Regardless of the Puncture Angle , a Tuohy Needle with SandBlasted Steel at the Tip of the Bevel Is a Valid Needle on the Ultrasonic Images

Background: A high ability to visualize the needle on the ultrasonic images is necessary to perform the ultrasound-guided nerve block safely. The Rafa Tuohy needleR (Vygon, Paris, France, Rafa) is a non-stimulating Tuohy needle with sand-blasted steel at the tip of the bevel. We examined the degree to which the Rafa enhanced the visibility of ultrasonic images compared with the non-coated Tuohy needle. Methods: We punctured the Blue Phantom. The dimensions of both the Rafa and the non-coated Tuohy needles were 18 G × 80 mm. The puncture angle is 30 degrees and 45 degrees from the Blue Phantom. We measured the intensity of the tip of the bevel at a depth of 0.5, 1.0, 1.5 and 2.0 cm for the puncture angle of 30 degrees, and 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 cm for the puncture angle of 45 degrees. Six anesthesiologists with more than seven years of experience performed three punctures using each needle. Results: As an outcome, we concluded that at a puncture angle of both 30 degrees and 45 degrees, the intensity of the non-coated Tuohy needle decreased with the depth. On the other hand, at an angle of 30 degrees, the intensity of the Rafa needle did not decrease, and at an angle of 45 degrees the intensity only decreased very slightly as the depth increased. Conclusions: The Tuohy needle with sand-blasted steel at the tip of the bevel provided greater visualization than the non-coated Tuohy needle on the ultrasound images.


Introduction
When we perform the ultrasound-guided nerve blocks, we will encounter complications such as nerve or organ injuries, and local anesthetic systemic toxicity [1]- [3].One of the reasons, which can cause some complications, is the poor visualization on the ultrasound images in performing the ultrasound-guided nerve blocks.Therefore, the needle has been devised in various ways in order to improve the visualization of the needle on the ultrasound images [4]- [7].The Rafa Tuohy needle R (Vygon, Paris, France, Rafa) is a non-stimulating Tuohy needle with sand-blasted steel at the tip of the bevel.We can predict that the modification would also enhance the visibility of ultrasonic images regardless of some puncture angles.In this study, we examined the degree to which the Rafa enhanced the visibility of ultrasonic images compared with the non-coated Tuohy needle.

Materials & Methods
We did not submit this study to an institutional review board due to lack of human testing with the Blue Phantom.We prepared the S-Nerve ultrasound system (SonoSite FUJIFILM, Washington, America) and the Blue Phantom for the peripheral nerve blocks (CAE Healthcare, Sarasota, FL).We punctured the Blue Phantom by using a 50-x high-frequency linear probe with a needle guide kit (Civco Medical Instrument Co., Orange City, IA).The dimensions of both the Rafa and the non-coated Tuohy needles were 18 G × 80 mm.The puncture angle was 30 degrees and 45 degrees to the skin.We used Image J software, which is an image-processing program designed for scientific multidimensional images, to measure the intensity of the tip of the bevel at a depth of 0.5, 1.0, 1.5 and 2.0 cm for the puncture angle of 30degrees, and 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 cm for the puncture angle of 45 degrees.Six anesthesiologists with more than seven years of experience performed the ultrasound-guided nerve block and made three punctures using each needle.

Statistics
The Student's t-test was used for statistical analysis, and significance was accepted at p < 0.05.The numerical variables of the intensity at the tip of the needle are expressed as mean (standard deviation) (cd/m 2 ).
In all the readings we took, the intensity of the Rafa was clearly higher than that of the non-coated needle (P < 0.0001).
In the test with the puncture angle set at 30 degrees, the intensity of the non-coated Tuohy needle decreased with the depth.On the other hand, the intensity of the Rafa did not decrease with the depth at all (Figure 1).
In the test with the puncture angle set at 45degrees, the intensity of the non-coated Tuohy needle decreased with the depth.On the other hand, the intensity of the Rafa decreased only slightly with the increase of depth (Figure 2).

Discussions
We could prove the high visualization of the Rafa based on the results gotten for all the points where we gathered  It has been generally reported that the larger the puncture angle is, the lower the visualization of the needle is [8] [9].Therefore, the risk of the deep nerve block has arisen in comparison with the superficial nerve block [10].This study also showed that the intensity of the non-coated Tuohy needle clearly decreased with the puncture angle and the depth.As the Rafa with sand-blasted steel at the tip of the bevel has shown validness on the ultrasound images regardless of the puncture angle and the depth, we are certain it will be effective for deep nerve blocks, such as the paravertebral nerve block and lumber plexus nerve block.It is also easy to check the tip position because only the tip is coated, not the entire needle.
The limitation of this study is caused by the lack of human study, due to the restrictions provided by the Blue Phantom, as it is not homogenous.Furthermore, we cannot measure the intensity at over 3 cm of depth because of the Blue Phantom.The puncture angles of this study are only 30 degrees and 45 degrees.In the future, we will need to perform this study in a clinical setting to confirm the clinical efficacy of this technique.As for the puncture angle, we will have to also perform the other puncture angles in next study.
In this study, the Rafa is a valid needle on the ultrasonic images.The Rafa will provide us the reliability and the safety to perform ultrasound-guided nerve blocks.

Assistance with the Letter
None.

Financial Support and Sponsorship
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Figure 1 .
Figure 1.The intensity of each needle for the puncture angle of 30 degrees.

Figure 2 .
Figure 2. The intensity of each needle for the puncture angle of 45 degrees.