<scp>TAP</scp> block terminology

We congratulate Niraj et al. on their recent paper comparing the analgesic efficacy of the four-quadrant transversus abdominis plane (TAP) block and continuous posterior TAP analgesia vs epidural analgesia in patients undergoing laparoscopic colorectal surgery 1. However, we would like to comment on both their terminology and their analgesic strategy. Niraj et al.'s ‘four-quadrant TAP block’ is identical to the ‘bilateral dual TAP (BD-TAP) block’ published previously 2, 3, in which both an upper and a lower TAP block are administered bilaterally to each hemi-abdomen to anaesthetise both the intercostal (upper TAP) plexus and the deep circumflex iliac artery plexus (lower TAP plexus), as described by Rozen et al. 4. Dual TAP blocks administered separately to each hemi-abdomen have already been shown to be necessary if anaesthesia of the entire antero-lateral abdominal wall is intended 3. As ‘four-quadrant TAP block’ refers to the four anatomical quadrants of the anterior abdominal wall, we would encourage adherence to the original name ‘BD-TAP block’, which refers more correctly to the extent of the anatomical TAP, namely the fascial space superficial to the entire transversus abdominis muscle which covers both the lateral and the anterior parts of the abdominal wall. Similarly, Niraj et al. use the term ‘posterior TAP block’ to describe injection of local anaesthetic and insertion of catheters into the neurovascular plane between the internal oblique and transversus abdominis muscles, with the transducer placed axially in the mid-axillary line on the lateral abdominal wall, when the term has previously been used to specify injections into the triangle of Petit 5-8. Injections between the internal oblique and transversus abdominis muscles in the mid-axillary line are called ‘lateral TAP blocks’ (T10-L1) 3, 6, 8. Segmental nerves T6-T9 emerge from the costal margin between the midline of the abdominal wall and the anterior axillary line to enter the TAP in the intercostal (upper TAP) plexus, whereas other large nerve trunk communications (in the lateral abdominal wall) are associated with the ascending deep circumflex iliac artery (lower TAP plexus) 4, and consequently the local anaesthetic spread, extent of sensory block and duration of analgesia produced by these approaches are significantly different. Again, we urge referral to the nomenclature established previously 3, 6, 8, to avoid confusion. To this end, 'subcostal TAP block', which infers block of the subcostal nerve (T12), should more properly have been referred to as ‘upper TAP block’, as it involves injection into the epigastric region to anaesthetise the intercostal nerves (T6-T9) 2-4. We commend Niraj et al. 1 for promoting administration of local anaesthetic to both the epigastric area and the lateral abdominal wall for laparoscopic surgery, pain after which is multifactorial and related to surgical incisions, intra-abdominal surgical trauma and insufflation of the peritoneum and abdominal wall muscles, causing traction of the blood vessels and nerves and the release of inflammatory mediators. However, because the authors were comparing their technique with epidural analgesia, we wonder if it might have been more appropriate to use continuous TAP blockade of the upper abdominal wall, in addition to that of the lower abdominal wall they describe.

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