syncope Flashcards
(36 cards)
what is syncope
transient loss of consciousness due to global cerebral hypoperfusion; acute onset and spontaneous complete recovery
what systolic BP results in syncope
<70mmHg
what is the most common form of syncope
vasovagal syncope
causes of transient loss of conciousness (5)
traumatic;
non-truamatic - syncope, elipepsy, psychogenic, misc (e.g. metabolic, toxins, haemorrhage etc.)
how to distinguish syncope from other TLOCs
syncope - rapid onset, short duration, spontaneous, complete recovery;
others are not characterised by these
4 syncope categories
reflex (60%); orthostatic (15%); cardiac; unkown
3 types of reflex syncope
vasovagal; situational; carotid sinus syndrome
reflex syncope - what triggers it, warning signs, who it occurs in
occurs due to a trigger e.g. emotional stress, injury, pain etc.
warning - there is a prodrome which lasts 30s-several mins where the pt feels fatigued, sweaty, dimming of vision, ringing in ears;
occurs in younger pts
vasovagal syncope pathway
trigger (exaggerated sympathetic activation) leading to –> increased vagal tone/prarsympathetic stimulation –> bradycardia, vasodilation of peripheral blood vessels –> hypotension –> cerebral hypoperfusion –> loss of conciousness
common triggers of vasovagal syncope (5)
pain; prolonged standing; fear; dehydration; stressful events
symptoms of vasovagal syncope
dizziness; fainting; feeling warm; nausea; ringing in ears; tunnel vision etc.
what is situational syncope
a form of reflexive syncope caused by specific situational triggers
examples of situational syncope (5)
micturition; defaecation; coughing; laughing; swallowing
who does micturition syncope affect more and what is the mechanism
affects men - usually benign in young men but associated with comorbidities.postural hypotension in older;
occurs when stretch receptors innervate the brainstem which upregulates parasymp.
what is the carotid sinus reflex
the carotid sinus is a dilation at the base of the internal carotid artery that contains baroreceptors which monitor BP
carotid sinus reflex pathway (2)
- ↑ BP –> ↓ symp. –(vasodilation)–> ↓TPR –> ↓BP
- ↑ BP –> stretch carotic barorecptors –> message sent to brainstem –> ↑ parasymp – (↓ HR + contractility)–> ↓ CO –> ↓BP
what can be done to test the carotid sinus reflex
carotid sinus massage - a normal response is a slight drop in HR/BP, an exaggerated response indicates carotid sinus hypersensitivity
what is carotid sinus syndrome
syncope without warning and hypersensitive CSM response (and reproducable syncope w CSM)
carotid sinus syndrome triggers examples (3)
head turning; shaving; tight collar (too much pressure on CS)
what can help exaggerated CSM
pacing
what is orthostatic hypotension
a form of low blood pressure that happens when standing after sitting or lying down - compensatory mechanisms are required to maintain BP as blood volume is redistributed around the body
orthostatic hypotension definition (stats)
↓systolic BP >20mmHg within 3mins of standing or a systopic BP of <90mmHg on standing
How is the arterial blood pressure adjusted as someone stands up after being in a lying
position?
When someone stands up the venous return falls due to gravity, Cardiac input diminishes and
arterial BP is reduced (↓preload) => Baroreceptors afferent firing is reduced – medullary centres inhibition reduced -> ↑sympathetic tone to arterioles and veins (vasoconstriction), Reduced vagal tone to SAN =>
↑myocardial sympathetic tone –> ↑HR -> ↑stroke work –> ↑ blood pressure
what occurs when standing up when there is no compensation
↓venous return -> ↓underfilled LV -> ↓SV -> ↓CO -> ↓BP
