The maximum duration of a single-injection peripheral nerve block is approximately 8–24 hours.1 Prolonging a peripheral nerve block may be desirable, and can be achieved with a continuous local anesthetic infusion via a perineural catheter. A continuous peripheral nerve block (CPNB) requires placement of a perineural catheter in the vicinity of a targeted peripheral nerve for the purpose of subsequently administering local anesthetic. Another term for this practice is perineural local anesthetic infusion. CPNBs are utilized for a wide variety of indications, most typically for anesthesia or analgesia in a peripheral nerve distribution. While not every application of CPNB has been exhaustively validated by randomized trials, continuous blocks have been reported for over 20 anatomic locations. The majority of described applications of CPNBs relate to the treatment of perioperative surgery-related pain.
HISTORY AND BACKGROUND OF CPNBs
The practice of continuous perineural analgesia has developed in parallel with technologic advances over nearly 70 years’ time. Methods for identification of the catheter target have included anatomic landmarks, paresthesias, electrical stimulation, fluoroscopy, and ultrasound.1 Continuous peripheral nerve blockade was described as early as 1946 by Ansbro.2 A series of patients undergoing upper extremity surgeries as long as 4 hours in duration received a cork-stabilized needle at the supraclavicular level of the brachial plexus.2 Other early reports include a similar practice in 1950 by Humphries.3 In 1951, Sarnoff and colleagues reported placement of a polyethylene tube advanced through an insulated needle placed adjacent to a peripheral nerve using electrical stimulation.4 By 1995, continuous perineural catheters were being inserted using multiple modalities. Pham-Dang and colleagues described fluoroscope-guided catheter placement adjacent to the brachial plexus within the axilla.5 In that same year, Guzeldemir reported using ultrasound to place an axillary brachial plexus catheter.6 By the late 1990s, ambulatory continuous peripheral nerve blocks gained popularity.7,8 Relatively small, light, and inexpensive portable infusion pumps permitted outpatient infusion.9
Equipment providing a continuous infusion has evolved from a simple cork stabilizing a delivery needle,2 to a catheter sheath advanced over a needle stylet,5 to epidural-type catheters threaded through stimulating needles.10,11,12 Stimulating catheters were introduced in an attempt to improve perineural location of the catheter tip,13 although they are being reported far less frequently due to the evolution of ultrasound-guided (nonstimulating) catheter insertion techniques.14 Whatever the technique or method of insertion, catheters are always placed within a tissue space that contains the plexus or nerve(s) of interest. (Figure 71–1) Patient selection for perineural catheters has also evolved from a solely hospital-based practice to inclusion of outpatient infusions.15 While adhering to patient selection criteria, continuous techniques can be applied to pediatric, pregnant, and geriatric patients, as well as healthy ambulatory patients and the critically ill. Reported locations for continuous nerve blocks span a multitude of anatomic sites in the ...