Autonomic Dysreflexia (AD) is an exaggerated sympathetic response to a noxious or painful stimuli below the level of the spinal cord injury. This means that the body responds to something painful or harmful by raising the blood pressure, but the brain cannot mediate this potentially dangerous rise in blood pressure because messages are blocked by the spinal cord injury.
The rise in blood pressure can be resolved by treating the cause of the AD. If the cause cannot be found or treated medication must be administered to control the blood pressure.
AD can only occur in people with spinal cord lesions around and above the T6 level, and after the reflexes have returned after the period of spinal shock that occurs at the time of injury. Because this condition affects only a very small percentage of the population there is a lack of awareness of it. It is important these people, their family, and carers know how to recognise and treat this life-threatening condition. It should also be noted that people with spinal cord injuries T6 and above usually have a lower blood pressure than the general population, so a blood pressure which is considered normal in the general population may be high for this group of people.
Something painful below the level of the spinal cord injury triggers a reflex and the body’s natural response is to raise the blood pressure by tightening the blood vessels. The brain gets information that the blood pressure is rising, and tries to moderate the blood pressure. It does this by slowing down the heart rate and trying to widen the blood vessels. However, the message to the blood vessels below the spinal cord injury is blocked by the spinal cord injury. Therefore, the blood vessels above the spinal cord injury widen, but the blood vessels below the level of the injury remain tight, causing the blood pressure to keep rising. Without intervention the blood pressure will continue to rise.