Regional Anesthesia Shifts to Ultrasound Guided Delivery

While regional anesthesia has existed for many decades, the development of highly advanced ultrasound systems over the last 20 years has changed the specialty’s practice substantially. Traditional regional anesthesia delivery relied upon anatomical landmarks and peripheral nerve stimulation to identify nerve location and guide the clinician.  Given the variability amongst people, and the difficulty of identifying anatomical landmarks in some patients, conventionally delivered regional anesthesia has a failure rate of up to 20%.[i] Undergoing multiple attempts at anesthesia administration can cause unnecessary patient pain and anxiety and performing such procedures can leave clinicians frustrated as well as causing schedule delays. Ultrasound guided regional anesthesia (USGRA) is able to provide real-time, cost-effective imaging for regional anesthesia procedures, potentially increasing the effectiveness and ease of regional anesthesia procedures.

Dr. Robert Raw, M.D., is Director of the Regional Anesthesia Study Center of Iowa (RASCI) at the University of Iowa Hospitals and Clinics, and has practiced using both conventional and ultrasound guided regional anesthesia. Dr. Rajnish Gupta, M.D., Assistant Professor of Anesthesiology at Vanderbilt University School of Medicine, was introduced to ultrasound guidance as a resident. Both are leaders in the field today.

A New Technique Emerges

Raw pursued USGRA as soon as it became truly feasible in a clinical environment. He saw basic questions surrounding the early practice of USGRA – most notably, how did ultrasound guidance equate with the utility, advisability and advantages of nerve-stimulation? “As an academic regional anesthesia teacher, it was clear I needed to be a debater rather than a listener,” Raw said. “Since the department would not buy an ultrasound for regional anesthesia, at that time, I bought my own system and regarded the machine costs simply as the cost of a learning course. The answers to those early questions are now largely answered, but many new questions have been raised since then.” Raw’s department has subsequently purchased 6 ultrasound systems dedicated to regional anesthesia, and Raw sold his early machine.

Gupta began learning ultrasound guided regional anesthesia during his residency at the University of Michigan. “At the beginning of my residency, about four years ago, students became frustrated pretty quickly with regional anesthesia delivery, partly because it’s difficult to gain a comfort level using nerve stimulators and landmarks to deliver anesthesia,” Gupta said. “During my last year, the hospital acquired a SonoSite MicroMaxx^™, and a few of us had our interest piqued by the machine. We got as much out of that ultrasound system as possible.” Much like Raw, Gupta has seen interest among existing faculty members and residents at Vanderbilt increase over the last few years.

“When I arrived at Vanderbilt, they had already purchased an ultrasound system for regional anesthesia,” Gupta said. “However, not very many people were comfortable with it. I pushed to learn more, and the value was evident – you could see structures, visualize the variability in people, see the needle and the anesthetic surround the nerves, it was amazing.” Significant advancements in ultrasound technology have continued to increase the level of detail and clarity available to anesthesiologists.

Both Raw and Gupta actively participate in research to advance the field of ultrasound guided regional anesthesia. Raw focuses primarily on clinical delivery of USGRA. “My specific interest will always be primarily in the clinical delivery of regional anesthesia to the benefit of patients and in persuading other anesthesiologists and also surgeons of those benefits,” explained Raw. “Therefore, I seek to design better blocks, better room setups, and better techniques that are more time efficient.” Additionally, Raw explores ultrasound as an investigational tool in studying nerve block injury, and he considers the information derived from the use of ultrasound in regional anesthesia research to be revolutionary.

Gupta agrees, particularly with regard to the study of anatomy related to nerve blocks. “We’re finding out that the structure model we were taught for a long time isn’t always right,” Gupta said. “You can mark the landmarks, and the nerve should be right underneath that, but when you use ultrasound, you discover the rule is actually variation.” Physicians are consistently finding variations of multiple kinds, from the nerve location itself to the relationship with surrounding tissue, and ultrasound facilities the visualization of the nerve location and the surrounding vascular, bony, muscular and visceral structures. Other modalities, including CT and MRI, could also provide guidance in this regard, but ultrasound is by far the most practical modality available.

Gupta’s research focuses on the training of doctors and resident in ultrasound guided regional anesthesia technique, a step key to the further adoption of USGRA. “There’s a huge variation in physical skill sets, the caliber of those skills and in levels of previous training,” Gupta said. “This means we need to find the best ways to get doctors up to speed accurately and effectively.”

Regional Anesthesia and Needle Guidance

Needle guidance companies, including CIVCO, have developed new needle guidance technology for the regional anesthesia market. CIVCO has multiple regional anesthesia solutions, including the Infiniti Needle Guidance system and the SonoSite L25 Series Needle Guide.  As with many ultrasound guided procedures, some clinicians prefer needle guidance for USGRA, while others choose to freehand during procedures.

Gupta has not relied upon needle guidance during the past, but is open to the possibility in the future, particularly while training residents. “Personally, I haven’t normally used one,” explained Gupta. “In the past, I’ve tried older systems, but they were designed for biopsy and vascular procedures, not regional anesthesia. They were made to be used out of plane. Recently, I’ve been investigating concepts similar to CIVCO’s Infiniti guide, which is constrained in the appropriate dimensions and flexible in others.” Infiniti provides accurate in-plane guidance, and offers multiple angle capabilities for both shallow and deep access.

Gupta admits that watching residents learn two-handed technique in potentially dangerous anatomical areas can be nerve-wracking. “As trainers, we need to improve their success rates and skills quickly,” he said. One of the most common problems is drift. “Your eyes are looking at the ultrasound screen, but you may not maintain alignment with your hands – the probe drifts away from the needle,” explained Gupta. “There are a variety of ways to maintain alignment, so we teach these and investigate the best solutions. CIVCO’s Infiniti^™ needle guide is one of these solutions.” The key to making needle guidance a useful training tool for regional anesthesia is specializing the technology to this intended use.

Raw, on the other hand, does not use a needle guidance system for regional anesthesia. “I certainly can see some merit in it for aspiration of large fluids collection and for biopsy of large tissue lesions,” Raw said.

Both Raw and Gupta use sterile covers in more complex regional anesthesia procedures. “We use a full sleeve sterile over when performing large, complex procedures, such as placing perineural catheters,” Raw explained. “This is when we use full wide field sterility, gowns, mask and gloves as well.”

Procedures are similar in Gupta’s facility. “We use sterile probe covers when placing nerve catheters since they are going to stay in for several days,” Gupta said. CIVCO offers a wide variety of probe covers to meet numerous clinical infection control needs.

With prominent clinicians on both sides of the issue, it remains to be seen whether needle guidance becomes a standard of care in regional anesthesia. Constant innovation on the part of ultrasound OEMs and needle guidance developers may well provide clinicians with further solutions, making needle guidance advantageous. Further, as noted by Gupta, needle guidance has huge potential as a training tool for physicians. As young doctors are trained using needle guidance for USGRA, they may continue to do utilize it beyond their training programs.

The Future of Ultrasound Guided Regional Anesthesia

Gupta and Raw agree that ultrasound’s role in regional anesthesia is permanent. “The last decade has been spent defining ultrasound’s role, and it’s pretty well established at this point,”

explained Gupta. “Ultrasound guidance isn’t a necessity, and many people do well without it, but it’s an integral part of current available tools. For many people, it’s an essential tool.” Over time, Gupta feels ultrasound guidance will lead to higher success rates and fewer complications in regional anesthesia.

Raw looks at the future of this field in two facets: clinical applications and technology advances. “Future clinical applications will be a steady process of evolution as doctors simply try things out,” Raw said. “Some ideas will be silly and some will be brilliant. Each new USGRA idea will be brilliant to its own inventor, but broad clinical process will slowly clarify the basic questions: is it safer, is it more effective, and is it easier?” This process of physician innovation will continue to improve and increase the clinical application of USGRA.

Expansion in transducer technology will be a key advancement over the next decade. “A greater variety of transducers being made available gives us more selection flexibility,” Raw said. “I see regional anesthesia dedicated transducers being designed with better hand holding ergonomics. I see multi-scan transducers that are actually complex multiple transducers in one, exploiting better and faster computing capacity of machines. The challenge is to see deeper, better, with faster frame refresh rates.” Raw also envisions enhanced fusion and high frequency transducers and faster refresh rates for portable ultrasound.

Raw emphasizes the importance of increased computing capacity and cart design in future ultrasound systems. “There will be a move towards fixed mini-cart mounted systems with very high computing capabilities,” he explained. “Cart mounted systems also need to have un-interruptible power systems built in. Foot print size is everything and slim, vertical carts are starting to get more common. We need slim standing high capacity systems, something between the mega top-end TEE grade machines, and the low-end hand portable machines.”

From his perspective, Gupta focuses on techniques for improvement in clinical delivery. “I’m not sure which techniques will win out over the next decade, but reducing hand-eye difficulties and maintaining the stability of the probe at the same time will be important,” he said. “Imaging techniques are constantly evolving, with higher resolution and then 3D visualization.” Gupta does see development in the application of 3D imaging to USGRA, which can be more difficult than application to tumor imaging or biopsy. “At a recent ASRA meeting, Ultrasonix displayed a pseudo-3D tracking system – you can see the tip tracking, but the image actually looks like the 2D image that you are used to,” Gupta said. “This kind of tip tracking increases accuracy, precision and speed, acquiring the image like it’s needed for medication delivery.” The SonixGPS technology mentioned by Gupta incorporates CIVCO’s eTRAX™ needle tip tracking system.

Ultrasound guidance for regional anesthesia traces its roots back to 1978, when the first procedure was performed and described for publication. Since then, a dedicated group of clinicians have researched and practiced the technique, and ultrasound OEMs have continually delivered advanced technology. “The level of detail we’re seeing now that we couldn’t see even five years ago is unbelievable,” commented Gupta. The past five years have marked a paradigm shift within regional anesthesia.[ii] Given the ability of USGRA to minimize patient discomfort, procedure length and nerve injuries while increasing success rates, ultrasound guidance for regional anesthesia will continue to expand and mature over the next decade.

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[i] “Introduction, General Comments.” Ultrasound for Regional Anesthesia. Web. 17 Jun 2010. <http://www.usra.ca/ut_intro_gc>.

[ii] “Center for Ultrasound-Guided Regional Anesthesia.” Dartmouth-Hitchcock Medical Center. . N.p., n.d. Web. 17 Jun 2010. <http://www.dhmc.org/dhmc-internet-upload/file_collection/reg_anes_for_web.pdf>.