• Ji Hoon Hong, Ji Hoon Park, and Jin Woo Shim.
• Department of Anesthesiology and Pain Medicine, Keimyung University Dongsan, Daegu, Korea.
• Pain Physician. 2023 May 1; 26 (3): 265272265-272.

BackgroundThe erector spinae plane block (ESPB) is a less invasive, safer, and technically easier procedure compared to the conventional neuraxial technique. Although the ESPB is a favored and easy technique compared to neuraxial block, there is no study with a large number of patients describing the exact spread level of injected local anesthetics.ObjectivesThe purpose of this study was to identify ESPB spread in the craniocaudal direction and the incidence of spread into the epidural space, psoas muscle, and intravascular system.Study DesignProspective design.SettingA tertiary university hospital, pain clinic.MethodsRight- or left-sided ESPBs (170 at L4) with fluoroscopy subsequent to ultrasound guidance due to acute or subacute low back pain were included. In this study, 10 mL (ESPB 10 mL group, contrast medium 5 mL) or 20 mL (ESPB 20 mL group, contrast medium 7 mL) of a local anesthetic mixture was injected. After confirming a successful interfascial plane spreading under ultrasound guidance, the remaining local anesthetic was injected under fluoroscopic guidance. The spread level of ESPB in the craniocaudal direction and the occurrence of injectate into the epidural space or psoas muscle was assessed using the saved fluoroscopic images. These images were compared between the ESPB 10 mL and ESPB 20 mL groups. Also, the presence or absence of intravascular injection during ESPB was assessed and compared between the ESPB 10 mL and ESPB 20 mL groups.ResultsThe ESPB 20 mL group had a more extensive caudal distribution of contrast medium than the ESPB 10 mL group. Also, the total number of lumbar vertebral segments was significantly higher in the ESPB 20 mL group than that of the ESPB 10 mL group (1.7 ± 0.4 vs 2.1 ± 0.4, P < 0.001). Among all injections performed in this study, epidural, psoas muscle, and intravascular injections occurred in 2.9%, 5.9%, and 12.9%, respectively.LimitationsOnly the craniocaudal direction was evaluated without evaluating the spread pattern in the medial to lateral direction.ConclusionThe ESPB 20 mL group showed a more extensive distribution of contrast medium than that of the ESPB 10 mL group. Inadvertent injections into the epidural space, psoas muscle, and intravascular system were observed. Among them, intravascular system injections were found to be the most common (12.9%).

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