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04 Nov

What is Autonomic Dysreflexia?

Autonomic dysreflexia[i] (AD) is also known as autonomic hyperreflexia. It describes a situation where the body exhibits an exaggerated reflex response to a problem or stimulus. A person with a high spinal cord injury is likely to be unable to consciously sense and respond to a damaging or irritating stimulus.

The body’s unconscious systems – the autonomic nervous system – respond to the problem, leading to rising blood pressure and other physical responses that can result in rapid deterioration, serious illness, seizures, or stroke. AD occurs in people with high spinal cord injuries – typically at T6 or higher – when the autonomic nervous system cascades this exaggerated and uncontrolled response to a stimulus.

If someone is suspected to have autonomic dysreflexia, this should be treated as a medical emergency, and finding the cause and treating the symptoms should be an immediate priority.

Why does Autonomic Dysreflexia (AD) happen?

People with spinal cord injuries at T6 or higher are most at risk of developing AD, the higher the injury, the higher the risk of AD.

People with high spinal cord injuries can sometimes develop serious physical problems[ii] without becoming directly aware of them or able to locate the site of the issue. The autonomic nervous system[iii] is the system which controls the unconscious activities of our body, things like heart rate, digestive processes and response to illness or irritants.

The autonomic nervous system has two branches which are involved in the development of AD: the sympathetic and parasympathetic nervous systems. They complement and oppose each other to balance the body’s need to respond to stimuli while remaining stable and able to relax appropriately.

The sympathetic nervous system is sometimes referred to as the ‘fight or flight’ system; it responds quickly to stimuli and helps us immediately in situations or, for example, danger or pain. The parasympathetic nervous system – the ‘rest and digest’ system – allows us to temper that response and maintain appropriate calm, enabling rest and normal function.

In people with spinal cord injuries, the balance between these two systems can be impaired and this is the cause of some of the symptoms and syndromes people with spinal cord injuries experience. Nervous system responses to stimuli below the site of injury are not relayed or responded to by the higher nervous system – i.e. the brain – and so can quickly become unbalanced. Add this to a person who can develop physical problems below the site of their injury which they cannot consciously sense or respond to, and we start to see seriously imbalanced autonomic responses – ‘autonomic dysreflexia’.

Autonomic dysreflexia causes uncontrolled hypertension – a dangerously high blood pressure – and can lead to seizures, strokes, and cardiac arrests.


Image courtesy of National Rehabilitation Hospital, Ireland

Causes of autonomic dysreflexia

AD occurs when the body reacts to a problem or stimulus and is not able to temper that reaction by appropriate balance within the autonomic nervous system. It occurs in people with high spinal cord injuries because they are not usually able to consciously identify or locate these issues; and because their autonomic nervous system can be disordered and disrupted by its own response to stimuli.

People with high spinal cord injuries are at direct risk of AD because of their neurological injury, and are also, indirectly, at higher risk of AD because of the results of their neurological injury – a higher likelihood of bowel or bladder dysfunction, for example.

Common triggers for AD[iv] include:

  • Bowel problems – commonly a distended bowel, pressure on the rectum from hard-to-pass stool, or more severe faecal impaction.
  • Bladder dysfunction – such as urinary retention, a blocked catheter, or a urinary tract infection.
  • Injury – which could be from relatively common problems like pressure damage or moisture lesions. Physical trauma such as a fall could also trigger AD, even with no signs of visible injury.
  • Tight clothing or straps – Sometimes loosening a restrictive waistband is enough to remove that irritating stimulus that triggers AD.

AD can also develop as a result of the stimulation of sexual intercourse and can be due to menstruation. It is common in people with high spinal cord injuries during pregnancy and childbirth. Pregnant women with high spinal cord injuries[v] and the people close to them should be extra vigilant over AD symptoms and early signs of labour.

The single biggest risk factor for autonomic dysreflexia is a high spinal cord injury, particularly at T6 or higher.

Some other neurological conditions can make people prone to AD, such as multiple sclerosis or some forms of brain injury.

The best way to reduce a person’s likelihood of developing AD is to identify and monitor their personal risk factors. Good nursing care with attention to bowel, bladder and skin care can eliminate some of the most common risks for AD. Having individually devised care plans identifying specific risk mean that everyone involved can identify risks, triggers, and early signs of AD.

Signs and symptoms

Often, the first symptom that a person with autonomic dysreflexia will report is a severe headache or describe a non-specific feeling of illness. As this can be an early warning sign of AD, it should be taken seriously and investigated further. Other signs to look for in AD include a high blood pressure, accompanied by a low heart rate.

Autonomic Dysreflexia New Zealand Spinal Trust

People with T6 or higher spinal cord injuries often have lower than average baseline blood pressure. Blood pressure that would not be out of range for other people could be significantly out of range for someone at risk of AD. It is important, therefore, to know what someone’s baseline blood pressure is to help identify a blood pressure that is abnormal for an individual. A systolic blood pressure – the first, higher number in a blood pressure reading – which is 20 – 40 mmHg or more higher than usual is a serious concern.

As people with a spinal cord injury typically have no neurological damage above the site of the injury, there can be a sharp demarcation between the appearance of the body above and below the site of injury. More usual signs of illness, such as heat and flushing to the skin, may occur above the site of injury. Conversely, below the site of injury, the skin may become cold and clammy, with goosebumps and possibly mottled skin.

Sometimes the ‘soft signs’ of illness are enough to identify a problem; feeling anxious or lethargic, confused or just generally unwell. The value of having family members or carers present who get to know the individual they are helping look after cannot be understated; knowing a person well means being able to spot when something isn’t right.

Preventing autonomic dysreflexia

The most common causes of AD can usually be prevented by good nursing care. Creating individualised plans of care can help identify risks and alert care teams, close friends and family members to early signs of problems.

Knowing the most likely risk factors for AD for an individual can help everyone to anticipate and avoid problems. Difficulties with the bladder and bowels are the most common causes of AD. This means tackling areas of risk such as:

  • Bladder emptying – People with spinal cord injuries may have a urinary catheter or may rely on other methods of continence care. Noticing when someone’s urine output tails off, if it’s been a long time since they passed urine, or if they have an unusually distended lower abdomen are all signs that formal or informal carers can look for to identify issues before they become serious problems. Catheters can become blocked and may need to be irrigated. Catheter and bladder care should be part of a training programme for anyone who helps care for someone with a high spinal cord injury.
  • Bowel emptying – People with high spinal injuries need careful bowel management; this may include a combination of laxatives and stool softeners, physical bowel management through manual evacuation of stool and good continence care. Monitoring the frequency of bowel movements can help to avoid serious problems such as faecal impaction, painful haemorrhoids, and bowel distension. Bowel problems are such a common cause of AD that NHS England released a patient safety alert[vi] in 2018 to promote understanding of the importance of bowel care in people at risk of autonomic dysreflexia.
  • Skin and pressure area care – People who are unable to make positional changes themselves, and who would be unable to feel developing damage to the skin or tissues need extra care to avoid pressure damage. Pressure damage – ‘bed sores’ – can occur anywhere where pressure acts upon soft tissues – commonly on the buttocks, sacrum, hips or even the bony prominences of the spine. Damage can also occur from tight straps from airway management devices or seatbelts, or even from the action of a catheter rubbing inside the urethra. Poor continence management also makes skin damage more likely. Damaged skin and underlying tissues, infection and fluid loss through wounds can all cause serious illness and trigger AD.
  • Preventing or treating infection – urinary tract infections (UTIs) are common and, again, good catheter care can go a long way towards helping prevent them. Being able to identify and treat a UTI in the early stages can prevent more serious problems. And carers can look out for signs such as an altered odour or colour of the urine. Wound care and management of any other indwelling devices is also an essential part of the caring role.


AD is a medical emergency. It’s important to identify and treat the cause, and that might actually be quite simple – irrigation of a blocked catheter or removal of some hard stool from the rectum may be enough to completely eradicate the irritating stimulus that has triggered the AD. Even if the cause can be easily identified and treated at home, however, the person experiencing AD symptoms still needs emergency medical care. Once the autonomic nervous system has been triggered, the symptoms go beyond the cause and may not resolve without treatment. People with AD need close observation, including ongoing blood pressure and heart rate monitoring.

Treatment for AD[vii], aside from identifying and removing the trigger, is to manage blood pressure. This may be through such simple methods as positional changes – going from a lying to sitting position can be enough to drop the blood pressure and improve the outlook. It may be necessary to use medications to bring the blood pressure down, and management of a very slow heart rate can include changes in medications. Sometimes a doctor may recommend a cardiac pacemaker[viii] if a profoundly slow heart rate is causing further problems.

Sometimes it is harder to identify the initial trigger, and in some people a trigger can be as simple, but easily overlooked, as restrictive clothes. At times, the trigger is less simple, such as the physical changes in pregnancy, and will require careful management and the input of specialists.

Living with the risk of autonomic dysreflexia

Monitoring for changes and managing some of the features of AD can be life-saving. And everyone who takes part in the care of someone with a high spinal injury should be able to identify risks and early signs of AD. Informal carers and the members of a formal care package can all help to prevent or manage this serious condition. Early identification and prompt treatment of the causes and features of autonomic dysreflexia saves lives.

There are now lots of resources online to help people learn more about autonomic dysreflexia, along with support groups and specialist services for people with spinal cord injury. These can be a helpful place to start. The best way to avoid and manage serious complications after a high spinal cord injury is through nursing and care teams with specialist training in the care of people with spinal cord injuries.

Having a full time care team who are dedicated to one individual client means that everyone involved is able to identify anything out of the ordinary and treat problems early. A care provider which enables their client to have a dedicated, full time team can provide a package of training tailored to the needs of that individual, meaning the most specialised possible care. Continuity of care and the chance to develop strong, long-term relationships are key in the prevention of serious problems, as well as overall quality of life for everyone involved.


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[i]Royal National Orthopaedic hospital. Autonomic Dysreflexia.

[ii]British Association of Spinal Cord Injury Specialists (BASCIS). Multidisciplinary Association of Spinal Cord Injury Professionals (MASCIP) Spinal Injuries Association (SIA) (2017). Statement on Autonomic Dysreflexia

[iii]Sharif, H., & Hou, S. (2017). Autonomic dysreflexia: a cardiovascular disorder following spinal cord injury. Neural Regeneration Research12(9), 1390.

[iv] Allen, K. J., & Leslie, S. W. (2019). Autonomic dysreflexia. In StatPearls [Internet]. StatPearls Publishing.

[v] Soh, S. H., Lee, G., & Joo, M. C. (2019). Autonomic dysreflexia during pregnancy in a woman with spinal cord injury: a case report. Journal of International Medical Research47(7), 3394-3399.

[vi]NHS Improvement (2018) Resources to Support Safer Bowel Care for Patients at Risk of Autonomic Dysreflexia. NHS Improvement Patient Safety Alert.

[vii] Gall, A., Turner-Stokes, L., & Guideline Development Group. (2008). Chronic spinal cord injury: management of patients in acute hospital settings. Clinical medicine8(1), 70.

[viii]Oh, Young-Min, and Jong-Pil Eun. “Cardiovascular dysfunction due to sympathetic hypoactivity after complete cervical spinal cord injury: a case report and literature review.” Medicine vol. 94,12 (2015): e686.