Editor-In-Chief: C. Michael Gibson, M.S., M.D. 
Synonyms and keywords: Autonomic hyperreflexia; autonomic dystonia
Autonomic dysreflexia is a massive sympathetic discharge that can occur in association with spinal cord injury or disease (e.g. multiple sclerosis). It is triggered by a variety of noxious stimuli, including bladder distension, irritation to the urinary tract, skin ulcers, fractures, abdominal emergencies, bowel impaction and uterine contractions. Sometimes the triggering factor is obscure.
The risk is greatest with cervical spinal cord lesions and is rare with lesions below T6. It has rarely been reported in spinal cord lesions as low as T10. The first episode may occur weeks to years after spinal cord injury takes place, but most people at risk (80%) develop their first episode within the first year after injury. The diagnosis is usually not subtle, although asymptomatic events have been documented. This condition is distinct and usually episodic, with the patient experiencing remarkably high blood pressure (often with systolic readings over 200 mm.Hg), intense headaches, profuse sweating, facial erythema, goosebumps, nasal stuffiness, and a "feeling of doom". An elevation of 40 mm. Hg. over baseline systolic should be suspicious for dysreflexia.
Older patients with very incomplete spinal cord injuries and systolic hypertension without symptoms are usually experiencing essential hypertension, not autonomic dysreflexia. Aggressive treatment of these elderly patients with rapidly acting antihypertensive medications can have disastrous results.
Autonomic dysreflexia differs from autonomic instability, a term used to describe the variety of modest cardiac and neurological changes that accompany a spinal cord injury, including bradycardia, orthostatic hypotension, and ambient temperature intolerance.
Proper treatment of autonomic dysreflexia involves immediate determination and removal of the triggering stimuli. Often, sitting the patient up and dangling legs over the bedside can reduce blood pressures below dangerous levels and provide partial symptom relief. Tight clothing and stockings should be removed. Catheterization of the bladder, or relief of a blocked urinary catheter tube may resolve the problem. The rectum should be cleared of stool impaction, using anesthetic lubricating jelly. If the noxious precipitating trigger cannot be identified, drug treatment is sometimes needed until further studies can identify the cause.
Drug treatment includes the rapidly acting vasodilators, including sublingual nitrates or oral clonidine. Topical nitropaste is a convenient and safe treatment -- an inch or two can be applied to the chest wall, and wiped off when blood pressures begin to normalize. Autonomic dysreflexia is abolished temporarily by spinal or general anaesthesia. These treatment are used during obstetric delivery of a woman with autonomic dysreflexia.
Autonomic dysreflexia can become chronic and recurrent, often in response to longstanding medical problems like soft tissue ulcers or hemorrhoids. Long term therapy may include alpha blockers or calcium channel blockers.
Autonomic dysreflexia is a medical emergency. Complications of severe acute hypertension can include seizures, pulmonary edema, myocardial infarction or cerebral haemorrhage. The cause of autonomic dysreflexia itself can be life threatening, and must also be completely investigated and treated appropriately to prevent unnecessary morbidity and mortality.
The Consortium for Spinal Cord Medicine has developed evidence-based clinical practice guidelines for the management of autonomic dysreflexia in adults, children, and pregnant women. There is also a consumer version of this guideline.
- Allman (2005) Emergencies in Anaesthesia, ISBN 0-19-852099-9, 188
- Lin (2003) Spinal Cord Medicine, ISBN 1-888799-61-7, 477
- Study of the occurrence of autonomic hyperreflexia (AHR) after intradural sacral posterior rhizotomy. UJUS 2009