Other investigations may be indicated according to the findings from the history and examination.
These can include:
CT head
CT has been shown to be unhelpful on a routine basis in identifying a cause for delirium and should be reserved for those with
- Focal neurological signs
- Confusion developing after head injury
- Confusion developing after a fall
- Evidence of raised intracranial pressure
- Those on antocoagulants
EEG
Although the EEG is frequently abnormal in those with delirium, showing diffuse slowing, its routine use as a diagnostic tool has not been fully evaluated. EEG may be useful where there is difficulty in the following situations:
- Differentiating delirium from dementia
- Differentiating delirium from non‑convulsive status epilepticus and temporal lobe epilepsy
- Identifying those patients in whom the delirium is due to a focal intracranial lesion, rather than a global abnormality
B12 and folate
Arterial blood gases
Specific cultures eg sputum, wound swabs
Lumbar puncture
Although various abnormalities have been seen in the CSF of patients with delirium, routine LP is not helpful in identifying an underlying cause for the delirium. It should therefore be reserved where there is reason to suspect a cause such as meningitis. This might include patients with the following features:
- Meningism
- Headache and fever
AXR for faecal loading
In the absence of definitive historical and physical examination findings, investigations usually include the following:
- FBC
- Urea and Electrolytes
- Urinalysis
- Chest x-ray
- Drug levels (if relevant)
- ECG
- Arterial blood gas
- CT and/or MRI, lumbar puncture and EEG may be considered only if no aetiology is identified from preliminary tests
