Evaluation of the efficacy of the lumbar sympathetic ganglion block and the use of perfusion index as a predictor of its technical success: a prospective observational study.

Background: This study aimed to evaluate the 4-week clinical efficacy of the lumbar sympathetic ganglion block (LSGB), assess the perfusion index (PI) as a marker for the LSGB's technical success, and examine the relationship between the PI change and post-procedure pain relief. Methods: In this prospective observational study, pain scores of 40 patients who underwent LSGB were measured using the Numeric Rating Scale (NRS) at pre-procedure, 20 minutes post-procedure, and at 1 and 4 weeks. The primary outcome was a positive LSGB response, defined as a reduction of ≥ 2 on the NRS at 20 minutes post-procedure. Skin temperature and PI were recorded every minute for 20 minutes post-procedure. The reliability of the PI was assessed using area under the curve (AUC) and receiver operating characteristic curves. Results: An immediate positive response to the LSGB was observed in 72.5% of patients, with 30.8% responding at 1 week and 17.9% responding at 4 weeks. NRS scores significantly decreased from baseline to 4.1 ± 2.5 immediately post-procedure and to 5.9 ± 2.7 at 4 weeks. A Δ PI of > 1.6% in the ipsilateral foot was a reliable indicator of technical success (sensitivity: 90.0%; specificity: 90.0%; AUC: 0.925; Conclusions: Although the number of LSGB responders declined over 4 weeks, overall pain levels significantly decreased. The PI may serve as a quick and reliable indicator of technical success, but it does not correlate with post-procedure pain relief.