Effects of regional intravenous guanethidine in patients with neuralgia in the hand; a follow-up study over a decade

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Abstract
A study on the effect of regional intravenous (i.v.) guanethidine blockade (RGB) was done over a 10 years period in patients with post-traumatic neuralgia. Seven patients, investigated with quantitative sensory testing (QST) before and after RGB between 1979 and 1982, were reinvestigated in the period 1990-1992. In addition to the RGB, 6 patients were subjected to a placebo procedure with tourniquet inflation and i.v. injection of saline at follow-up. All patients had ongoing pain and stimulus-induced pain (hyperalgesia) in one hand. The QST was done by an independent observer who was blind with regard to the different treatments. Three patients with long-lasting relief of ongoing pain and significant reduction of stimulus-induced pain after RGB, were classified as having sympathetically maintained pain (SMP) both at 1st examination and at follow-up 10 years later. In 2 patients, classified as having sympathetically independent pain (SIP), neither the ongoing pain nor the hyperalgesia improved at any occasion. Two patients, classified as SMP in 1979-1982, changed to SIP at follow-up. Placebo had no significant effect on the hyperalgesia to heat, cold or vibration in the 6 SMP/SIP patients tested. In conclusion, some patients with neuralgia, diagnosed 17-26 years ago, still had long-lasting pain relief from an i.v. RGB, whereas others consistently had no such effect. None obtained long-lasting pain relief from placebo. This supports the notion that different pathophysiological mechanisms are involved in post-traumatic neuralgia.