Transient Loss of Consciousness

Author(s): Sandeep Hothi and David Sprigings

The causes of transient loss of consciousness (TLoC) (Box 9.1) can usually be differentiated by a detailed history taken from the patient and any eyewitnesses (Tables 9.1 and 9.2), supplemented by the examination findings and a careful review of the ECG (Table 9.3). Further investigation may be needed for definitive diagnosis.

Risk-stratification is important, as patients at low risk of serious adverse events can be discharged from the emergency department.
The assessment of the patient with transient loss of consciousness is summarized in Figure 9.1.

Priorities ⬆ ⬇

Is transient loss of consciousness related to acute disease?
Consider those acute diseases which may be associated with TLoC:
- Major arrhythmias (Chapters 39, 40, 41, 42, 43, 44)
- Acute coronary syndrome (Chapters 45 and 46)
- Pulmonary embolism (Chapter 57)
- Aortic dissection (Chapter 50)
- Subarachnoid haemorrhage (Chapter 67)
- Rapid blood loss and other cause of hypovolaemia (Chapters 73 and 74)
- Hypoglycaemia (Chapter 81)
These patients will typically have other symptoms (e.g. headache, chest pain, breathlessness) or abnormal physiological observations (e.g. hypotension). Further assessment and management of these diseases is given in the corresponding chapters.
Was transient loss of consciousness due to syncope or a seizure?
- A detailed history will usually allow syncope (defined as TLoC due to global cerebral hypoperfusion (Box 9.2)) to be differentiated from seizure (Tables 9.1 and 9.2).
- Involuntary movements (including tonic-clonic seizures, after 30 s of cardiac arrest) are common in syncope, and should not be interpreted as necessarily indicating epilepsy.
- Further management of the patient after a generalized seizure is given in Chapter 16.
Admit or discharge?
High-risk features warranting admission for inpatient management include:
- Suspicion of acute disease causing syncope (see 1. above)
- Evidence of significant structural or ischaemic heart disease, or the presence of heart failure
- Clinical (e.g. exertional syncope) or ECG features (Table 9.3) suggesting arrhythmic syncope
- Abnormal physiological observations
- Major comorbidities
Advice to discharged patients

Driving

As a general rule, any patient who has had TLoC must not drive until specialist assessment has been completed and they have been advised by the specialist that they may drive.
Patients who have had typical vasovagal syncope while standing, with a reliable prodrome, may continue to drive and need not notify the DVLA.
Consult the guidelines of the Driver and Vehicle Licensing Agency (DVLA) (available online at: www.gov.uk/dvla/fitnesstodrive).

Occupational issues

Working patients who have had TLoC should be given advice on the implications of the episode for health and safety at work and any action they must take to ensure the safety of themselves and other people. They should inform their occupational health department.

Suspected cardiovascular cause

Patients waiting for cardiovascular assessment should be advised to return to the emergency department in the event of a further episode. If TLoC occurred during exercise, or there is evidence of structural heart disease or an abnormal ECG, they should be advised not to exercise until the assessment has been completed, and the management plan should be discussed with a cardiologist before discharge.

Suspected epilepsy

See Chapter 16 for the advice you should give to patients after a generalized seizure.

Further Management ⬆ ⬇

Outline

Probable Vasovagal Syncope
Suspected Arrhythmic Syncope
Unexplained Syncope

Probable Vasovagal Syncope

Give advice to the patient on avoiding action to take in the event of prodromal symptoms. Muscle clenching (leg crossing and arm tensing/hand grip) can prevent progression to syncope.
If there have been recurrent episodes with significant impact on quality of life or with high risk of injury, arrange a tilt-table test with cardiology follow-up: pacing may be considered for patients with a pronounced cardio-inhibitory response (typically prolonged asystole).

Suspected Arrhythmic Syncope

The choice of ECG monitoring depends on the frequency of episodes and the presence or absence of heart disease. Patients with high-risk features (see above) should be admitted for investigation. For those without high-risk features, recommendations for ECG monitoring are:

TLoC at least several times a week: Holter monitoring (up to 48 hours if necessary)
TLoC every 1–2 weeks: external event recorder
TLoC infrequently (less than once every two weeks): implantable event recorder

Unexplained Syncope

For patients with suspected carotid sinus hypersensitivity, and for those with unexplained syncope who are aged ≥60 years, carotid sinus massage should be the initial investigation (Table 9.4).
For other patients with unexplained syncope, and those with negative testing for carotid sinus hypersensitivity, ambulatory ECG monitoring should be done (see above).

section name header

Information ⬇

Priorities ⬆ ⬇

Further Management ⬆ ⬇

Further Reading ⬆