Benjamin Wedro, MD, FACEP, FAAEM
Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.
Melissa Conrad Stöppler, MD
Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
In this Article
- Introduction to fainting (syncope)
- What causes fainting (syncope)?
- Heart rhythm changes
- Heart structural conditions
- Heart valve conditions
- Sudden cardiac death
- Postural hypotension
- Vasovagal syncope
- Orthostatic hypotension
- Vertebrobasilar system
- Electrolyte imbalance
- Other medications and drugs
- What are the signs and symptoms of fainting (syncope)?
- How is fainting (syncope) diagnosed?
- What is the treatment for fainting (syncope)?
- Can fainting (syncope) be prevented?
- Fainting (Syncope) At A Glance
Dehydration, or lack of water in the body can similarly cause fainting or syncope. This can be caused by excessive loss of water from vomiting, diarrhea, sweating, or by inadequate fluid intake. Some illnesses like diabetes can cause dehydration by excess loss of water in the urine.
Blood vessels need to maintain their tone so that the body can withstand the effects of gravity with changes in position. When the body position changes from lying down to standing, the autonomic nervous system (the part of the brain not under conscious control), increases tone in the blood vessel walls, making them constrict, and at the same time increases the heart rate so that blood can be pumped upward to the brain. As people age, blood vessels may become less resilient, and orthostatic hypotension (relative low blood pressure with standing) may occur and cause syncope.
Blood vessels to the brain are no different than any other blood vessels in the body and are at risk for narrowing with age, smoking, high blood pressure, high cholesterol, and diabetes. While most people are aware of the carotid arteries that supply the thinking parts of the brain, another set of arteries supply the base of the brain. This vertebrobasilar system is also at risk for narrowing, and should there be a temporary disruption in the blood flow to the midbrain and the reticular activating system, fainting or syncope may occur. The vertebral arteries run to the brain in the back of the neck and are encased in bony tunnels. If blood flow in these arteries is disrupted, the brain stem and reticular activating system may turn off, causing syncope.
Next: Electrolyte imbalance
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