Re-modified thoracoabdominal nerves block through the perichondrial approach at the 9th intercostal space provides analgesia in the upper abdomen: a volunteer study.

We previously reported that administering local anesthetic into the space between the endothoracic fascia, diaphragm, and costodiaphragmatic recess (SEDIC) at the 10th intercostal space via the re-modified thoracoabdominal nerves block through the perichondrial approach (RM-TAPA) effectively anesthetizes the lower abdomen (T9-T12). However, the analgesic area obtained by RM-TAPA was distinct from prior reports of M-TAPA, which achieved broader analgesic effects from T4 to L1. The aim of this study was to verify the range of analgesic effects when local anesthetics are administered into the SEDIC at the 9th intercostal space, which was estimated to be close to the needle tip of the M-TAPA, in ten healthy volunteers. Each volunteer received 20 mL of 0.2% ropivacaine into the SEDIC at the 9th intercostal space, and sensory blockade was assessed 1 h post-injection using a pinprick test. RM-TAPA performed at the 9th intercostal space provided adequate analgesia from T6 to T10. The analgesic effect on the lateral cutaneous branches was more pronounced on the right side than on the left. These findings imply that optimizing needle position and injection site in RM-TAPA, tailored to specific surgical needs, represents a refinement in perioperative pain management strategies.