The Learning Curve of Lumbar Epidural Ultrasonography - When is Competency Reached?
Abstract Number: 103
Abstract Type: Original Research
Background and Aims: Epidural ultrasound teaching is becoming an important part of obstetric anesthesia training. Currently we do not know how many scans and hours of training are required before competency is reached. Therefore we aimed to use a novel technique to determine the learning curve including number of scans required to reach competency.
Methods: Anesthetic trainees were shown a 10 minute narrated presentation and given a 15 minute hands-on tutorial. They were assessed on a subject using a 2-5mHz ultrasound probe.They had to perform the following competency tasks: correct identification of the randomly assigned inter vertebral space, mark the ideal needle insertion point(IIP) and measure the depth to the ligamentum flavum-duramater complex (two session; minimum 60 trials with 5 min. limit). Expert marking was performed in advance with an UV marker. UV light illumination allowed comparison between the trainee and expert mark. Feedback was given after each scan.
Statistical methods: Statistical analysis was performed using SPSS. In addition to descriptive statistics, mixed linear regression and logistic regression were used to examine subject and scan sequence effects on performance. A cusum chart for individual subjects were produced.
Results:5 Trainees participated in the study. The average ideal insertion point (IIP) distance relative to the bench mark was 5.2 mm (95% CI = 4.9, 5.3; range 0 to 19; median = 5.0). There were significant difference in the average distances between subjects (p = 0.02).Also, the scan sequence significantly effected the average IIP distance (p = 0.04), with the distance reducing with increasing number of scans. Based on a 5mm tolerance relative to the bench mark, on average 34.6% of scans were unacceptable. There was a significant scan sequence effect (p = 0.01), with a higher rate of unacceptable scans among the earlier scans.
In terms of continued training, there is an ongoing performance issue. Subjects achieved acceptable distances relatively quickly, but were unable to maintain this performance on all subsequent scans. There was, however, a tendency for a higher rate of acceptable scans around number 40.
Of the 350 scans, subjects correctly identified the inter vertebral space on average 97.4% of the time.
Conclusions:Accurate marking the IIP for lumbar epidurals is a advanced ultrasound skill that probably requires at least 40 scans (4 hours of scanning in our study)to achieve competency.