Continuous nerve blocks are an important tool for postoperative pain management, providing sustained analgesia with minimal local anesthetic volume [1]. To allow for effective analgesia using continuous nerve blocks, the catheter tip must be placed close to the nerve [2]. However, one of the challenges encountered in this technique is catheter migration [1]. Catheter migration refers to the unintended movement of the catheter away from the target nerve or site of action. This may result in inadequate delivery of local anesthetic to the target nerve, leading to suboptimal pain relief. Further, malpositioned catheters can cause unintentional nerve injury, vascular puncture, or local anesthetic toxicity—complications that can prolong hospitalization and delay recovery. As the use of continuous nerve blocks expands, with some patients even discharged with peripheral catheters and ambulatory pumps, catheter migration issues have become more pertinent.

There are several factors that contribute to catheter migration in continuous nerve blocks. These include patient mobility, catheter insertion techniques, catheter characteristics, and imaging technology for insertion. Patient mobility in particular can displace the catheter from its initial placement site. One study that evaluated catheter migration in volunteers who performed standardized physical exercises at regular intervals found a 15% overall dislocation rate [3]. This brings to light the importance of localizing catheters even after initial insertion. Additionally, catheters come in two designs: single- and multi-orifice. However, there is a lack of evidence suggesting design choice affects the success of catheter analgesia or impacts migration [1].

In contrast, the selected technique for catheter insertion does impact success. Using a blind technique, where the needle is positioned close to the nerve and a catheter is threaded over the needle tip, can provide successful nerve block with inaccurate placement. Some studies have shown 60-70% of catheters being malpositioned using this technique [4]. To improve success and migration rates, stimulating catheters were developed. Stimulation of the catheter tips allows for muscle twitches to direct the catheter to the optimal placement close to the nerve [5]. However, the benefits of these catheters are somewhat limited, and recent meta-analyses showed that ultrasound-guided catheter placement was associated with a higher success rate than nerve stimulation [6].

Recently, new developments in ultrasound allowing for 3 and 4-dimensional modalities and color imaging are improving catheter tip localization [1]. Not only does this imaging allow for correct catheter placement and reduced risk of migration, but it can also enhance safety in continuous nerve blocks. As catheter migration continues to be a pertinent issue in anesthesia and pain medicine, continuing to improve peripheral nerve catheter technology can further enhance perioperative and analgesic management of patients. 

References

1. Elsharkawy H, Maheshwari A, Farag E, et al. Development of technologies for placement of perineural catheters. J Anesth 2016;30:138–47.
2. Grant SA, Nielsen KC, Greengrass RA, Steele SM, Klein SM. Continuous peripheral nerve block for ambulatory surgery. Reg Anesth Pain Med. 2001;26(3):209–14.
3. Marhofer D, Marhofer P, Triffterer L, Leonhardt M, Weber M, Zeitlinger M. Dislocation rates of perineural catheters: a volunteer study. Br J Anaesth. 2013;111(5):800–6.
4. Capdevila X, Biboulet P, Morau D, Bernard N, Deschodt J, Lopez S, d’Athis F. Continuous three-in-one block for postoperative pain after lower limb orthopedic surgery: where do the catheters go? Anesth Analg. 2002;94(4):1001–6
5. Pham-Dang C, Kick O, Collet T, Gouin F, Pinaud M. Continuous peripheral nerve blocks with stimulating catheters. Reg Anesth Pain Med. 2003;28(2):83–8.
6. Schnabel A, Meyer-Friessem CH, Zahn PK, Pogatzki-Zahn EM. Ultrasound compared with nerve stimulation guidance for peripheral nerve catheter placement: a meta-analysis of randomized controlled trials. Br J Anaesth. 2013;111(4):564–72.