What is fainting and what causes it?
Often, a fainting episode has no medical importance, but sometimes it results from a serious illness, condition, or disorder. Every case of fainting should be treated as a medical emergency until the cause is known and signs and symptoms have been treated.
Anybody who has recurring fainting episodes should see a doctor.
Here are some key points about fainting. More detail is in the main article.
- Fainting, or syncope, is usually caused by a lack of oxygen in the brain.
- Fainting should be treated as a medical emergency until the cause is known.
- Symptoms can include falling down, blurred vision, and confusion.
- Possible causes include dehydration, low blood pressure, alcohol use, and diabetes.
- Treatment depends on the cause of the underlying condition.
Fainting happens when not enough blood and oxygen reaches the brain.
Syncope, or fainting, usually results from hypoxia, or a lack of oxygen to the brain.
Causes include problems with the lungs or blood circulation and carbon monoxide poisoning.
Fainting is a mechanism to help a person survive.
If brain blood and oxygen levels drop considerably, the brain immediately shuts down all other non-vital parts of the body so that resources can focus primarily on vital organs.
When the brain detects lower levels of oxygen, the body will start breathing faster, or hyperventilating, to bring levels back up again.
The heart rate will also rise in order to get more oxygen into the brain. This rise in the heart rate results in hypotension, or a drop in blood pressure, in other parts of the body. The brain receives extra blood, at the expense of other parts of the body.
Hyperventilation combined with hypotension may result in short-term loss of consciousness, muscle weakening, and fainting.
There can be different underlying causes of syncope.
Neurocardiogenic syncope results when something triggers a short-term malfunction of the autonomous nervous system (ANS). It is also known as neurally mediated syncope (NMS).
The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils, urination, and sexual arousal. Most of these actions are involuntary, but some, such as breathing, can also be done consciously.
There will be a drop in blood pressure and the heartbeat and pulse rate will slow down. This causes a temporary interruption in the brain's blood and oxygen supply.
Possible triggers include:
- suddenly seeing something that is unpleasant or shocking, such as blood
- sudden exposure to an unpleasant sight or experience
- sudden emotional upset, for example when receiving bad news
- extreme embarrassment
- standing still for a long time
- being in a hot and stuffy place for a long time
Occupational, or situational, syncope is a type of neurocardiogenic syncope, but the link is physical rather than emotional, mental, or abstract.
Triggers may include:
- coughing or sneezing
- laughing or swallowing
- defecating or urinating
- demanding physical activities, such as lifting a heavy weight
Orthostatic hypotension can happen when a person faints after stands up rapidly from a seated or lying down position.
Gravity pulls blood down to the legs, resulting in lower blood pressure elsewhere.
Normally, the body's nervous system reacts by raising the heart beat and narrowing blood vessels. This stabilizes blood pressure.
However, if something undermines this stabilization process, there may be poor blood and oxygen supply to the brain, leading to fainting.
- Dehydration: If body fluid levels drop, so will blood pressure. This can make it harder for the body to stabilize blood pressure, resulting in less blood and oxygen reaching the brain.
- Untreated diabetes: A person with diabetes may urinate more often, leading to dehydration. High blood glucose levels can lead to damage in some nerves, especially those that regulate blood pressure.
- Some medications: Diuretics, beta-blockers and anti-hypertensive drugs may cause orthostatic hypotension in some people.
- Alcohol: Some people faint if they consume too much alcohol in a short space of time.
- Some neurological conditions: Parkinson's disease and other conditions affect the nervous systems, and this can lead to orthostatic hypotension.
- Carotid sinus syndrome: Pressure on the pressure sensors in the carotid artery can cause fainting. These pressure sensors are known as the carotid sinus. The carotid artery is the main artery that supplies blood to the brain.
If the carotid sinus is over-sensitive, blood pressure may drop if it is physically stimulated, resulting in fainting. Examples include turning the head to one side, wearing a tight collar or tie, or pressing over the carotid sinus while shaving.
This is more common among males aged over 50 years.
Cardiac syncope: An underlying heart problem can cause a drop in blood and oxygen supply to the brain.
Possible conditions include:
- arrhythmias, or abnormal heart beat
- stenosis, a blockage of the heart valves
- hypertension, or high blood pressure
- a heart attack, when a heart muscle dies because of a lack of blood and oxygen
This cause of fainting will usually need treatment and monitoring.
Sometimes a coughing fit can cause a fainting episode.
The sign of fainting is a sudden loss of consciousness.
The following signs and symptoms may happen before a fainting episode:
- a feeling of heaviness in the legs
- blurred or "tunnel" vision
- feeling warm or hot
- lightheadedness, dizziness, a floating feeling
When a person faints, they may:
- fall over or slump
- appear unusually pale
- experience a drop in blood pressure and a weak pulse
Apart from distinguishing types of fainting by their causes, there is also near-syncope and syncope.
Pre- or near-syncope is when the person can remember events during the loss of consciousness, such as dizziness, blurred vision, muscle weakness. They may remember falling before hitting their head and losing consciousness.
Syncope is when the individual may remember the feelings of dizziness and loss of vision, but not the fall.
If there is an underlying health condition, it will need to be treated. Treatment will help prevent future fainting episodes.
Often, no further treatment is needed. To avoid further episodes, the person should avoid triggers, such as long periods standing still, dehydration, and being in hot and stuffy places.
If the sight or thought of injections or blood make a person feel faint, they should tell the doctor or nurse beforehand. The health care professional can then make sure the patient is in a safe position, such as lying down, before any procedure begins.
Beta blockers are mainly used to treat high blood pressure, but they may help if neurocardiogenic syncope interferes with a person's quality of life.
What to do if somebody faints
If you feel faint:
- Find somewhere to sit or lie down.
- When sitting, place your head between your knees.
- When you do get up, do so slowly.
If you see somebody fainting:
- Place the patient on their back, facing up
- If they are breathing, raise their legs about 12 inches above heart level to restore blood flow to the brain.
- Try to loosen all belts, ties, collars, and restrictive clothing.
- When the person comes round, do not let them get up too quickly.
- If they remain unconscious for more than about a minute, put them in the recovery position and get emergency medical help
If the person is not breathing:
- Check for breathing, coughing, or movement
- Make sure the airway is clear
- If there is no sign of breathing and circulation, start cardiopulmonary resuscitation (CPR).
- Continue CPR until either help arrives or the patient starts breathing on their own
- Put them in the recovery position and stay with them until help comes
- If the individual was injured and is bleeding after the fall, apply direct pressure to control the bleeding.
If heart pain is followed by fainting, help should be sought.
Sometimes what looks like a simple fainting episode may be something more serious, such as a stroke.
If the person experiences numbness in the face, paralysis, weakness, numbness in an arm or slurred speech, they need emergency medical help.
People should see their doctor if:
- they had chest pains, or an irregular or pounding heart beat before losing consciousness
- they have a history of heart disease
- fainting resulted in an injury
- fainting was preceded by fecal or urinary incontinence
- they are pregnant
- they experience recurring episodes of fainting
- they have diabetes
- they were unconscious for more than a few minutes.
The doctor will need to know about:
- the person's medical history and any medications being taken
- whether this was an isolated case, and, If not, details of previous episodes
- family history, for example whether any close relatives have heart disease
- what the person was doing, where they were, and what happened just before fainting occurred
- any other symptoms
The doctor will listen to the patient's heart to assess for underlying heart conditions. If signs and symptoms suggest a heart problem, the person may need to see a cardiologist.
Tests may include:
- an electrocardiogram (ECG), to check the electrical activity of the heart
- carotid sinus stimulation, to determine whether this triggers symptoms of lightheadedness or dizziness
- blood tests, to check for anemia, diabetes, or an infection
- tilt-table test, to monitor blood pressure, heart rhythm, and heart rate while the person is moved from a lying down to an upright position
- a Holter monitor test, where the patient wears a portable device for which records all their heartbeats.
The monitor is worn under the clothing. It records information about the electrical activity of the heart while the person carries out their normal activities for 1 to 2 days.
The device has a button that can be pressed if specific symptoms are felt. Records will show what heart rhythms were present at that moment.
If none of these tests reveal anything unusual, the doctor will probably conclude that the patient had neurocardiogenic syncope. No treatment will be needed.