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

• 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)

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

• 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

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

• 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.