Autonomic Hyperreflexia

Question 1

What is autonomic hyperreflexia?

Answer 1

a syndrome of widespread sympathetic discharge in patients with chronic spinal cord lesions (usually at or above T7 level) in response to stimuli below the lesion

Question 2

So, explain how autonomic hyperreflexia works:

Answer 2

Sympathetic stimulation below the level of the lesion causes a reflex arc leading to massive sympathetic efferent discharge below level of lesion (descending inhibitory signals are unable to modulate afferent input from below the level of the lesion)
The ensuing HTN initiates corrective reflexes such as bradycardia and vasodilation

Question 3

What do you see below the lesion in AH?

Answer 3

pallor, pilomotor erection, intense somatic and visceral muscle contraction and increased spasticity

Question 4

Above the lesion in AH?

Answer 4

flushing of face and neck, mucous membrane and conjunctival congestion, intense sweating, mydriasis (dilation)

Question 5

What things can you see in AH?

Answer 5

Bradycardia, AV block, PACs, PVCs
Headache, seizures, SAH 
Dyspnea, pulmonary edema 
Blurred vision 
Anxiety, agitation 
Chest pain/myocardial ischemia

Question 6

DDX for AH:

Answer 6

Chronic HTN
Hypertensive crisis of other etiology
Pheochromocytoma
Drug toxicity

Question 7

How do you manage this?

Answer 7

Communicate with surgeon and remove precipitating stimulus
Consder deepening anesthesia if under GA
If epdiural being used-consider raising level of block
Treat severe HTN-and look for evidence of end organ damage (pulmonary edema, EKG changes, seizures)

Question 8

How would you treat the severe HTN in AH?

Answer 8

Alpha blocking agents: phentolamine (5 mg IV PRN)
direct vasodilators (hydralazine 10-20 mg IV)
Sodium nitroprusside: 1microgram/kg/min up to 4 mcg/kg/min
Calcium channel blockers (nicardipine 5 mg/hr, titrate up to 15 mg/hr max