Fainting is a temporary loss of consciousness and muscle tone. It is caused by not having enough blood flow to the brain.
When there is not enough blood flow to the brain, passing out protects the brain from damage. People who faint generally lose muscle tone and fall to the ground. When someone is lying on the ground, the blood being pumped out of the heart doesn't have to fight gravity to get to the brain. Those who faint have a relaxed body, which uses less energy. This also makes it easier for the heart to pump blood to the brain.
The cause of fainting may be minor or it may be life-threatening. Often, no cause can be found. The following diseases and conditions may cause fainting:
Additional factors that can cause fainting are as follows:
There may be other causes as well. In some cases, no cause is found.
A person who faints usually becomes quite pale and may sweat heavily. The individual may be nauseated. Most people who pass out wake up in less than 2 minutes. There are several things a healthcare provider may want to know after a person has fainted, such as:
The healthcare provider will also ask about other medical conditions. The provider will want to know what medications the person is taking. All of these things can be clues as to the cause of the fainting.
Diagnosis of fainting starts with a medical history and physical exam. This may be all that is needed to make the diagnosis and determine the cause. The healthcare provider may order one or more of the following tests:
It is usually not possible to prevent fainting. An individual should seek treatment for underlying conditions, such as anemia or diabetes. Drinking enough fluids is important in preventing dehydration. A diet high in fiber and fluids can help prevent straining to have a bowel movement. A person with a history of fainting should stand up slowly. Those who feel as though they may faint should sit or lie down. This simple step often prevents fainting.
People who faint may hurt themselves when they fall. Long-term effects are mainly related to the underlying cause of the fainting. Those who have heart disease often have an increased risk of complications and death.
Fainting is not contagious and poses no risk to others.
First aid for a person who has fainted includes the following steps:
If the person has signs of circulation, he or she has probably fainted. The individual should be left on the ground and both legs should be elevated. This helps improve blood flow to the brain. The person should remain lying down for at least 10 minutes, even if he or she wakes up. After that, he or she should get up slowly and sit in a chair for a few minutes. The person should have help when trying to stand up. Someone who gets up too fast and without help may faint again.
Most of the time, no further treatment is needed for fainting. If the person faints repeatedly or has other symptoms, more treatment may be needed. Following are some of the common treatments:
All medications have possible side effects. These may include allergic reactions, stomach upset, and headaches. Surgery carries a risk of bleeding, infection, and allergic reactions to anesthesia. Blood transfusions may cause allergic reactions or infections.
Those who have simple fainting usually need no further monitoring or treatment. Those who have heart disease may need ongoing treatment for many years. Most people are able to return to normal activities after treatment. Those with frequent fainting may need to avoid certain activities, such as climbing ladders or driving.
Specific monitoring depends on the underlying cause of the fainting. It may range from none at all to intense monitoring and follow-up. Any new or worsening symptoms should be reported to the healthcare provider.
Author:Adam Brochert, MD
Editor:Crist, Gayle P., MS, BA
Reviewer:Eileen McLaughlin, RN, BSN
Harrison's Principles of Internal Medicine, 1998, Fauci et al.
Instructions for Patients, 1994, Griffith et al.