Near-Fainting: Vagal Reaction

Fainting (syncope) is a temporary loss of consciousness (passing out). It is associated with a loss of postural tone. Postural tone is the constant contraction of the muscles in your body to help keep your body upright. It also helps blood return towards the heart and brain. Syncope occurs when there is reduced blood flow to the brain due to this common vagal reaction. A vagal reaction is a reflex response that causes a sudden drop in your blood pressure, and your pulse to slow down. If the pulse is low enough, the blood pressure falls and causes fainting or near-fainting. Lying down usually stops the reaction very quickly.

These are symptoms of near-fainting:

• Feeling lightheaded or like you are going to faint

• Weak pulse

• Nausea

• Sweating

• Blurred vision or feeling like your vision is "blacking out"

• Palpitations

• Chest pain

• Trouble breathing

• Cool and clammy skin

Causes for near-fainting include:

• Sudden emotional stress like fear, pain, panic, sight of blood

• Straining or overexertion, straining while using the toilet, coughing, sneezing

• Standing up too quickly, or standing up for too long a time

• Pregnancy

Home care

The following will help you care for yourself at home:

• Rest today and go back to your normal activities as soon as you are feeling back to normal.

• If you become light-headed or dizzy, lie down right away or sit with your head lowered between your knees.

• Stay hydrated and do not skip meals.

• Don't stand for long periods or stay in hot places

• Do what you can to prevent constipation. If you bear down excessively when trying to have a bowel movement, this can trigger a vagal response

There may be other causes for a vagal response and near-syncope. For example, this can happen after open-heart surgery when the heart muscle is inflamed and irritated.

Check with your doctor to see if there is testing you need such as a tilt-table test, heart rhythm monitoring, or blood tests. Review the medicines you take with your healthcare provider and pharmacist to be sure the symptoms you have are not a side effect of a medicine.

Follow-up care

Follow up with your healthcare provider, or as advised. 

If you are having frequent episodes of near-syncope or vagal reactions, be cautious about activities such as driving that could harm yourself or others if you were to faint. Do not drive or operate heavy machinery if you are feeling like you may faint.

Call 911

Call 911 if any of these occur:

• Another fainting spell occurs, and it is not explained by the common causes listed above

• Fainting or loss of consciousness

• Chest, arm, neck, jaw, back, or abdominal pain

• Shortness of breath

• Weakness, tingling, or numbness in one side of the face, one arm or leg

• Slurred speech, confusion, trouble walking or seeing

• Seizure

• Blood in vomit or stools (black or red color)

When to seek medical advice

Call your healthcare provider right away if you have occasional mild lightheadedness, especially when standing up.

Note about concussion

If you had an injury to the head, it is possible that you could have a concussion (mild brain injury). Symptoms of a concussion can show up later. For this reason, be alert for symptoms of concussion once you’re home. 
Seek emergency medical care if you have any of the symptoms below over the next hours to days:

• Headache
• Nausea or vomiting
• Dizziness
• Sensitivity to light or noise
• Unusual sleepiness or grogginess
• Trouble falling asleep
• Personality changes
• Vision changes
• Memory loss
• Confusion
• Trouble walking or clumsiness
• Loss of consciousness (even for a short time)
• Inability to be awakened

During the time period that you’re watching for concussion symptoms:

• Don’t drink alcohol or use sedatives or medicines that make you sleepy.
• Don’t drive or operate machinery.
• Don’t do anything strenuous, such as heavy lifting or straining.
• Limit tasks that require concentration. This includes reading, watching TV, using a smartphone or computer, and playing video games.
• Don’t return to sports, exercise, or other activity that could result in another injury.

Ask your healthcare provider when you can safely resume these activities.