National Spinal Cord Injury Association Resource Center

Factsheet #17:
What is Autonomic Dysreflexia?

AD occurs primarily because of an imbalance in the body systems which control the blood pressure. The human body is an incredibly complicated and beautifully balanced machine. There are balances to each system of the body, including the blood pressure. One of the major ways the body controls blood pressure is by tightening or relaxing little muscles around the blood vessels. When the muscles contract, the blood vessels get smaller and blood pressure increases. Imagine a garden hose with water streaming through it; when you put your thumb over the opening of the hose, reducing the opening for the water to flow through, the water shoots out at a higher pressure. Similarly, when the blood vessels are smaller, the blood rushes around your body at higher pressure.

When a noxious stimulus occurs, a reflex is initiated that causes the blood vessels to constrict and raises the blood pressure. In an intact spinal cord, this same stimulus also sets in motion another set of reflexes that moderates the constriction of blood vessels. However, in someone who has SCI at the T-6 level or above, the signal which tells the blood vessels to relax cannot get through the spinal cord because of the injury. Some of the nerves at the T-6 level also control the blood flow to and from the gut, which is a large reservoir of blood. Uncontrolled activity of these nerves may cause the blood from the gut to flow into the rest of the blood system. The result is that blood pressure can increase to dangerous levels and the increase in blood pressure must be controlled by outside means.

Topics covered in this fact sheet include:

How do I recognize Autonomic Dysreflexia?

Common sources of Autonomic Dysreflexia

What to do...

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