[Gr. synkopē, fainting]
Transient, usually sudden loss of consciousness, accompanied by an inability to maintain an upright posture.
Syncope is common, accounting for about 1% to 3% of all hospital admissions in the U.S.
The most frequent causes of syncope are vasovagal (the common fainting spell), cardiogenic (esp. arrhythmogenic, valvular, or ischemic), orthostatic (as from dehydration or hemorrhage), and neurogenic (as from seizures). Many medications (such as sedatives, tranquilizers, excessive doses of insulin), food allergies, hypoglycemia, hyperventilation, massive pulmonary embolism, aortic dissection, atrial myxoma, carotid sinus hypersensitivity, coughing, urination, and psychiatric disease can also result in syncope.
SYMPTOMS AND SIGNS
The patient typically complains of having suffered a sudden and unexpected fall to the ground, with loss of awareness, and then rapid recovery of orientation. Lacerations, abrasions, or other injuries occasionally result from the fall.
The patient's history may contain useful clues. For example, if the patient stood up just before losing consciousness, an orthostatic cause is likely; if a patient is confused or disoriented for a long time after losing consciousness, seizures are probable; if a young patient passes out while at a wedding or other stressful event, vasovagal syncope is likely. The diabetic patient who becomes agitated and sweaty before passing out should be rapidly assessed and treated for low blood sugar.
The examination of the patient may reveal the cause, e.g., a loud aortic murmur may point to valvular heart disease, or a pale patient with orthostatic vital signs may be dehydrated or bleeding. Electrocardiographic monitoring after the event may reveal arrhythmias or evidence of ischemia. Depending on clinical circumstances, further evaluation may include carotid sinus massage, 24-hr ambulatory monitoring, month-long event monitoring, implantable loop monitoring, tilt-table testing, echocardiography, or psychiatric evaluation. In most cases, despite thorough evaluation, a precise diagnosis is not determined.
Any person with sudden loss of consciousness should be placed in a supine position, preferably with the head low to facilitate blood flow to the brain. At the same time, a clear airway should be ensured. Clothing must be loosened, esp. if the collar is tight.
Fainting (one form of syncope) is usually of short duration and is counteracted by placing the person supine. If recovery from fainting is not prompt and complete, a prompt assessment of airway, breathing, circulation, and cardiac rhythm is needed; assistance should be obtained and the person transported to a hospital. A person who refuses hospital evaluation after recovering from a fainting episode should be encouraged to visit a physician for examination as soon as possible.
Although many people rely heavily on their automobiles for daily activities, the freedom to operate a motor vehicle must be balanced against the risk to the patient and the public if loss of consciousness occurs while the patient is driving a motor vehicle. As a result, most patients who have suffered loss of consciousness severe enough to warrant medical attention have restrictions placed on their privilege to drive by state law.
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