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 - HTN 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 HTN
• 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

History

• Unopposed PSNS above lesion

1. Burry vision, miosis
2. Headaches
3. Anxiety
4. Bradycardia associated with rises in BP
5. Sweating, flushing
6. Nasal congestion

• Unopposed SNS below lesion

1. Pale, cool skin
2. Piloerection, goose bumps

Physical

• 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)
• Profuse sweating/flushing above the level of lesion (especially in the face, neck, and shoulders)
• Possible to be asymptomatic

Differential Diagnosis

Hypertension

• Hypertensive emergency
• Stroke
• Sympathetic crashing acute pulmonary edema
• Ischemic stroke
• Intracranial hemorrhage
• Preeclampsia/Eclampsia
• Autonomic dysreflexia
• Scleroderma renal crisis
• Acute glomerulonephritis
• Type- I myocardial infarction
• Volume overload
• Urinary obstruction
• Drug use or overdose (e.g stimulants, especially alcohol, cocaine, or Synthroid)
• Renal Artery Stenosis
• Nephritic and nephrotic syndrome
• Polycystic kidney disease
• Tyramine reaction
• Cushing's syndrome
• Obstructive sleep apnea
• Pheochromocytoma
• Hyperaldosteronism
• Hyperthyroidism
• Anxiety
• Pain
• Oral contraceptive use

Treatment

• HTN should abate once offending agent corrected - normal is SBP 90-110 mmHg

1. Check urinary catheter for any blockage or twisting
2. If cath blocked, gently irrigate bladder with NS at body temp
3. If cath is draining, suspect fecal impaction and check rectum for stool with lidocaine jelly lube - gentle disimpaction to follow
4. Place in an upright position to allow gravitational pooling of blood to reduce BP
5. Careful inspection of nonsensate areas to identify the source of painful stimuli
   1. (e.g. catheter, restrictive clothing, leg bag straps, abdominal supports, orthoses)

• BP meds with SBP > 150, use short-acting since offending agent must be corrected; use with caution in CAD
  • Nifedipine immediate release
  • NTG paste or sublingual NTG

Disposition

• Admission

See Also

• Spinal Trauma (Main)

References

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