Red flag symptoms: Delirium

A carer's account is valuable when assessing the acutely confused.

Red flags

  • Alterered consciousness
  • Age <65 years
  • Head trauma
  • Neurological signs
  • Severe headache
  • Delirium tremens
  • Vomiting
  • Unavailable history

Delirium, or acute confusion, tends to arise secondary to a sudden insult to the brain and is potentially reversible. Chronic confusion usually involves an irreversible change to neuroanatomy. Timely diagnosis and intervention is the key to optimising patient outcome.

Commonly, a person with delirium appears newly agitated and aggressive. Delirium can also be hypoactive in nature, with associated social withdrawal, increased somnolence and a reduction in appetite.

Delirium in someone with chronic confusion is also regularly missed. It is thought that up to two-thirds of all cases of delirium go undiagnosed, with poor patient outcome.1 Following admission, 90% of cases have the cause for their delirium identified within a few hours and full recovery of mental function is the rule.


When assessing an acutely confused patient, a regular carer's account is valuable. Pay attention to recent trauma, particularly head injury, recent changes to medications or environment, and past episodes of confusion, substance abuse or neurological or mental illness. Delirium secondary to alcohol withdrawal (delirium tremens) is a medical emergency. Differential diagnoses include psychosis, depression and dementia.

Acute confusion is particularly common in the elderly,2 with infection and medication being the most common causes. Neurological examination, an assessment of hydration status, BP and glucose measurement are recommended.

Patients who suddenly find it more difficult to communicate may display symptoms of acute confusion; the ears should be examined and hearing and visual aids checked. Reduced conscious level, features of raised intracranial pressure or other new neurological signs are red flags and should trigger urgent secondary care assessment.

If the cause is not easily determined, there should be a low threshold for secondary care referral. Untreated delirium has been associated with increased morbidity and mortality.3

A useful aide-memoire is "HIDEMAP":

  • Hypoxia
  • Infection
  • Drugs
  • Endocrine (such as diabetes mellitus)
  • Metabolic (hyper/ hypocalcaemia)
  • Alcohol
  • Psychosis
Possible causes
  • Infection
  • Medications
  • Toxins, such as non-prescription drugs
  • Vascular disease
  • Metabolic
  • Epilepsy - post-ictal state
  • Vitamin B deficiency
  • Endocrine dysfunction
  • Head injury
  • Neoplasia
  • Urunary retention
  • Constipation


Treatment of delirium focuses on correcting the causative insult. It may take a week or more for the delirium to resolve and the minority of patients will be a risk to themselves or others.

If verbal de-escalation techniques are unsuccessful, a small amount of antipsychotic medication may be considered.4

Delirium in the under-65s is much rarer and is considered a red flag. History of onset is key. Infection and substance misuse are the most common causes.

Special caution should be paid when there is no history available, with a low threshold for secondary care referral. It can be difficult to differentiate psychosis from confusion and a full mental state examination should be considered.

  • Dr Cumisky is a GP in Bath

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This is an updated version of an article that was published in November 2011


1. MJ 2001; 322: 144-9.
2. J Neurol Neurosurg Psychiatry 2004; 75(3): 362-7.
3. BMJ 2007; 334: 842-6.
4. NICE. Delirium: diagnosis, prevention and management. CG103; London, NICE 2010.

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