Fainting (syncope):Partial or complete loss of consciousness with interruption of awareness of oneself and ones surroundings. When the loss of consciousness is temporary and there is spontaneous recovery, it is referred to assyncopeor,innonmedical quarters, fainting. Syncope accounts for one in every 30 visits to an emergency room. It is pronounced sin-ko-pea.
Syncope is due to a temporary reduction inbloodflow and therefore a shortage ofoxygento thebrain. This leads to lightheadedness or a "black out" episode, a loss of consciousness. Temporary impairment of the blood supply to the brain can be caused by heart conditions and by conditions that do not directly involve the heart:
Non-cardiac causes: Syncope is most commonly caused by conditions that do not directly involve the heart. These conditions include:
- Posturalorthostatic hypotension: Drop inblood pressuredue to changing body position to a moreverticalposition after lying or sitting;
- Dehydration causing a decrease in blood volume.
- Blood pressure medications leading to low blood pressure.
- Diseases of the nerves to the legs in older people (especially with diabetes or Parkinson's disease) when poor tone of the nerves of the legs draws blood into the legs from the brain.
- High altitude.
- Brain stroke or "near-stroke" (transient ischemic attack).
- A migraine attack.
- Fainting after certain situations (situational syncope) such as:
- Blood drawing,
- Urinating (micturition syncope),
- Defecating (defecation syncope),
- Swallowing (swallowing syncope), or
- Coughing (cough syncope)
Cardiac causes: Heart conditions that can cause syncope or fainting due totemporary loss of consciousnessinclude:
- Abnormal heart rhythms (heart beating too fast or too slow).
- Abnormalities of theheart valves(aortic stenosis or pulmonic valvestenosis).
- High blood pressure in the arteries supplying thelungs(pulmonary arteryhypertension).
- Tears in theaorta(aortic dissection).
- Widespreaddiseaseof theheart muscle(cardiomyopathy).
To be sure, many of the causes of temporary loss of consciousness can be detected by a careful history. Dizziness after standing up in an older person suggestspostural hypotension. Temporary loss of consciousness after urinating, defecating, or coughing suggests situational syncope.Cardiaccauses of temporary loss of consciousness such asaortic狭窄或心肌病是建议的occurrence of theeventduring exercise. Signs of weakness localized to certain areas of the body with temporary loss of consciousness suggeststroke.
The blood pressure andpulseare tested in the lying, sitting, and standing positions. Unequal blood pressures in eacharmis asignof aorticdissection. The heart is examined with astethoscopeto listen for sounds that canindicatevalve abnormalities. The nervous system is tested forsensation, reflexes, andmotorfunction to detect conditions of the nerves and brain. An EKG is done to check forabnormalheart rhythms. Other tests may include echocardiograms, rhythm monitoring tests (heart event recorders), andelectrophysiologictesting for abnormalities of the heart's electrical system.
When heart conditions are not suspected, tilt-tabletesting can be used to detect causes of temporary loss of consciousness. Tilt-table testing involves placing the病人on a table with afoot-support. The table is tilted upward and blood pressure and pulse is measured while symptoms are recorded in various positions.
No treatment is needed for many non-cardiac causes of syncope (such as postural hypotension,vasovagal reaction, and situational syncope). The person regains consciousness by simply sitting or lying down. The person is thereafter advised to avoid trigger situations, to notstrainwhile eliminating, to sit when coughing, to lie down for blood drawing, etc.
Older people should have their medications reviewed and caution is advised to slow theprocessof changing positions from lying to standing. This simple technique can allow the body to adjust to the new position (as the nerves tocirculationof the legs adjust slower in older persons).
