Autonomic Dysreflexia in Spinal Cord Injury

  1. Disease/Disorder:
    • Autonomic dysreflexia (AD) in spinal cord injury (SCI) is a potentially life-threatening syndrome characterized by an exaggerated response of the autonomic nervous system to a stimulus originating below the level of injury, resulting in a sudden increase in blood pressure.
    • Any stimulus below the level of injury may cause AD in SCI, the most common being bladder or bowel distention.
    • Genitourinary causes include bladder or urethral distention, detrusor sphincter dyssynergia, urinary tract infections, nephrolithiasis, epididymitis, testicular torsion, vaginal dilation (including labor), penile stimulation, and intercourse.
    • Gastrointestinal causes include bowel distention or impaction, acute abdomen (including appendicitis and cholecystitis), gastroesophageal reflux disease, gastric ulcers, and anal fissures.
    • Other causes include ingrown toenails, pressure ulcers, sunburn, deep venous thrombosis, and fractures.
    • Procedures that cause AD in SCI include urodynamics, cystoscopy, vibratory stimulation, electroejaculation, and functional electrical stimulation.
    Epidemiology including risk factors and primary prevention
    • AD in SCI typically occurs in people with levels of injury at T6 or higher, although it has been reported with levels of injury as low as T10.
    • The incidence of AD in SCI reported in the literature ranges from 48% to as high as 90% depending on the characteristics of the SCI population being studied.
    • The focus of prevention of AD in SCI has been on educating patients to recognize its signs and symptoms and removing triggering factors related to the bladder. Most important is to help a patient acquire a consistent and reliable method of bladder drainage and prevention of bladder overdistention.
    • Although most common in the setting of traumatic SCI, AD has also been reported in non-traumatic disorders involving the spinal cord. For example, there have been a few case reports of AD in patients with multiple sclerosis.
    • AD in SCI results from loss of supraspinal control of the sympathetic nervous system.  During an episode of AD, sympathetic activity predominates below the level of injury and parasympathetic activity predominates above the level of injury.
    • AD begins with a strong sensory input from peripheral nerves below the level of injury, which ascend through the spinothalamic tract and posterior columns of the spinal cord.  This stimulus incites a reflex sympathetic response from the adjacent preganglionic sympathetic neurons located in the intermediolateral cell column below the level of injury.  This sympathetic surge ultimately leads to widespread vasoconstriction below the level of injury, most significantly in the splanchnic vasculature.  There is an increase in peripheral arterial blood pressure, potentially leading to hypertensive crisis.
    • The brain responds in two ways to the increase in blood pressure:
      • The brainstem attempts to reduce blood pressure via the intact vagal nerve, which, via parasympathetic input, might result in bradycardia, particularly if the injury is caudal to the 4th thoracic spinal segment.  Regardless, bradycardia, in itself, is not effective in reducing blood pressure against the powerful vasoconstriction in the splanchnic vasculature.
      • Descending inhibitory impulses are sent down the spinal cord from the brain, but are not able to reach most of the sympathetic outflow due to the spinal cord injury.  This results in a parasympathic response above the level of injury, including dilation of blood vessels in the brain, but not an overall reduction in blood pressure.
    • The development of autonomic dysreflexia is correlated with aberrant sprouting of peptidergic afferent fibers into the spinal cord and denervation hypersensitivity of adrenergic receptors below the injury.
    Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)
    • AD is rarely detected earlier than one month after an acute SCI.
    • AD usually presents for the first time between 6 months and 1 year after an acute SCI.
    Specific secondary or associated conditions and complications
    • Seizures, intracerebral hemorrhage, subarachnoid hemorrhage, and myocardial infarction are potential complications of AD in SCI.  There have been case reports of neurogenic pulmonary edema associated with AD in SCI.
    • Numerous pathologic arrhythmias have been associated with AD, including premature ventricular contractions and second degree AV block.
  2. Essentials of Assessment
    • Symptoms vary among individuals but often include a combination of, headache, flushing and profuse sweating above the level of injury, nasal congestion, blurry vision, and anxiety.
    • The headache is usually pounding and located in the frontal and occipital areas.
    • Some patients are asymptomatic.
    Physical examination
    • Physical findings, in general, are due to sympathetically mediated effects below the level of injury and parasympathetically mediated effects above the level of injury, although sacral parasympathetic stimulation can occur as well (see letter e).
    • An increase in blood pressure of 20 to 40 mmHg or higher above baseline for adults, and 15 mm Hg or higher in adolescents and children, is the most common finding. 
    • Bradycardia is present in a classic presentation, particularly if the injury is caudal to the 4th thoracic spinal segment, but this is not always the case.  Tachycardia occurs often, if not more commonly.
    • Mydriasis may occur if the level of injury is above T1.
    • Penile erection and seminal fluid emission may occur due to sacral parasympathetic stimulation.
    • Pallor and piloerection occur below the level of injury.
    Laboratory studies
    • Laboratory studies are not commonly used to evaluate AD, and are obtained only after the most common etiologies (bladder distention and bowel impaction).
    • The choice of laboratory studies depends on the clinical evaluation.  A complete blood count (CBC), for example, might be needed to evaluate for leukocytosis if a urinary tract infection (UTI) is suspected as the etiology for AD.
    • Imaging studies are commonly used to evaluate AD in SCI, but only after the most common etiologies (bladder distention and bowel impaction) have been ruled out, and are based on clinical findings.
    • Plain x-rays may be used to screen for factures, nephrolithiasis, or gallstones.
    • Lower extremity ultrasound may be used to screen for DVT.
    Supplemental assessment tools
    • Currently no assessment tools specific for evaluating AD in SCI are available.
    • The International Spinal Cord Society has developed an autonomic standards assessment form, which includes a section on the autonomic control of blood pressure.
  3. Rehabilitation Management and Treatments
    Available or current treatment guidelines
    • The Consortium for Spinal Cord Medicine has published clinical practice guidelines titled Acute Management of Autonomic Dysreflexia: Adults with Spinal Cord Injury Presenting to Health-Care Facilities.1 It provides an algorithm as a summary of its 24 treatment recommendations. There is also a consumer version of this guideline.
    At different disease stages
    • The most basic tenet of treatment for AD in SCI is rapid recognition of its signs and symptoms and subsequent prompt removal of the precipitating factor.
    • Blood pressure monitoring is paramount.  Once symptoms of AD are identified, the patient’s blood pressure must be checked immediately.  During an acute episode of AD, the blood pressure should be monitored frequently.  Once the blood pressure is normalized, the blood pressure should be monitored for at least 2 hours to ensure that AD does not recur.
    • The following steps are recommended for the initial evaluation of AD in SCI:
      • If the blood pressure is elevated and the patient is supine, sit the patient up and loosen any restrictive clothing or devices.
      • If the blood pressure continues to be elevated, evaluate the urinary system (the most common cause of AD in SCI).
        • Catheterize the patient if an indwelling urinary catheter is not in place.  If available, instill 2 percent lidocaine jelly into the urethra and wait several minutes before inserting the catheter.
        • If the individual has an indwelling catheter, check the system for kinks or obstructions.  If the catheter appears to be blocked, gently irrigate the bladder with a small amount of body temperature fluid, such as normal saline.  If the catheter is not draining and the blood pressure is still elevated, remove and replace the catheter, instilling 2 percent lidocaine jelly into the urethera before doing so.  Avoid tapping on or manually compressing the bladder. 
      • If the blood pressure continues to be elevated, evaluate the lower bowels for fecal impaction.
        • If the blood pressure is above 150 mm Hg, consider pharmacologic management with an antihypertensive agent that has a rapid onset and short duration of action in order to reduce the systolic blood pressure prior to checking for fecal impaction.
        • Instill a topical anesthetic agent such as 2 percent lidocaine jelly generously into the rectum and wait approximately 5 minutes.  Then insert a lubricated finger into the rectum and check for the presence of stool, and, if present, gently remove it.
      • If the blood pressure continues to be elevated, consider admitting the patient to a hospital for pharmacologic treatment of blood pressure and evaluation for other causes of the dysreflexia.
    • Pharmacologic treatment
      • There are no studies determining the most effective pharmacologic agent to use to treat AD.
      • The most commonly used agents are nitrates and nifedipine.
        • If 2 percent nitroglycerin ointment is used, 1 inch may be applied to the skin.  Nitrates are contraindicated in patients taking cGMP-phosphodiesterase type 5 inhibitors.
        • Nifedipine should be used with caution in patients who cannot tolerate a hypotensive episode with reflex tachycardia, such as elderly patients with coronary artery disease.
      • Other agents that have been used include hydralazine, mecamylamine, diazoxide, phenoxybenzamine, beta-blockers, terazosin, prazosin and captropril.
    Coordination of care
    • Patients with SCI at risk for AD can carry a wallet-sized information card with them and provide it to emergency, urgent care and other healthcare providers.  This card can help providers not familiar with AD recognize it and follow a basic treatment protocol.
    • If a pregnant women with a spinal cord injury at or above T6 presents with signs or symptoms of AD, consider coordinating care with an obstretric healthcare provider.
    Patient & family education
    • Patients and families should be educated on the signs and symptoms of AD during rehabilitation by a healthcare provider.
    Translation into practice: practice "pearls"/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills
    • Always consider AD in the evaluation of elevated blood pressure or a headache in a person with SCI.
  4. Cutting edge/emerging and unique concepts and practice
    Cutting edge concepts and practice
    • There are ongoing efforts to establish more objective criteria (for example using urodynamics or measuring sympathetic skin responses) for establishing the presence of AD and to characterize its severity.
  5. Gaps in the evidence-based knowledge
    Gaps in the evidence-based knowledge
    • Given the improvement in recognizing and treating AD in SCI, it will be important to establish current incidence and prevalence rates. When more objective criteria are developed for diagnosing AD, new and established treatments can be evaluated and compared more rigorously.
    1. Paralyzed Veterans of America/ Consortium for Spinal Cord Medicine.  Acute management of autonomic dysfunction: adults with spinal cord injury presenting to health-care facilities. Washington (DC): Paralyzed Veterans of America (PVA); 2001 Jul. 29 p. [138 references].  Available at: National Guidelines Clearinghouse. http://www.guideline.gov. NGC: 002190. Accessed May 10, 2011.\


    Other Resources

    Karlsson AK.  Autonomic dysreflexia. Spinal Cord. 1999;37:383-391.

    Krassioukov A, Warburton DE, Teasell R, Eng JJ, Spinal Cord Injury Rehabilitation Evidence Research Team.  A systematic review of the management of autonomic dysreflexia after spinal cord injury. Arch Phys Med Rehabil. 2009;90(4):682-95.

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