Red flag symptoms: Loss of consciousness

Red flag symptoms to look out for in presentations of loss of consciousness, including possible causes, appropriate investigations and when to refer.

(Photo: Science Photo Library/Getty Images)
(Photo: Science Photo Library/Getty Images)

Red flag symptoms

  • Preceding chest pain
  • Preceding dyspnoea
  • Preceding headaches
  • Preceding palpitations
  • Preceding abdominal pain
  • Associated weakness of arm, face or leg
  • Associated with exercise or posture
  • Blood loss
  • Evidence of GI bleeding
  • Associated tongue biting, urinary incontinence or prolonged limb jerking
  • New medication
  • Preceding lightheadedness
  • Known diabetic on an oral hypoglycaemic or insulin

Taking a history

Taking a detailed history often leads to the cause of loss of consciousness.

Explore the patient's agenda. What would they like to happen? Find out why the patient has presented, and their thoughts and fears about the possible diagnosis.

A collateral history will also be useful.

Key questions to ask

  • When did the episodes start?
  • If this is an acute problem, have there been any associated symptoms?
  • Has there been any fever?
  • What happens before the episodes occur?
  • In general, what is the patient doing when loss of consciousness occurs?
  • Does this happen in warm or crowded environments?
  • Do they have warning symptoms?
  • Is there any associated light-headedness, headaches, chest pain, palpitations, abdominal pain or shortness of breath?
  • Are the episodes ever witnessed? If so, what does the witness notice? Useful information may include changes to skin colour before the event.
  • Did anyone film it? It is not uncommon for people to use smart technology to film events as they occur
  • Is there any limb jerking during the event? If so, ask the patient to demonstrate it, if possible. How long does this last?
  • Does the patient report any tongue biting or urinary incontinence during the event?
  • How long does it take the patient to come round and how do they feel when they do?
  • Has the patient ever experienced these episodes before and if so, did they seek medical attention and receive a diagnosis?
  • Has there been any obvious GI bleeding?
  • Does the patient take any regular prescribed or non-prescribed medication, and is any of the medication new?

Enquire about any family history of sudden death and complete the history by asking about smoking and alcohol consumption. Recreational drugs may also be relevant. Establish the patient's occupation

It may be important to know if the patient drives, because their diagnosis may need to be reported to the DVLA.

Consider if any additional measures might be necessary to support the patient at home.

Possible causes

  • MI
  • Intracerebral haemorrhage
  • Pulmonary embolus
  • Ruptured AAA
  • Drop attacks
  • Paroxysmal brady- or tachyarrhythmias
  • Simple vasovagal syncope
  • Epilepsy
  • Orthostatic hypotension
  • Drugs, for example antihypertensives
  • Severe anaemia
  • Cardiomyopathy
  • Sepsis
  • Hypoglycaemia
  • Severe electrolyte imbalance such as hyponatraemia
  • Pseudo seizures
  • Sick sinus syndrome/complete heart block (both have underlying aetiologies)
  • Postural tachycardia syndrome (in those who have had COVID-19 over 12 weeks ago) as a manifestation of long COVID
  • Addison's disease/Addisonian crisis


Remote examination via telephone

  • Can the patient provide a BP, pulse, oxygen saturations, temperature, blood glucose measurement if relevant?

Remote examination via video consultation

  • How do they look?
  • Do they appear in distress?
  • Can they provide a BP, pulse, temp, oxygen sats, blood glucose measurement if relevant?

Face-to-face examination

  • Ensure appropriate PPE is worn for face-to-face examination.
  • Examination should include BP and pulse. Check if the pulse rate is regular. Check lying and standing BP.
  • Auscultate the heart sounds, listening for any added sounds or murmurs.
  • A focused neurological examination may be necessary. Examine the pupils and their reaction to light and accommodation. You might also examine the fundi. Palpate for the aorta if indicated.

Possible investigations

Investigations may include the following:

  • Blood tests including FBC, U&Es, ferritin, HbA1c, cortisol
  • Spot blood glucose if the patient is diabetic on oral antiglycaemic agents or insulin
  • Lying and standing BP
  • ECG - 12-lead 24 or 48 hour
  • Echocardiogram
  • Gastroscopy
  • Colonoscopy
  • Abdominal ultrasound scan
  • CT/MRI head
  • Tilt table testing (via your local falls and syncope service)
  • Short synacthen test

When to refer

If clear that there is a postural drop, or evidence of hypoglycaemia and a contributing medication is established then consider a medication review and active follow up.

If the patient is acutely unwell or a life-threatening emergency is suspected, you will need to admit them directly to hospital.

Refer to neurology if a diagnosis of epilepsy is suspected. The patient may require a CT head and EEG.

Refer to the falls clinic if the diagnosis is unclear and the patient is having recurrent episodes.

Discovery of iron deficiency anaemia may require referral to your local iron deficiency anaemia clinic, depending on local policy.

A diagnosis of abdominal aortic aneurysm (AAA) will require urgent referral to a vascular surgeon, depending on the size of the AAA.

Detection of arrhythmia, heart block or cardiomyopathy will require assessment by a cardiologist.

Consider referral to endocrinology if Addison's disease is suspected.

Regarding the patient's fitness to drive, refer to DVLA guidance if the diagnosis is unclear and the symptoms are still occurring. Further DVLA advice will depend on the diagnosis.

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  • Dr Singh is a GP in Northumberland

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