Acute Confusion

Differential Diagnosis

Common Diagnoses

  • Hypoxia (Respiratory and Cardiac)
  • Systemic Infection
  • Cerebrovascular Accident (CVA: Stroke and Transient Ischaemic Attack [TIA])
  • Hypoglycaemia
  • Diabetic Ketoacidosis (DKA)

Occasional Diagnoses

Rare Diagnoses

Ready Reckoner

Key distinguishing features of the most common diagnoses

Hypoxia InfectionCVAHypoglycaemiaDKA
Central CyanosisYesPossibleNoNoNo
Focal WeaknessNoNoPossiblePossibleNo

Possible Investigations

Likely:Urinalysis, blood sugar (usually glucometer), pulse oximetry.

Possible:FBC, CXR, ECG, cardiac biomarkers, TFT.

Small Print:Calcium, digoxin levels, CT scan.

  • Acute confusion has so many causes and possible presentations that it is difficult to provide a definitive guide of investigations for the GP. A number of investigations might be considered according to the clinical picture and social circumstances; in the majority of cases, the patient will be admitted and necessary tests arranged by the hospital.
  • Urinalysis is very helpful if possible: Look for glucose and ketones (DKA), specific gravity (dehydration), pus, blood and nitrite in UTI. Ketones alone in starvation.
  • A blood glucometer reading is more practical than a formal blood glucose in the acute situation to diagnose hypo- and hyperglycaemia.
  • Pulse oximetry: To detect hypoxia.
  • FBC: Raised WCC in infections. Raised MCV helpful pointer to excess alcohol and myxoedema.
  • U&E important, especially if any signs of dehydration or on diuretics.
  • LFT and TFT: Alcohol, disseminated malignancy and hypothyroidism should always be considered.
  • CXR: May reveal a cause of hypoxaemia (e.g. pneumonia, cardiac failure).
  • ECG, cardiac biomarkers: If silent infarct suspected as cause.
  • Calcium: To detect possible hypo- or hyperparathyroidism.
  • Digoxin levels: For digoxin toxicity.
  • CT scan: Invariably a hospital-based investigation in acute confusion – may reveal spaceoccupying lesion, blood or infarct.

Top Tips

  • The key to management is establishing that the confusion really is acute rather than a gradual deterioration of cognition. This requires a careful history from someone who knows the patient well.
  • Don’t forget a drug history – if little information is available on a visit, check the patient’s medication cupboard.
  • In acute confusional states, it can be difficult to obtain useful clinical pointers from the patient’s history. The examination therefore assumes greater importance than usual.

Red Flags

  • It is virtually impossible to reach a firm diagnosis and treat safely in the home. Be very sure of yourself if you choose not to admit.
  • Central cyanosis is an ominous sign. Give oxygen, if possible, and dial 999.
  • In a diabetic on treatment, always check the blood sugar – remember that hypoglycaemia can produce confusion with neurological signs, mimicking a CVA.
  • Altered physiological responses in the elderly may result in a normal pulse and temperature even in the presence of significant infection. Don’t be misled by this.
  • Ask if any other household members have been unwell – carbon monoxide poisoning could affect others too.
Report errors, or incorrect content by clicking here.