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What is it?
  • A life-threatening syndrome that can occur in individuals with cord injuries above T6 (most common in quadriplegia). 
  • Develops after resolution of initial spinal shock (after spinal cord reflexes return) and continues for the rest of their lives.
  • Triggered by any noxious stimulous (full bowel or bladder, temperature change or painful stimulus)
  • Autonomic dysreflexia is a pathologic response to pain or other noxious stimuli, and is characterized by sympathetic activation (vasoconstriction and hypotension)
  • Incomplete inhibition of the response occurs above the level of the injury (with facial flushing, vasodilation and sweating) with peristent activation below the level of the injury (ongoing hypertension and vasoconstriction below the level of the lesion).  This will persist until the casuse of the autonomic dysreflexia is removed
  • Distention or contraction of the bladder or bowel, or stimulation of skin or pain receptors triggers a sympathetic response (from intact autonomic reflex arc) below the level of the lesion.
  • The release of catecholamines causes vasoconstriction and hypertension. 
  • Hypertension stimulates baroreceptors in the carotid sinus, aorta and cerebral vessels.  This causes the parasympathetic nervous system to be stimulated, which attempts to restore the BP back to normal.  There is inhibition above the lesion with a slowing of the heart rate and vasodilation above the level of the lesion. 
  • Inhibition messages are unable to relax the blood vessels below the cord lesion which causes persistent hypertension.
  • Vasoconstriction below the level of the cord injury causes the hypertension to persist. 
SIgns and Symptoms
  • Hypertension (only needs to be 20-30 mmHg above baseline; a low baseline BP is common among patients with chronic spinal cord injury). 
  • Hypertension  and vasoconstriction persists below the level of the cord injury. Skin is cold and clammy below the lesion.
  • Vasodilation above the level of the cord injury causes facial flushing, headache, nasal congestion, blurred vision, nausea and diaphoresis. 
  • Inhibition causes bradycardia.
  • Pilomotor spasm (goose flesh) can also occur. 
  • Horner's is a less common finding that can occur with autonomic dysreflexia.  It is caused by dysruption of the sympathetic pathways.  Sympathetic stimulation of the pupil causes dilation; loss of sympathetic causes pupillary constriction usually on one side. This can cause blurred vision.  Horner's also causes eyelid drooping and loss of sweating of the face on the side of the constricted pupil.
  • Find and remove cause.  Possible causes include:
    • bladder distention 
    • bladder infection
    • fecal impaction
    • cold or draft on the skin
    • tight shoe lace
    • pressure sores
    • sharp objects pressing on skin
    • ingrown nails
  • Treat hypertension:
    • calcium channel blockers such as nifedipine (biting down on a nifedipine gel capsule is the treatment of choice)
    • ganglionic blocking agents such as hydralazine
  • If fecal impaction is the cause, blood pressure control is the priority.  Topical anaesthetic agents should be applied rectally until the blood pressure is controlled. 
  • Maintain meticulous bowel routine.
  • Monitor bladder catheter for obstruction; ensure intermittent catheterization frequency is sufficient (e.g. increase catheterization frequency when fluid intake increases or diuretics are used).
  • Careful skin inspection and frequent position changes. 
  • Maintain appropriate clothing to protect against drafts.
  • Teach patient to recognize signs and symptoms.


Brenda Morgan
Clinical Nurse Specialist , CCTC
Updated: January 15, 2019


O'Donnell, W. (1987). Neurological management in patient with acute spinal cord injury. Critical Care Clinics. July. pp 612.

Quail, S. (1996). Handbook of Critical Care Nursing. Springhouse: Toronto. pp. 638.

Thelan, L., Urden, L., Lough, M., and Stacy, K. (1998). Critical Care Nursing: Diagnosis and Management. Mosby: Toronto. pp. 1067-1068.