Skin temperature in the neuropathic diabetic foot

Several authors have reported higher skin temperature in the feet of diabetic subjects with autonomic neuropathy. We reexamined this association in a cross-sectional study of 712 veterans with diabetes mellitus. Potential subjects included all diabetic patients enrolled in a general internal medicine clinic at a veterans affairs healthcare system. Sensory neuropathy was defined as any pedal insensitivity to the 5.07 monofilament. Autonomic neuropathy was determined using standard cardiovascular reflex tests. An infrared surface scanner was used to measure foot skin temperature at multiple sites. Subjects with sensory neuropathy had lower mean plantar foot skin temperature than those without (28.4 degrees C vs. 28.9 degrees C, P=.0101). Autonomic neuropathy as a dichotomous variable was unrelated to foot skin temperature. Foot skin temperature, though, negatively correlated with greater drop in systolic blood pressure with standing, which is an indicator of autonomic neuropathy (r=-.08, P=.0385). Adjustment for potential confounding factors using multiple linear regression analysis resulted in diminution of the associations between foot skin temperature and sensory neuropathy or orthostatic blood pressure drop, but the latter association remained statistically significant in the right foot. Diabetic veterans with sensory or autonomic neuropathy do not have higher foot skin temperature. Our results suggest that skin temperature may be slightly lower with higher orthostatic blood pressure fall. Other causes exist for the frequently observed differences in skin temperature in the feet of diabetic subjects.