Low Blood Pressure (cont.)
IN THIS ARTICLE
Major allergic reactions (anaphylactic shock) can cause marked dilation of blood vessels and low blood pressure, associated with:
When standing quickly, it may take a second or two for the body to make adjustments to constrict blood vessels and push blood up to the brain. If there is a delay, then this time of relative low blood pressure may cause symptoms. It can be exacerbated or seen more often in patients who are pregnant, have diabetes, are dehydrated, or taking high blood pressure medications.
One of the complications of diabetes is damage to the nerves in the body, including those in the autonomic nervous system. In those people with diabetes who have autonomic dysfunction, orthostatic hypotension can occur. The blood vessels are unable to adjust to quick positional changes.
Micturition Syncope (Fainting During Urination or Bowel Movements)
One of the most common causes of syncope, (passing out or fainting), occurs when a person strains to urinate or have a bowel movement. This stimulates the vagus nerve, increasing acetylcholine in the body and dilating blood vessels, causing blood pressure to fall and decreasing blood supply to the brain. Though it is frightening and may result in a fall, micturition syncope is self-limiting, resolves quickly, and may need little treatment.
Medically Reviewed by a Doctor on 7/28/2015
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