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Blackouts

A blackout is a transient, spontaneous LOC followed by complete recovery. The causes of it include:

  • Neurally-mediated syncope (e.g. Vasovagal syncope)

  • Epilepsy

  • Postural hypotension

  • Cardiac abnormalities


Causes

Neurally-mediated syncope - This includes:

  • Vasovagal syncope (fainting) - Most common. This is where there's LOC lasting around 2 mins, with a very quick recovery. The 3 main features of it are:

    • Posture - blackout occurred after prolonged standing

    • Provoking factors - e.g. pain or a medical procedure

    • Prodromal symptoms - sweating or feeling hot before blackout

  • Carotid sinus syndrome - Hypersensitive carotid sinus baroreceptor → excessive bradycardia +/- vasodilation on minimal stimulation e.g. head-turning

  • Situational syncope - Faint w/identifiable trigger


Features suggesting Epilepsy - Tonic-clonic movements, lateral tongue-biting, urinary incontinence, post-ictal drowsiness/confusion


N.B. Tongue-biting is typically lateral in epilepsy, compared to at the tip of the tongue in syncope.


Features suggesting Postural hypotension - Unsteadiness, Light-headedness, Use of antihypertensives/diuretics


Features suggesting a Cardiac abnormality - ECG changes, evidence of heart failure, faint on exertion, prodromal palpitations. Common cause of this is Aortic Stenosis.


Investigations

History! - Important things to ask here include:

  • Before – Any prodrome? What were they doing? Trauma?

  • During – LOC? Limb jerking? Tongue-biting? Incontinence? Pallor? Duration?

  • After – Time to recover? Lethargy? Confusion? Ache/weakness?

  • Previous episodes, FHx, Drugs


N.B. If possible, a collateral history should be taken.


Very important to tell the patient that they must not drive!


After a history is taken, the next thing to do if find the cause of their syncopal episode. This can be done by:

  • Assess vital signs, L/S BP (lying/standing)

  • ECG

  • Documenting details of the event (w/collateral hx from a witness if possible)

  • Determining whether there have been any previous blackouts, considering the person’s medical and family hx of cardiac disease/sudden cardiac death, and reviewing whether any current medication may have contributed



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