Fainting is a temporary loss of consciousness. If you're about to faint, you'll feel dizzy, lightheaded, or nauseous. Your field of vision may "white out" or "black out." Your skin may be cold and clammy. You lose muscle control at the same time, and may fall down.

Fainting usually happens when your blood pressure drops suddenly, causing a decrease in blood flow to your brain. It is more common in older people. Some causes of fainting include

• Heat or dehydration
• Emotional distress
• Standing up too quickly
• Certain medicines
• Drop in blood sugar
• Heart problems

When someone faints, make sure that the airway is clear and check for breathing. The person should stay lying down for 10-15 minutes. Most people recover completely. Fainting is usually nothing to worry about, but it can sometimes be a sign of a serious problem. If you faint, it's important to see your health care provider and find out why it happened.

What is syncope?

Syncope is used to describe a loss of consciousness for a short period of time. It can happen when there is a sudden change in the blood flow to the brain. Syncope is usually called fainting or “passing out.”

There are different types of syncope; they depend on the part of the body affected or the cause of blood flow changes. Syncope can also be a symptom of heart disease or other heart problems. It also may show a higher risk for some neurological conditions like neuropathy.

The symptoms of syncope that usually happen before someone loses consciousness include:

• Feeling dizzy
• Feeling lightheaded
• Feeling like they have to vomit

• Vision that becomes unclear or blacks out
• Cold or clammy skin

People who experience syncope may pass out for a minute or two. They will slowly come back to normal. Syncope can happen in healthy people. It affects all ages, but happens most often in seniors.

The first thing to look for is that the person is still breathing after they faint. The individual should lie down for 10 to 15 minutes if they can in a cool, quiet area. If this is not possible, they should sit up with their head between their knees. Sipping on cold water can also help. People tend to recover within a few minutes to a few hours.

Treatment focuses on finding out the causes and trying to avoid passing out. When you start to feel symptoms there are some things you can do to help prevent fainting. For example, try to:

• Make a fist
• Cross your legs
• Squeeze your thighs together
• Tighten the muscles in your arms

Syncope can be life-threatening if it is not treated the right way.

Learn About Clinical Trials

Clinical trials are studies that allow us to learn more about disorders and improve care. They can help connect patients with new and upcoming treatment options.

How can I or a loved one help improve care for people with syncope?

Consider participating in a clinical trial so clinicians and scientists can learn more about the syncope and related conditions. Clinical research uses human volunteers to help researchers learn more about a disorder and perhaps find better ways to safely detect, treat, or prevent disease.

All types of volunteers are needed—those who are healthy or may have an illness or disease—of all different ages, sexes, races, and ethnicities to ensure that study results apply to as many people as possible, and that treatments will be safe and effective for everyone who will use them.

Fainting, also called syncope, is a temporary loss of consciousness caused by a decreased blood flow to the brain. Although fainting has a variety of possible causes, it is usually triggered by pain or anxiety. Sometimes people faint after vaccination. People who faint might fall and injure themselves if they are not sitting or lying down at the time that they lose consciousness. Sometimes when people faint, their muscles twitch and their bodies make jerking movements; this can sometimes be confused with seizures but are not actual seizures.

Fainting can happen after many types of vaccinations.

Fainting can be triggered by many types of medical procedures. In fact, CDC has received reports of people fainting after nearly all vaccines. Fainting after getting a vaccine is most commonly reported after three vaccines given to adolescents: HPV, MCV4, and Tdap. Because the ingredients of these three vaccines are different, yet fainting is seen with all of them, scientists think that fainting is due to the vaccination process and not to the vaccines themselves. However, there is not yet a definite answer about whether an ingredient of the vaccines is responsible for the fainting or if adolescents are simply more likely than children or adults to experience fainting.

About 3% of men and 3.5% of women report fainting at least once during their lifetimes, but it is not known just how often fainting happens after vaccination. Because fainting usually has no lasting effects, it is hard to study using medical records-based systems. However, the Vaccine Adverse Event Reporting System (VAERS), receives many reports of syncope each year, and many more are likely to go unreported.

Fainting can be common among adolescents after vaccination.

Reports from the Vaccine Adverse Event Reporting System (VAERS) shows that fainting after vaccinations is common in adolescents. One study of VAERS reports found that 62% of syncope reports were among adolescents 11 to 18 years old. However, because syncope may not always be reported, VAERS data cannot be used to determine how often fainting happens after vaccination.

Falls after fainting can cause injuries.

Fainting itself is generally not serious, but harm from related falls or other accidents can cause injury. The main concern is head injury. In a study of syncope-related VAERS reports, 7% of the fainting reports were coded as serious; 12% of these involved head injuries. Although fainting itself might or might not be preventable, it is important to prevent injuries when people do faint.

Fainting and related injuries after immunization can be prevented.

Giving patients a beverage, a snack, or some reassurance about the procedure has been shown to prevent some fainting. Studies are being done to look more into these strategies. However, many falls due to fainting can be prevented by having the patient sit or lie down. For this reason, experts recommend having patients sit in a chair or lay down when they receive a vaccination. In addition, patients should be observed for 15 minutes after vaccination.

If a patient does faint after a vaccination, she or he should be observed by medical personnel until she or he regains consciousness so that further treatment needs can be determined. If fainting happens outside the medical setting and the patient does not recover immediately, contact local emergency medical services. Patients who faint after vaccination generally recover within a few minutes.

For an adult, normal resting HR will be in the range of 60–100 bpm. Bradycardia is the condition in which resting rate drops below 60 bpm, and tachycardia is the condition in which the resting rate is above 100 bpm. Trained athletes typically have very low HRs. If the patient is not exhibiting other symptoms, such as weakness, fatigue, dizziness, fainting, chest discomfort, palpitations, or respiratory distress, bradycardia is not considered clinically significant. However, if any of these symptoms are present, they may indicate that the heart is not providing sufficient oxygenated blood to the tissues. The term relative bradycardia may be used with a patient who has a HR in the normal range but is still suffering from these symptoms. Most patients remain asymptomatic as long as the HR remains above 50 bpm.

Bradycardia may be caused by either inherent factors or causes external to the heart. While the condition may be inherited, typically it is acquired in older individuals. Inherent causes include abnormalities in either the SA or AV node. If the condition is serious, a pacemaker may be required. Other causes include ischemia to the heart muscle or diseases of the heart vessels or valves. External causes include metabolic disorders, pathologies of the endocrine system often involving the thyroid, electrolyte imbalances, neurological disorders including inappropriate autonomic responses, autoimmune pathologies, over-prescription of beta blocker drugs that reduce HR, recreational drug use, or even prolonged bed rest. Treatment relies upon establishing the underlying cause of the disorder and may necessitate supplemental oxygen.

Tachycardia is not normal in a resting patient but may be detected in pregnant people or individuals experiencing extreme stress. In the latter case, it would likely be triggered by stimulation from the limbic system or disorders of the autonomic nervous system. In some cases, tachycardia may involve only the atria. Some individuals may remain asymptomatic, but when present, symptoms may include dizziness, shortness of breath, lightheadedness, rapid pulse, heart palpations, chest pain, or fainting (syncope). While tachycardia is defined as a HR above 100 bpm, there is considerable variation among people. Further, the normal resting HRs of children are often above 100 bpm, but this is not considered to be tachycardia. Many causes of tachycardia may be benign, but the condition may also be correlated with fever, anemia, hypoxia, hyperthyroidism, hypersecretion of catecholamines, some cardiomyopathies, some disorders of the valves, and acute exposure to radiation. Elevated rates in an exercising or resting patient are normal and expected. Resting rate should always be taken after recovery from exercise. Treatment depends upon the underlying cause but may include medications, implantable cardioverter defibrillators, ablation, or surgery.

Figure 19.32 Autonomic Innervation of the Heart Cardioaccelerator and cardioinhibitory areas are components of the paired cardiac centers located in the medulla oblongata of the brain. They innervate the heart via sympathetic cardiac nerves that increase cardiac activity and vagus (parasympathetic) nerves that slow cardiac activity.