Beyond Ultrasound Guidance for Regional Anesthesiology
Despite its popularity, ultrasound (US)–guided regional anesthesiology is associated with significant limitations. The latter can be attributed to either the US machine (ie, decreased ability to insonate deep neural structures, as well as the thoracic spine) or the operator. Shortcomings associated with the operator can be explained by errors in perception (ie, ambiguous criteria for needle/catheter tip–to–nerve proximity and subparaneural local anesthetic injection) or interpretation. Perhaps the greatest confusion afflicting US-guided regional anesthesiology originates from an intellectual misconception pertaining to its application. Increasingly, authors are using US to identify interfascial planes where local anesthetic can be injected thereby “discovering” new truncal blocks. Often these novel blocks suffer from a lack of proper randomized, comparative validation.
Fortunately, solutions have been proposed to remedy many shortcomings associated with US guidance. The inability of US to reliably insonate deep neural structures can be circumvented with adjunctive neurostimulation. Fluoroscopy and waveform analysis have been proven to increase the success rate of thoracic epidural blocks. For continuous nerve blocks, combined US-neurostimulation may provide an objective end point (ie, an evoked motor response) for neural proximity and subparaneural positioning of the catheter tip. Finally, the solution to the plethora of nonvalidated US-guided blocks is both elegant and simple. New nerve blocks should answer a specific clinical need, and their first descriptions should take the form of an adequately powered, observer-blinded, randomized comparison against the established standard of care or, at the very least, a large case series (eg, a Brief Technical Report).