Autonomic dysreflexia

Background

  • Syndrome of massive imbalanced reflex sympathetic discharge from strong stimulus below level of spinal lesion
  • Carotid and aortic baroreceptors result in strong vagal response with bradycardia and vasodilation above level of injury, but cannot inhibit sympathetics below level of injury - hypertension remains dysregulated by the CNS
  • Occurring in patients with spinal cord injury (SCI) above the splanchnic sympathetic outflow (T5-T6)
  • Splanchnic innervation from T5-T9
  • Lesions below T6 allow descending inhibitory PSNS control to decrease splanchnic tone, preventing hypertension
  • Medical emergency given dangerous sequelae of elevated blood pressure

Common triggers (due to strong stimuli below level of injury)

  • Bladder distension ~80%
  • Bowel distension, fecal impaction ~15%
  • Pressure ulcers

Clinical Features

Possible to be asymptomatic

Unopposed PSNS above lesion

  • Blurry vision, miosis
  • Headaches
  • Anxiety
  • Bradycardia associated with rises in BP
  • Profuse sweating/flushing (especially in the face, neck, and shoulders)
  • Nasal congestion

Unopposed SNS below lesion

  • Pale, cool skin
  • Piloerection, goose bumps

Differential Diagnosis

Hypertension

Evaluation

  • A sudden significant rise in systolic and diastolic blood pressures
    • Usually associated with bradycardia
    • SBP >140 mm Hg (in a patient with SCI above T6)

Management

hypertension should abate once offending agent corrected (normal = SBP 90-110 mmHg)
  1. Remove offending agent
    • Check urinary catheter for any blockage or twisting
      • If cath blocked, gently irrigate bladder with NS at body temp
      • If cath is draining, suspect fecal impaction and check rectum for stool with lidocaine jelly lube - gentle disimpaction to follow
    • Careful inspection of nonsensate areas to identify the source of painful stimuli
      • e.g. catheter, restrictive clothing, leg bag straps, abdominal supports, orthoses
  2. Directly lower blood pressure (if #1 fails)
    • Place in an upright position to allow gravitational pooling of blood to reduce BP
    • BP meds if SBP > 150
      • Use short-acting (since offending agent must be corrected); use with caution in CAD
      • Nifedipine immediate release
      • Nitroglycerine sublingual

Disposition

  • Admission

See Also

References

  • Gunduz H, Binak DF. Autonomic dysreflexia: an important cardiovascular complication in spinal cord injury patients. Cardiol J. 2012;19(2):215-9.