The use of Ultrasound Guided Regional Anaesthesia (USRA) has increased over the last decade.
Theoretically, ultrasound imaging may increase efficacy and safety by allowing visualization
of the needle pathway and local anaesthetic spread around the nerve. In addition to knowledge
of anatomy and general principles of ultrasonography, USRA requires learning new skills such
as image interpretation, needle-beam alignment, and needle trajectory tracking. The hand-eye
coordination required during needle advancement requires practice to master because the
needle must be properly aligned with the ultrasound probe in order to maintain the needle
path in the beam at all times. Adding to the difficulty, hand and needle movements can occur
in three axes, but an ultrasound image is seen in only two dimensions. Since the ability to
acquire the necessary skills to perform USRA is subjective and not yet validated, it is
difficult to recommend a single, effective training pathway.
Currently, the only method of supervised training before performing an USRA procedure on an
actual patient involves practicing needle insertion in a phantom or cadaver. Studies
assessing the impact of learning using these methods are lacking. It is possible that some
practitioners may choose alternative one-off learning methods. Such methods are not
standardized and are thus difficult to evaluate.
This was a single site, prospective, pre-test-post-test, randomized study conducted after
Institutional Review Board (IRB) approval. Thirty subjects, including medical students,
practicing anaesthesiologists and anaesthesia residents in training at the Penn State Hershey
Medical Center, were recruited by formal email invitation to participate. Written consent was
obtained from each participant before their inclusion in the study and each participant
completed a pre-study form. Once enrolled in the study, participants were given 10 minutes to
familiarize themselves with both the ultrasound equipment (SonoSite, MTurbo, Bothell, WA,
USA) and the phantom model (MiniSim™ Upper Extremity Series, Life tech Inc., Stafford, Texas,
USA). They also viewed a pre-recorded video demonstrating the task they were to perform. As a
pre-test, participants performed the required Needle Insertion Accuracy (NIA) task 3
consecutive times and were assessed using a scoring form adapted from the Mayo Clinic. After
completing the pre-test, participants were randomly divided into two groups, experimental and
control, by a computer-generated randomization list (SAS Institute, Cary, NC). Participants
were blinded to their group assignment.
Previously, we have reported details of the new learning tool. Briefly, all spatial movements
occur in three dimensions which can be labeled the x-axis, the y-axis and the z-axis. A video
camera records movement in two axes. By placing a second video camera at 90 degrees to the
first camera, the third axis can be recorded as well as one axis in common with the first
camera. Video recordings are stored electronically on a hard-drive and can be reviewed
individually or in combination, at normal speed, or slowed if necessary. Still images can
also be obtained.
The experimental group was allowed to practice the same pre-test task using the same
ultrasound machine and phantom model. On a single computer screen, they were able to
visualize their hand and needle movements along with the position of the ultrasound probe.
The control group was allowed to practice the same pre-test task using the same ultrasound
machine and phantom model but without the added visual aid. Both groups were allowed to
practice their pre-test tasks for a maximum of 30 minutes, and recorded their self-assessment
as proficient or not proficient at that time. Both groups then performed the post-test, which
was the same task used for the pre-test, and each trainee was evaluated using the same
scoring tool. To avoid subjective variations and inter-rater variability, all evaluations
were recorded by a single blinded investigator.
Statistical analysis Pre- and post-test mean scores (ranging from 5 to15) were analyzed using
statistical methods to determine whether this new learning tool improved NIA skills required
with USRA. Pre-test and post-test scores (ranging from 5 to 15) were obtained in triplicate
and averaged to produce a representative assessment for each participant. The primary
endpoint was change in NIA score from baseline, i.e., the score difference obtained by
subtracting the mean pre-test score from the mean post-test score. A sample size of 15
subjects per group (experimental and control) provides 80% power to detect an effect size of
1, based on a two-sided t-test with a 5% error probability (calculated using G*Power version
3.1). Analysis of the primary endpoint utilized a two-sided, two-sample t-test at the 5%
level of significance. Secondary analyses evaluated the intervention effect on novice
trainees, and trainees with prior USRA experience. Score differences for individual NIA
skills (movement, alignment, approach, target, location) were also analyzed.
- Health Care professional