Blackout Flashcards
What is the difference between syncope and loss of conciousness?
loss of conciousness can be due to syncopal and non-syncopal causes
What is syncope?
form of loss of conciousness with the cause being hypoperfusion
What are the syncopal causes of blackout?
- Reflex
- Cardiac
- orthostatic
- cerebrovascular
What is the reflex cause of syncope?
- Activation of primitive reflex that leads to mammals play dead when faced with danger (different people have different threshold)
- Heart rate slows, BP drops, reducing cerebral perfusion leading to syncope
What are examples of reflex syncope?
- Vasovagal syncope
- Carotid sinus hypersensitivity
- Situational syncope (e.g. micturition)
What is the cardiac mechanism for syncope?
Pathologies causing a reduction in cardiac output (arrhythmias or outlet obstruction) can also lead to syncope
What are cardiac syncope examples?
- Arrhythmias
- Structural cardiac pathology causing outflow obstruction (e.g. aortic stenosis, hypertrophic obstructive cardiomyopathy)
What is the orthostatic mechanism for syncope?
- Low BP on sitting or standing
- When stand up vasconstriction happens to compensate for loss of BP, takes a few secs so heart rate increases temporaily
- If reduced intravascular volume (e.g. dehydration) and/or normal autonomic response (transient tachycardia and peripheral vasoconstriction) to standing is blunted (e.g. due to drugs or autonomic neuropathy) are vulnerable to blackouts
What are examples of orthostatic syncope?
- Drugs (anti-hypertensive, anti-sympathetic)
- Dehydration
- Autonomic instability
- Baroreceptor dysfunction (in hypertensive patients)
What is the cerebrovascular mechanism for syncope?
Non cardiac structural causes of reduced cerebral perfusion e.g. obstructions to the blood flow between heart and brain
What are example of cerebrovascular syncope?
- Verterbrobasilar insufficiency
- Subclavian steal
- aortic dissection
What are non-syncopal causes of transient loss of conciousness?
- Intoxication (e.g. alcohol, sedatives)
- Head trauma
- Metabolic (mainly hypoglycaemia)
- Psychogenic (non-epileptic) seizure
- Epileptic seizure
- Narcolepsy
What are differentials for loss of consciousness with a young patient?
vasovagal syncope (presyncopal sensation)
What are differentials for loss of consciousness with a middle aged patient?
- Vasovagal syncope
2. Cardiac arrhythmias (no warning)
What are differentials for loss of consciousness with a old patient?
Orthostatic hypotension
Which medications can cause orthostatic hypotension?
- diuretics
- ACE inhibitors
- beta blockers
- alpha blockers
- CCBs
What do you ask about the incident of loss of conciousness?
- any warning
- any precipitating factors
What can you suggest if there was no warning?
- cardiac cause (cardiac arrythmias)
- cerebrovascular cause (e.g. subclavican steal syndrome)
What differentials would you think if there was warning?
other cause e.g. aura before epileptic seizure, dizziness preceding a vasovagal episode
What are examples of precipitating factors?
exercise, standing up, fear, pain
What would a postural trigger suggest?
orthostatic hypotension
What would loss of consciousness caused by head turning suggest?
carotid sinus hypersensitivty
What would blackout while sitting or lying down suggest?
cardiac arrythmias
what would passing out with exercise suggest?
primary cardiac pathology
- aortic stenosis
- cardiomyopathy
- cardiac channelopathy (long QT syndrome)
What would symptoms immediately following vigorous arm activity suggest?
subclavian steal
What would recent head trauma and blackouts maybe suggest?
Subdural Haemarrohage in elderly and alcoholic which may be precipitated by head trauma days or weeks earlier and may be associated with subsequent seizures
What would a short lived episode suggest?
- vasovagal
- arrythmias
What would biting their tongue down during the episode suggest?
epileptic seizure
What would moving their limbs or were they incontinent of urine or faeces during the episode suggest?
vasovagak