To the Editor:— Hebl’s response1to the case report by Koff et al. 2highlights the quagmire that anesthesiologists have been stuck in since the invention of the nerve stimulator. This quagmire is “How close can I get to the nerve?” Because mechanical trauma and the risk of intraneural injection are two risk factors we have control over, shouldn’t we be asking instead “How can I stay away from the nerve?”
Great regional anesthesiologists such as Winnie, Beck, and Dalens have published elegant block techniques using a detailed understanding of anatomy and fascial planes that do not require immediate proximity of the needle to the nerve.3–5Today, we can use high-resolution ultrasound to visualize nerves, blood vessels, and fascial planes. Why not use this new technology to position the needle accurately in a fascial plane containing the nerve rather than as the “visual equivalent of a nerve stimulator”? Small wonder that those still trying to “position the tip of the needle next to the nerve and get a donut sign” have not demonstrated any outcome differences using ultrasound techniques.
At the University of Utah (Salt Lake City, Utah), we have adopted the philosophy correctly stated by Marhofer et al. 6: “Nerves are not blocked by the needle but by the local anesthetic.” The results have been encouraging. All of our techniques for single and continuous nerve block placements are performed by injection into fascial planes containing the nerve and not by attempting to place the needle in close proximity to the nerve. We have performed more than 6,000 blocks using only ultrasound guidance, including more than 3,800 continuous catheters. A recent prospective study of 200 single and continuous interscalene blocks performed here using only ultrasound guidance showed a success rate of 99%, with only 1% of patients having mild, transient sensory deficits.7This is a considerable improvement over existing data for nerve stimulator techniques.8,9Our published data for 620 outpatients with ultrasound-guided femoral, sciatic, and interscalene catheters also show high success and low complications in comparison with nerve stimulator techniques.10As ultrasound gains more widespread application, additional outcome data will follow.
To say that ultrasound will not significantly improve patient safety is shortsighted. Many of the early techniques for ultrasound-guided blocks are still a variation on the nerve stimulator theme of “put the needle as close as possible to the nerve.” As we learn to use ultrasound to stay away from the nerve instead of getting close to it, we may be pleasantly surprised by the results. Dr. Hebl and others suggest that in ultrasound we have not found the “holy grail” of regional anesthesia.1,11In our opinion, it could be the “holy grail”; we simply must know how to use it.
*University of Utah, Salt Lake City, Utah. jeff.swenson@hsc.utah.edu
