[Evaluating the learning curve for the transversus abdominal plane block: a prospective observational study]

Anesthesia is a medical specialty where a large number of technical skills need to be mastered with the learning curve for these skills depending on both the technique and the individual involved. The transversus abdominis plane (TAP) block has demonstrated its effectiveness especially in postoperative analgesia following midline laparotomy. It is usually described as a simple technique even though little is known about the learning curve for this block. The purpose of this study was to determine the learning curve for ultrasound-guided TAP block in anesthesiologists who had no prior experience performing the block.

This was a prospective observational study performed in gynecological and general surgery patients at the University Hospital Center of Nancy (France) between November 2011 and June 2012. After a short theoretical training, sixresidents were asked to perform, 20 TAP blocks under the supervision of a senior staff physician. The success of the procedure involved the visualization and identification of the different muscle planes, the peritoneum, the tip of the needle, an evaluation of the effectiveness of the block (sensory block), the absence of intervention from the supervisor, the absence of complications, less than three attempts, and a satisfaction score by the supervisor > 7 on a 0-10 rating scale. A learning curve/cummulative summation (LC-CUSUM) was generated.

The six residents performed all 20 TAP blocks. All residents had already performed ultrasound-guided procedures. The procedure was considered mastered after performing 16 blocks on average for a 90% success rate. The average time (SD) to complete the block decreased from 6.8 (4.1 min) at the beginning to 2.8 (1.3) min at the end of the study. There was a decrease in the number of repositionings of the needle and in the number of interventions by the supervisor throughout the study. The LC-CUSUM analysis revealed that all residents had acquired the TAP block technique within 20 procedures.

This study demonstrates that the TAP block can be rapidly mastered even if the learning curve varies due to inter-individual differences in dexterity and in the ease of obtaining the ultrasound images.