The analgesic efficacy of single-injection peripheral nerve blocks (PNBs) is limited to 8 to 24 hours. A longer duration of analgesia is often desirable, but the options are limited. For the interscalene brachial plexus block, liposome bupivacaine (Exparel) has been approved by the US Food and Drug Administration (FDA) as single-injection analgesia for up to 72 hours. As of April 2021, Exparel is now also approved in EU for interscalane and femoral nerve blocks as well. A longer duration of analgesia can also be accomplished with a continuous infusion of local anesthetic (LA) via a perineurally placed catheter. This method requires a high degree of skill and management, but the equipment is usually available worldwide. Continuous peripheral nerve blocks (CPNBs) are utilized for a wide variety of indications, most typically for anesthesia or analgesia in an increasing number of clinical indications, also as fascial sheath catheters (e.g., pectoralis, erector spinae infusions). The majority of reported applications of CPNBs relate to the treatment of perioperative pain. While there are reports on their new applications, many of the increasing numbers of proposed catheter infusions lack clear evidence-based information on their efficacy.
HISTORY AND BACKGROUND OF CONTINUOUS PERIPHERAL NERVE BLOCKS
The practice of continuous perineural analgesia has developed in parallel with technological advances over nearly 70 years’ time. Methods for identification of the catheter target have included anatomic landmarks, paresthesias, electrical stimulation, fluoroscopy, and ultrasound (US). Continuous peripheral nerve blockade was described as early as 1946 by Ansbro. A series of patients having upper extremity surgeries received a cork-stabilized needle at the supraclavicular level of the brachial plexus. Other early reports include a similar practice in 1950 by Humphries. In 1951, Sarnoff et al. reported placement of a polyethylene tube advanced through an insulated needle placed adjacent to a peripheral nerve using electrical stimulation. By 1995, continuous perineural catheters were being inserted using multiple modalities. Pham-Dang et al. described fluoroscopy-guided catheter placement adjacent to the brachial plexus within the axilla.
Guzeldemir reported using US to place an axillary brachial plexus catheter. By the late 1990s, ambulatory CPNBs gained popularity. Relatively small, light, and inexpensive portable infusion pumps permitted infusion of local anesthetics through the perineurally placed catheters in hospital and outpatient settings.
Equipment for continuous perineural infusion has evolved from a simple cork stabilizing a delivery needle, to a catheter sheath advanced over a needle stylet, to epidural-type catheters threaded through stimulating needles. Stimulating catheters were introduced in an attempt to improve the accuracy of the placement of the catheter tip, although this technology has been largely phased out with the wider use of ultrasound to document the catheter tip placement and local anesthetic spread.
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 8-1). Patient selection for perineural catheters ...