The transversus abdominis plane block: a valuable option for postoperative analgesia? A topical review

The transversus abdominis plane (TAP) block is a newly described peripheral block involving the nerves of the anterior abdominal wall. The block has been developed for post-operative pain control after gynaecologic and abdominal surgery. The initial technique described the lumbar triangle of Petit as the landmark used to access the TAP in order to facilitate the deposition of local anaesthetic solution in the neurovascular plane. Other techniques include ultrasound-guided access to the neurovascular plane via the mid-axillary line between the iliac crest and the costal margin, and a subcostal access termed the 'oblique subcostal' access. A systematic search of the literature identified a total of seven randomized clinical trials investigating the effect of TAP block on post-operative pain, including a total of 364 patients, of whom 180 received TAP blockade. The surgical procedures included large bowel resection with a midline abdominal incision, caesarean delivery via the Pfannenstiel incision, abdominal hysterectomy via a transverse lower abdominal wall incision, open appendectomy and laparoscopic cholecystectomy. Overall, the results are encouraging and most studies have demonstrated clinically significant reductions of post-operative opioid requirements and pain, as well as some effects on opioid-related side effects (sedation and post-operative nausea and vomiting). Further studies are warranted to support the findings of the primary published trials and to establish general recommendations for the use of a TAP block.