Background: Epidural anesthesia continues to play a central role in postoperative analgesia. Epidural catheter breakage and fragment retention in the body is a complication related to epidural anesthesia. To reduce the risk of epidural catheter damage by epidural needles, needles with special changes to the heel of the bevel are commercially available. The present study aimed to assess the effectiveness of blasting and drilling treatments at the heel of the epidural needle bevel to determine which treatment is more appropriate. Methods: The epidural needles with blasting, drilling, or no treatment to the heel of the bevel were prepared. The catheter was pulled out from the tip of the epidural needle, folded back 180˚, and then pulled up at a speed of 400 mm/min until it was fractured. The force needed to break the catheter (FB) was measured. Subsequently, low-density polyethylene (0.05 mm) was vertically penetrated with the needles at a speed of 200 mm/min, and the maximum force at penetration (FP) was measured. Results: The FB values for the blasted, drilled, and control needles were 21.3, 12.23, and 6.27 N, respectively (p < 0.01). The FP values for the blasted, drilled, and control needles were 0.82, 0.69, and 0.73 N, respectively. Conclusion: Blasting treatment is the most effective approach for the prevention of catheter rupture; however, it can increase the puncture force.
Various postoperative analgesia methods have been proposed and developed in recent years, but epidural anesthesia continues to play a central role in postoperative analgesia and has been reported to be an effective analgesic tool. Complications related to epidural catheter placement, including epidural catheter breakage and fragment retention in the body, have been reported. A retained broken catheter was first reported by Bonica et al. [
Catheter rupture generally occurs at the time of removal. When a knot forms or when the catheter gets stuck at the spinous process or vertebral arch, forcible extraction can cause catheter rupture [
We assessed the effectiveness of blasting and drilling treatments at the heel of the epidural needle bevel to determine which treatment is more appropriate. In addition, we examined whether these treatments at the heel affect the needle puncture force.
We prepared 18-gage 96.5-mm-long Tuohy needles (Unisis, Tokyo, Japan) without inner stylets. Blasting and drilling treatments were applied to the heel of the bevel, and those needle treatments were performed by Unisis Corporation. The blasted needle (BN) was processed with minute beads blown at high speed onto the heel, whereas the drilled needle (DN) was processed with a drill rotating at high speed to file the edge and inner side of the heel. The control needle (CN) did not receive any treatment at the heel. The measured dimensions of the needles are presented in
Outer diameter (mm) | Inner diameter (mm) | Thickness (mm) | α (˚) | β (˚) | Height (mm) | Bevel length (mm) | |
---|---|---|---|---|---|---|---|
Specification value | 1.27 | 1.07 | - | 9 | 19 | 1.400 | - |
Allowable range | 0.02 to −0.01 | 0.02 to −0.01 | - | +2 to −1 | +2 to −1 | +0.20 to 0 | - |
Blasted needle | 1.28 | 1.06 | 0.11 | 10.06 | 18.10 | 1.412 | 2.943 |
Drilled needle | 1.28 | 1.06 | 0.11 | 10.36 | 18.14 | 1.424 | 2.933 |
Control needle | 1.28 | 1.06 | 0.11 | 10.22 | 18.40 | 1.466 | 2.867 |
Blasted needle Drilled needle Control needle
We initially investigated whether the two different treatments of the heel of the bevel, blasting and drilling, were appropriate for the prevention of catheter rupture. For assessment, we conducted a laboratory study. A compact tabletop tester (EZ-Test, Shimadzu, Kyoto, Japan) was used to measure the breaking force of the catheter. The epidural needle was fixed vertically on the tester. The catheter (Unisis® 22G, 900 mm, polyurethane) was pulled out from the tip of the needle and was folded back 180˚, and one side of the catheter was fixed while another side was gripped by the jig of the tester. The catheter was then pulled up at a speed of 400 mm/min until it was fractured. The force needed to break the catheter (FB) was measured. This experiment was repeated 10 times with each needle. Additionally, we investigated the durability of the catheter itself without the needle. The catheter with one end fixed was pulled up by the tester until it was sheared, and the force (FB catheter) was measured.
We subsequently measured the puncture force. A precision universal tester (Autograph AG-1, Shimadzu) was used to measure the puncture force. The epidural needle without a stylet was vertically set in the tester. Then, a low-density polyethylene film (0.05 mm; Nipolon® 183, Tosoh, Tokyo, Japan) was vertically penetrated at a speed of 200 mm/min, and the maximum force at penetration (FP) was measured. We adjusted the needle speed to 200 mm/min because it was visually identical with the speed of clinical use. Each needle penetrated the film 10 times.
One-way ANOVA was carried out with GraphPad Prism 7 (GraphPad Software Inc., San Diego, CA, USA), and Turkey’s test was used for multiple comparisons. A p-value < 0.05 was considered to indicate a significant difference.
The FB of each needle is presented in
The FP exhibited a bimodal waveform with two peaks (
Retention of an epidural catheter inside the body is uncommon, but some cases have been occasionally reported. To our knowledge, this is the first study to examine the influence of epidural needle treatment at the heel of the bevel on epidural catheter rupture. We found that the FB of the BN was larger than that of the DN, and the intensity was almost equivalent to the force needed to break the catheter without a needle. Thus, blasting treatment at the heel was more effective than drilling treatment as an approach to prevent catheter breakage. Nevertheless,
Blasted needle | Drilled needle | Control needle | Catheter only | |
---|---|---|---|---|
FB (mean [SD]) (N) | 21.30 (1.54)** | 12.23 (2.05)** | 6.27 (0.75)** | 24.00 (2.23)** |
**p < 0.01. FB: the force needed to break the catheter, catheter only: the force needed to break the catheter without a needle. Each value was significantly different between groups.
Blasted needle | Drilled needle | Control needle | |
---|---|---|---|
FP 1st peak (mean [SD]) (N) | 0.42 (0.02) | 0.44 (0.05) | 0.42 (0.02) |
FP 2nd peak (mean [SD]) (N) | 0.82 (0.04) ** | 0.69 (0.02) | 0.73 (0.03) |
**p < 0.01. FP 1st peak: the maximum force measured when the tip of the needle penetrated the film. FP 2nd peak: the maximum force measured when the heel of the needle penetrated the film. There was no significant difference among needles in FP 1st peak. In FP 2nd peak, FP of blasted needle was the largest compared to drilled needle and control needle (p < 0.01).
drilling treatment was effective, as the FB was significantly greater than the control FB, indicating that drilling treatment can prevent catheter breakage to a certain extent. When treatment was not applied to the heel, the FB was significantly smaller and the cut of the catheter appeared smooth and resembled a cut by a blade. Therefore, to decrease the frequency of epidural catheter retention, some effective treatment is necessary at the heel of the epidural needle. We examined whether treatment at the heel has some effect on the needle puncture force. The first peak of the waveform in the puncture force experiment, which was obtained when the needle tip passed through the film, had almost the same value among the three needles. The second peak of the waveform, which was obtained when the needle heel passed through the film, had a significantly higher value in the BN than in the DN and CN. The surface of the BN appeared rough (
Catheter rupture is thought to be associated with excessive extension of the catheter being clamped by the lamina, osteophyte, and occasionally strained muscles during removal. At the time of insertion, the catheter may be cut when the needle is pushed or rotated into the vertebral body or the lamina with the catheter out from the tip of the needle. The characteristics of the broken catheter may explain the mechanism of its breakage. The catheter is stretched when it breaks during removal, but it is not stretched when it breaks during insertion [
In conclusion, treatment of the heel of the epidural needle bevel, especially blasting treatment, can significantly increase the cutting force for the catheter and is important for the prevention of catheter rupture and damage.
We would like to thank the Unisys Corporation for producing and providing us needles we used in this study.
The authors declare no conflicts of interest regarding the publication of this paper.
Urimoto, G., Ito, K., Saito, K., Tetsu, S., Yamazaki, K. and Suzuki, T. (2019) Influence of Epidural Needle Treatment at the Heel of the Bevel on Catheter Breakage. Open Journal of Anesthesiology, 9, 1-7. https://doi.org/10.4236/ojanes.2019.91001