RT Journal Article SR Electronic T1 EP055 Spread of the local anesthetic via modified thoracoabdominal nerve block through perichondrial approach (M-TAPA): a volunteer study JF Regional Anesthesia & Pain Medicine JO Reg Anesth Pain Med FD BMJ Publishing Group Ltd SP A101 OP A101 DO 10.1136/rapm-2024-ESRA.128 VO 49 IS Suppl 1 A1 Aikawa, Katsuhiro A1 Kurokawa, Tatsuya A1 Miyata, Kazuma A1 Ito, Tomoki A1 Morimoto, Yuji YR 2024 UL http://rapm.bmj.com/content/49/Suppl_1/A101.abstract AB Please confirm that an ethics committee approval has been applied for or granted: Yes: I’m uploading the Ethics Committee Approval as a PDF file with this abstract submissionBackground and Aims Modified thoracoabdominal nerve block through perichondrial approach (M-TAPA) is a novel truncal block first reported by Tulgar et al in 2019. It has been reported to anesthetize a broad thoracoabdominal area; however, the neuroanatomical mechanisms remain unclear. Therefore, we conducted a volunteer study employing magnetic resonance imaging (MRI) to investigate the diffusion pattern of the local anesthetic responsible for extensive sensory area.Methods This study was approved by the Institutional Review Board of Hokkaido University Hospital. Three healthy male volunteers were involved. Bilateral M-TAPA was performed, administering 25 mL of Gadavist® containing 0.15% levobupivacaine on each side. The local anesthetic was precisely injected between the origin of the transversus abdominis muscle and the costal cartilage following Tulgar’s description. One hour following the administration, the sensory area and local anesthetic diffusion were assessed using pinprick tests and MRI, respectively.Results The 6 blocks in the 3 volunteers were evaluated. The sensory loss areas at 1 hour after M-TAPA were; T9, T9–10, T9–10, T8–9, T9, and T9–10. No effect was observed in the lateral area. The MRI revealed that local aneshtetic was distributed in the transversus abdominis plane near the injection point, and the compartment on the surface of the parietal peritoneum.Abstract EP055 Figure 1 The sensory areas 1 hour following M-TAPAAbstract EP055 Figure 2 The MRI imaging of the local anesthetic spreadConclusions In this study, the sensory loss of M-TAPA was limited to the T8–10 in the anterior abdominal wall. Also, MRI tests did not detect a local anesthetic diffusion pattern that could lead to broad anesthetized area. These results indicate the necessity of caution in presuming the extensive anesthetized area of M-TAPA.