The insertion of catheters percuTaneously to allow the infusion of local anesthetic solutions was initially described by Ansbro in 1946.¹ Techniques for placement of catheters have evolved from elicitation of paresthesias, to fascial clicks,² and subsequently to fluoroscopy,³ nerve stimulator, and ultrasound imaging. The most popular method for inserting catheters is a through-the-needle technique (Fig. 14.1), although catheter-over-the-needle techniques have been reported as well. Placement of a continuous catheter offers some distinct advantages compared to single-injection techniques. In particular, the duration of nerve blockade is a major advantage. Although there are many adjuncts that have been studied to increase the duration of single-injection peripheral nerve blockade, none have been shown to consistently result in analgesia for multiple days to weeks as can catheter techniques.^4,5 A catheter can also permit titration of the dose of local anesthetic to increase analgesia or decrease motor blockade to encourage participation in physical therapy. Catheters also provide flexibility in discontinuation and continuation of infusion as dictated by patient care. These benefits have encouraged the use of catheters throughout the body.

Continuous nerve blockade is used to provide analgesia for surgeries of the upper extremity (Fig. 14.2), thoracic and abdominal areas (Fig. 14.3), and lower extremity (Fig. 14.4). Upper extremity applications include blocks at the interscalene, supraclavicular, cervical paravertebral, suprascapular, infraclavicular, and axillary sites. Thoracic and abdominal catheter techniques include paravertebral, intercostal, epidural, transversus abdominis plane, rectus sheath, and ilioinguinal/iliohypogastric blocks. Finally, catheters for lower extremity surgeries may be inserted at the lumbar plexus, femoral, parasacral, paravertebral, lateral femoral cuTaneous, obturator, fascia iliaca, sciatic, and saphenous regions. The use of ultrasound helps identify the nerves in many of these techniques and allows flexibility in the approach to each. As experience with continuous catheter techniques in a myriad of anatomic regions has accumulated, so has the literature on proper placement, use, and complications.

Peripheral nerve blockade has been associated with neurologic injuries; catheter knotting^{6, 7and 8}; catheter migration and dislodgement; catheter obstruction; fluid leakage; neural irritation⁹; inflammation; colonization; abscess formation; sepsis; hematoma formation^10,11; myotoxocity¹²; and catheter shearing, breakage, and retention. Inaccurate placement of catheters has also been reported, with catheter tips too far from the nerve, intraneural placement, intravascular insertion, inadvertent intrathecal or epidural penetration, and intrapleural placement. Considering these risks and complications, it is essential to ensure proper placement of the catheter and confirm its position, especially if they are to be used in the ambulatory setting.