What is fainting?

Children faint for many different reasons. Sometimes children pass out when they get hurt, see blood, or are otherwise upset or scared. Fainting often occurs when a child suddenly stands up from a sitting or lying position. Some children faint from holding their breath during tantrums. In these cases, fainting occurs because blood flow to the brain is cut off for a short time.

When children faint, their legs or arms often twitch or jerk slightly a few times. This is not a seizure or fit. Children usually awaken seconds after fainting.

Most of the time fainting is nothing to worry about. Children who faint often outgrow it. But if your child faints again, tell your doctor. The doctor may want your child to have more tests to rule out other causes.

Fast or slow arrhythmias may cause you to pass out. You may fall and injure your head, break an arm or leg, or get other injuries. If you're driving, you may crash. Also, passing out (syncope) may be a sign that you're at risk for a life-threatening arrhythmia.

Syncope is transient. That means you wake up soon after you faint. You may wake up because the arrhythmia stops on its own and your heart rhythm and blood pressure go back to normal. Even if the arrhythmia doesn't stop, you may still regain consciousness.

When syncope is caused by an arrhythmia, it most often happens while you are standing or sitting. The loss of consciousness causes you to fall to the floor. After you are lying down, blood flow returns to your brain, even though your blood pressure may remain low. When enough blood flow returns to your brain, you will likely wake up.

To find the cause of fainting, a doctor will do a physical exam and ask questions about the fainting episode.

The doctor may want to do tests. These tests may include:

• Blood tests.
• Heart tests such as ECG, ambulatory monitoring (with a Holter monitor or event monitor, for example), echocardiogram, or an exercise stress test.
• A tilt table test. This test checks how your body responds to changes in position.
• Tests for nervous system problems, such as CT scan of the head, MRI of the brain, or EEG.

If you know you tend to faint at certain times (such as when you get a shot or have blood drawn), it may help to:

• Sit with your head between your knees or lie down if you feel faint or have warning signs such as feeling dizzy, weak, warm, or sick to your stomach.
• Drink plenty of fluids so you don't get dehydrated.
• Stand up slowly.

You may need to see a doctor if you have ongoing dizziness or fainting. Ask your doctor when it is safe to drive.

Fainting is caused by a drop in blood flow to the brain. After you lose consciousness and fall or lie down, more blood can flow to your brain so you wake up again.

Most causes of fainting are usually not signs of a more serious illness. In these cases, you faint because of:

• The vasovagal reflex, which causes the heart rate to slow and the blood vessels to widen, or dilate. As a result, blood pools in the lower body and less blood goes to the brain. This reflex can be triggered by many things, including stress, pain, fear, coughing, holding your breath, and urinating.
• Orthostatic hypotension, or a sudden drop in blood pressure when you change position. This can happen if you stand up too fast, get dehydrated, or take certain medicines, such as ones for high blood pressure.

Fainting caused by the vasovagal reflex is often easy to predict. It happens to some people every time they have to get a shot or they see blood. Some people know they are going to faint because they have symptoms beforehand, such as feeling weak, nauseated, hot, or dizzy. After they wake up, they may feel confused, dizzy, or ill for a while.

Some causes of fainting can be serious. These include:

• Heart or blood vessel problems such as a blood clot in the lungs, an abnormal heartbeat, a heart valve problem, or heart disease.
• Nervous system problems such as seizure, stroke, or TIA.

Sometimes the cause is unknown.

Fainting is a sudden, brief loss of consciousness. When people faint, or pass out, they usually fall down. After they are lying down, most people will recover quickly.

The term doctors use for fainting is syncope (say "SING-kuh-pee").

Fainting one time is usually nothing to worry about. But it is a good idea to see your doctor, because fainting could have a serious cause.