Evaluation of cutaneous sensory block area following a novel approach to transversus abdominis plane block: an observational study

Cheng XuSai KongYongzhu ChenJie Lu^*Aizhong Wang^*

• Shanghai Sixth People's Hospital, Shanghai Jiao Tong University, Shanghai, Shanghai Municipality, China

BACKGROUND: Ultrasound-guided transversus abdominis plane (US-TAP) block is currently used as part of a multimodal analgesic regimen in anterior abdominal wall surgery, but the distribution of cutaneous sensory block area (CSBA) shows significant interindividual variation. We predeveloped a novel US-TAP block approach, and this study aims to assess the CSBA following the novel US-TAP block approach. Methods: Sixteen patients undergoing elective laparoscopic cholecystectomy (LC) received bilateral novel US-TAP blocks with a total of 40 mL of 2.5 mg/mL ropivacaine. Measurements were taken 45 minutes after block administration. CSBA was mapped using cold sensation and a sterile marker, photodocumented, and transferred to a transparency. The area of the CSBA was calculated from the transparencies. Results: The median CSBA of the novel US-TAP approach was 332 cm² (IQR 297–413 cm²; range 258–466 cm²). In all patients, the CSBA showed wide periumbilical distribution. In all 32 unilateral blocks (100%), both epigastric and infraumbilical components were present; and in 16 of the 32 blocks (50%), the CSBA extended to the abdominal wall lateral to the vertical reference line through the anterior superior iliac spine. Fourteen patients (88%) had resting NRS scores of 3 or lower within 24 hours postoperatively. Conclusions: The novel US-TAP approach produces a broad dermatomal CSBA, covering much of the abdominal wall around the umbilicus. Clinical trial registration: Chinese Clinical Trial Registry, ChiCTR2300077899.