Impaired oxygen utilization in skeletal muscle of CRPS I patients.

BACKGROUND The purpose of this study was to evaluate oxygen extraction and utilization in end stage chronic complex regional pain syndrome type I (CRPS I) patients undergoing amputation and to relate these to muscle histology of the amputated limb. MATERIALS AND METHODS In 25 patients with severe CRPS I requiring amputation of the affected limb venous blood samples and in 11 patients skeletal muscle specimens were analyzed. RESULTS The mean venous oxygen saturation (S(v)O(2)) value (94.3% ± 4.0%) of the affected limb was significantly higher than S(v)O(2) values found in healthy subjects (77.5% ± 9.8%) pointing to a severely decreased oxygen diffusion or utilization within the affected limb. Histologic analysis showed a significant decrease of type I fibers and a significant increase of type IIB fibers. Ultrastructural investigations of soleus skeletal muscle capillaries revealed thickened endothelial cells and thickened basement membranes. Muscle capillary densities were decreased in comparison with literature data. High venous oxygen saturation levels were partially explained by impaired diffusion of oxygen due to thickened basement membrane and decreased capillary density. CONCLUSION This study shows that venous oxygen saturation is significantly increased in chronic end stage CRPS I patients corresponding with impaired oxygen diffusion. The abnormal skeletal muscle findings points to severe disuse but only partially explain the impaired diffusion of oxygen; mitochondrial dysfunction seems a likely explanation in addition.