Pain relief following post-ganglionic sympathetic blockade with I.V. guanethidine

Thirty-one patients with pain in one or both hands associated with sympathetic dystrophy or Raynaud's disease were studied before and after the administration of a placebo and guanethidine 10mg i.v. Before and after the injections each patient reported his pain and had sympathetic activity assessed by: (1) palmar sweating; (2) skin temperature; (3) hand blood flow and (4) the ice response of hand blood flow. There was no significant change in any index after the placebo injection, nor was there any change in palmar sweating after guanethidine. Following guanethidine there were significant changes in reported pain (P less than 0.001), skin temperature (P less than 0.05), hand blood flow (P less than 0.001) and the ice response of hand blood flow (P less than 0.001). The results confirm the importance of the post-ganglionic sympathetic nervous system in the transmission of pain in these patients.