What is the role of IV regional sympathetic blocks in the treatment of complex regional pain syndrome (CRPS)?

Updated: Jun 20, 2018
  • Author: Gaurav Gupta, MD; Chief Editor: Stephen A Berman, MD, PhD, MBA  more...
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Studies assessing IV regional sympathetic blocks have been performed using several agents. Guanethidine is thought to act by depleting norepinephrine, although the drug has also been shown to have serotonergic and anticholinergic activity. [110] In a literature review, 7 controlled trials concluded that IV regional blocks with guanethidine provide little analgesia compared with a placebo or no treatment. [111, 112, 113, 114, 115, 116, 117, 76] One study demonstrated that applying a series of guanethidine blocks did not result in a better outcome than using just one. [117]

Bretylium has also been used to achieve an IV regional sympathetic block. Its proposed mechanism of action is thought to be similar to guanethidine's. A single non‑placebo-controlled study of IV bretylium regional sympathetic block compared bretylium with lidocaine in 12 patients and reported that bretylium resulted in a significantly longer duration of pain relief. [118]

Other controlled trials compared different agents that can be used for IV regional sympathetic blocks, including droperidol, ketanserin, reserpine, and atropine. [1] Droperidol, an alpha-adrenergic antagonist, provided no pain relief for 6 patients who responded to prior stellate ganglion blocks. [119] Ketanserin, a serotonin type-2 antagonist, was studied in 9 patients who reported significant pain relief for several weeks compared with saline. [120] Two controlled studies assessed reserpine, another norepinephrine-depleting drug, in patients who experienced prior relief from stellate ganglion blocks, but these studies reported no significant pain relief. [112, 113] No pain relief from anticholinergic atropine was reported in patients who had previously responded to IV guanethidine regional sympathetic blockade, either. [121]

Another significant question is the mechanism of pain relief with IV regional sympathetic blocks. The beneficial responses associated with this procedure may result solely from the ischemic tourniquet block rather than the injected medication. Significant A-β and A-δ fiber conduction blockage with clinically evident sensory changes has been demonstrated with only a tourniquet. [122]

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