Assessment of endothelial function in complex regional pain syndrome type I using iontophoresis and laser Doppler imaging

Objectives. To assess microvascular endothelial function in patients with complex regional pain syndrome type I (CRPS) compared with healthy controls, as measured by iontophoresis of vasoactive chemicals and laser Doppler imaging. Methods. Microvascular blood flow was stimulated locally in affected and contralateral limbs of patients with CRPS (n = 17) and in control subjects (n = 16) using iontophoresis of the endothelial-dependent vasodilator acetylcholine (ACh) and the endothelial-independent vasodilator sodium nitroprusside (NaNP). Changes in blood flow were measured using laser Doppler imaging. Comparisons were made between right and left limbs and between patients and controls. Results. No significant differences in blood flow [expressed as a median percentage increase from baseline (interquartile range)] were detected between affected and contralateral limbs in patients with CRPS for ACh [affected 237 (95-344); unaffected 251 (152-273)] or for NaNP [affected 102 (49-300); unaffected 190 (53-218)]. In addition, there were no significant differences between patients and healthy controls [controls, ACh 216 (119-316); controls, NaNP: 122 (48-249)]. Conclusions. In this pilot study, CRPS was not associated with impairment of microvascular endothelial function. This may be a true result or may reflect the diversity of the CRPS disease process.