A Double Blinded Randomized Controlled Trial on the Effects of Four Sequential Maneuvers on Ultrasound Guided Nerve Block Performance

After watching the training video, each volunteer will be placed in front of a set up identical to the video seen. Adjacent to this set up, a single fellowship trained regional anesthesiologist known as the assessor is situated with a screen that allows real time viewing of the ultrasound screen seen by the volunteer. The assessor is blinded to the assignment of the volunteer. Also, the assessor does not have any visualization of the volunteer. This prevents visualizing hand or body movement that may cause a bias. The same assessor is used for the whole study to provide consistent assessment of the task.

The task involves the volunteer directing an 80 mm echogenic Pajunk needle into 3 targets in a standardized homemade phantom. The targets simulate the nerve roots commonly found in the interscalene block. Thus, they are arranged diagonally to simulate the nerve root position commonly seen. Also, they are arranged on a tilt relative to the flat surface of the phantom to simulate the direction the nerve travels. This is important as the tilt of the target requires the volunteer to tilt the probe so that their incidental ultrasound wave is perpendicular to the target for the brightest reflection to occur. This phenomenon is known as anisotropy. This increases the realism of the task that cannot be imitated by commercially available phantoms.

There are 3 goals that the volunteer must fulfill in performing their task. Firstly, they must direct the needle to the 12 o'clock position of the 3 targets. Secondly, they must achieve maximal ultrasound image brightness of the 3 targets at all times. Thirdly, the entire needle must be visualized at all times.

If the needle is not in the correct position, the assessor will verbally inform the volunteer to redirect it to the correct position. If the target images are not at their brightest, the assessor will verbally inform the volunteer not to manipulate the needle towards the target until the targets are at their brightest. Clinically, this functions to prevent the needle being inserted inside the nerve as the targets are not clearly seen. Thirdly, if the needle is visualized entirely, the volunteer will be told to stop manipulating the needle towards the target until the needle is fully visualized by manipulating the probe. A timer records the cumulative time the needle is not in full visualization. Clinically, this functions to prevent the needle being inserted into a nerve or structure that it should not.

After all 3 targets have been completed, the volunteer repeats the task a total of 3 times.