Chapter 49

It has been well established that peripheral nerve blocks and neuraxial blocks provide superior analgesia for the treatment of acute pain, especially postoperative pain. The main limitation of these modalities is that acute postoperative pain usually outlasts the relief afforded by single-injection techniques. As a result, continuous peripheral nerve blocks have been developed to overcome these limitations, to extend analgesia beyond duration of a single-injection method, and to allow for greater ability to titrate sensory–motor differentiation of the blockade. Unlike the case for single-injection techniques, continuous nerve block via a perineural catheter, can be discontinued or the infusion changed if unwanted side effects occur. The main emphasis during the past decade has been to develop catheters and techniques that allow relatively simple, accurate, and noninvasive catheter placement to ensure effectiveness and to reduce secondary block failure. These aims have been largely accomplished in the past decade; the current efforts seek to define indications and infusion strategies for continuous peripheral nerve blocks, especially in the setting of outpatient surgery.

Two techniques are currently used to place perineural catheters: the nonstimulating catheter technique described by Steele and colleagues1 and the stimulating catheter technique.2 With a nonstimulating technique, an insulated needle (usually a Tuohy needle) is inserted near a nerve with the aid of a nerve stimulator. Saline or a local anesthetic agent is then injected through the needle to “expand” the perineural space, and a catheter (usually an epidural, multiorifice catheter) is inserted. This technique is relatively simple to perform and provides a reliable primary block (local anesthetic agent injected through the needle). However, because the catheter is placed without confirmation of the tip position, the success rate of the secondary block (infusion through the catheter) may be lower than for the primary block.

With the stimulating catheter technique, an insulated needle (typically a Tuohy needle) is inserted close to a nerve, and a nerve stimulator is used, similar to the procedure for a nonstimulating technique (Figure 49–1). Once the nerve or plexus is electrolocalized, a catheter with an electrically conductive connection to the tip of the catheter (a spring wire2 or a steel stylet3) is then inserted through the needle (Figure 49–2). This allows stimulation of the nerve via the catheter to ensure accurate positioning. With this technique, both the bolus dose and continuous infusion of local anesthetic are injected through the catheter. This technique requires a few extra steps; however, the confirmation of the needle tip position logically should provide a lower risk of secondary block failure due to more accurate catheter placement.4

###### Fig. 49-1

The first step is nerve localization techniques identical to those with nonstimulating catheters. Shown here is the needle insertion for femoral nerve block.

###### Fig. 49-2

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