Joseph M. Neal, M.D.
Committee on Regional Anesthesia

These are exciting times for regional anesthesia enthusiasts. In this brief report, I discuss three important areas of advancement in the subspecialty: 1) innovative techniques for optimizing and extending the duration of peripheral nerve blockade, 2) scholarly initiatives to define best practice and 3) enhanced ability to localize nerves. Heightened interest in regional anesthesia is further underscored by the ASA House of Delegates’ decision in October 2003 to create a Committee on Regional Anesthesia, which is charged with coordinating and advancing educational opportunities pertaining to this vital component of anesthetic practice. Serving as chair of the 2004 Committe on Regional Anesthesia is Terese T. Horlocker, M.D.

Optimizing and extending peripheral nerve blockade
While the 1990s brought tremendous advances in neuraxis-mediated postoperative analgesia, the first decade of the new millennium promises similar breakthroughs in peripheral nerve, local anesthetic blockade. Innovation comes in two forms. First, largely thanks to our European colleagues, we have come to understand the added value of seeking multiple nerve stimulations and perineural injections as a means of enhancing peripheral nerve blocks. Although they are not advantageous for the interscalene or supraclavicular approaches because of the tightly configured neural anatomy in those locations, multiple injections clearly improve block quality and perhaps hasten onset time when applied to more widely spaced nerves, such as with the axillary, infraclavicular or lateral popliteal approaches. More importantly anesthesiologists now have the ability to prolong peripheral nerve blockade beyond the duration of bupivacaine or ropivacaine.

The use of continuous perineural catheters has prompted a flurry of clinical trials within the academic community and a heightened interest among private-practice anesthesiologists. Initial randomized clinical trials demonstrate the ability of continuous catheters to provide superior analgesia as compared to placebo, thereby limiting opioid-induced side effects. In logical progression, current studies are attempting to document further outcome benefits, especially in the ambulatory setting or with rehabilitation after total joint replacement. Advances in catheter and infusion pump technology should further enhance catheter-based analgesia. For example the ability of stimulating catheter systems to ensure a perineural location of the catheter tip now must be proven to enhance postoperative analgesia as compared to the older and less expensive systems that are designed to be placed blindly. Furthermore, despite not yet being commercially available, sustained-release microsphere and liposomal preparations of local anesthetic or opioid hold great promise for prolonging analgesia.

Defining best clinical practice
As in other areas of medical practice, we are faced daily with practical questions about how best to conduct our practice in the absence of definitive evidence; yet the “holy grail” of suitably powered randomized clinical trials is largely unavailable. The American Society of Regional Anesthesia and Pain Medicine (ASRA) has been a leader in developing two facets of scholarly inquiry aimed at providing practitioners with extensively reviewed and widely available resources related to managing the day-to-day challenges of patient care.

An example of the first initiative is documenting our current understanding of brachial plexus anesthesia. In 2001, a panel of experts examined the existing upper-extremity anesthesiology literature, and the ensuing review article was published in 2002.¹ The entire source document, including anatomic images, is available to ASRA members and can be found at <www.asra.com>. A similar review of lower-extremity regional anesthesia is scheduled for fall 2004.

The second category of scholarly inquiry takes the form of expert opinion panels convened to exhaustively search the literature and make recommendations for best practices pertaining to common clinical dilemmas that have “no right answer.” The Society’s flagship effort in this regard was its 1998 “Guidelines on Neuraxial Anesthesia and Anticoagulation,” which were subsequently updated in 2002. Essential recommendations from this panel are available at <www.asra.com> with the full report published in Regional Anesthesia and Pain Medicine.² ASRA recently completed a similar Consensus Conference on Infectious Complications of Regional Anesthesia at its 2004 Annual Spring Meeting on March 11-14 in Orlando, Florida. This conference considered such practical concerns as acceptable aseptic technique when placing blocks or pain management hardware, the risks of performing regional techniques in the infected or immunocompromised patient and defining proper infectious prophylaxis prior to placing continuous delivery systems. Proceedings of this conference will be published in late 2004 in Regional Anesthesia and Pain Medicine.

The ASRA 2005 Spring Meeting on April 21-24 in Toronto, Ontario, Canada, will consider neurologic complications of regional anesthesia and pain medicine by analyzing how to manage persistent paresthesia, when it is appropriate to perform regional techniques in anesthetized patients and the risks of performing regional techniques in patients with pre-existing neurological conditions.

Enhancing nerve localization
Performing regional anesthesia is easier when one can quickly and accurately localize the target nerve or plexus. Two promising areas of accelerated investigation are noteworthy. First are the studies seeking to understand the nature of needle-to-nerve proximity. Despite decades of experience with nerve localization, which was first based on paresthesia-seeking techniques and more recently on peripheral nerve stimulation, our understanding of these modalities is rudimentary. Why do we sometimes elicit a paresthesia before we observe a peripheral nerve stimulator-induced motor response? What exactly does a paresthesia represent? How do we improve nerve stimulator design to ensure proximity to the target nerve without impalement? These seemingly basic questions have gained importance as we begin to relate peripheral neuroanatomy to the properties of nerve stimulation.

Perhaps even more exciting is the commercial development of high-frequency ultrasonic probes that allow us to actually visualize the target nerve. Initial clinical studies document the ability of this technology to identify peripheral nerves; what must now be shown is whether it can actually improve block performance and safety. At the very least, ultrasonography is likely to become a valuable tool in our quest to understand needle-to-nerve proximity and its implied relationship to patient safety.

In spite of decreased research funding, increased patient care demands and diminishing academic output as measured by fewer American submissions to anesthesiology journals, great progress is being made in regional anesthesia. Practitioners of regional anesthesia are justifiably optimistic that their efforts to optimize blocks, identify best practices and better localize nerves will benefit our current and future patients.


References:

1. Neal JM, Hebl JR, Gerancher JC, Hogan QH. Brachial plexus anesthesia: Essentials of our current understanding. Reg Anesth Pain Med. 2002; 27:402-428.

2. Horlocker TT, Wedel DJ, Benzon H, et al. Regional anesthesia in the anticoagulated patient: Defining the risks. Reg Anesth Pain Med. 2003; 28:172-197.

Joseph M. Neal, M.D., is a staff anesthesiologist at Virginia Mason Medical Center, Seattle, Washington.