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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.
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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.
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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
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