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Syncope is a topic covered in the 5-Minute Emergency Consult.

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  • 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.


  • Neutrally 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 sec
      • 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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Rosen, Peter, et al., editors. "Syncope." 5-Minute Emergency Consult, 5th ed., Lippincott Williams & Wilkins, 2016. Emergency Central, emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307119/all/Syncope.
Syncope. In: Rosen P, Shayne P, Barkin AZ, et al, eds. 5-Minute Emergency Consult. 5th ed. Lippincott Williams & Wilkins; 2016. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307119/all/Syncope. Accessed April 24, 2019.
Syncope. (2016). In Rosen, P., Shayne, P., Barkin, A. Z., Wolfe, R. E., Hayden, S. R., Barkin, R. M., & Schaider, J. J. (Eds.), 5-Minute Emergency Consult. Available from https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307119/all/Syncope
Syncope [Internet]. In: Rosen P, Shayne P, Barkin AZ, Wolfe RE, Hayden SR, Barkin RM, Schaider JJ, editors. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2016. [cited 2019 April 24]. Available from: https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307119/all/Syncope.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Syncope ID - 307119 ED - Rosen,Peter, ED - Shayne,Philip, ED - Barkin,Adam Z, ED - Wolfe,Richard E, ED - Hayden,Stephen R, ED - Barkin,Roger M, ED - Schaider,Jeffrey J, BT - 5-Minute Emergency Consult UR - https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307119/all/Syncope PB - Lippincott Williams & Wilkins ET - 5 DB - Emergency Central DP - Unbound Medicine ER -