Fainting typically occurs in connection with both physical and mental strain, and especially if a person does not feel well to start with. Fainting can be caused by a number of factors linked to a person's heart, circulation, blood pressure and breathing. The type of fainting attack described here is the most frequent and can happen at any time to otherwise healthy people. What triggers fainting? Things that trigger fainting include stressful situations, excitement and pain. This could include visiting the doctor for a blood sample, or being in an overheated or overcrowded room. Fainting typically occurs in connection with both physical and mental strain, and especially if a person does not feel well to start with. Fainting can occur suddenly and unexpectedly. Often, everything goes black. The person then turns pale, starts sweating and possibly feels sick. It can happen while standing, sitting down or if one gets up too quickly. What to do if someone feels faint Usually people have some idea that they're going to faint and can warn the people around them. If you know someone is going to faint, or suspect that it is going to happen, help the person lie down, preferably with their head low and the legs raised. This helps the blood flow back to the brain. Never try to get them up, as this will only make the problem worse. If they become unconscious, it rarely takes more than a few minutes to regain consciousness completely, although the arms and legs might still feel weak. If a person tries to get up too fast, they may feel dizzy and perhaps even faint again. If a person feels faint and isn't able to lie down, they should sit instead, putting their head between their knees. A friend should hold the person's hand behind his or her head and press downwards. At the same time, the person feeling faint should push their head upwards. This makes the blood flow to the brain, reducing the symptoms and reducing the risk of fainting.
Fainting (syncope) is a defence mechanism used by the brain. If the supply of blood and oxygen to the brain becomes too low, the brain will immediately take any available blood and oxygen from the rest of the body at the expense of other bodily functions. Your breathing rate will be increased (hyperventilation) as your brain tries to increase its supply of oxygen. Your heart rate will also increase, to pump more blood from the rest of your body to your brain. The increase in heart rate will lead to a loss of blood pressure in the rest of your body (hypotension) as blood is diverted to your brain. The combination of hyperventilation and hypotension can then lead to a temporary loss of consciousness and muscle weakness, resulting in fainting. There are different types of fainting which are caused by the blood supply to the brain being interrupted for different reasons. The different types of fainting are explained below.
Neurally mediated syncope
Neurally mediated syncope is also called reflex syncope. Neurally means that it is related to the nervous system, which is made up of your brain, nerves and spinal cord. There are three types of neurally mediated syncope. They are:
vasovagal syncope
situational syncope
carotid sinus syndrome
These are explained in more detail below.
Vasovagal syncope
Vasovagal syncope occurs when something triggers a temporary malfunction in your autonomic nervous system. The autonomic nervous system is the part of the nervous system responsible for regulating many of the body’s automatic functions, such as heartbeat and blood pressure. The malfunction in the autonomic nervous system causes a drop in your blood pressure and a reduction in your heartbeat. This leads to a temporary interruption to your brain’s blood supply.
Vasovagal syncope may be caused by:
sudden exposure to an unpleasant sight or experience, such as the sight of blood
standing for long periods of time
spending a long time in hot or stuffy environments
a sudden intense episode of stress, emotional upset, fear or anxiety
a sudden feeling of pain
Situational syncope
Situational syncope is also a type of fainting related to the nervous system. It occurs when a bodily function or activity places a sudden strain on your autonomic nervous system. Possible causes of situational syncope include:
coughing
sneezing
swallowing
laughing
passing stools
urinating
some physical activities, such as weightlifting, although this could also be a sign of an underlying heart problem (see cardiac syncope, below)
Situational syncope may also occur after eating a meal or exercising.
Carotid sinus syndrome
The carotid sinus is a collection of sensors in the carotid artery. The carotid artery is located in your neck and is the main artery that supplies blood to your brain. The carotid sinus helps to regulate the flow of blood through the carotid artery into your brain. Some people can develop a hypersensitive carotid sinus. This means that any physical stimulation of the carotid sinus can cause the sensors suddenly to trigger a drop in blood pressure, resulting in fainting. This condition is known as carotid sinus syndrome. Examples of physical stimulation that may affect your carotid sinus include:
turning your head to one side
wearing a tight collar
shaving over the part of your neck that contains the carotid sinus
Carotid sinus syndrome is very rare in people who are under 40 years of age. It is most common among older men.
When you faint, you will feel weak and unsteady before passing out for a short period of time, usually only a few seconds. Fainting can happen when you are sitting down, standing up or when you get up too quickly. Warning symptoms
Just before losing consciousness, you may experience the following symptoms: yawning a sudden, clammy sweat nausea (feeling sick) fast, deep breathing confusion feeling lightheaded blurred vision or spots in front of your eyes ringing in your ears This is followed by a loss of strength and a loss of consciousness. It only takes a few seconds to run through these symptoms, and there may be very little warning before you collapse. In some cases, there may be no other symptoms to warn you that you are about to faint. When you collapse to the ground, your head and heart are on the same level. This means that your heart does not have to work as hard to push blood up to your brain. You should return to consciousness after about 20 seconds. In rare cases, you may remain unconscious for longer, perhaps several minutes.
Treatment for fainting (syncope) will depend on whether there is an underlying cause. See Fainting - causes for more information about the possible causes of fainting.
Treating the underlying cause
If your GP finds an underlying cause for your fainting, treating it should help prevent further fainting episodes. For example, if you are diagnosed with type 2 diabetes (where there is too much glucose in the blood) you may be advised to take regular exercise and eat a healthy diet. If you are diagnosed with a heart condition, you may need to have further tests and treatment. For example, there are several different medicines that can be used to treat heart disease, which is where your heart's blood supply is blocked by a build-up of fatty substances in the main blood vessels
Treating neurally mediated syncope
Neurally mediated syncope, also called reflex syncope, includes:
vasovagal syncope
situational syncope
carotid sinus syndrome
Treatment for neurally mediated syncope involves avoiding any possible triggers. If you are not sure what caused your fainting episode, your GP may suggest that you keep a diary of any symptoms you experience and what you were doing at the time that you fainted, to help identify possible causes. There are also steps that you can take to avoid losing consciousness if you think that you may be about to faint. See If someone is about to faint for more information.
Vasovagal syncope
Vasovagal syncope occurs when something triggers a temporary malfunction in your autonomic nervous system. This is the part of the nervous system that is responsible for regulating many of the body’s automatic functions, such as heartbeat and blood pressure. In most cases of vasovagal syncope, further treatment is not required. However, you may find it useful to avoid potential triggers, such as:
spending a long time on your feet
hot and stuffy environments
If you know that injections or medical procedures (such as blood tests) make you feel faint, you should tell the doctor or nurse beforehand. They will then be able to make sure you are lying down during the procedure.
Situational syncope
Situational syncope is caused by a bodily function or activity that places a sudden strain on your autonomic nervous system, such as sneezing or laughing. There is no specific treatment, but avoiding the triggers may help. For example, if coughing has caused you to faint, it may be possible to suppress your urge to cough and therefore avoid fainting. Carotid sinus syndrome Carotid sinus syndrome is where pressure on your carotid sinus causes you to faint. Your carotid sinus is a collection of sensors in the carotid artery, which is the main artery in your neck that supplies blood to your brain. You can avoid fainting by not putting any pressure on your carotid sinus, for example, by not wearing shirts with tight collars. In some people, carotid sinus syndrome can be treated by having a pacemaker fitted. A pacemaker is a small, battery-operated device that is inserted into your chest to help your heart beat regularly. See the Health A-Z topic about Pacemaker implantation for more information about the procedure
Treating orthostatic hypotension
Orthostatic hypotension is a type of fainting that occurs when you stand up suddenly. This is because your nervous system does not stabilise your blood pressure quickly enough. By avoiding anything that lowers your blood pressure you should be able to prevent fainting. For example, you should:
make sure you do not get dehydrated, for example, by limiting how much alcohol you drink
avoid medication that can lower your blood pressure, but do not stop taking a prescribed medication unless you are advised to do so by your GP or another qualified healthcare professional who is responsible for your care
See the Health A-Z topic about Low blood pressure - treatment for more information and advice about orthostatic hypotension.
Medication
Several different medications have been tested for the treatment of fainting. Guidelines for treating fainting from the European Society of Cardiology found that most medications had disappointing results.
The data suggested that taking medication long term for occasional fainting is not effective. However, taking a single dose of a medication before an activity that is known to trigger fainting might work. For example, taking a dose of medicine an hour before you know you will be standing for a long period of time may prevent you from fainting.
At the moment this theory has not been proven. The medication in question, midodrine, is also unlicensed in the UK. This means that the manufacturers of midodrine have not applied for a licence for the medication. In other words, the medication has not undergone clinical trials (a type of research that tests one treatment against another) to see if it is effective and safe.
If someone is about to faint
If you know or suspect that someone is going to faint, you should help the person to lie down, preferably in a position where their head is low and their legs are raised.
If it is not possible for the person who is feeling faint to lie down, sit them down with their head between their knees. Gently, but firmly, push their head down while they try to push their head upwards. This will encourage the blood to flow to their brain, reducing their symptoms and helping them to recover more quickly.
Physical counterpressure manoeuvres
Physical counterpressure manoeuvres are movements that are designed to raise your blood pressure and prevent you losing consciousness. One study found that just under a third of people who fainted regularly who were trained in physical counterpressure manoeuvres fainted within a year, compared with half of those who were not trained in using these measures.
Physical counterpressure manoeuvres include:
crossing your legs
clenching the muscles in your lower body
squeezing your hands into a fist
tensing your arm muscles
You need to be trained in how to carry out these movements correctly. You can then carry them out if you experience any symptoms that suggest you are about to faint, such as feeling lightheaded.
If someone has fainted
If a person faints and does not regain consciousness within one or two minutes, you should put them into the recovery position. To do this, you should:
place the person on their side so they are supported by one leg and one arm
open their airway by tilting their head back and lifting their chin
monitor their breathing and pulse continuously
You should then dial 999 to request an ambulance and stay with the person until medical help arrives.
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