Eds.), Understanding pathophysiology (2nd ed., pp. 89–136). Sydney, Australia: Mosby Elsevier.

Hshieh, T. T., Fong, T. G., Marcantonio, E. R., & Inouye, S. K. (2010). Cholinergic deficiency hypothesis in delirium: A synthesis of current evidence. The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 63(7), 764–772. doi: 10.1093/gerona/63.7.764

Hunt, S. (2013). Older adulthood. In J. Crisp, C. Taylor, C. Douglas, & G. Rebeiro (Eds.), Potter and Perry’s fundamentals of nursing (4th ed., pp. 440–462). Sydney, Australia: Mosby Elsevier.

Shaw, V., Lewis, S., & Moyle, W. (2008). Nursing management: Alzheimer’s disease and dementia. In D. Brown & H. Edwards (Eds.), Lewis’s medical-surgical nursing: Assessment and management of clinical problems (2nd ed., pp. 1660–1678). Sydney, Australia: Mosby Elsevier.