Autonomic Hyperreflexia
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Becomes a concern a few weeks after spinal cord injury
Sympathetic overactivity is common with transections above T6 but unusual
with injuries below T10
Results from interruption of normal descending inhibitory impulses
Cutaneous or visceral stimulation below level of injury can induce autonomic
dysfunction
o Below transection – hypertension and vasoconstriction following
sensory delivery to spinal cord by intact peripheral nerves to
spinothalamic and posterior columns with resulting activation of
sympathetic discharge from intermediolateral gray (most significantly
in the subdiaphragmatic / splanchnic vasculature)
o Above transection – baroreceptor mediated reflex bradycardia and
vasodilation through intact receptors in the neck via cranial nerves IX
and X; cardiac arrhythmias
Dysreflexic episode: increase in SBP >20-30mmHg (Resting BP is decreased
in patients with SCI)
27% of patients with incomplete tetraplegia, 91% with complete
Most commonly triggered by irritation of bladder or colon
Regional anesthesia / deep general can prevent hyperreflexia
Direct vasodilators and alpha-adrenergic blockers should be available
Complications: severe HTN leading to pulm edema, MI, CVA, retinal
detachment, seizure, death
Sx: Severe H/A (caused by vasodilation above injury), Anxiety, Profuse
sweating and flushing and piloerection above injury, Dry pale skin below
(vasoconstriction), blurry vision, congestion, arrhythmias
Methods to prevent bladder irritation as an inciting factor: botulinum toxin
into the detrusor muscle, intravesical capsaicin, sacral denervation,
intersphincteric anal block, epidural / spinal,
Ineffective methods: anticholinergics, topical lidocaine
Pharmocologic tx: nifedipine, captopril, terazosin, prazosin, beta-blockers,
hydralazine
Sources:
Morgan, Mikhail. Clinical Anesthesiology.
Krassioukov A, et al. A Systematic Review of the Management of Autonomic
Dysreflexia After Spinal Cord Injury. Arch Phys Med Rehabil. 2009. Vol 90.
Furlan JC, et al. Cardiovascular Complications after acute spinal cord injury:
pathophysiology, diagnosis, and management. Neurosurg Focus. 2008.