NOREPINEPHRINE AND EPINEPHRINE LEVELS IN AFFECTED VERSUS UNAFFECTED LIMBS IN SYMPATHETICALLY MAINTAINED PAIN

Objective: To test the hypothesis that there is relative sympathetic h yperactivity in the affected limb in patients with sympathetically mai ntained pain syndromes by measuring serum norepinephrine and epinephri ne in the affected versus the unaffected sides. Design: Venous pool sa mples were drawn just proximal to the affected area and from an identi cal site on the unaffected side. Serum norepinephrine and epinephrine were measured by high-pressure liquid chromatography with electrochemi cal detection. Subjects: Sixteen women and seven men with a mean age o f 44.4 years diagnosed as having sympathetically maintained pain on th e basis of a positive response to paravertebral block and a criteria-b ased diagnostic scheme. Results: The serum norephinephrine level was s ignificantly lower in the affected limbs than the unaffected limbs (p = 0.024). The serum epinephrine level was not significantly different. Conclusions: These results are not consistent with the hypothesis of segmental sympathetic hyperactivity in the affected limb in sympatheti cally maintained pain and support a hypothesis of peripheral receptor upregulation with pathologic response to circulating catecholamines. O ther possible explanations are discussed.