How is an IV regional sympathetic block administered for pain management?

Updated: Jun 19, 2018
  • Author: Anthony H Wheeler, MD; Chief Editor: Meda Raghavendra (Raghu), MD  more...
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Answer

Answer

Intravenous regional sympathetic blockade entails injection of an antiadrenergic agent into the venous system of a limb with CRPS after the circulation is occluded temporarily with a tourniquet. An experienced interventionist, preferably an anesthesiologist, should perform this procedure. This procedure was originally developed using guanethidine, which can induce a prolonged, unselective sympathetic blockade by displacing NE from presynaptic vesicles and preventing NE uptake.

Guanethidine causes an initial release of NE, followed by NE depletion, which results in long-lasting interruption of adrenergic activity. Blockade may last for hours, days, and occasionally, weeks because of the high affinity of guanethidine for binding to sympathetic nerve endings, and also because guanethidine is eliminated slowly. Unfortunately, parenteral guanethidine is no longer available, since the drug is no longer used for the treatment of hypertension by the IV route.

Other possible candidates for alpha-adrenergic blockade include reserpine, which causes NE storage vesicle depletion and blocks NE reuptake; however, this drug has proved relatively ineffective and produces many adverse effects. Blockade of presynaptic (alpha2) and postsynaptic (alpha1) receptors can be performed with phentolamine, which is reversible, usually with duration of effect of less than 24 hours.

Blockade of postsynaptic (alpha1) receptors can be induced by prazosin; however, a parenteral form of this drug has not yet been approved, and investigation for this indication is insufficient to date. IV sympathetic blockade is particularly useful for patients in need of sympathetic blockade who are taking anticoagulant medications. Patients who are sensitive or experience excessive toxic systemic reactions to LA may be candidates for IV blockade.


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