Authors: Riga M et al.
Journal: Cureus, Volume 18, Issue 1, Article e101365
Summary
This simulator-based technical study examined how the length of the flexible distal segment of a straight echogenic perineural catheter influences the likelihood of achieving a successful coiling maneuver. Coiling is clinically relevant because it may provide a safety margin that reduces catheter tip displacement during continuous peripheral nerve blocks.
Using a Blue Phantom sciatic nerve block simulator, investigators systematically varied the length of the unsupported distal catheter segment by retracting the integral stylet. Distal flexible lengths ranging from 3 to 10 cm were tested across 80 total experiments using a non-sequential design. The primary outcome was binary: successful coiling versus failure to coil.
The relationship between distal flexibility and coiling success followed a sigmoidal functional-response curve. Probit regression modeling demonstrated that the probability of coiling increased with greater distal flexibility before plateauing. A distal flexible length of approximately 7.0 cm was associated with a 90% probability of successful coiling, while 8.1 cm corresponded to a 95% predicted probability.
The study was conducted entirely in a simulator rather than biological tissue. While the phantom material exhibits viscoelastic and self-healing properties similar to human tissue, the inability to perform saline injection prior to catheter advancement limits direct clinical generalizability. Coiling was assessed using two-dimensional ultrasound imaging with offline video review, and interobserver variability was negligible.
Occasional kinking of the coiled distal catheter segment was observed but was infrequent and typically resolved by partial uncoiling. The investigators avoided testing distal lengths exceeding 10 cm due to the risk of knotting and did not examine lengths below 3 cm, which were hypothesized to be insufficient for forming a closed loop.
Overall, this work is framed as hypothesis-generating rather than practice-defining and serves as a foundation for future clinical studies examining catheter coiling behavior in vivo.
What You Should Know
• This was a simulator-based technical study, not a clinical trial.
• Increasing distal flexibility improves coiling probability up to a plateau.
• A distal flexible length around 8 cm maximized predicted coiling success.
• Findings may not directly translate to living tissue or all catheter designs.
• Clinical trials are needed before applying this technique routinely.
Key Points
• Study type: regional anesthesia simulator-based technical study.
• Device: straight 20G echogenic perineural catheter with integral stylet.
• Design: 80 experiments using a non-sequential methodology.
• Analysis: probit regression of coiling success vs distal flexible length.
• Main finding: 8.1 cm distal flexibility optimized coiling probability.
Thank you for allowing us to share this article from Cureus.