Efficacy of modified thoracoabdominal nerves block through perichondrial approach in open gynecological surgery: a prospective observational pilot study and a cadaveric evaluation.

Background: Modified thoracoabdominal nerves block through perichondrial approach (M-TAPA) was first described as a peripheral nerve block by Tulgar in 2019. This technique provides an analgesic effective range from Th7-11 with a single puncture per side. Although the efficacy and effective duration of M-TAPA have been reported, further examination is required. Therefore, this study aimed to evaluate the analgesic range and effective duration of M-TAPA in open gynecologic surgery.

Methods: Following approval, 10 adult female patients scheduled for open radical hysterectomy via a vertical incision or laparotomy using a midline incision from under the xiphoid process to the symphysis pubis were enrolled. The primary outcome was the number of anesthetized dermatomes at 2 and 24 h postoperatively. Secondary outcomes included numerical rating scale scores and the total amount of fentanyl used. Cadaveric evaluation was performed to assess the spread of the dye.

Results: The median numbers (interquartile range) of anesthetized dermatomes at 2 and 24 h postoperatively were 6 (5-7) and 6.5 (5-7) in the anterior cutaneous branch area and 5 (4-7) and 7 (5-7) in the lateral cutaneous branch area, respectively. There was an 85% chance of simultaneously acquiring analgesia in areas innervated by Th8-11, including complete block in areas innervated by the anterior cutaneous branches of Th9-10. Cadaveric evaluation showed the spread of the dye in Th8-11.

Conclusions: M-TAPA may have analgesic effects in the areas supplied by the anterior cutaneous branches of Th8-11.

Trail Registration: IRB approval (No.2700; registered on July 10, 2020) and registration (UMIN Clinical Trials Registry: UMIN000041137 ; registered on July 17, 2020).