Diseases - Syncope + Shock | Flashcards
Syncope definition
Transient loss of consciousness due to cerebral hypoperfusion,
characterized by
rapid onset,
short duration,
and spontaneous complete recovery
What is transient loss of consciousness
A state of real or apparent loss of consciousness with loss of awareness characterised by amnesia, loss of motor control, loss of responsiveness, and a short duration
Can result from
Trauma
Syncope
Epileptic seizure
3 types of syncope
Reflex
Orthostatic
Cardiac
Neural reflexes involved in reflex syncope
Cardioinhibition - Vagal stimulation decreases HR which decreases CO
Vasodepression - depression of sympathetic activity to blood vessels + vasodilation which decreases SVR, venous return and CO
3 types of Reflex syncope
Vasovagal syncope
Situational syncope
Carotid sinus syncope
Vasovagal syncope
Faint triggered by emotional distress or Orthostatic stress (standing for a long time)
Associated with
Pallor
Sweating
Nausea
Main risk is fall injury
Manage using - education, reassurance, avoidance of triggers and hydration
Situational reflex syncope
Faint during or immediately after a specific trigger e.g. cough or swallowing
Management:
Treat cause if possible
Avoid dehydration and excessive alcohol
Cardiac permanent pacing may be required
Carotid sinus reflex syncope
Triggered by mechanical manipulation of the neck
Common in elderly males
Associated with carotid artery atherosclerosis
Management:
Cardiac permanent pacing is generally recommended
Orthostatic hypotension - definition + risk factors
Results from failure of baroreceptor responses to gravitational shifts in blood, when moving from horizontal to vertical position
Risk factors:
Elderly
Certain Medications
Certain diseases
Reduced intravascular volume
Prolonged bed rest
Orthostatic hypotension - symptoms + test
Symptoms:
Light headedness, dizziness, blurred vision, faintness and falls
Positive result indicated by a drop within 3 minutes of standing from lying position
- In systolic BP of at least 20 mmHg with or without symptoms
- In diastolic BP of at least 10 mmHg with symptoms
Cardiac syncope
Cardiac event causing sudden drop in Cardiac output
- arrhythmias
- acute MI
- structural cardiac disease - aortic stenosis, hypertrophic cardiomyopathy
- other cardiovascular disease - pulmonary embolism, aortic dissection
Cardiac syncope suspected if
Syncope during excretion or when supine
Family history
Sudden onset palpitations followed by syncope
What is shock
An abnormality of the circulatory system resulting in inadequate tissue perfusion and oxygenation - can lead to anaerobic metabolism, which will cause metabolic waste products to accumulate, resulting in cellular failure
3 types of shock
Hypovalemic
Cardiogenic
Obstructive
Hypovalemic shock
Shock due to decrease in blood volume leading to inadequate tissue perfusion
Either due to:
- Haemorrhage - direct blood loss
- Non-haemorrhage - decrease in ECFV
Compensatory mechanisms in Hypovalemic shock
- body can maintain BP until >30% of blood is lost
- In haemorrhagic shock baroreceptor reflex causes patient to become tachycardic
- SVR increases through vasoconstriction - cool peripheries
Myogenic response - intrinsic ability of smooth muscle to alter SVR
Cardiogenic shock
Decreased cardiac contractility (e.g. due to acute MI)
→ decreased stroke volume → decreased CO and BP
→ inadequate tissue perfusion
Obstructive shock
Shock associated with physical obstruction of the great vessels or heart itself
- cardiac tamponade - fluid sac around heart fills with blood putting pressure on the heart
- pulmonary embolism
- tension pneumothorax - increased intrathoracic pressure -> decreased venous return
Distributive shock - 2 types
Neurogenic - spinal cord injury
Vasoactive shock - septic shock, anaphylactic shock
Neurogenic distributive shock
Loss of sympathetic tone to blood vessels and heart causing massive venous and arterial dilation and heart rate slows
Vasoactive distributive shock
Release of massive vasoactive mediators causing massive venous and arterial vasodilation
Increased capillary permeability causing decreased venous return
General Management of shock
ABCDE approach
High flow oxygen
Management for Hypovalemic shock
Volume replacement
Management for cardiogenic shock
Inotropes
Management for tension pneumothorax
Immediate chest drain
Management for anaphylactic shock
Adrenaline
Management for septic shock
Vasosupressors
