Autonomic Dysreflexia

Know about your autonomic nervous system

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How the autonomic nervous system normally works

The autonomic nervous system is the part of the nervous system that supplies the internal organs, such as blood vessels, stomach, intestine, liver, kidneys, bladder and genitals.

The autonomic nervous system has two main divisions:

  • Sympathetic
  • Parasympathetic

After the autonomic nervous system receives information about the body and external environment, it responds by stimulating body processes, usually through the sympathetic division, or inhibiting them, commonly through the parasympathetic division.

The autonomic nervous system controls internal body processes:

  • Blood pressure
  • Heart and breathing rates
  • Body temperature
  • Digestion
  • Metabolism which affects body weight
  • The balance of water and electrolytes, for example, sodium and calcium
  • The production of body fluids, for example, saliva, sweat and tears
  • Urination
  • Defecation
  • Sexual response.

Many organs are controlled primarily by either the sympathetic or the parasympathetic division. Sometimes the two divisions have opposite effects on the same organ. For example, the sympathetic division increases blood pressure while the parasympathetic division decreases it. Overall, the two divisions work together to ensure the body responds appropriately to different situations.

What is normal blood pressure

Normal baseline blood pressure for most people is: 120/80 mmHg.

Blood pressure changes depending on what a person is doing and other factors, including:

  • Smoking
  • Being overweight or obese
  • Lack of physical activity
  • Too much salt in the diet
  • Too much alcohol consumption (more than 1-2 drinks per day)
  • Stress
  • Older age
  • Genetics.
Blood pressure (BP) category
Systolic BP (upper number)
Less than 120
Less than 80
Less than 80
High blood pressure (Stage 1)
High blood pressure (Stage 2)
140 or higher
90 or higher
Blood pressure crisis
Higher than 180
Higher than 120
What does research tell you?

People with a higher level (cervical and upper thoracic) spinal cord injury are more likely to experience a lower blood pressure (by around 20 mmHg) than those with lower level or incomplete spinal cord injury during the first month of rehabilitation, which may persist in the longer term. 

Effects of a spinal cord injury on the autonomic nervous system

Autonomic dysreflexia is a medical condition that causes a rapid rise in blood pressure of people with a spinal cord injury, at or above the T6 spinal level. The condition is rare below the T6 spinal level.

Autonomic dysreflexia occurs when there is a problem in your body below the level of your spinal cord injury causing irritation and overactivity in the part of the nervous system responsible for controlling blood pressure. In other words, it is a response by the body when pain and discomfort are experienced, although your spinal cord injury prevents that message from getting through to your brain.

Autonomic dysreflexia is a medical emergency as the high blood pressure can lead to a stroke, fitting or death. It therefore calls for immediate action to find and treat the cause of the Autonomic dysreflexia.

Do you know?

People with a complete spinal cord injury have a much higher incidence of autonomic dysreflexia: 91% with a complete injury versus 27% with an incomplete injury.

Irritation below the level of the spinal cord injury
Signal reaches the injured spinal cord resulting in massive constriction of the blood vessels below the level of injury
Leads to very high blood pressure
Brain detects a sudden rise in blood pressure and attempts to control the rise by sending signals via spinal cord to blood vessels, which are blocked
Signals from brain cannot get through below the level of injury, but a different nerve (called the vagus) tries to compensate
This results in a lowering of the heart rate down to 40-50 beats per minute

Causes of autonomic dysreflexia

Autonomic dysreflexia is most commonly triggered by a cause related to either bladder or bowel, but can be triggered by other stimuli.

Bladder causes

  • Overfull bladder from kinked or blocked catheter or full leg bag
  • Urinary tract infection
  • Kidney stones
  • Procedures such as catheter change or tests where the bladder is distended.

Bowel and abdominal causes

  • Constipation
  • Irritation from rectal examination or
    enema insertion
  • Inflamed haemorrhoids
  • Stomach ulcers, gallstones or appendicitis.

Other common causes include:

Skin causes

  • Excess pressure from contact with hard or sharp objects
  • Pressure injuries (sores)
  • Ingrown toenails
  • Burns
  • Insect bites.

Sexual activity

In males

  • Genital stimulation, especially with a vibrator
  • Orgasm (ejaculation)
  • Problems with the testicles (e.g., pressure on testicles).

In females

  • Menstruation or labour
  • Infections of vagina or uterus.
What does research tell you?

One of the most common causes of autonomic dysreflexia is bladder distension, which alone can account for up to 85% of episodes.

female hand writing results of a blood pressure test with blood test monitor in the background


Quick quiz

You may wish to see how much your knowledge has grown by taking this quick quiz.

Manage problems

Management of autonomic dysreflexia

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Manage a problem ‘just-in-time’

Serious complications can arise if autonomic dysreflexia is not managed in a timely way and/or occurs repeatedly.

You could experience:

  • Changes in the brain’s electrical activity, which can cause fits or seizures.
  • Bleeding in the retina, the light sensitive tissue of the eye, causing severe vision impairment (retinal haemorrhage).
  • Excess fluid in the lungs called pulmonary oedema.
  • Organ damage:
    • Heart attack, which can lead to heart failure.
    • Poor functioning of the kidneys (renal insufficiency), which can lead to kidney failure.
  • A rupture or leak in a blood vessel in the brain, called cerebral haemorrhage.
  • Death.

‘Just-in-time’, or the right care at the right place at the right time, will reduce risk and prevent complications. As a result, you will maintain your quality of life, independence, health and wellbeing.

elderly woman in wheelchair clutching at her chest in pain

Be proactive and take responsibility for managing your own health risks

This involves:

  • Learning to understand why autonomic dysreflexia occurs, what causes it and how to deal with it.
  • Becoming a partner in decision-making with your doctor and other health professionals.
  • Carrying an AD emergency treatment card in your wallet at all times.
  • Developing an individual autonomic dysreflexia management plan.
  • Engaging in ongoing health and wellness activities for preventing autonomic dysreflexia:
    • Maintaining a healthy bladder function.
    • Maintaining a healthy bowel function.
    • Preventing other potential causes of autonomic dysreflexia.
    • Knowing what to do when you have autonomic dysreflexia.
    • Scheduling an annual check-up.

Managing an episode

Self-management tips

Immediate actions to be performed by yourself or a carer:
  1. Sit up, if lying down
  2. Loosen or remove any tight clothing
  3. Search for a cause (check your Bladder first), eliminate cause if possible
  4. Check blood pressure if possible
  5. Call a relative or a friend for help.
Actions if warning signs do not subside and/or blood pressure remains high
  1. Call the emergency number Triple Zero: Dial 000
  2. Keep looking for the cause/s
  3. Monitor your blood pressure every 5 minutes
  4. Take your prescribed medication/s. See next page for details.

What to do when your autonomic dysreflexia subsides?

Monitor for any re-occurrence.

Please note: You may be at risk of another episode in next 24-48 hours.

What to do when problem still persists and blood pressure still remains high?

Call an ambulance.

Dial 000


Autonomic dysreflexia is most commonly triggered by a BLADDER or BOWEL cause. Check for kinks in catheter or blockage to flow or over-full leg bag.

Tight clothing
This commonly include abdominal binders, shoes or leg braces, leg bag strap, external catheter tape, clothes or elastic hose or bandages.

Check regularly for expiry dates.

Keep calm and call for help.

What does research tell you?

  • An acute episode of autonomic dysreflexia can lead to an increased susceptibility to further episodes due to an excess of chemicals, called catecholamines, circulating in your blood. These chemicals make it more likely for autonomic dysreflexia to be triggered by stimuli like muscle stretches, bowel care or other activities that usually do not aggravate autonomic dysreflexia.
  • Monitoring of your blood pressure for appropriately 48-72 hours after an episode of autonomic dysreflexia is recommended. During this time any medical procedures should be kept to a minimum.


Medications for treating autonomic dysreflexia

Before starting on any medication, always read the instructions and ensure this medication is safe to take with other medications. Check the dose and possible side effects, as well as the expiry date and contraindications.

Autonomic dysreflexia is commonly treated with two medications that can be self-administered:

  • Glyceryl Trinitrate (GTN) is manufactured as a mouth spray, a chewable tablet and a skin patch. You need a prescription from your doctor.
  • Other blood pressure medications. Captopril is manufactured as a chewable tablet. You need a prescription from your doctor.

How to take Glyceryl Trinitrate (GTN)

nitroglycerin aerosol spray packaging sample

One spray under tongue
Dose: 400mcg per spray
Product name: Nitrolingual pump spray


Bottle of anginine
Half tablet under tongue Dose: 300mcg per tablet Product name: Anginine


patch for How to take Glyceryl Trinitrate (GTN) packaging sample

One patch on chest or arm
Dose: 5mg per 24 hours
Product name: GTN transdermal patch

Check blood pressure in 5 to 10 minutes

No effect or little effect
on your high blood pressure


Low or normal
blood pressure


Second spray under tongue
Dose: 400mcg per spray

Spit out residual spray



Take other half tablet under tongue
Dose: 300mcg per tablet

Spit out residual tablet



Do not remove the patch
Dose: 5mg per 24 hours

Remove the patch

Low or normal
blood pressure


Spit out residual spray


Spit out residual tablet


Remove the patch

Alert! icon

Be aware that up to 3 doses of spray or tablet can be given in 30 minutes.

Do not take GTN if you have used medications for erectile dysfunction, such as Sildenafil (Viagra), Vardenafil (Levitra) or Tadalafil (Cialis) in the last 3-4 days. 

Do not take medications for erectile dysfunction, such as Sildenafil (Viagra), Vardenafil (Levitra) or Tadalafil (Cialis), within 24 hours after taking GTN.

How to take Captopril

Captopril will sometimes be prescribed instead of GTN because:

  • GTN spray, tablets or patch are unavailable.
  • You have used Viagra, Vardenafil or Cialis for erectile dysfunction within the last 3-4 days so you are not allowed to take GTN due to the risk of it lowering your blood pressure too much.

Dose: 25mg per tablet
Brand name: Capoten

Takes about 3 minutes to dissolve

Check blood pressure in 15 minutes

No effect or little effect
on your high blood pressure

Low or normal
blood pressure

Dial 000

Spit out the residual tablet

Low or normal
blood pressure

Spit out the residual tablet

What does research tell you?

Nifedipine bite-and-swallow capsules, previously used for treating autonomic dysreflexia in Australia, are no longer available due to risks associated with use in people treated for other conditions, such as chest pain (angina) or high blood pressure (hypertension).

Recurrent autonomic dysreflexia

This refers to an episode of autonomic dysreflexia that recurs soon after an initial episode because the underlying cause has not been resolved, got worse or you may be more at risk.

After a severe and prolonged episode, certain activities that do not usually cause autonomic dysreflexia, e.g., muscle stretching or bowel care, can lead to symptoms. 

How to self-manage recurrent autonomic dysreflexia

  • Monitor your symptoms and blood pressure for at least 4 hours after resolution of the autonomic dysreflexia episode to ensure a rise in blood pressure does not recur.
  • Autonomic dysreflexia may resolve due to taking medication, not because the underlying cause has been resolved. Recurrence may be expected if the underlying cause has not been correctly identified and resolved.

Frequent autonomic dysreflexia

This refers to episodes of autonomic dysreflexia that occur on a regular basis.
  • Regularly monitor your symptoms and know your baseline blood pressure.
  • Autonomic dysreflexia may occur frequently because of an underlying cause.
  • If you have frequent episodes of autonomic dysreflexia, consult with your doctor to investigate and rule out any underlying causes, which may include:
    • Recurrent urinary tract infections
    • Bladder and kidney stones
    • Bowel constipation
    • Other medical conditions.

Prevent problems


How to prevent problems and maintain a healthy autonomic nervous system

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Self-management tips

First and foremost things to do

blood pressure monitor

Record your normal blood pressure

Autonomic Dysreflexia Emergency Card

Always carry your personalised autonomic dysreflexia emergency card with you

Bottle of anginine

Ask your doctor to prescribe medicine for autonomic dysreflexia to keep on hand, and check expiry dates regularly

Healthy tips to prevent Autonomic Dysreflexia

  • Ensure catheter tube is not kinked and flowing freely
  • Drink plenty of water to prevent catheter blockage
  • Perform regular intermittent catheterisation
  • Regularly empty your leg bag.

  • Ensure catheter tube is not kinked and flowing freely
  • Drink plenty of water to prevent catheter blockage
  • Perform regular intermittent catheterisation
  • Regularly empty your leg bag.

  • Eat a well-balanced diet
  • Take medications as prescribed
  • Drink plenty of water to prevent constipation
  • If constipated, perform evacuation gently
  • Have a regular bowel routine.

fruit and nuts in the shape of a glass with straw


  • Perform regular pressure relief and inspect skin at least daily
  • Check equipment (including cushion, wheelchair and other surfaces) regularly
  • Do not wear tight clothes and shoes
  • Avoid potential causes for burns, such as carrying hot liquids in your lap or sitting too close to a fire or heater
  • Practice good foot care to prevent ingrown toenails.

image of an ingrown toenail on a foot

Important Notes

Be aware of other stimuli such as a bone fracture, extreme temperatures or sexual activity.

“Don’t be afraid to seek information for yourself.”

Person with spinal cord injury

Take home messages

blood pressure monitor

your GP to check your blood pressure at every visit so you know your normal blood pressure

If you are at risk of autonomic dysreflexia, consider having a blood pressure monitor at home.

blood pressure monitor
Autonomic Dysreflexia Emergency Card

to carry your autonomic dysreflexia emergency card with you

If you do not have one, ask your spinal cord injury care provider to arrange one for you.

doctors checklist with stethoscope and pen lying on top
illustration of an ambulance back view

autonomic dysreflexia as an emergency

Dial 000 for an ambulance if your autonomic dysreflexia does not resolve.

mobile phone with triple zero on screen

Check if you have a problem

Check if you have a problem

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Warning signs

The following warning signs are indicators that there may be a serious problem. Autonomic dysreflexia occurs when you experience a sudden rise in your blood pressure of 20 mmHg or more above your normal blood pressure.

Please note: Your normal blood pressure may be quite low at other times, so the early rise in blood pressure may still be within the range considered normal for a person without a spinal cord injury.

The signs and symptoms of autonomic dysreflexia include any of the following:

icon of person with lightening bolt on head
Pounding headache
icon of nasal area
Stuffy nose
icon of person with drip over their head
Profuse sweating
icon of eye with cross through it and drop in centre
Blurred vision
icon of torso covered in rash
Blotchiness or rash over skin
icon of person laughing over toilet
Nausea or feeling unwell
icon of arm with goosebumps
Goosebumps and chills
icon of person blowing out a small amount of air
Shortness of breath
or feeling anxious

Management index

Autonomic dysreflexia can vary in its duration and/or frequency as described in the table below.

Autonomic dysreflexia resolves quickly
Autonomic dysreflexia does not resolve – this is an emergency
Autonomic dysreflexia
Cause identified, an episode of autonomic dysreflexia that resolves quickly (and does not recur)

An episode of autonomic dysreflexia that does not subside and/or blood pressure remains high

Recurrent autonomic dysreflexia

Frequent autonomic dysreflexia

There is no such thing as mild, moderate or severe autonomic dysreflexia. Every case of autonomic dysreflexia is an emergency.

If warning signs do not subside and/or blood pressure remains high, call 000 for an ambulance.