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