Blackout Flashcards
Define syncope.
A form of loss of consciousness in which hypoperfusion of the brain is the cause
List the four main mechanisms of syncope.
Reflex – caused by a primitive reflex that leads mammals to play dead. It causes a temporary drop in blood pressure.
Cardiac
Orthostatic
Cerebrovascular – non-cardiac structural causes of reduced cerebral perfusion (RARE)
How can the cardiac causes of syncope be further divided?
Arrhythmia Outflow obstruction (e.g. aortic stenosis, HOCM)
What can cause orthostatic hypotension?
Blunting of the normal autonomic response to standing up (vasoconstriction + rise in heart rate)
DUE TO
- drugs or autonomic nephropathy (anti hypertensives, anti sympathetic)
- dehydration
-baro-receptor dysfunction
- autonomic instability
What are some of the causes of syncope (that fall under the four mechanisms)?
Reflex - Vasovagal syncope - Other: carotid sinus hypersensitivity Cardiac - Arrhythmias - Outflow obstruction Orthostatic/postural hypotension (delay in the autonomic reaction to standing up) - Drugs (anti hypertensive, anti sympathetic) - Dehydration - Autonomic instability - Baroreceptor dysfunction Cerebrovascular - Vertebrobasilar insufficiency - Subclavian steal syndrome - Aortic dissection
List some non-syncopal causes of blackout.
Intoxication (alcohol, sedatives) Head trauma Metabolic - (hypoglycaemia) Psychogenic (non-epileptic) Epileptic seizure
What is the most common cause of blackout in:
Young
Middle-aged
Elderly
The young -Vasovagal
The middle-aged- Vasovagal + arrhythmia
The elderly - Postural hypotension
Which classes of medications are commonly associated with orthostatic hypotension?
ACE inhibitors Diuretics Beta-blockers Alpha-blockers CCBs
List three questions that are important to ask about the event preceding the blackout.
Was there any WARNING?
Were there any PRECIPITATING FACTORS?
Was there any HEAD TRAUMA?
Which causes of collapse may be associated with symptoms preceding collapse?
Epileptic seizure – patients may experience a prodromal aura
Vasovagal – patients may experience vagal symptoms (e.g. sweating, pallor, nausea, dizziness)
Which causes of collapse tend to occur with no warning?
Cardiac causes
NOTE: arrhythmias may cause preceding palpitations
List some factors that may precipitate collapse and state the underlying cause of collapse that they are associated with.
Standing up – postural hypotension
Exercise – cardiac pathology (e.g. aortic stenosis, HOCM, long QT)
Head turning – carotid body hypersensitivity
Vigorous arm activity – subclavian steal syndrome
Vasovagal has many precipitants (e.g. fear, heat, standing for a long time)
List two questions that are important to ask about what happened during the collapse.
HOW LONG did the blackout last?
Was there any TONGUE-BITING, MOVEMENT OF LIMBS or INCONTINENCE of urine or faeces?
What feature of the collapse is pathognomonic with an epileptic seizure?
Tongue-biting
What question is important to ask about the state of the patient after the collapse?
Did the patient RECOVER SPONTANEOUSLY or were they CONFUSED afterwards?
List five key components that should be explored in the patient’s past medical history.
Previous episodes of collapse Diabetes Cardiac illness Peripheral vascular disease (ask about intermittent claudication because they may not have had a PVD diagnosis) Epilepsy Anaemia Psychiatric illness
List some important features of the drug history that help narrow the differential for collapse.
Insulin and other hypoglycaemics
Antihypertensives
Vasodilators
Anti-arrhythmics (paradoxically predisposes to arrhythmia)
Antidepressants (hypotension may be a side effect)
Warfarin and other anticoagulants
List some important features of the social history.
Alcohol
Use of stimulant recreational drugs (e.g. cocaine) – can cause tachyarrhythmia and drop cardiac output
What key question must be asked about the family history of the patient?
Have you had any close relatives who have died suddenly below the age of 65?
List some key features of general examination that allow narrowing of the differential diagnosis.
Tongue-biting
Dehydration
Head trauma
List some features of the cardiovascular examination that may indicate a cardiac cause of collapse.
Irregular pulse – AF
Ejection-systolic murmur – aortic stenosis
Carotid bruits – carotid artery stenosis
What test is important to perform in order to check for orthostatic hypotension?
Lying/standing blood pressure
How is orthostatic hypotension clinically defined?
Systolic drop > 20 mm Hg
Diastolic drop > 10 mm Hg
Why are focal neurological signs important to pick up?
Peripheral neuropathy may be caused by diabetes
Parkinson’s disease can lead to autonomic dysfunction
List three important blood investigations that should be performed in a patient with collapse and state the reasons for using them.
FBC – anaemia can worsen oxygen starvation of the brain
U&Es – check for biochemical evidence of dehydration + electrolyte abnormalities
Capillary blood glucose – exclude hypoglycaemia + check for undiagnosed diabetes
What other investigation is important to perform in a patient with collapse?
ECG – check for arrhythmia
NOTE: a normal ECG does not exclude a cardiac cause because arrhythmia may be paroxysmal
List three causes of aortic stenosis.
Bicuspid aortic valve
Senile calcification
Rheumatic fever
Define status epilepticus.
Seizures lasting for > 30 mins or repeated seizures without regain of consciousness in between
