Fainting

Dizziness (pre-fainting) is the sensation of approaching fainting.

Fainting (syncope) is a sudden, short-term loss of consciousness in which a person falls to the ground or slides down from the seat, followed by a return to consciousness. A person lies motionless, muscles are relaxed, legs and arms can be cold, the pulse is weak, breathing is shallow.

Before fainting, weakness or dizziness may develop. Other symptoms may include nausea, sweating, "veil before the eyes" or tunnel vision, tingling of the lips or fingers, chest pain, or heart palpitations. Less commonly, fainting occurs suddenly, without any alarming symptoms.

Convulsions, which occur due to a violation of the electrical activity of the brain, and cardiac arrest, in which the heart completely stops beating, also lead to loss of consciousness, but are not considered fainting. However, some people who faint experience brief muscle twitches resembling cramps.

Fainting can happen at any age, but the dangerous causes of fainting are more common among older people.

Causes of fainting

Loss of consciousness occurs only when the general functions of the brain are impaired. This disorder usually occurs when there is a decrease in total blood flow to the brain. Sometimes, however, at an acceptable level of blood flow, the blood does not contain enough oxygen or glucose (blood sugar) that the brain needs to function.

There are several mechanisms for reducing blood flow to the brain. Most often, the cause is an obstacle to the normal return of blood to the heart (and, therefore, a decrease in cardiac output). Less commonly, the cause is a violation of the pumping function of the heart (usually heart disease). Although strokes reduce blood flow to the brain, it only affects part of the brain. Thus, strokes rarely cause fainting, except for strokes, which affect the part of the brain responsible for maintaining consciousness.

The most common causes of jaundice in newborns are:

• strong emotions (e.g., fear, pain, or the sight of blood);
• cough or tension when defecating or urinating;
• prolonged stay in a standing position;
• abrupt rising;
• pregnancy;
• the use of certain medications;
• idiopathic syncope (this means that the cause cannot be identified).

These common causes almost always cause fainting only when staying in an upright position. After the fall, the blood flow to the brain increases, and consciousness is quickly restored, although the state of health returns to normal only after a few minutes or hours. Some people feel tired or overwhelmed for a few more hours. These causes, as a rule, do not pose a serious problem, unless the person is injured in a fall.

Many of these causes are associated with a decrease in the return of blood to the heart. Strong emotions (particularly those caused by the sight of blood) or pain can activate the vagus nerve. Activation of the vagus nerve dilates blood vessels, reducing the return of blood to the heart, and slows the heart rate. Both of these factors cause dizziness and sometimes fainting (called vasovagal syncope or neurocardiogenic syncope).

Tension during bowel movements, urination, or coughing increases chest pressure. An increase in chest pressure can activate the vagus nerve, as well as reduce the return of blood to the heart – two factors that cause fainting.

Healthy people can faint when standing still for a long time (this phenomenon, called "fainting on the parade ground", is most common among soldiers), because in this situation one of the mechanisms for returning blood to the heart is not involved - the active work of the muscles of the legs.

Too abrupt transition to an upright position can cause fainting, because changing position leads to the accumulation of blood in the legs, resulting in a drop in blood pressure. Normally, the body quickly raises the heart rate and constricts blood vessels to maintain blood pressure. If the body does not have time to compensate for these phenomena, dizziness and sometimes fainting often develop. Some diseases of the brain and spinal cord, prolonged bed rest and some medications (in particular, for the treatment of high blood pressure) can interfere with this compensation and lead to fainting when getting up.

Hormonal changes in early pregnancy also sometimes lead to fainting.

Low blood sugar (hypoglycemia) first causes confusion, dizziness, trembling and other symptoms, and if the hypoglycemia is severe or continues for a long time, it can lead to loss of consciousness. That is, with hypoglycemia before fainting, warning signs usually occur - the symptoms described above. As a rule, the cause of hypoglycemia is the use of drugs for the treatment of diabetes, in particular, insulin. In rare cases, a tumor that produces insulin develops.

Less common but more serious causes include:

• diseases of the heart valves (most often the aortic valve);
• heart rate that is too high or too low.
• blockage of the pulmonary artery by a blood clot (pulmonary embolism);
• myocardial infarction or other diseases of the heart muscle.

Diseases of the heart valves can obstruct the flow of blood from the heart. If the heart rate is too high, the heart is not able to fill with blood sufficiently in a short period of the heart cycle, so in such a situation, the heart pumps less blood. With a very slow heart rate, the heart cannot pump enough blood. Blood clots in the lungs can prevent the heart from pumping enough blood. With myocardial infarction, fainting is rare (more common in the elderly). Other not-so-common heart muscle diseases called cardiomyopathies can also cause fainting, especially during exercise, usually due to an abnormal heart rhythm.

Although most strokes do not cause fainting, a stroke or transient ischemic attack (TIA) caused by impaired blood flow to certain blood vessels at the base of the brain (vertebrobasilar stroke) can lead to fainting. Similarly, migraines that affect these blood vessels sometimes lead to fainting.

Examination for fainting

If possible, witnesses of fainting should provide the doctor with a description of the event, since a person who has lost consciousness may not remember anything.

Warning signs

Certain symptoms and signs that accompany fainting are cause for concern. They include:

• fainting during physical exertion;
• several episodes in a short period of time;
• sudden fainting without precursor symptoms or any apparent cause;
• fainting before or after possible heart symptoms, such as chest pain, palpitations, or shortness of breath;
• more mature age;
• significant trauma as a result of fainting;
• family history of sudden death, fainting during exercise, or repeated episodes of fainting or seizures that have not been identified.

When to see a doctor

Although most causes of fainting do not pose serious problems, it is still necessary to consult a doctor to rule out serious causes. Persons who faint should immediately consult a doctor, especially if there are warning signs.

What does the doctor do?

First, doctors ask the patient about their symptoms and medical history. Then a physical examination is performed. Based on the results of anamnesis and medical examination, it is often possible to assume the cause of fainting and plan the necessary examinations in each case.

The doctor will ask about the events that led to the episode of fainting. He will ask whether the patient was working, arguing, or being in a potential situation of emotional distress. He will be interested in whether the patient was lying or standing, and, if so, for how long. He will also ask about symptoms that occurred immediately before or after the event, including whether the patient felt dizzy, weak, nauseous, sweating, "veil before the eyes" or tunnel vision, tingling of the lips or fingers, chest pain, or heart palpitations.

The doctor will also ask witnesses to describe the episode. Sudden, unexpected fainting with no precursor symptoms or no apparent cause suggests heart disease. If fainting is preceded by a short episode of symptoms such as dizziness, nausea, yawning, "veil before the eyes" or sweating, if it occurs at the peak of pain or an unpleasant situation, it is probably vasovagal syncope that is not dangerous.

The doctor will ask about previous episodes of dizziness or fainting, other diseases, medications, or symptoms that may be associated with fainting. The doctor will also examine for injury as a result of fainting.

Then the doctor will measure the main indicators of the state of the body. Heart rate and blood pressure are measured in the supine position and after 1-3 minutes of standing position. The doctor will listen to the heart for abnormal sounds caused by the movement of the heart valves or abnormal blood flows. He will perform a neurological exam for signs of stroke.

Carrying out analyses

An examination is usually prescribed if the patient does not have a visible harmless emotional reason, while in general they feel good. The doctor prescribes examinations taking into account the alleged cause:

• electrocardiography (ECG);
• continuous ambulatory ECG (Holter monitor or event monitor);
• measurement of oxygen in the blood (pulse oximetry);
• measurement of sugar levels in capillary blood (from a finger);
• sometimes ultrasound examination of the heart (echocardiography);
• sometimes a study using an orthostatic stand;
• sometimes blood tests;
• In rare cases, an imaging study of the central nervous system (brain and spinal cord).

In general, if fainting leads to injury or occurs several times (especially for a short period), it is advisable to prescribe a more in-depth examination. In the absence of a suspected heart or brain problem, imaging studies of the heart and brain are usually not performed.

People with suspected heart disease, including myocardial infarction, heart rhythm disturbances, or heart valve disease, are usually referred to the clinic for evaluation.

An ECG is performed. An ECG can reveal an abnormal heart rhythm or other heart problems, but sometimes, if the heart rhythm disturbances are resolved, it shows the norm. Sometimes a doctor will refer a person to the hospital for the purpose of monitoring heart function for 24 hours. Less commonly, doctors may suggest that the patient wear a small heart monitor at home (the so-called permanent ambulatory ECG monitoring). Or, in rare cases, doctors may implant a recording device under the skin.

The level of oxygen in the blood is measured. Pulse oximetry is performed during or immediately after an episode to determine low blood oxygen levels (which may indicate a blood clot). If the oxygen level in the blood is low, the doctor will order computed tomography (CT) angiography (with intravenous contrast) or lung scintigraphy to detect a blood clot.

Laboratory tests are prescribed if the results of a physical examination indicate their necessity. At the same time, all women of childbearing age are prescribed a pregnancy test.

Echocardiography can be prescribed for fainting associated with physical exertion, heart murmurs or fainting when moving to an upright position.

An orthostatic test is sometimes performed on patients who faint when standing up. It is also used to examine patients with exercise-induced fainting if no cause has been identified by echocardiography or stress test.

A stress test is performed if there is a suspicion of a heart rhythm disturbance caused by physical exertion. It is often prescribed to patients with exercise-related symptoms.

An electrophysiological (EF) study involves examinations that record electrical activity and examine the heart's electrical pathways using wires that run through blood vessels in the heart. EF testing is sometimes performed if other examinations do not reveal cardiac arrhythmias in individuals with unexplained recurrent episodes of syncope, with unexplained warning signs, and with a history of heart failure due to myocardial infarction.

If seizures are suspected, electroencephalography may be performed.

If a disease of the central nervous system is suspected, CT and magnetic resonance imaging of the head and brain can be performed.

Treatment of fainting

Certain treatments depend on the cause. For example, patients who faint due to heart rhythm disturbances may need to have a pacemaker and/or defibrillator.

If a person loses consciousness, first of all it is necessary to check whether he is breathing. If a person does not breathe, others should call emergency medical care and begin cardiopulmonary resuscitation (CPR), including the use of an automated external defibrillator (AED) if available. As soon as the patient arrives at the hospital, doctors begin treating the cause of the fainting with medication or appropriate measures, such as direct current cardiac defibrillation to restart the heart, or appropriate medication or surgery to release blocked arteries.

If breathing is maintained, the person should remain in the prone position. If a person moves to an upright position too quickly, fainting may recur.

Doctors may ask a person who has fainted to refrain from driving and working with machinery until the cause of the fainting is determined and treatment is prescribed, because if the cause is an unrecognized heart defect, then the next episode may end in death.

The main thing that older people need to know

Older people lose consciousness especially easily because the flow of blood to the brain decreases with age. The most common cause of fainting in the elderly is the inability to quickly adapt blood pressure when moving to an upright position. Blood flow decreases as arteries become stiffer and unable to adapt quickly to new conditions, lack of physical activity reduces muscle activity that pushes blood through the veins back to the heart, and heart disease reduces the efficiency of pumping blood.

In the elderly, fainting is often caused by several causes. For example, the combination of taking several medications to treat heart disease or high blood pressure and standing in a stuffy church during a long or emotional service can lead to fainting, although each individual factor alone may not be enough to cause fainting.

Key Points

• Fainting usually occurs as a result of insufficient blood flow to the brain.
• Most causes of fainting are not dangerous.
• Some less common causes are serious or potentially fatal.
• If the fainting has a visible cause (such as strong emotions), previous symptoms (such as dizziness, nausea or sweating), and its symptoms stop after a few minutes, then it is probably vasovagal syncope that does not pose a serious danger.
• Fainting due to heart rhythm disturbances usually happens suddenly and is characterized by rapid recovery.
• Doctors may ask a person who has fainted to refrain from driving and working with machinery until the cause of the fainting is determined and treatment is prescribed, because if the cause is an unrecognized heart defect, then the next episode may end in death.
• If fainting is caused by a slowing of the heart rate, it may be necessary to install a pacemaker.