Anesthesiologists' learning curves for ultrasound assessment of the lumbar spine

Ultrasound assessment of the lumbar spine to facilitate neuraxial anesthesia has recently received much attention. The transfer of knowledge pertaining to this skill has never been studied. The purpose of this study was to determine the amount of teaching needed to achieve competence in spinal ultrasound.

Participants were given reading material and a link to a video presentation on spinal ultrasound. As well, they attended a 45-min lecture followed by a 30-min hands-on workshop. They were then assessed individually 1-2 weeks later. The assessment was performed on a live model using a low frequency curved ultrasound probe (2-5 mHz). Participants were asked to determine, at random lumbar spinal levels, the optimal insertion point and the depth to the ligamentum flavum-dura mater unit (up to 20 trials, 2 min per trial). Feedback was provided by an expert for each incorrect task. The learning curves were constructed, using the cumulative sum method, by comparing the participants' results with those of a benchmark established by experts. Statistical analysis was performed using STATA 9.2 for Macintosh (College Station, TX, USA).

A total of 308 anesthesiologists were approached and 18 anesthesiologists participated in the study. Only five of the 18 participants (27%) achieved competence in determining the interspace, with a median number of 11 attempts (range 8-18). None of the participants achieved competence in determining either the insertion point or the depth to the ligamentum flavum-dura mater unit.

Under the study conditions, 20 supervised trials plus teaching sessions were not enough for the participants to achieve competence in different aspects of ultrasound assessment of the lumbar spine. These results may well be considered when planning teaching sessions and workshops in the future.