We read with interest the summary article on trunk blocks for abdominal surgery, including the transversus abdominis plane (TAP) block [1]. The TAP block originally described from work by Mc Donnell et al [2-3] is a technique our author has adopted, and largely found to be successful for anterior wall abdominal surgery in general surgery and obstetrics and gynaecology.

However, our enthusiasm for this technique is not always shared or sustained by colleagues (from specialty trainees up to consultants) learning the landmark technique, who quickly become frustrated by non-functioning blocks, and uncomfortable patients during the recovery period.

In our experience, it was found that approximately 20 TAP blocks had to be performed before some consistency in block performance could be seen, such that patients were comfortable in the post-operative phase. During teaching episodes, our feedback highlighted two common problems: the lumbar triangle of Petit was often more posterior than anaesthetists anticipated, and the regional anaesthesia needle was often introduced horizontally rather than perpendicular to the skin.

The recent article by Greaves et al. refreshingly suggests a move from competency to excellence or expert practice [4]. However, the acquisition of expert performance is challenging. It has been suggested by Ericsson that expert performance must involve deliberate sustained practice [5]. This can be achieved by massed (intensive learning) or distributed (shorter periods of learning spread over a longer timeframe) practice.

Clearly McDonnell et al. are experts in this domain, and we would be interested to know how many TAP blocks McDonnell et al (and also their trainees) had to perform before gaining proficiency in TAP blocks. Furthermore, how many before expert performance was attained?  It would also be informative to know if massed or distributed practice was more useful for training in their opinion? Finally, were there any other common optimizations of technique used when teaching the TAP block?

Perhaps this will provide some guidance to others, and perpetuate use of TAP blocks where ultrasound is not freely available.

 A Dharmarajah

 V Sodhi

Department of Anaesthesia, Hammersmith and Queen Charlotte's Hospital, Imperial College Healthcare NHS Trust, London, UK

E-mail: aynk@imperial-anaesthesia.org.uk

References

1. Finnerty O, Carney J, McDonnell JG. Trunk blocks for abdominal surgery. Anaesthesia 2010;65 :76-83.

    2.   McDonnell JG, O'Donnell B, Curley G. The Analgesic Efficacy of Transversus Abdominis Plane Block After Abdominal Surgery: A  Prospective Randomized Controlled Trial. Anesthesia & Analgesia 2007;104:193-197.

    3.   McDonnell JG, Curley G, Carney J et al. The analgesic efficacy of transversus abdominis plane block after caesarean delivery: a randomized controlled trial. Anesthesia & Analgesia 2008;106: 186-91.

    4.   Smith AF, Greaves JD. Beyond competence: defining and promoting excellence in anaesthesia. Anaesthesia 2010;65:184-191.

    5.   Ericsson KA. Deliberate practice and the acquisition and maintenance of expert performance in medicine and related domains. Academic medicine 2004;79:S70-S81.

Many thanks to Drs Dharmarajah and Sodhi for raising a few practical questions in relation to performing the TAP block via the landmark technique. We would advise that an anaesthetist would have to perform approximately 50 blocks to achieve competence. This might seem very high but can easily be achieved on busy gynaecology, obstetric, urology and general surgery lists. We would encourage use of the block even for laparoscopic procedures, as it contributes to analgesia and the anaesthetist is able to perform two blocks per procedure. 

It must be remembered that the block is an opioid sparing agent as part of a multimodal analgesia regimen.  Epidural analgesia is the gold standard analgesia for laparotomy, and the TAP block combined with paracetamol, NSAIDS, opiates, +/- ketamine is a good alternative. We advise that all patients undergoing laparotomy still receive intraoperative morphine 0.15mg/kg approximately, with regular simple analgesics postoperatively. The patient may still need supplemental opioid in recovery and this should not be denied.

Regarding the position of the Lumbar Triangle of Petite, I refer back to the original description of the landmark technique (1). The top of the iliac crest is palpated from anterior to posterior until the edge of the latissimus dorsi muscle is palpated. In Figure 1 the triangle of petite is indicated and is always posterior to the mid-axillary line.  Hopefully this visual will reassure trainees that they are correct in finding the triangle of petit more posterior than expected. We would still advocate that the needle be placed perpendicular to the skin at all times. In performing the double pop technique there is considerable variation in the ‘sensation’ of loss of resistance between patient groups. In children or healthy, athletic adults, firm pressure is required to traverse the fascial layers. The obstetric or cachectic patient will have a very ‘soft’ loss of resistance.

The obese patient can be challenging and it can be difficult to differentiate between a true ‘pop’ and passing the needle through pockets of adipose tissue.  We would advise that an assistant stand at the same side of the operator (opposite to the side being blocked), and pull the ‘spare tire’ / adiposity cephalad. The operator places the index and middle finger open in the skin, compresses and holds the skin firmly. This usually improves the differentiation between true ‘pop’ from passing the needle through adipose tissue.  Finally, the triangle can sometimes be palpated more easily by adducting the lower limb away from the side being blocked.

We hope this is helpful advice and would encourage anaesthetists to persist with this helpful, safe block.

Dr Olivia Finnerty, MB, FCARCSI

Dr John McDonnell, MB, MD, FCARCSI

References

1. McDonnell JG, O'Donnell B, Curley G. The Analgesic Efficacy of Transversus Abdominis Plane Block After Abdominal Surgery: A Prospective Randomized Controlled Trial. Anesthesia & Analgesia 2007;104:193-197.

Figure 1: Anatomical boundaries of the Triangle of Petit.