Blackout Flashcards
Syncopal causes of transient LOC can be explained with what mechanism
- Reflex - primitive reflex –> HR slows and BP drops. Reduces cerebral perfusion
- Cardiac - CO decreases e.g. due to arrhythmia/outlet obstruction
- Orthostatic - low BP on sitting or standing. Standing up causes sudden drop in BP (compensated for by vasoconstriction). Vasoconstriction takes a couple of seconds —> therefore transient HR increase to maintain BP. Patients with reduced intravascular volume (e.g. dehydrated) vulnerable.
- Cerebrovascular - non-cardiac structural causes of reduced cerebral perfusion. Uncommon
What are syncopal and non-syncopal causes of blackout?
Syncopal:
Reflex: Vasovagal syncope
Cardiac: Arrhythmias
Orthostatic: Drugs (e.g. anti-hypertensives, anti-sympathetics)
Cerebrovascular causes: vertebrobasilar insufficiency
Non-syncopal: Intoxication Head trauma Metabolic (mainly hypoglycaemia) Pyschogenic seizure Epileptic seizure
What is the most common cause of LOC in young patients
Vasovagal syncope - patients describe warning sensation (in stomach), going pale and clammy, and know LOC inbound
What is the most common cause of LOC in middle-aged patients
Vasovagal syncope and cardiac arrhythmias - arrhythmias usually secondary to IHD. Patients describe losing consciousness without warning - e.g. while playing sport / without obvious trigger
What is the most common cause of LOC in elderly patients
Orthostatic hypotension caused by medications -eg diuretics, ACEi, B blockers, a blockers (inability to constrict main capacitance veins), CCBs. Patients describe LOC after standing up - causes significant morbidity
Before LOC, what should we know?
- Any warning? - no warning = cardiac cause (/cerebrovascular cause). Arrhythmias may be precipitated by palpitations. Other causes of LOC often have warning e.g. aura before epilepsy, dizziness before vasovagal)
- Precipitating factors? - postural triggers = orthostatic hypotension. Other precipitating factors = vasovagal episode. LOC due to head turning = carotid hypersensitivity. During exertion = cardiac pathology (e.g. HOCM/aortic stenosis)
- Recent head trauma? - Subdural haemorrhages? (esp in elderly and alcoholics).
During LOC, what should you know?
- Duration of unconsciousness - seconds or minutes? LOC due to vasovagal or arrhythmia = seconds
- Any tongue biting / urine/faeces incontinence? - tongue biting = epileptic seizure. Twitching/incontinence = vasovagal
After LOC, what should you know?
- Spontaneous recovery? How long to recover? Any confusion after recovery? - Spontaneous recovery = not metabolic/neurological cause. Slow recovery with confusion = epileptic seizure.
What elements of the PMH are important to know for LOC?
- Happened before?
- Diabetes - predisposes vascular disease, hypoglycaemia, polyuria + dehydration, autonomic dysfunction (which can cause orthostatic hypotension)
- Cardiac illness - palpitations and chest pain? = indicates cardiac cause. Arrhythmias may arise after infarction. Aortic stenosis/HOCM may cause LV outflow obstruction
- PVD? - claudication? associated with CAD –> atherosclerosis.
- Epilepsy
- Anaemia - can contribute to hypoxia –> hypo perfusion
- Psychiatric illness
What do you need to know in the drug history for LOC?
- Insulin/oral hypoglycaemic
- Antihypertensives
- Vasodilators
- Antiarrhythmics
- Antidepressants - hypotension SE of some medications
- Warfarin / anticoagulants –> more vulnerable to subdural haemorrhages
What elements of the social history do you want to know?
Alcohol?
Stimulant recreational drugs? - cocaine/amphetamines stimulate heart –> can cause tachyarrhythmias and drop CO
What elements of the family history do you want to know?
Sudden death in any relations <65 y/o? - some cardiomyopathies and arrhythmias are hereditary
On examination of someone with LOC, what should you examine
Tongue
Dehydration - ?hypovolaemia
Head trauma
Heart - slow/irregular pulse = AF/heart block. Aortic stenosis/murmurs = outflow obstruction and cerebral hypo perfusion
Carotid bruits - ?carotid artery stenosis
BP - ?orthostatic hypotension
Focal neurological signs
What investigations must you perform in someone with LOC
- Bloods: capillary blood glucose (exclude hypoglycaemia), FBC (anaemia), U&Es (biochemical evidence of dehydration + electrolyte imbalance causing arrhythmia)
- ECG
- If history indicates, do: Echocardiogram (?valve lesion), carotid sinus massage (carotid sinus sensitivity), bran scan (?epilepsy)
What lifestyle advice do you give someone with vasovagal syncope?
Sit or lie down if you feel like you’re going to faint
