Effectiveness and safety of new umbilical paramedian semilunaris approach for transverse abdominis plane block: a prospective, single-arm, observational, evaluation study.

Background: The transversus abdominis plane (TAP) block is a widely used, safe and effective technique for abdominal surgery analgesia, but its range of blocking is not sufficient for some surgeries requiring a large incision. Here we present the novel concept of an ultrasound-guided linea semilunaris block, a modified approach to TAP block, which can potentially offer a wider blocking range. Methods: Patients undergoing open colorectal surgery at the Shanghai Jiaotong University Affiliated Sixth People's Hospital between May and July 2021 were enrolled to receive ultrasound-guided linea semilunaris block. All blocks were performed in the holding area of the operating theater under routine hemodynamic monitoring while patients were conscious with low-dose opioids. All patients were supine, and a linear probe identified the semilunar line as the connection between the transverse and rectus muscles. Next, 20 mL of 0.25% ropivacaine was injected in the semilunar line using the in-plane technique bilaterally. The main indicator of the blocking range was measured. Postoperatively, the visual analog score (VAS) from 4 to 24 h (every 2 h), the time of the first remedial analgesia, the bowel movement starting time and complications were also recorded. Results: A total of 31 potentially eligible studies were identified for inclusion. The extent of the cutaneous sensory block was: 3.46±0.59 cm below the xiphoid, 1.74±0.37 cm above the symphysis pubis, 2.02±1.24 cm outside the left midclavicular line, and 2.19±1.25 cm outside the right midclavicular line. The highest and lowest median [interquartile range (IQR)] VAS pain scores were 4 [4-5] of 10 h and 2 [1-2] of 4 h postoperatively. The bowel movement starting time was 3.7±1.1 days after gastrointestinal surgery. There were four patients with nausea and vomiting but none had adverse reactions attributable to local anesthetic (LA) poisoning. Conclusions: The ultrasound-guided umbilical paramedian semilunaris approach to TAP block is a safe and effective technique in clinical practice, which may provide more effective analgesia than traditional TAP block for open colorectal surgery with a median abdominal incision. Further randomized controlled trials are needed to confirm our results.