Why do people feel dizzy and faint?

Q: Why do people faint?

Q: Why do I faint when I get fever?

Krishna: First let me tell you why people faint.

Syncope (pronounced “sin-ko-pea”) is the medical term for fainting or passing out.

Fainting, or passing out, is a temporary loss of consciousness from a sudden decrease of blood flow to your brain. An episode usually lasts a few seconds or minutes. Most are harmless, but if you faint often or have other symptoms, you should seek medical attention.

People faint  when their vagal system is more active ( the vagus nerve, also known as the vagal nerves, are the main nerves of your parasympathetic nervous system. This system controls specific body functions such as your digestion, heart rate, breathing, cardiovascular activity, reflex actions, such as coughing, sneezing, swallowing, and vomiting  and immune system). That is  

• During emotional circumstances, or with medical/dental procedures.
• When in pain (especially abdominal pain, or during a period).
• During or directly after a meal, especially if you haven’t eaten for a while.
• After a long period of standing still (in a queue or at a reception).
• After sitting very still, especially then standing.
• In warm surroundings (in a restaurant, warm weather, standing in a hot shower or sauna).
• Directly after exercise.
• When you have not had enough rest.
• During illness, nausea or fever.
• Low blood pressure (can cause dizziness and fainting)

What Is the Vasovagal Reflex? It is an automatic response responsible for feeling faint. The vasovagal reflex is an automatic response that stimulates your vagus nerve. It can affect your central and peripheral nervous system, as well as your cardiovascular system. When triggered, the vagus nerve sends a message to the brain that may cause a sudden drop in your blood pressure and heart rate. This can make you feel faint. Some people are more susceptible to involuntarily triggering the reflex.

The word vasovagal describes the two parts of your body that cause the response: "vaso" refers to your blood vessels and "vagal" refers to your vagus nerve.

The vagus nerve stimulates certain muscles in the heart that help to slow heart rate. When it overreacts, it can cause a sudden drop in heart rate and blood pressure, resulting in fainting. This is known as vasovagal syncope. Factors that can trigger this include pregnancy, emotional stress, and pain, but there may be no clear cause.

Most fainting is triggered by the vagus nerve. It connects the digestive system to the brain, and its job is to manage blood flow to the stomach. When food enters the system, the vagus nerve directs blood to the stomach and intestines, pulling it from other body tissues, including the brain. Unfortunately, the vagus nerve can get a little too excited and pull too much blood from the brain. Some things make it work harder, such as bearing down to have a bowel movement or vomiting. Medical conditions that drop blood pressure amplify the effects of the vagus nerve—even extreme pain from menstrual cramps.

Alongside this type of fainting, you may experience: warmth, nausea, tunnel vision, ringing in the ears, excessive sweating, low blood pressure, slow or irregular heartbeat.

If you experience fainting, it’s a good idea to see a doctor to rule out potential serious causes. To prevent it, a doctor may recommend drinking plenty of fluids or avoiding standing up quickly.

Micturition (or post-micturition) syncope is fainting while urinating or immediately after urinating. This is likely due to a severe drop in blood pressure. Micturition syncope is most common in older men and usually when getting up at night from a deep sleep.

The exact cause of micturition syncope isn't fully understood. But it may be related to a fall in blood pressure when you get up suddenly and stand at the toilet. Or this may happen when a full bladder empties very quickly. This is thought to cause a sudden drop in blood pressure.

The most common reason for fainting is a sudden drop in blood pressure, which reduces blood flow and oxygen to your brain. There are many reasons why a drop in blood pressure could lead to a temporary loss of consciousness:

• Cardiac syncope: This type of syncope involves fainting because of a heart problem. Many heart conditions can affect how much oxygenated blood your heart can pump to your brain. This type makes up 15% of fainting incidents.
• Carotid sinus syncope: This type of syncope can happen when something pinches or constricts the carotid artery in your neck. The carotid artery is a blood vessel that supplies your brain. This type of fainting can occur when someone wears a very tight collar, stretches or turns their neck too much, or has a bone in their neck that’s pinching their artery.
• Vasovagal syncope: This can occur when a person experiences a stressful event. Examples include the sight of blood, emotional stress, physical trauma, emotional trauma or pain. The stressful event stimulates a bodily reflex called the vasovagal reaction. Your heart slows down and pumps less blood, so your blood pressure drops. Then, your brain doesn’t get enough oxygenated blood, and you faint. Certain bodily movements or functions also can naturally cause a drop in blood pressure that may lead to fainting spells. Examples include when a person pees, poops, coughs or stretches.

Other possible causes of fainting

You may faint because of:

• Certain medications that treat high BP, such as diuretics (water pills), calcium channel blockers and angiotensin-converting enzyme (ACE) inhibitors. Other examples include nitrates for heart disease, antipsychotics for mental health disorders, antihistamines for allergies and opiods for pain.
• Dehydration or overheating.
• A neurologic condition, such as a seizure disorder or stroke.
• A sudden drop in blood sugar, as may happen in a person who has diabetes.
• An unknown reason, which happens in up to 50% of fainting cases.

Other activities that may cause fainting : 

• Skipping too many meals.
• Hyperventilating (breathing too fast).
• Working, playing or exercising too hard, especially in the heat.
• Standing up too quickly.
• Using alcohol, marijuana or illegal drugs.

Some people pass out when they see blood. Anxiety, panic disorder, and stress can stimulate the vagus nerve and lead to a loss of consciousness.

The vagus nerve stimulates the parasympathetic nervous system, which slows down the pulse rate and lowers blood pressure.  Some people are hypersensitive to the vagus nerve, and stimulation can result in a loss of consciousness.

Why does that happen?

When you are upright, standing or sitting still, blood drops under the influence of gravity down into your legs. With more blood held in your legs, less blood returns to the heart, and the amount of blood the heart can pump around the body diminishes, and the blood pressure in the circulation will begin to drop.

Usually the body counteracts this and tries to maintain the blood pressure, by constricting  the blood vessels in the legs and abdomen, and by making the heart beat faster. In some people, these attempts to maintain the blood pressure are ineffective in the specific situations when the fainting reaction occurs.

So when you begin to feel sweaty and faint this is because instead of constricting, some blood vessels get even wider (“vaso-dilate”), and the heart instead of speeding up may slow down or even stop momentarily. The result of this faulty response is that the heart cannot pump enough blood to the brain, and the lack of oxygen reaching the brain then makes you pass out. This is called Vasovagal syncope. (Syncope, pronounced sin-co-pee, is the greek / medical term for a blackout caused by not enough blood reaching the brain).

If you faint to the floor, or lie down before fainting (and if possible raise your legs), blood immediately returns to your heart, which can then pump blood to your brain again, and you regain consciousness. If you stay sitting up, your brain will remain starved of oxygen for longer, and during your faint you might even have jerky movements, that can be misinterpreted as a fit. Some people are incontinent during a profound faint. Again this is not evidence that the collapse was a fit.

Feeling ill and nauseous after a faint is very common, and is part of the digestive “vagal” activation, which often also makes you feel washed out for a time after a faint.

Why this fainting reaction happens more often to some people than to other? Some people seem to have more powerful “vagal” reactions in certain situations.

What happens then?

As the vasovagal fainting reaction begins, there is often light headedness, ringing in the ears, and feeling sweaty and nauseous. You may start yawning, and others may notice you have gone grey and sweaty. There is often a desire to get some fresh air (“air-hunger”), or to go urgently to the toilet (but standing up to go outside or to the toilet can then bring on the faint!).

As the blood pressure falls further, there is visual disturbance with black spots in front of the eyes, a feeling of becoming distant, and then one faints. People often recognise the symptoms, but sometimes the same people get very little warning and can pass out more suddenly.

During a faint, if someone feels your pulse it will usually be slow (during a seizure or fit it is usually fast). Some jerky movements may occur, especially if the person is still sitting or slouched with their head higher than their body.

When coming round after a faint, the person often feels awful, sickly and may vomit, or even have diarrhoea. Often there is prolonged fatigue after a faint.

But remember this: Being susceptible to fainting is not a serious disease. However, hurting yourself, sometimes seriously, while fainting is bothersome. 

How can you avoid this situation? Try to work out in which particular set of circumstances you are most likely to faint. Then try to avoid these sets of circumstances.

When you face them, what should you do?

Ensure you drink enough fluids (tea, coffee and alcohol don’t count), especially on hot days, or if you have been exercising or have had diarrhoea or vomiting. Your urine should be clear. Avoid alcohol if you are hot – both heat and alcohol relax your blood vessels, lowering your blood pressure.

”Isotonic” fluids can be especially helpful – these are “sports” drinks that contain some salt and minerals, to help keep your circulation properly hydrated.  But avoid the ones with caffeine.

Avoid large meals on an empty stomach.

If you recognise the start of any symptoms of the fainting reaction, try to lie down immediately, ideally with your legs elevated. Sitting bent forward with your head down between your legs may help, but is not ideal as your legs remain down, and though abdominal compression might help, it might also worsen the vagal reaction, prolong your symptoms and delay recovery.

Remember, it is better to decide to lie down and remain conscious, than to pass out and wake up on the floor in a mess.

Once you begin to feel faint, do not stand up quickly, or stand still (eg outside for fresh air)

If you faint, do not try to sit up or get up quickly when you come round - you may faint again!

And don't get out of bed suddenly — first, sit on the edge of the bed and move your legs, making sure you aren't dizzy or lightheaded before getting up. 

you can prevent fainting when you know what causes you to faint. Pay attention to specific activities or situations that make you faint. For example, if getting up too quickly sometimes makes you faint, learn to take your time standing up. You can also move your legs to help your blood move before you stand up.

If you notice how you feel just before you faint, you can try certain strategies to prevent it: Make a fist with your hand. Tense your arms. Cross your legs. Squeeze your thighs together. Lie down. Sit, lean forward and put your head between your knees.

  How to treat it: 

First aid for fainting If someone loses consciousness: Make sure the person’s airway is clear. Check that the person is breathing. Check that their heart is beating. Call emergency services or seek immediate medical attention if they’re hurt. Start CPR if the person isn’t breathing or if you don’t feel a pulse. Ask someone to look for an automated external defibrillator (AED) if needed.

When someone faints and then wakes up: Encourage them to sit down or lie down for 10 to 15 minutes (sometimes longer, until symptoms pass). Check for any injuries that might need medical attention (such as a head injury or a cut). Suggest that they sit forward and lower their head below their shoulders and knees. Offer ice or cold water.