The Transversus Abdominis Plane (TAP) block has been an extraordinary addition to our multi-modal analgesic regimens post abdominal surgery. Since the first report there have been nearly two hundred peer review articles. However it is evident that not all blocks are the same and that the needle endpoint determines the characteristics of the analgesic profile obtained. What is generally recognized is that in order to replicate the pattern of spread attributed to the original landmark based technique  the needle endpoint needs to be more posterior than the mid-axillary approach. In fact as we now know the localized effects of the TAP block in the transversus abdominis plane bear only minor importance in terms of the analgesic efficacy obtained and it is the extension of local anaesthetic agent beyond the TAP plane to the thoracic paravertebral space that is vital in order to obtain extensive analgesia and prolonged action of the injected local anaesthetic solution.
We described the Quadratus Lumborum (QL1) block in 2007 at the ESRA (GB & I) Annual Scientific Meeting in Exeter. The basic concept is the deposition of local anaesthetic solution adjacent to the antero-lateral aspect of the QL muscle. The spread pattern obtained by this approach was similar to that of the landmark based TAP block, in that there was subsequent extension into the thoracic paravertebral space . This concept was further examined by Professor Børglum et al  and in his transmuscular approach he expertly placed the needle tip anterior to the QL muscle. He further refined his approach by cleverly adopting a posterior approach to the QL block using the ‘Shamrock’ sign (the erector spinae, the QL and the Psoas being the leaves and the transverse process of L4 the stem). The deposition of local anaesthetic agent into the plane between the QL and the Psoas resulted in reliable spread to the thoracic paravertebral space and is a safe option as the abdominal cavity is protected by the psoas muscle so that, for experienced practioners, the needle can be easily followed in its track to the inter muscular fascial plane.
However the optimal needle tip positioning remains elusive. Our group has also been interested in this idea for some time and. previously with Dr. Parras and Prof. Prats-Galino, while investigating the QL1 block we also looked at placing the needle posterior to the QL muscle and we coined this approach the QL2 block (fig.1 upper). Using MRI software updates used on the development of the serratus plane block we revisited the images we previously obtained (fig.1 middle). While spread to the thoracic paravertebral space was observed with both approaches our initial report suggests a more complete picture with the posterior approach (fig.1 lower), hydrodissecting the posterior border of the quadratus lumborum muscle outside the fascia. This is particularly important, as the deeper one has to go the poorer the images obtained. The ability to obtain similar spread patterns, as with the QL1 and the original TAP blocks with a more superficial approach will allow for safer, reliable blocks to be performed in the clinical setting.
Abu Dhabi, UAE
J. G. McDonnell
Galway University Hospital
No external funding and no competing interests declared.
- McDonnell JG, O’Donnell B, Heffernan A, Power C, Laffey JG. The analgesic efficacy of transversus abdominis plane block after abdominal surgery: a prospective randomized controlled trial. Anesthesia and Analgesia 2007; 104:193-7.
- Carney J, Finnerty O, Rauf J, Bergin D, Laffey JG, McDonnell JG. Studies on the spread of local anaesthetic solution in transversus abdominis plane blocks. Anaesthesia 2011; 66: 1023-30
- Børglum J, Jensen K, Moriggl B, Lönnqvist P, Christensen AF, Sauter A, Bendtsen TF. Ultrasound-Guided Transmuscular Quadratus Lumborum Blockade. http://www.bjaoxfordjournals.org (accessed 13/12/2013).
Fig. 1 upper. Representation of the optimal point of injection in both QLB I and II.
Fig. 1 middle. Coloured representation of the gadolinium in the ultrasound pictures with the QLB I (middle left) and the QLB II (middle right).External oblique (eo), internal oblique (io), transversus abdominis (ta) and quadratus lumborum muscles (QL).
Fig. 1 lower. Distribution of gadolinium in a 3D reconstruction with the QLB I (left) and QLB II (right).Spread into the paravertebral space is more intense in the QLB type II.
Published with the written consent of the patient.