The medical term for fainting is syncope. Fainting is a sudden loss of consciousness, usually temporary and typically caused by a lack of oxygen in the brain. The brain oxygen deprivation has many possible causes, including hypotension (low blood pressure).
The following words or phrasal expressions also mean to faint: to pass out, to black out, to fall unconscious, to fall in a faint. The verbs to come to and to come round mean to recover consciousness.
Contents of this article:
Here are some key points about fainting. More detail and supporting information is in the main article.
- The scientific term for fainting is syncope.
- Fainting is usually caused by a lack of oxygen in the brain.
- Every case of fainting should be treated as a medical emergency until the cause is known.
- In Victorian England, women would faint to appear fashionably frail.
- Symptoms can include blurred vision and confusion.
- There are a different types of fainting, one of which is orthostatic hypotension.
- Potential causes of fainting include dehydration, alcohol and diabetes.
- Treatment of fainting depends on the causes of the condition.
What is syncope?
Fainting can sometimes be a sign of a more serious illness, or nothing to worry about at all.
If oxygen levels are below 16% at atmospheric pressure most people faint due to hypoxia. If oxygen levels fall below 11% individuals may die by suffocation. The amount of oxygen in the air depends on its partial pressure - inhaling pressurized gas while scuba diving which is below 16% oxygen does not cause hypoxia (because the air is pressurized).
Syncope due to hypoxia may also be caused by malfunctioning lungs, problems with blood circulation, or carbon monoxide poisoning. Some people faint at the sight of blood, or when receiving an injection or seeing somebody having one.
In Victorian England (19th Century) fainting in women was a commonplace stereotype, as well as modern portrayals of that period. Some believe that the respiratory effects of tight corsets worn at the time may have been a contributory factor. However, during Victorian times aristocratic women were encouraged to display a feminine frailty by fainting at dramatic moments.
Children sometimes play a game (fainting game) in which they deliberately restrict blood flow to the brain in order to trigger syncope - this is dangerous and may cause brain damage, and even death.
Near-syncope vs syncope
- Pre- or near-syncope (a pre- or near-syncoptic episode) - this is when the person can remember events during the loss of consciousness, such as dizziness, blurred vision, muscle weakness, as well as the fall before hitting their head and losing consciousness.
- Syncope (a syncoptic episode) - this is when the individual may remember the feelings of dizziness and loss of vision, but not the fall.
Symptoms of syncopeThe hallmark sign is evident to anyone around - the patient passes out, faints, suddenly loses consciousness.
The following signs and symptoms may precede a fainting episode:
- A feeling of heaviness in the legs
- Blurred vision
- Feeling warm or hot
- Lightheadedness, dizziness, a floating feeling
- The individual may be falling over
- The patient may be slumping
- The person may be unusually pale
- There may be a drop in blood pressure
- There may be a weak pulse.
Causes of syncope
Syncope is a mechanism used by the brain to help us 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 (hyperventilating) to bring levels back up again.
The heart rate (pulse) will also rise in order to get more oxygen into the brain. This rise in the heart rate results in hypotension (drop in blood pressure) in other parts of the body, because the brain is flooded with 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 syncope (fainting).
There are different types of fainting, which describe the underlying cause for loss of blood/oxygen supply to the brain:
Neurocardiogenic syncope (also known as reflex syncope, vasovagal episode, vasovagal response, vasovagal attack, vasovagal syncope) - occurs when something causes a short-term malfunction of the autonomous (autonomic) nervous system (ANS). The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils, micturition (urination), and sexual arousal. Whereas most of its actions are involuntary, some, such as breathing, work in tandem with the conscious mind.
The patient experiences hypotension (drop in blood pressure) and a slower heartbeat (pulse rate), causing the brain's blood/oxygen supply to be temporarily interrupted. Possible triggers include:
- Suddenly seeing something that is unpleasant or shocking, such as blood
- Being suddenly exposed to a horrible/frightening experience, such as a huge gorilla running into a room straight up to you and screaming in your face
- Becoming suddenly emotionally upset, such as when hearing about the death of a loved one
- An extremely embarrassing situation or event
- Standing still for long periods. Sometimes soldiers standing guard, or people in church may faint
- Being in a hot and stuffy place for a long time.
Occupational syncope - this is also a type of neurocardiogenic syncope, but the link is physical rather than emotional, mental or abstract. Examples of the many possible triggers are included:
Sometimes a coughing fit can cause a fainting episode.
- Defecating (passing stools, feces)
- Lifting a heavy weight, and some other demanding physical activities
Orthostatic hypotension - this is when a person stands up rapidly from a seated or lying down position and faints; gravity pulls blood down to the legs, resulting in lower blood pressure elsewhere. The body's nervous system reacts by raising the heart beat and narrowing blood vessels, stabilizing blood pressure. However, sometimes something undermines this stabilization process, resulting in poor blood/oxygen supply to the brain, and the individual faints.
Orthostatic hypotension may be caused by:
- Severe dehydration - if body fluid levels drop, so will blood pressure. If this continues for long enough the nervous system finds it harder to stabilize blood pressure, resulting in less blood/oxygen reaching the brain, raising the risk of fainting.
- Untreated diabetes - the patient urinates much more frequently and becomes dehydrated. If blood glucose levels go to high there may be damage to some nerves, especially those that regulate blood pressure.
- Some medications - some diuretics, beta-blockers and anti-hypertensive drugs may cause orthostatic hypotension in some patients.
- Alcohol - some people may pass out if they consume too much alcohol in one sitting. One moment they are chatting away (perhaps with slurred speech), when suddenly they slouch over, resting their head on a table, as if asleep.
- Some neurological conditions - such as Parkinson's disease, may have problems with their nervous systems, which lead to orthostatic hypotension.
- Carotid sinus syndrome - temporary unconsciousness resulting from pressure on the pressure sensors (carotid sinus) in the carotid artery (the main arteries that supply blood to the brain). Some patients may have an over-sensitive (hypersensitive) carotid sinus in which blood pressure drops when any physical stimulation of the carotid sinus occurs, resulting in fainting. This may occur when the individual turns his head to one side, wears a tight collar or tie, or presses over the carotid sinus while shaving. The condition is more common among males aged over 50 years.
Cardiac syncope - an underlying heart problem causes a drop in blood/oxygen supply to the brain. Possible conditions include:
Tests and diagnosis of syncopeIt is not easy to differentiate a simple fainting episode from something more serious, such as a stroke. If the patient experiences numbness in the face, paralysis, weakness, numbness in an arm or slurred speech you should seek emergency medical help.
People should see their doctor if:
- Before losing consciousness there were chest pains, arrhythmia (irregular heart beat) or a pounding heartbeat (palpitations).
- Fainting resulted in an injury
- The fainting was preceded by fecal incontinence
- The fainting was preceded by urinary incontinence
- There is a history of heart disease
- They are pregnant
- They experience recurring episodes of syncope
- They have diabetes
- They were unconscious for more than a few minutes.
- Details of any medications you are currently taking
- Whether this was an isolated case of fainting. If not, details of previous episodes
- Your family history - e.g. are there any close relative with heart disease
- Your medical history.
- What symptoms you felt
- What you were doing
- Where you were.
Heart pain followed by fainting is a sign that help should be sought.
- ECG (electrocardiogram) - the doctor may order an ECG to check for the electrical activity of the heart. Electrodes are attached to the patient's skin to measure electrical impulses given off by the heart. The impulses are recorded as waves and displayed on a screen (or printed). An irregularity of heart action is generally obvious right away.
- Carotid sinus - the doctor may massage the carotid sinus to determine whether this triggers symptoms of lightheadedness or dizziness.
- Blood tests - these may be ordered to check for anemia, diabetes or an infection.
- Tilt-table test - this test monitors the patient's blood pressure, heart rhythm and heart rate while he/she is moved from a lying down to an upright position. A healthy patient's reflexes cause the heart rate and blood pressure to change when moved to an upright position - this is to make sure the brain gets an adequate supply of blood. If the reflexes are inadequate, they could explain the fainting spell(s).
- Holter monitor test - the patient wears a portable device which records all his/her heartbeats. It is worn under the clothing and records information about the electrical activity of the heart while the individual goes about his/her normal activities for one or two days. It has a button which can be pressed if specific symptoms are felt - then the doctor can see what heart rhythms were present at that moment.
What to do if somebody feels faintYou feel faint:
- Don't stay standing up. Find somewhere to either sit or lie down.
- If you manage to sit down place your head between your knees.
- When you do get up, do so slowly.
- Place the patient on his/her back, facing up
- If the individual is breathing, raise their legs about 12 inches (30 centimeters) 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 the patient into the recovery position and get emergency medical help
- Check the patient's airway for any obstruction and check for vomiting
- Check for breathing, coughing or movement (signs of circulation). If you cannot detect any, start CPR (cardiopulmonary resuscitation). Continue administering CPR until either help arrives or the patient starts breathing on his/her own
- If the individual was injured and is bleeding after the fall, apply direct pressure to control the bleeding.
Treating syncopeIf the fainting is found to be caused by an underlying health condition, that will need to be treated, which should help prevent syncoptic episodes.
- Treating neurocardiogenic syncope - in the majority of cases no further treatment is needed. Avoid the triggers, such as long periods standing still, dehydration, and being in hot and stuffy places. This may help prevent future episodes.
- Injections and blood - 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 (lying down) before any procedure begins.
- Beta-blockers - this medication is primarily used for the treatment of high blood pressure (hypertension). However, it may help patients whose neurocardiogenic syncope interferes with their quality of life. The side effects of beta-blockers may include fatigue, cold extremities (hands and feet), slow heartbeat (pulse rate), nausea, and diarrhea. Although rare, the following side effects are also possible - erectile dysfunction (impotence, problems either getting or sustaining an erection), nightmares, and sleep disturbances.