Sympatholytic Effect of the High Thoracic Erector Spinae Plane Block

Background: The erector spinae plane block (ESPB), which was introduced for the management of thoracic pain, is a technically easy and relatively noninvasive ultrasound (ULSD)-guided technique. Although the ESPB is used widely in variable clinical situations, its sympatholytic effect has never been studied. Objectives: The purpose of this study is to demonstrate the sympatholytic effect of the high thoracic ESPB by comparing the blocked and unblocked sides of patients' upper extremities, using the changes in the perfusion index (PI). Study design: Prospective, single-group, and open-label study. Setting: The study was carried out in the pain clinic of a tertiary university hospital. Methods: This study included 47 patients with upper extremity pain and various diseases who received T2 or T3 ESPBs using 20 mL of 0.2% ropivacaine. For the evaluation of the sympatholytic effect, measurements were taken on the numeric rating scale (NRS), the neck disability index (NDI), and the PI. Results: The PIs of the blocked sides demonstrated significant increases at 10, 20, and 30 minutes compared to the PIs of the baseline and unblocked sides (P < 0.001). The PI ratio at 10 minutes was 2.74 +/- 1.65, which was the highest value during the measurement period. Until 30 minutes after the ESPB, the PI ratio was significantly higher in the blocked side than in the unblocked side. During the study period, significant reductions in NRS and NDI scores were found irrespective of disease entity. Limitation: The period of PI measurement was only 30 minutes, so we could not determine the time point when the PI returned to the baseline value. Conclusion: The high thoracic ESPB was effective in relieving upper extremity pain in diverse disease entities, and the PIs of patients' blocked sides demonstrated significant increases over the baseline value and contralateral unblocked sides.