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HomeAnswersWhat is "Autonomic Dysreflexia?"

What is “Autonomic Dysreflexia?”

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Autonomic Dysreflexia, also known as Hyperreflexia, means an over-activity of the Autonomic Nervous System causing an abrupt onset of excessively high blood pressure. Persons at risk for this problem generally have injury levels above T-5. Autonomic dysreflexia can develop suddenly and is potentially life threatening and is considered a medical emergency. If not treated promptly and correctly, it may lead to seizures, stroke, and even death.

AD occurs when an irritating stimulus is introduced to the body below the level of spinal cord injury, such as an overfull bladder. The stimulus sends nerve impulses to the spinal cord, where they travel upward until they are blocked by the Lesion at the level of injury. Since the impulses cannot reach the brain, a Reflex is activated that increases activity of the sympathetic portion of autonomic nervous system. This results in spasms and a narrowing of the blood vessels, which causes a rise in the blood pressure.

Signs & Symptoms

  • Pounding headache (caused by the elevation in blood pressure)
  • Goose Pimples
  • Sweating above the level of injury
  • Nasal Congestion
  • Slow Pulse
  • Blotching of the Skin
  • Restlessness
  • Hypertension (blood pressure greater than 200/100)
  • Flushed (reddened) face
  • Red blotches on the skin above level of spinal injury
  • Sweating above level of spinal injury
  • Nausea
  • Slow pulse (< 60 beats per minute)
  • Cold, clammy skin below level of spinal injury


There can be many stimuli that cause autonomic dysreflexia. Anything that would have been painful, uncomfortable, or physically irritating before the injury may cause autonomic dysreflexia after the injury.

The most common cause seems to be overfilling of the bladder. This could be due to a blockage in the urinary drainage device, bladder infection (cystitis), inadequate bladder emptying, bladder spasms, or possibly stones in the bladder.

The second most common cause is a bowel that is full of stool or gas. Any stimulus to the rectum, such as digital stimulation, can trigger a reaction, leading to autonomic dysreflexia.

Other causes include skin irritations, wounds, pressure sores, burns, broken bones, pregnancy, ingrown toenails, appendicitis, and other medical complications.

In general, noxious stimuli (irritants, things which would ordinarily cause pain) to areas of body below the level of spinal injury. Things to consider include:

  • Bladder (most common) – from overstretch or irritation of bladder wall
    • Urinary Tract Infection
    • Urinary retention
    • Blocked Catheter
    • Overfilled collection bag
    • Non-compliance with Intermittent Catheterization program
  • Bowel – over distention or irritation
    • Constipation / impaction
    • Distention during Bowel program (digital stimulation)
    • Hemorrhoids or anal fissures
    • Infection or irritation (eg. appendicitis)
  • Skin-related Disorders
    • Any direct irritant below the level of injury (eg. – prolonged pressure by object in shoe or chair, cut, bruise, abrasion)
    • Pressure sores (Decubitus Ulcer)
    • Ingrown toenails
    • Burns (eg. – sunburn, burns from using hot water)
    • Tight or restrictive clothing or pressure to skin from sitting on wrinkled clothing
  • Sexual Activity
    • Over stimulation during sexual activity [stimuli to the pelvic region which would ordinarily be painful if sensation were present]
    • Menstrual cramps
    • Labor and delivery
  • Other
    • Heterotopic Ossification (“Myositis ossificans”, “Heterotopic bone”)
    • Acute abdominal conditions (gastric ulcer, colitis, peritonitis)
    • Skeletal fractures


Treatment must be initiated quickly to prevent complications.

  • Remain in a sitting position, but do a Pressure Release immediately. You may transfer yourself to bed, but always keep your head elevated.
  • Since a full bladder is the most common cause, check the urinary drainage system. If you have a Foley or Suprapubic Catheter, check the following:
    • Is your drainage full?
    • Is there a kink in the tubing?
    • Is the drainage bag at a higher level than your bladder?
    • Is the catheter plugged?

After correcting an obvious problem, and if your catheter is not draining within 2-3 minutes, your catheter must be changed immediately. If you do not have a Foley or suprapubic catheter, perform a catheterization and empty your bladder.

If your bladder has not triggered the episode of autonomic dysreflexia, the cause may be your Bowel. Perform a digital stimulation and empty your bowel. If you are performing a digital stimulation when the symptoms first appear, stop the procedure and resume after the symptoms subside.

If your bladder or bowel are not the cause, check to see if:

  • You have a Pressure Sore
  • You have an ingrown toenail
  • You have a fractured bone.

Identify and remove the offending stimulus whenever possible. Often, this alone is successful in allowing the syndrome to subside without need for pharmacological intervention. It is also good for the person with the symptoms to be sitting up with frequent blood pressure checks until the episode has resolved. [In hospital-based settings or in high-risk individuals / persons who have recurrent episodes, consideration should be given having atropine at the bedside]

Suspected cause = bladder? Check catheter – remove kinks if found, empty urinary collection bag, irrigate catheter. If catheter is not draining, replace it immediately. If an intermittent catheterization program is in place, a straight catheterization should be performed immediately with (slow drainage to prevent bladder spasms).

Suspected cause = bowel? If episode happens during digital stimulation, stop stimulation until symptoms and signs subside. Consider use of a prescribed anesthetic ointment to suppress the noxious stimulus. If the issue is impacted stool, disimpact. If it occurs while doing a bowel program in bed, try commode-based bowel evacuation. Consider use of abdominal massage instead of digital stimulation.

Suspected cause = skin? Loosen clothing. Check for source of potential offending stimulus – check for pressure sores, toenail problems, soles of the feet.

If symptoms persist despite interventions such as the foregoing, notify a physician.


Medications are generally used only if the offending trigger/stimulus cannot be identified and removed – or when an episode persists even after removal of the suspected cause. Potentially useful agents include:

  • Immediate/emergent
    • Procardia – 10 mg. p.o./sublingual
    • Nitroglycerine – 1/150 sublingual or 1/2 inch Nitropaste topically
    • Clonidine – 0.1 to 0.2 mg. p.o.
    • Hydralazine – 10 to 20 mg. IM/IV
  • Chronic (recurrent episode prevention)
    • Prazosin (“Minipress”) – 0.5 to 1.0 mg. daily
    • Clonidine (“Catapres”) – 0.2 mg. p.o. b.i.d.


The following are precautions you can take which may prevent episodes:
Frequent pressure relief in bed/chair
Avoidance of sun burn/scalds (avoid overexposure, use of #15 or greater sunscreen, watch water temperatures)
Maintain a regular bowel program.
Well balanced diet and adequate fluid intake
Compliance with medications
Persons at risk and those close to them should be educated in the causes, signs and symptoms, first aid, and prevention of autonomic dysreflexia.
If you have an Indwelling Catheter:
Keep the tubing free of kinks
Keep the drainage bags empty
Check daily for grits (deposits) inside of the catheter.
If you are on an intermittent catheterization program, catheterize yourself as often as necessary to prevent overfilling.

If you have spontaneous voiding, make sure you have an adequate output.
Carry an intermittent catheter kit when you are away from home.
Perform routine skin assessments.


If you are unable to find the stimulus causing autonomic dysreflexia, or your attempts to receive the stimulus fail, you need to obtain emergency medical treatment. Since all physicians are not familiar with autonomic dysreflexia (hyperreflexia) and its treatment, you should carry a card in your billfold that describes the condition and the treatment required.

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