Critical Care Trauma Centre


Autonomic Dysreflexia

What is it?
  • A life-threatening syndrome that can occur in individuals with cord injuries above T6 (most common in quadriplegia). 
  • Autonomic dysreflexia is a pathologic response to pain or other noxious stimuli, and is characterized by hypertension, bradycardia and vasodilation above the level of the cord injury.
  • Can develop any time after the period of spinal shock ends.
  • 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.  The heart rate decreases (vagal nerve), but inhibitory messages are unable to relax the blood vessels below the cord lesion. 
  • Vasoconstriction below the level of the cord injury causes the hypertension to persist. 
SIgns and Symptoms
  • Vasoconstriction causes hypertension and decreased peripheral circulation below the level of the cord injury.
  • 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. 
  • 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
  • Treat hypertension:
    • ganglionic blocking agents such as hydralazine
    • calcium channel blockers such as nifedipine
  • 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 Educator, CCTC
May 11, 2001

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.