The cut-off rate of skin temperature change to confirm successful lumbar sympathetic block.

The purpose of this study was to find the best cut-off value for the rate of change in temperature of the plantar surface of the foot for predicting the success of lumbar sympathetic block (LSB). A total of 185 LSBs were performed on 82 patients via a posterolateral approach under fluoroscopic guidance. Successful LSB was considered to have occurred when changes in the ipsilateral temperature between pre-block and post-block were > or = 2 degrees C. A receiver operating characteristic (ROC) curve for the minimum rate of temperature change was constructed as a predictor of the onset of a successful LSB. The area under the ROC curve was 0.971 at the rate of 0.4 degrees C/min with a sensitivity of 89.5% and a specificity of 91.8%. Achieving a rate of temperature change of 0.4 degrees C/min within approximately 5 min of the injection of local anaesthetic could be used as an indicator of the onset of successful LSB.