Basal blood flow in complex regional pain syndrome does not necessarily indicate vasoconstrictor nerve activity.

Objectives: To quantitatively investigate simultaneous skin blood flow and sweating in a patient with complex regional pain syndrome. Method: Using one probe, skin blood flow and sweating were measured on the affected and non-affected sides at baseline and after activation of sympathetic system in a 47-year-old woman with complex regional pain syndrome type I of the left hand. Results: Basal sweating, sympathetic sweat response, basal blood flow, sympathetic flow response, and attrition rate of blood flow (the ratio of sympathetic flow response to basal blood flow) of the affected side were greater than those on the non-affected side. Conclusions: Although sympathetic nerve activity (sympathetic flow response) appeared greater on one side, basal blood flow was also greater on that side. These contradictory results suggest that some factor or factors increase basal blood flow despite a higher sympathetic nerve tone on the side. Comparing basal blood flow on one side to the contralateral side does not necessarily indicate lesser vasoconstrictor nerve activity on that side. Advantages of simultaneous measurement of skin blood flow and sweating with a single probe may make the method useful.