• Fainting

    (Syncope)

    Definition

    Fainting is the sudden loss of consciousness.

    Causes

    In general, fainting is caused by decreased blood flow to the brain.
    Blood Flow to the Brain
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    This can occur due to:

    Risk Factors

    Risk factors include:

    Symptoms

    Symptoms include:
    • Sudden loss of consciousness
    • Inability to remain standing or sitting
    • Consciousness regained without any need for intervention
    • Dizziness or lightheadedness before losing consciousness

    When Should I Call My Doctor?

    Call your doctor if you are having episodes of fainting. This is especially important if you:
    • Have a heart condition
    • Have a job where you or others may be at risk if you faint (for example, airline pilot, bus driver, machinist)

    When Should I Call for Medical Help Immediately?

    Call for medical help or go to the emergency room right away if you have:
    • Weakness or numbness of face, arm, or leg, especially on the left side of the body
    • Confusion
    • Loss of balance, coordination problems
    • Vision problems
    • Severe headache
    • Rapid, irregular heartbeat; chest pain

    Diagnosis

    Your doctor will ask about your symptoms and medical history. He or she will do a physical exam.
    Tests may include:
    • Blood tests—to look for anemia, hypoglycemia, low potassium, and low magnesium
    • Electrocardiogram (EKG)—a test that records the heart's activity by measuring electrical currents through the heart muscle
    • Holter monitoring—a mobile EKG test that is performed over 24 hours (or more) while you go about your usual daily activities
    • Head computed tomography (CT) scan—a type of x-ray that uses a computer to make pictures of the brain
    • Electroencephalogram (EEG)—a test that records the brain's activity by measuring electrical currents through the brain
    • Magnetic resonance imaging (MRI) of the brain—a test that uses magnetic waves to make pictures of structures inside the head
    • Echocardiogram—a test that uses high-frequency sound waves (ultrasound) to examine the size, shape, and motion of the heart
    • Tilt table testing—a tilted table that is used to provoke syncopal symptoms (medicine may be used)
    • Cardiac catheterization—a tube-like instrument inserted into the heart through a vein or artery (usually in the arm or leg) to detect problems with the heart and its blood supply
    • Magnetic resonance angiogram (MRA) and CT angiogram (CTA) tests—to evaluate the blood vessels inside the brain

    Treatment

    Treatment will depend on the underlying condition that has caused fainting. For example:
    • Abnormal heart rhythms can be treated with medicines. They can also be treated with a pacemaker.
    • If medicine is causing syncope, it may need to be changed or stopped.
    • Anemia or other blood abnormalities should be treated.
    If you are diagnosed as having fainted, follow your doctor's instructions.

    Prevention

    If you are prone to fainting:
    • Know the warning signs (such as dizziness or lightheadedness). If you feel that you are going to faint, sit or lie down right away.
    • Get up slowly and carefully from lying down. Start by sitting up for a minute and then stand up.
    • Drink plenty of fluids.
    • Discuss dietary changes with your doctor.
    • Avoid using alcohol or other drugs.
    There are certain physical maneuvers that rapidly raise blood pressure and blood flow to the brain. They are called physical counterpressure maneuvers. When these are done during warning signs, you may be able to prevent fainting. Examples include:
    • Crossing your legs while tensing the muscles of legs, abdomen, and buttocks
    • Forcefully squeezing a rubber ball or other object as hard as possible (use your dominant hand)
    • Gripping one hand with the other while tensing both arms and raising the elbows slightly

    RESOURCES

    American Academy of Family Physicians http://www.aafp.org

    American Heart Association http://www.heart.org

    CANADIAN RESOURCES

    Alberta Health http://www.health.alberta.ca

    Health Canada http://www.hc-sc.gc.ca

    References

    Benditt D, Goldstein M. Fainting. American Heart Association, Circulation website. Available at: http://circ.ahajournals.org/content/106/9/1048.full. Published 2002. Accessed January 17, 2012.

    Cecil RL, Goldman L, et al. Cecil Textbook of Medicine. 21st ed. Philadelphia, PA: WB Saunders Company; 2000.

    Chen LY, Benditt DG, et al. Management of syncope in adults: an update. Mayo Clin Proc. 2008;83(11):1280-1293.

    Dambro MR, Griffith JA. Griffith's 5-Minute Clinical Consult. Baltimore, MD: Lippincott, Williams, and Wilkins; 2001.

    Fainting: first aid. Mayo Clinic website. Available at: http://www.mayoclinic.com/health/first-aid-fainting/FA00052. Updated December 13, 2011. Accessed January 17, 2012.

    Miller TH, Kruse JE. Evaluation of syncope. Am Fam Physician. 2005;72(8):1492-1500.

    2/6/2007 DynaMed's Systematic Literature Surveillance. Available at: http://dynamed.ebscohost.com/about/about-us: van Dijk N, Quartieri F, Blanc JJ, et al. Effectiveness of physical counterpressure maneuvers in preventing vasovagal syncope: the Physical Counterpressure Manoeuvres Trial (PC-Trial). J Am Coll Cardiol. 2006;48(8):1652-1657.

    Revision Information

    • Reviewer: n/a
    • Review Date: 06/2012
    • Update Date: 00/61/2012
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