Syncope and collapse Flashcards
Syncope definition:
Transient, self-limiting loss of consciousness with an inability to maintain postural tone
It has a relatively rapid onset with variable warning symptoms and is followed by spontaneous recovery
Pre-syncope:
Light-headedness without loss of consciousness
Drop attack:
Loss of posture without loss of consciousness
Coma:
Loss of consciousness without spontaneous recovery
Collapse:
Sudden, and often unannounced, loss of postural tone (going weak), which is often, but not necessarily always, accompanied by loss of consciousness
3 categories of Syncope:
Reflex/neural mediated
Orthostatic hypotnesion
Cardiac causes
Reflex/neural mediated causes of syncope:
- Vasovagal syncope
- Situational syncope
- Carotid sinus syncope
Vasovagal syncope:
Most ocmmon typw of syncope
Caused by a sudden drop in BP and a reduction in blood flow to the brain
Caused by vasodilation, bradycardia and/or increased PNS activity
Orthostatic vasovagal syncope
Emotional vasovagal syncope due to fear, phobia and pain
Situational syncope:
Loss of consciousness after defecation, swallowing, micturation and/or coughing
Caused by abnormal autonomic control - cardioinhibitory response, vasodepressor response, both
Carotid sinus syndrome:
Carotid baroreceptors react too strongly to detecting increased pressure -> leadds to an excessive drop in BP
I.e. when someone ties a tie too tight - glossopharyngeal nerve is compressed -> activate cardiac vagal efferent nerve fibres
Often in men over 50
Orthostatic hypotension causes:
-Volume depletion
- Autonomic depletion
Use the acronym DAAD:
Drugs - BP, diuretics, TCA’s
Autonomic insufficiency - Parkinson’s, DM, shy-dragger, adrenal insufficiency
Alcohol
Dehydration
Volume depletion causes:
- Hemorrhage, vomiting, diarrhea
- Autonomic faliure - affects vasodilation and vasoconstriction - can be caused by primary autonomic faliure - ex. due to old age, parkinson’s disease
Pathophysiology of Syncope:
Global hypoperfusion of both the cerebral cortices or focal hypoperfusion of the reticular activating system in the midbrain
__% reduction in cerebral blood flow causes syncope
35
Cessation of cerebral perfusion for ____ seconds causes syncope
5-10
San Francisco Syncope Rule:
High risk for a serious cause of syncope:
40% mortality in 2 years after unexplained and recurrent syncope is anyone who has structural heart disease (CHF), anemia, hematocrit <30%, ECG abnormality, SOB, or htn (SBP<90mmhg)
Cardiac causes:
*** most dangerous
- Rarely causes syncope but may lower the threshold for syncope
- Arrhythmia
- Sturctural defects - aortic stenosis, hypertrophic cardiomyopathy, prosthetic vavle dysfunction, MI
- Great vessel defects - PE, acute aortic dissection
Neurocardiogenic syncope:
Vigorous myocardial contraction of relatively empty LV -> activates myocardial mechanoreceptors and vagal afferent nerve fibres that inhibit sympathetic activity and increase parasympathetic activity -> vasodilation and syncope
Drop in BP and fixed HR?
Dysautonomic disorder
Drop in BP and increase in HR?
Vasodialtion or volume depletion
Insignificantdrop in BP and marked HR increase
Postural orthostatic tachycardia
Orthostatic htn is defined as a fall in sys BP of at least __ mmHg or dia BP of at least __ mmHg when a person stands
20
10
Monitoring after Syncope:
History
Physical ex
Medication review
ECG
Carotid sinus massage to assess carotid sinus hypersensitivity - CONTRAINDICATED if carotid bruit present or TIA/stroke
High-risk work-up:
Holter monitor, echo, stress test, ischemic evaluation, posterior circulation imaging of the brain if you suspect neurological syncope
Syncope patients considered low-risk?
High suspection of vasovagal or neuroardiogenic etiology
Vasovagal syncope treatment:
B-blockers
SSRI’s
Fludrocortisone (also for postural htn)
a-adrenoreceptor agonist
Disopyramide (vagolytic antiarrhythmic)
Permanenr dual chamber cardiac pacing
Compression stockings for orthostatic htn
___ reduction in cerebral blood flow
35%
Cessation of global perfusion for _____ -> syncope
5 to 10 seconds
Drop in BP w/ fixed HR =
Drop in BP w/ increased HR =
Insignificant drop in BP w/ markedly increased HR =
ANS failure
Volume depletion/ vasodilation
Postural orthostatic tachycardia syndrome
Shock management:
- Intubate early to ensure adequate oxygenation
- Keep central venous pressure above 8mmHg w/ IV fluids
- Keep mean arterial BP above 65mmHg
- Keep hematocrit above 30%
Early recognition is key use inotropes if required by the heart
Crystalloids:
Contents
Application
Place of action
Half life
Examples
Dose
- Electrolytes (small)
- First line of choice for volume resuscitation
- 25% in plasma, 75% expands interstitial volume
- Short HL - 30-60 mins
Sodium chloride 0.9%, sodium lactate
1000mL
Colloids:
Contents
Examples
Dose
- Large solute molecules that do not pass from plasma to interstitial fluid
- 75% in plasma, 25% expands interstitial volume
- Longer HL - 2-4 hours
- Suitable for small volume resuscitation
Albumin, dextran, fresh frozen plasma, packed RBC’s
300-500mL
Infusion of one liter of 0.9% NaCl adds ____ mL to the plasma volume and ____mL to the interstitial volume. The total increase in extracellular volume _____mL is slightly greater than the infused volume. This is the result of fluid shift from the intracellular to extracellular fluid.
275
825
1,100
5% dextrose:
composition
mechanism
- 50g dextrose in 1kg of water
- The dextrose slows down transfer of water into the ICF to prevent cellular lysis from over-swelling
- Even distribution (ECF, ICF
Normal CVP:
Normal CPWP:
8-12mmHg
4-14mmHg
Endotracheal intubation can cause hypo or hypertension?
Typically Hypo but can be hyper under stress and hypoxia
Goals of treatment:
Urine >0.5mL/kg/h
CVP 8-12 mmHg
MAP 65-90 mmHg
CVo2 conc. - >70%
Position in shock:
supine
Packed RBC’s:
What is it? Indications?
Blood is centrifuged at 3000revs/min.
1 unit of packed cells increases Hg by 1g/dL and hematocrit by 3%
- Used when whole blood may overload the circulation
1 - symptomatic chronic anemia w/o hemorrhage
2 - acute sickle crisis
3 - cardiac failure
4 - acute blood loss (30% or more)
5 - perioperative anemi
FFP vs Cryoprecipitate
Cryoprecipitate
- Derived from plasma
- Concentrated form of certain clotting factors (fibrinogen, factor 8, vwf, fibronectin)
- Undergoes thawing and centrifuging
- Cryoprecipitate is primarily used to treat bleeding or to prevent bleeding in patients with specific coagulation disorders, such as hypofibrinogenemia (low fibrinogen levels), von Willebrand disease, and hemophilia A. It is particularly rich in fibrinogen, making it effective in cases where fibrinogen levels need to be quickly replenished, such as in massive bleeding or during surgical procedures.
FFP
- Liquid portion of blood that is seperated from whole blood and frozen within hours of collection
- FFP is used to replace multiple coagulation factors in patients with significant deficiencies or abnormalities in coagulation. It is often indicated in patients with liver disease, disseminated intravascular coagulation (DIC), massive transfusion, and certain congenital coagulation disorders. FFP can also be used as an emergency treatment for acute bleeding when specific factor concentrates are not available.
Hg, hct levels required for transfusion:
Hg <10g/dL
Hct <30%
Start transfusion slowly for first ____ mins @ _____
15
2mL/min
Febrile transfusion reaction:
- Fever, chills, malaise
- Acetominophen, supportive
- Most common transfusion reaction
Hemolytic transfustion reaction:
- Immediate fever/ chills, headache, N/V, dark urine, hypotension
- Vigorous crystalloid infusion + diuretic to maintain urine output
- Most serious reaction
Allergic reaction:
- Urticaria or hives
- Antihistamines
Transfusion-related acute lung injury:
- Indistinguishable from ARDS
- Supportive
Delayed transfusion reaction:
- Fall in Hg, rise in bilirubin
- Supportive
Transfusion-associated graft versus host disease:
- Rash, elevated LFT’s, pancytopenia
- Supportive
- Immunocompromised patenients
- Use irradiated blood products
