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Brown: Atlas of Regional Anesthesia, 3rd ed., Copyright © 2006 Saunders, An Imprint of Elsevier
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Catheter dislodgement continues to be a problem for many physicians using continuous peripheral infusion techniques. In our experience, tunneling the catheter subcutaneously has eliminated a large number of catheter dislodgements. A variety of tunneling techniques are described, but most are variations of the following description.

The first decision during catheter tunneling is whether a skin bridge is to be used. Using a skin bridge allows easier catheter removal, and it is typically used during short-term catheterization (1–7 days). The technique of catheter tunneling without a skin bridge is often used for longer catheterizations (more than 7 days). The latter has the theoretical advantage of minimizing catheter infection.

After the type of tunneling (skin bridge or no skin bridge) is chosen, the stylet of the Tuohy needle ( Fig. 2-3 A ) is used as the catheter guide and directed to enter the skin 2 to 3 cm from the catheter exit site (for a skin bridge technique). If a non-skin-bridge technique is chosen, the stylet enters the skin through the catheter insertion site. With each technique the stylet is advanced to the desired skin exit site subcutaneously over a distance of approximately 10 cm, or the length of the stylet. The Tuohy needle is then advanced in a retrograde fashion over the stylet ( Fig. 2-3 B ). Next, the stylet is removed, and the catheter is advanced through the needle ( Fig. 2-3 C ) until it is secure and the needle can be withdrawn, leaving the catheter tunneled. If a skin bridge technique is used, a short length of plastic tubing is inserted to protect the skin under the skin bridge ( Fig. 2-3 D ).

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Figure 2-3a  Image of skin bridge and non-skin-bridge techniques used to secure the catheters. A, Touhy stylet being inserted. B, Touhy needle being passed over a stylet as a guide.

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Figure 2-3b  C, Proximal catheter end being threaded into a Touhy lumen. D, Catheter and needle being withdrawn through the final skin entry site.

After the catheter tunneling is complete, the catheter should be checked for stable distal catheter positioning. The SnapLock device (Arrow International, Reading, PA), which allows continuous nerve stimulation via the catheter, is attached to the catheter. The syringe containing the local anesthetic agent is attached to the SnapLock ( Fig. 2-4 ). Then, while still stimulating the catheter and eliciting a motor response, injection of the local anesthetic is started. The evoked motor response should cease immediately with the injection. Saline, when injected through the catheter, has the same discontinuation of motor response, but when water is injected it does not. This is due to dispersion of the current by the conductive fluid (local anesthetic or saline); more current is therefore required to produce a motor response.

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Figure 2-4  Image of SnapLock device and implications of local anesthetic injection through a catheter being stimulated and the appropriate fade of current response. A, SnapLock device attached to a catheter. B, Alligator extension placed in a SnapLock device. C, Syringe attached to a SnapLock device. D, Stimulation pattern sought through catheter stimulation. It should fade with injection of local anesthetic to confirm correct placement.

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