Correlation Between Temperature Rise After Sympathetic Block and Pain Relief in Patients with Complex Regional Pain Syndrome

Objective Determine the correlation between post-sympathetic block temperature change and immediate- and intermediate-term pain relief. Design Retrospective analysis. Setting Academic setting. Subjects Seventy-nine patients with complex regional pain syndrome who underwent sympathetic block. Methods Pre- and post-block temperatures in the affected extremity and pain scores immediately (based on 6-hour pain diary) after the block and at the intermediate-term 4- to 8-week follow-up were recorded. Post-block pain reductions of 30-49% and >= 50% were designated as partially sympathetically maintained pain and sympathetically maintained pain, respectively. A decrease in pain score >= 2 points lasting >= 4 weeks was considered a positive intermediate-term outcome for sympathetic block. Results A weak correlation was found between immediate-term pain relief and the extent of temperature rise for the cohort (R = 0.192, P = 0.043). Greater immediate-term pain reduction was reported among patients who experienced a temperature increase >= 7.5 degrees C (mean 4.1; 95% confidence interval [CI]: 3.33 to 4.76) than among those who experienced a temperature increase <2 degrees C (2.3; 95% CI: 1.36 to 3.31) or >= 2 degrees C to <7.5 degrees C (2.9; 95% CI: 1.8 to 3.9; P = 0.036). The correlations between temperature increase and intermediate-term pain score reduction at 4-8 weeks (R = 0.052, P = 0.329) and between immediate- and intermediate-term pain relief (R = 0.139, P = 0.119) were not statistically significant. Conclusions A weak correlation was found for those who experienced greater temperature increases after the block to also experience greater immediate pain relief. Higher temperature increase cutoffs than are typically used might be necessary to determine whether a patient with complex regional pain syndrome has sympathetically maintained pain.

Automated summary

The study found a weak correlation between temperature increase after sympathetic block and immediate pain relief. Patients with greater temperature increases reported more significant immediate pain reduction. There was no significant correlation between temperature increase and intermediate-term pain score reduction, as well as between immediate and intermediate-term pain relief.