Transversus abdominis plane blocks for rescue analgesia after major abdominal surgery

TRANSVERSUS Abdominis Plane (TAP) block has been receiving increasing attention in the anaesthesiological literature. Two systematic reviews published in 2010 and 2011 concluded that a TAP block reduces the need for post-operative opioid requirements and opioid-related side-effects. However, a Cochrane review from December 2010 was less optimistic, stating that studies comparing a perioperative TAP block with either no intervention or placebo were very few and provided only limited evidence for these benefits. Also, the authors did not find any published studies comparing a TAP block with other regional anaesthetic techniques, such as epidural analgesia or local anaesthetic infiltration. All randomized studies described in these reviews used the classical TAP approach half-way between the iliac crest and the costal margin and only five of these studies used ultrasound to identify the correct fascial plane. In three ultrasound studies, the blocks were performed bilaterally and in two, they were performed unilaterally. With one exception, the surgical procedures were in the lower abdomen and only one study included patients undergoing major surgery, albeit gynaecological. In this issue of Acta Anaesthesiologica Scandinavica, Børglum et al. describe a new ultrasoundguided four-injection technique of a TAP block to provide rescue analgesia after major abdominal surgery in 25 patients who had severe pain. All blocks were performed in the Recovery Room after either failure or rejection of other analgesic modalities. All patients reported significant pain reduction after the blocks and were rapidly discharged to surgical wards. Most did not require any opioids in the next 6 h and were mobilized. The clinical relevance of this method is obvious: reduction of pain and improved patients’ flow in the immediate post-operative period. It is also for the first time that four separate injections were used to anaesthetize the entire antero-lateral abdominal wall. Although the injections above the umbilicus were described previously as a subcostal TAP block, the area of analgesia was limited to the upper abdominal wall. The novelty of the approach proposed by Børglum and colleagues is that it combines a classical TAP block, which anaesthetizes dermatomes at and below the umbilicus (T10–L1) with one of the two variants of an intercostal TAP block (medial or lateral), which should anaesthetize dermatomes above the umbilicus (T6–T9). This technique takes into consideration the complex innervation of the abdominal wall. Three recently published cadaver studies assessed the anatomy of the thoracolumbal T6–L1 nerves, which supply the anterolateral abdominal wall. All segmental nerves branch extensively and communicate with adjacent nerves forming the plexus. The nerves T6–T9 enter the TAP between the midline and the anterior axillary line, T6 just lateral to the linea alba, and the others at progressively lateral positions. Therefore, the classical TAP block, where local anaesthetic injections are administered in the middle axillary lines, is unlikely to anaesthetize the areas above the umbilicus. This limits the use of this block to lower abdominal surgery. Even the subcostal TAP block is unlikely to anaesthetize the dermatomes T6–T8. Moreover, the anatomical study cited by Børglum et al’s. revealed the presence of a fascial layer within TAP and emphasized the necessity of local anaesthetic’s infiltration deep into the fascia of the internal