What is fainting caused by vascular reflex?

Fainting is a temporary loss of consciousness caused by not enough blood reaching the brain. Vascular reflex is a response of the blood vessels that causes their walls to relax. Fainting as a result of vascular reflex is the most common and least worrisome form of fainting.

How does it occur?

When the walls of the blood vessels relax, the vessels enlarge. This enables them to hold more blood and allows the blood to pool in the part of the body that is lowest, usually the legs. Therefore, there is less blood in the upper part of your body, especially the brain, causing you to faint.

A vascular reflex can be caused by:

• standing up suddenly, which can cause blood pressure to drop (orthostatic hypotension)

• prolonged bed rest

• prolonged standing

• pregnancy

• dehydration

• varicose veins

• bleeding

• straining too hard to make bowel movements

• drugs such as diuretics (water pills), calcium-channel blocking agents, L-dopa (levodopa), and antihypertensives

• vigorous exercise, which can cause changes in blood pressure

• emotional upsets, such as fear, which can affect blood pressure

• crowded, hot surroundings where there's a lack of fresh air.

Orthostatic hypotension is common with people who have spinal cord disease and neuropathies such as diabetic neuropathy. It commonly occurs in the elderly and in almost everyone who is bedridden for more than a week.

What symptoms may occur before fainting?

Symptoms that may occur before you faint include:

• nausea

• sweating

• pale skin

• lightheadedness.

How is it diagnosed?

To discover the cause of fainting, your doctor will ask about your symptoms and your medical history. He or she will examine you to help rule out other reasons for fainting. Your doctor will take your blood pressure and pulse while you are in a resting position and while you are standing.

The doctor may order the following lab tests:

• Electrocardiogram (ECG): A recording of the electrical activity of the heart.

• Echocardiogram: A recording that uses ultrasound waves to examine the structure of the heart. The waves are passed through the chest to the heart and the results are recorded.

• Blood sugar test: A lab test used to measure the amount of glucose in the bloodstream. Low blood sugar can cause fainting.

How is it treated?

Follow these first aid guidelines for fainting:

• If the person is unconscious and is breathing normally, lay him or her flat. Raise the legs above the level of the chest to return more blood to the brain.

• If the person is unconscious and has no pulse or is not breathing, give CPR if you know how and call 911.

• If the person remains unconscious for 2 minutes or more, call 911.

In every case, the underlying cause of the fainting should be identified and treated to minimize recurrence.

How long will the effects last?

Fainting spells usually last from only a few seconds to a couple of minutes. If you feel faint, sit down, lean forward, and put your head between your knees, allowing more blood to the brain. If you can lie down with your feet up, this is even more helpful.

How can I take care of myself?

• Avoid straining to make bowel movements.

• If hot, humid weather causes you to feel faint, use a fan or air conditioner during heat spells. Drink plenty of fluids, and don't go out in the heat of the day.

What can be done to help prevent fainting caused by vascular reflex?

• Avoid sudden changes in position.

• If you have low blood sugar, eat small meals 5 or 6 times during the day as recommended by your doctor.

• Review your medications and their side effects with your doctor.