Autonomic Dysreflexia

Question 1

What is the pathophysiology of Autonomic Dysreflexia?

Answer 1

• A strong sensory input (not necessarily noxious) is carried into the spinal cord via intact peripheral nerves. The most common origins are bladder and bowel.
• This strong sensory input travels up the spinal cord and evokes a massive reflex sympathetic surge from the thoracolumbar sympathetic nerves, causing widespread vasoconstriction, most significantly in the sub diaphragmatic (or splanchnic) vasculature. Thus, peripheral arterial hypertension occurs.
• The brain detects this hypertensive crisis through intact baroreceptors in the neck delivered to the brain through cranial nerves IX and X (Vagus).
• The brain attempts 2 manoeuvres to halt the progression of this hypertensive crisis. First, the brain attempts to shut down the sympathetic surge by sending descending inhibitory impulses. These impulses do not get to most sympathetic outflow levels because of the spinal cord injury at T6 or above. Inhibitory impulses are blocked in the injured spinal cord
• In the second manoeuvre, the brain attempts to bring down peripheral blood pressure by slowing the heart rate through an intact vagus (parasympathetic) nerve; however, this compensatory bradycardia is inadequate and hypertension continues. In summary, the sympathetic prevail below the level of neurologic injury, and the parasympathetic nerves prevail above the level of injury.
• Once the inciting stimulus is removed, reflex hypertension resolves.
• This condition is distinct and usually episodic, with the patient experiencing remarkably high blood pressure (often with systolic readings over 200mm. Hg), intense headaches, profuse sweating, facial erythema, Goosebumps, nasal stuffiness, and a “feeling of doom”.
• Erythema may be present in skin above the lesion
• A patient with elevation in BP of 20 - 40mmHg over baseline systolic should be considered for dysreflexia.
• Note: Paraplegics and quadriplegics may normally have low systolic BP (90-100) and a small rise may constitute HTN

Question 2

What are the causes of Autonomic Dysreflexia?

Answer 2

• any painful stimuli
• most common is full bladder or full bowel
• other causes include: skin irritations, wounds, pressure sores, burns, broken bones, pregnancy, appendicitis

Question 3

What are the symptoms of autonomic dysreflexia?

Answer 3

• Severe headache (feeling of doom)
• Sweating (above the level on injury)
• Facial flushing
• Blurred vision/retinal detachment
• Nasal congestion/snuffiness
• Seizures, ICH, Piloerection
• Bradycardia – cardiac arrest

Question 4

Recite the Autonomic Dysreflexia CPG

Answer 4

Question 5

Why do we use GTN for Autonomic Dysreflexia?

Answer 5

• to prevent cerebral catastrophe
• GTN acts directly on the vasoconstriction causing the HTN

Question 6

Must you always transport the autonomic dysreflexia pt to hospital?

Answer 6

yes

Question 7

Review the anatomy of the spinal cord

Answer 7

Question 8

What is the role of the SNS and PNS on blood pressure control

Answer 8

SNS
- constricts blood vessels and increases BP
- increases HR
- increases blood flow to skeletal muscles

PNS
- decreases HR
- dilates blood vessels
- decreases flow to skeletal muscles