Fainting doesn't sound like a serious medical problem. After all, characters in novels and movies faint - usually because of fright or a profound emotional reaction - and they always recover quickly, without ill effects. In reality, fainting can signal a heart problem or other serious cause.

"Syncope" (pronounced sin-ko-pee) is the medical term for a sudden loss of consciousness. "She experienced a syncopal episode" is medical jargon for "she fainted." Syncope is caused by a temporary loss of blood supply to the brain.

There are many terms used to describe the underlying causes of syncope (such as vasovagal, situational, orthostatic and arrythmogenic). Now, medical staff usually try to put a fainting episode into one of these three main categories:

1. Cardiac syncope, caused by some type of heart or circulatory system problem, such as irregular heartbeats or congestive heart failure.

2. Noncardiac syncope, which has some other cause, such as low blood sugar, dehydration, strong emotional experience, pain or a neurological problem (a small stroke or bleeding in the brain).

3. Unknown cause. In about 20 percent of cases, no cause for fainting can be found.

Sometimes it's obvious why a person faints. As a nurse, I've witnessed several patients faint at the sight of a needle before an injection or immediately after getting a shot.

Years ago, I had a roommate who thought it was healthy to fast - no food or water - a day each month. One day when he was fasting, he decided to go on a 20-mile bike ride in hot weather. He made it home, got off his bike and fainted in the garage. This was because of dehydration, which caused low blood pressure. He wasn't getting enough blood to his brain. Once he came to and drank a lot of water, he recovered quickly.

Most of the time, people have a sense they are going to faint before they do; they may feel overly warm, sweaty, dizzy or light-headed, have blurred vision and/or feel nauseated.

Sometimes, a person may feel heart palpitations or chest pain before fainting. When these symptoms are present, it's very important to have a medical evaluation for heart problems that can cause syncope.

If there is no obvious cause for a fainting episode (such as fright or pain), immediate medical evaluation is important to check for a serious problem. This is especially important if a person experiences repeated fainting spells.

It is rare for children to faint. In very young children, fainting can be triggered by a breath-holding episode. If a child faints while exercising, or complains of heart palpitations or chest pain, they should be medically evaluated immediately becuase this could indicate a serious heart problem.

It is more common for elderly people to faint, most often because of a heart problem.

If a person faints and hits their head, they should seek health care immediately to check for a head injury.

When a patient reports a fainting episode, the health-care provider will take a careful history of the event. Be prepared to answer these questions:

• What were you doing and what happened before you fainted?

• Were you lying down, sitting or standing?

• Had you been exercising?

• Did you experience any symptoms before you fainted (lightheadedness, nausea, headache, heart palpitations, chest pain, weakness, double vision)?

• Are you on any new medications or new doses of medications?

If someone witnessed a fainting episode, it's helpful if they can come to the emergency room or appointment with the patient to tell what they saw. This can help medical staff determine whether it was indeed a fainting episode or perhaps a seizure.

Kathryn B. Brown is a family nurse practitioner with a master's degree in nursing from OHSU. Is there a health topic you would like to read about? Send ideas to kbbrown@eastoregonian.com. You can find more local health news and information in the Health section at www.dailyastorian.info