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A: Syncope is an abrupt, transient loss of consciousness that typically lasts for several seconds to a few minutes, usually followed by prompt recovery. It occurs in all age-groups but is most common among older adults. Syncope usually occurs as a result of disrupted blood flow to the brain caused by a drop in blood pressure. It can be cardiac, noncardiac, or unknown (most common) in origin.

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Cardiac causes include cardiac outflow obstruction, as in aortic stenosis; valvular disorders, such as mitral valve prolapse; low-flow states, such as cardiomyopathy; and dysrhythmias. Cardiac-related syncope may involve a sudden loss of consciousness even if the patient is supine. When he regains consciousness, he'll probably feel weak and fatigued.


The most common noncardiac cause is vasomotor syncope, usually as a result of postural hypotension (a drop in blood pressure of 20 mm Hg from sitting to standing). Other noncardiac causes include vasovagal (or situational) syncope, which can be induced by stress, pain, overheating, coughing, swallowing, or straining during defecation or urination; drug-induced syncope (vasodilators, calcium channel blockers, diuretics, beta-blockers, and alcohol use); neurologic events, such as a seizure; and metabolic abnormalities, such as hypoxemia, hypoglycemia, and hypothyroidism.


Syncope with sudden onset and no preceding symptoms occurring before, during, or after exertion may suggest an underlying cardiac problem. A gradual loss of consciousness might indicate hypoglycemia, postural hypotension, or vasovagal syncope.


Diagnostic tests include complete blood cell count, serum electrolyte levels, cardiac enzymes tests, serum drug and alcohol levels, arterial blood gas values, chest X-ray, ECG, electroencephalogram, echocardiogram, computed tomography scan of the head or lungs, and ventilation-perfusion scanning. Other tests that may be performed include continuous Holter monitoring, electrophysiology studies, and a tilt table test, which involves placing the patient on a table at a 70-degree angle while his heart rate and blood pressure are monitored.


Treatment depends on the cause. Syncope that's cardiac in origin may be treated with drug therapy or an invasive cardiac procedure, such as pacemaker insertion or valve replacement. If syncope is situational and constipation is the cause, using a stool softener or adding fiber to the diet may help reduce straining. Glycemic control can help avoid syncope caused by hypoglycemia. If syncope is medication-related, a simple change in the medication may be all that's needed. Midodrine (Proamatine), a drug that increases peripheral vascular resistance, may be ordered to help prevent syncope from postural hypotension.


Teach your patient not to ignore or fight any signs of fainting and instruct him to sit or lie down until he feels better. Tell him to get up slowly from a lying position, change positions slowly, and avoid standing for long periods. Stress the importance of avoiding straining during defecation and urination.


Finding the cause of your patient's syncope may be difficult, but with a little bit of detective work, it's a piece of cake!!


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Rumm M, Brenner B. Syncope. Accessed June 4, 2007.