A dysesthetic syndrome can
occur after sympathectomy; it usually is transient but sometimes can be persistent.
Chemical sympathectomy is transient and should be used initially for diagnostic purposes to
establish the involvement of SNS and hence inhibition of sympathetic activity (eg, increased limb
temperature or ocular Horner signs) without evidence of sensory somatic blockade (eg,
hypoesthesia to pinprick and cold stimuli).
For chemical sympathectomy, 2 basic techniques are used.
Injections of local anesthetic around sympathetic paravertebral ganglia that project to the
affected body part (sympathetic ganglion block): This will affect all components of the
sympathetic outflow to an extremity (adrenergic vasoconstrictor, cholinergic sudomotor, and adrenergic pilomotor).
Intravenous regional block: This will prevent the release of only norepinephrine from the sympathetic terminals within the region of application (ie, distal to the tourniquet).
Eugenia-Daniela Hord, MD, Instructor, Departments of Anesthesia and Neurology, Massachusetts General Hospital Pain Center, Harvard Medical School
