Syncope
Basics
Description
Description
- Transient loss of consciousness associated with loss of postural tone
- Ultimately, it is the lack of oxygen to the brainstem reticular–activating system, which results in a loss of consciousness and postural tone
- Most commonly, an inciting event causes a drop in cardiac output
- Cerebral perfusion is re-established by autonomic regulation as well as the reclined posture, which results from the event
- Accounts for 3% of ED visits
Pregnancy Considerations
- Pregnant patients frequently experience presyncope or syncope from various causes. 5% of patients experience syncope, 28% experience presyncope throughout their pregnancy
- Placenta acts as an AV malformation, causing decreased SVR that potentiates orthostatic symptoms
- Fetus lying on IVC can lead to neurogenic and hypovolemic syncope
- Pregnant patients at higher risk of DVT/pulmonary embolism (PE), UTI, seizures (preeclampsia), valvular incompetencies. Must exclude these diagnoses in ED evaluation
Geriatric Considerations
- Elderly with highest incidence as well as increased morbidity
- >1/3 will have numerous potential causes
Etiology
Etiology
- Neurally mediated syncope:
- Reflex response causing vasodilatation and bradycardia with resulting cerebral hypoperfusion
- Vasovagal (common faint):
- Often incited by pain or fear
- Prodromal findings are usually present
- Typically lasts <20 s
- Tilt-table testing is the gold standard to diagnose
- Carotid sinus syncope:
- Cough, sneeze
- GI stimulation (e.g., defecation)
- Micturition
- Orthostatic:
- Positional changes cause abrupt drop in venous return to heart
- Volume depletion:
- Severe dehydration (e.g., vomiting, diarrhea, diuretics)
- Hemorrhage (see “Hemorrhagic Shock”)
- Autonomic failure:
- Diabetic or amyloid neuropathy
- Parkinson disease
- Drugs (e.g., β-blockers) and alcohol
- Cardiac arrhythmias:
- Typically sudden and without prodromal symptoms
- Tachydysrhythmia or bradydysrhythmia
- Inherited syndromes (e.g., long QT syndrome, Brugada syndrome)
- Pacemaker/implantable cardioverter defibrillator malfunction
- Structural cardiac or cardiopulmonary disease:
- Valvular disease (especially aortic stenosis)
- Hypertrophic cardiomyopathy
- Acute myocardial infarction
- Aortic dissection
- Pericardial tamponade
- Pulmonary embolus
- Neurologic:
- Transient spike in intracranial pressure that exceeds cerebral perfusion pressure
- Postsyncopal headache is almost universal
- May be presentation of a subarachnoid hemorrhage
- Cerebrovascular steal syndromes
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Citation
Schaider, Jeffrey J., et al., editors. "Syncope." 5-Minute Emergency Consult, 6th ed., Lippincott Williams & Wilkins, 2020. Emergency Central, emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307119/all/Syncope.
Syncope. In: Schaider JJJ, Barkin RMR, Hayden SRS, et al, eds. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2020. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307119/all/Syncope. Accessed October 7, 2024.
Syncope. (2020). In Schaider, J. J., Barkin, R. M., Hayden, S. R., Wolfe, R. E., Barkin, A. Z., Shayne, P., & Rosen, P. (Eds.), 5-Minute Emergency Consult (6th ed.). Lippincott Williams & Wilkins. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307119/all/Syncope
Syncope [Internet]. In: Schaider JJJ, Barkin RMR, Hayden SRS, Wolfe RER, Barkin AZA, Shayne PP, Rosen PP, editors. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2020. [cited 2024 October 07]. Available from: https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307119/all/Syncope.
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