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Autonomic Dysreflexia

Patient Information

Patient Information on Autonomic Dysreflexia and SCI


Pathophysiology of AD

Pharmacological Management of Acute AD

Management of AD

Prevention Strategies

Krassioukov A, Blackmer J, Teasell RW, Eng JJ (2018). Autonomic Dysreflexia Following Spinal Cord Injury. In Eng JJ, Teasell RW, Miller WC, Wolfe DL, Townson AF, Hsieh JTC, Connolly SJ, Noonan VK, Loh E, Sproule S, McIntyre A, Querée M, editors. Spinal Cord Injury Rehabilitation Evidence. Version 6.0. Vancouver: p 1- 50.


Key Points

  • The identification and removal of the possible trigger and subsequent decrease of afferent stimulation to the spinal cord is the most effective prevention strategy in clinical practice.
  • Botulinum toxin injections into the detrusor muscle or external urethral sphincter seem to be a safe and valuable therapeutic option in SCI patients who perform clean intermittent self-catheterization and have incontinence resistant to anticholinergic medications. Its use in the prevention of AD is less well defined.
  • Capsaicin and its analogue, resiniferatoxin, are effective in the management of AD in patients with SCI.
  • Anticholinergics do not appear to be sufficient for the management of AD in SCI.
  • Sacral deafferentation may reduce AD during urodynamic investigations.
  • Urinary bladder surgical augmentations may diminish or resolve episodes of AD.
  • Lidocaine anal block can limit the AD response in susceptible patients undergoing anorectal procedures.
  • Topical lidocaine may prevent AD during digital bowel stimulation but does not prevent AD during anorectal procedures.
  • Adequate anesthesia (spinal or epidural if possible) is needed with vaginal delivery, Caesarean delivery or instrumental delivery.
  • Anesthesiologists and surgeons dealing with SCI patients must know how to recognize the AD syndrome, how to prevent its occurrence and how to manage it.
  • Epidural anesthesia is preferred and effective for most women with AD during labour and delivery.
  • Anesthesia should be used during surgical procedures in individuals with SCI despite apparent lack of sensation.
  • Topical anesthetic is not effective for the prevention of AD during FES.
  • Nifedipine may be useful to prevent or control AD in SCI individuals; however, serious adverse effects from its use may occur similar to those reported in other populations.
  • Nitrates are commonly used in the control of AD in SCI; however, no studies have been done to show their effectiveness or safety in SCI.
  • Preliminary evidence suggests that captopril is effective for the management of AD in SCI.
  • There is limited evidence for the use of Terazosin as an agent for control of AD in SCI individuals.
  • Prazosin can prophylactically reduce severity and duration of AD episodes in SCI.
  • It is not known whether Phenoxybenzamine is effective for the management of AD in SCI.
  • Prostaglandin E2 is effective for reducing BP responses during eletroejaculation.
  • Sildenafil has no effect on AD responses in men with SCI during ejaculation.

1.0 Executive Summary

What is autonomic dysreflexia?

Autonomic dysreflexia (AD) is a potentially life-threatening condition that can affect people who have had a spinal cord injury at the level of T6 or above (sometimes as low as T8, though rare – nerves from T6 control a large group of blood vessels that supply the lower body and many of the organs of the abdomen, such as the stomach and intestines; generally speaking, the higher the level of injury, the more likely it is that the circulatory system will be affected1,2,3. People with complete injuries are more often affected than people with incomplete injuries.

AD is a medical emergency that requires an immediate response. It occurs more often in the long term phase of SCI, but can happen in the first few months after injury as well. Episodes of autonomic dysreflexia are usually brief in duration and in most cases have an identifiable trigger that causes the episode3,4,5,6.

What are the signs and symptoms of autonomic dysreflexia?

The main sign of autonomic dysreflexia is a sudden rise in blood pressure. An increase of 20 to 30 mmHg above your patient’s normal systolic blood pressure is considered to indicate autonomic dysreflexia. Since the normal blood pressure of a person with a spinal cord injury can often be 15 to 20 mmHg lower than a person without a spinal cord injury, blood pressure can be in the range of ‘normal’ or ‘slightly elevated’ and still indicate an episode of AD. This rise in blood pressure is usually accompanied by other symptoms. These can range from not feeling anything or having some mild discomfort and a headache to a life-threatening emergency where symptoms can be severe. Symptoms can range from not feeling anything or having some mild discomfort and a headache to a life threatening emergency where symptoms can be severe. It is important for patients and clinicians to be able to recognize the symptoms of AD so you can act accordingly. Clinicians should also be aware that in some individuals with SCI, AD could occur without any symptoms and this condition known as a silent or asymptomatic AD 7,8. While autonomic dysreflexia happens most often in the long term stage after injury, it can happen on occasion in the immediate post-injury period.

Signs and symptoms of autonomic dysreflexia:

  • Sudden rise in blood pressure of 20 to 30 mmHg above the person’s normal systolic blood pressure (main symptom)
  • Change in heart rate – usually a slow heart rate which can sometimes become rapid or irregular
  • Pounding or throbbing headache
  • Profuse sweating, flushing or blotching of the skin above the level of injury
  • Goosebumps or hair standing on end above the level of injury
  • Dry and pale skin below the level of injury • Increased number and severity of muscle spasms
  • Metallic taste in the mouth
  • Feeling anxious or a feeling of impending doom
  • Nasal congestion
  • Blurred vision
  • Seeing spots
  • Nausea
  • Difficulty breathing or a feeling of chest tightness

Why does autonomic dysreflexia happen?

Autonomic dysreflexia is the result of overactivity of the sympathetic nervous system in response to a strong sensory stimulus below the level of injury. This stimulus is often something that is noxious or irritating, such as a wound or tight clothing, but can also be a normal function of the body, such as an overly full bladder or bowel. In response to this stimulus, the sympathetic nervous system signals the arteries to constrict, which increases blood pressure. This increase in blood pressure is followed by a slowing of the heart rate which can then sometimes become irregular. Because of the damage to the spinal cord, the body can’t effectively control the blood pressure and restore it to normal, resulting in autonomic dysreflexia. The most common trigger is irritation of the bladder or bowel.

Triggers of autonomic dysreflexia


Bladder issues

  • Urinary tract infection
  • Urinary retention
  • Blocked catheter
  • Overfilled collection bag
Bowel issues

  • Distention or irritation of the bowel
  • Constipation or impaction of the bowel
  • Hemorrhoids
  • Infection or irritation of the bowel
Skin issues

  • Pressure ulcers
  • Extreme heat or cold
  • Pressure or pinching of the skin
  • Ingrown toenails
  • Burns
  • Tight clothing
  • Any direct irritant below the level of the injury
Sexual activity and reproductive processes

  • Overstimulation
  • Reproductive activity
  • Menstrual cramping
  • Labor and delivery
Other causes

  • Heterotopic ossification
  • Acute abdominal conditions (such as ulcers)
  • Fractures


What should I do if my patient has an episode of Autonomic Dysreflexia?

Autonomic Dysreflexia is a medical emergency and requires immediate treatment. The most effective treatment strategy is to identify the trigger of the episode and reduce the stimulation that is causing it. The goal of intervention is to alleviate symptoms and avoid the complications associated with uncontrolled hypertension9,10,11,12. If the conservative treatments for autonomic dysreflexia are not effective in reducing blood pressure and it remains at or above 150 mmHg, drug treatments are used. This involves the use of fast-acting anti-hypertensive drugs to rapidly lower the elevated blood pressure.

Steps to take for patient with autonomic dysreflexia: 

1. Move patient into an upright sitting position

2. Check blood pressure, and recheck every 5 minutes

3. Loosen tight clothing

4. Search for and eliminate the cause of the incident where one can be identified

a. Check bladder

b. Check bowel

c. Check skin

5. Seek medical attention if there is no reduction in blood pressure after following these steps

Source: Consortium for Spinal Cord Medicine 2001.

Which prevention methods are effective?

Preventing an AD episode is far more effective than treating one13. Researchers have done studies on a number of different treatments to see which ones are helpful in preventing incidents of autonomic dysreflexia14,15.

Capsaicin: Studies have shown that administering the chemical compound Capsaicin, and its more concentrated cousin Resiniferatoxin, into the bladder by a catheter, can decrease the number of episodes of AD during bladder procedures16,17,18.

Surgical bladder augmentation: Some early evidence suggests that surgery to augment the bladder may also reduce or resolve episodes of AD19,20,21,22.

Sacral denervation: Sacral deafferentation surgery may reduce bladder-related episodes of AD23,24.

Botulinum toxin: One study has demonstrated that injections of Botulinum toxin into the muscles of the bladder is effective in reducing episodes of AD25, which is supported by previous findings26,27,28,29,30.

Anticholinergic medications: The use of anticholinergic medications does not appear to be effective in preventing AD during bladder procedures31.

Lidocaine: A lidocaine anal block has been found to limit the AD response in patients undergoing anorectal procedures. Topical lidocaine may prevent AD during digital bowel stimulation, but not during anorectal procedures32,33,34.

Anesthesia for use during pregnancy and labour: Studies have found that the use of adequate anesthesia (spinal or epidural if possible) is needed with vaginal, Caesarean, or instrumental delivery to prevent AD during labour. Epidural anesthesia is preferred and effective for most women with SCI35,36,37,38.

Anesthesia for use during general surgery: Anesthesia should be used during surgery for people with SCI despite the apparent lack of sensation, in order to prevent AD. Anesthesiologists and surgeons dealing with patients with SCI need to be able to recognize, prevent and manage it39,40.

Topical anesthesia during functional electrical stimulation (FES) treatment: Studies have found that the application of topical anesthesia is not effective in preventing AD during FES treatment. More research is required to understand how to prevent AD during FES41.

Stoma surgery: There is preliminary evidence that stoma surgery may reduce the number of incidents of autonomic dysreflexia, if other treatments have failed to improve management of neurogenic bowel42.

Where can I find more information?

For more information please click through the rest of the Autonomic Dysreflexia chapter (https://scireproject.com/evidence/rehabilitation-evidence/autonomic-dysreflexia-re/) and consult a Doctor who specializes in SCI and/or Cardiovascular issues.